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Home My WebLink AboutDRC-2011-007137 - 0901a06880257ac9July 11, 2011 VIA E-MAIL AND OVERNIGHT DELIVERY Denison IVIines (USA) Corp. 105017th Street, Suite 950 Denver, CO 80265 USA Tel: 303 628-7798 Fax: 303 389-4125 www.denisonmines.com Mr. Rusty Lundberg Department of Environmental Quality 195 North 1950 West P.O. Box 144850 Salt Lake City, UT 84114-4850 Re: State of Utah Groundwater Discharge Permit ("GWDP") No. UGW370004 Transmittal of Revised Discharge Minimization Technology Monitoring ("DMT") and Cell 4A and 4B Best Available Technology Operations and Maintenance ("BAT O&M") Plans Dear Mr. Lundberg: This letter transmits Denison Mines (USA) Corp's ("Denison's") proposed revisions to the White Mesa Mill DMT and BAT O&M Plans. These revisions respond to the requirements in Part 1.H.7 of the revised GWDP transmitted by the Utah Division of Radiation Control to Denison in a Draft Memorandum dated June 30, 2011. For ease of review we have provided both redline and clean versions of each document. Attachment 1 contains both versions ofthe DMT Plan, and Attachment 2 contains both versions ofthe BAT O&M Plan. Denison has previously submitted proposed redline changes to the DMT Plan on June 23, 2011. The enclosed DMT Plan Revision 11.2 incorporates all the changes proposed in Denison's June 23, 2011 submittal, as well as the changes required by the June 30, 2011 GWDP revision. The enclosed DMT and BAT O&M Plan revisions also incorporate minor additional corrections or amended language necessary to reflect current operations. Please contact me if you have any questions or require any further information. Yours very truly, DENISON MINES (USA) CORP. Jo Ann Tischler Director, Compliance and Permitting cc: David C. Frydenlund N:\DMT Plan\July 2011 DMT revision for permit\07.11.11 transmittal Revisions DMT and BAT O and M.doc ENERGYSOLUTIONS NOTICE OF 60-DAY COMMENT PERIOD AND PUBLIC INFOfuVl:ATION MEETING Notice is hereby given that EnergySolutions, LLC has requested a Class 3 modification to its State-issued Part B Permit to revise the top of waste design and to expand its Mixed Waste embankment at the Clive facility. Concurrent with this request, EnergySolutions requests approval to begin Phase I of cover construction over the Mixed Waste embankment. This Pennit modification affects Attachment 1I-1-7, Closure Plan, Attachment II-9, Construction QAIQC Manual, Attachment II-II, Facility Drawings, Module V, Disposal in Landfills, and Module VI, Groundwater Monitoring. EnergySolutions is also requesting Temporary Authorization for the revised top of waste desi!,'11 and to begin building Radon Barrier for Phase I of cover construction over thc Mixed Waste embankment. Any comments on this modification should be submitted to Mr. Scott Anderson, Director, Utah Division of Solid and Hazardous Waste, Utah Department of Environmental Quality, P.O. Box 144880, Salt Lake City, Utah 84114-4880. The 60-day comment peliod for this modification will end on September 19, 2011, or within 60 days of the initial date of publication of this notice, whichever comes later. A public information meeting for this modification will be held August 15, 2011, at 7:00 PM at the Tooele County Courthouse, 47 South Main Street, Tooele, Utah. (Enter at the South side ofthe parking lot and go downstairs). For more information about this modification, contact: Facility Contact Person: Sean McCandless, EnergySolutions. Telephone: (801) 649-2000. Division Contact Person: Otis Willoughby, Utah Division of Solid and Hazardous Waste, P.O. Box 144880, 195 North 1950 West, Salt Lake City, Utah 84114-4880. Telephone: (801) 536-0220. The modification requests and suppOliing documents are available to be copied and for public review at the Utah Division of Solid and Hazardous Waste or at the offices of EnergySolutions, 423 West 300 South, Suite 200, Salt Lake City, Utah, on business days from 9:00 a.m. to 12:00 p.m. and from 1:00 p.m. to 4:00 p.m. The Pennittee's compliance history during the life of the pennit being modified IS available from the Division contact person. E D c B A 1 6" THICK TYPE A FILTER ZONE ~-. ,-'Co- 6" MIN THICK TYPE B FILTER ZONE 60 MIL HDPE LINER (TEXTURED 80TH SIDES) 12" THICK TEMPORARY --1':t-~J;::;;;;'9::.cc COVER 2 TYPE DETAIL-SIDE SLOPE 12" THICK TYPE A RIP RAP NTS TYPICAL SIDE SLOPE COVER DETAIL TYPE A FILTER ZONE, THICKNESS VARIES, 6" MIN DETAIL-DITCH OUTER SLOPE NTS 1 TYPICAL PERIMETER DITCH COVER DETAIL 2 12" THICK SACRIFICIAL SOIL 12 oz./sy NON-WOVEN GEOTEXTILE 2' OF 5x10-8 CM/SEC RADON BARRIER 3 6" THICK A FILTER 6" MIN THICK TYPE B FILTER ZONE - 60 MIL HOPE LINER (TEXTURED 80TH SIDES) 4 18" THICK TYPE 8 RIPRAP 12" THICK SACRIFICIAL SOIL 1 2 oz./sy NON-WOVEN GEOTEXTILE 2' OF 5x10-8 CM/SEC RADON 8ARRIER 12" THICK TEMPORARY---~~~~~G±SG02i12it2~B2~~~~ COVER 6" MIN THICK TYPE B FILTER ZONE - 60 MIL HOPE LINER (TEXTURED 80TH SIDES) 12" THICK TEMPORARY -~--",,-. COVER 3 DETAIL-TOP SLOPE NTS TYPICAL TOP SLOPE COVER DETAIL 18" THICK TYPE 8 RIPRAP 12" THICK SACRIFICIAL SOIL 12 oz./sy NON-WOVEN GEOTEXTILE 2' OF RADON BARRIER DETAIL-SHOULDER NTS 4 5 5 6 COVER MATERIAL GRADATIONS (ASTM C-136) TYPE A RiP RAP 0100<= 16 INCH 090 <= 12 Ii'iCH D 50 >= 4-1/2 INCH Dl0 >= 2 INCH D 5 > == NO. 200 SIEVE TYPE B RIP RAP D 100<= 4-1/2 INCH 050 >== 1-1/4 INCH D 10 >= 3/4 INCH D 5 > = NO. 200 SIEVE TYPE A FILTER ZONE D 100<= 6 INCH D 70 <= 3 INCH D 50 <= 1.57 INCH (40 mm) D 15 <= .85 INCH (22 mm) 010 >= NO. 10 SIEVE (2mm) D5 >= NO. 200 SIEVE TYPE B FILTER & SACRIFICIAL SOIL TYPE B FILTER & SACRIFICIAL SOIL MATERIAL GRADATIONS ARE DETERMINED BY THE FOLLOWING SPECIFICATION: D1S (MAX) FILTER Dss (MIN) SOIL MUST BE < 5 DsO ( MAX) FILTER D50 (MIN) SOIL MUST BE <= 25 TYPE B FILTER Dl00 <= 1.5 INCH TYPE B FILTER MIN PERMEABILITY == 3.5 em/sec SACRIFICIAL SOIL MIN MOISTURE @ 15 aim == 3.5% TYPE A FILTER & SACRIFICIAL SOIL MATERIAL GRADATIONS SHALL MEET THE FOLLOWING SPECIFICATION: D15 FILTER DS5 son::-MUST BE <= 4 015 SOIL DS5 FILTER MUST BE <= 4 NOTE: ADDITIONAL MATERIAL SPECIFICATIONS RELATED TO COVER CONSTRUCTION ARE LOCATED IN THE CONSTRUCTION QUALITY ASSURANCE/QUALITY CONTROL MANUAL UNDER THE APPLICABLE WORK ELEMENT. 6 E D FINAL DRA,~ING 11009 W05 Attachment 1 Engineering Justification Report EnergySolutions Mixed Waste Embankment – Expansion Project Engineering Justification Report Revision 0 July 18, 2011 EnergySolutions Mixed Waste Expansion Project Engineering Justification Report July 18, 2011 Revision 0 Page 2 of 59 Table of Contents 1.0 INTRODUCTION .............................................................................................................................................. 4 1.1 REFERENCES .............................................................................................................................................. 7 1.2 APPENDICES ............................................................................................................................................... 9 2.0 DESIGN CRITERIA OF THE PRINCIPAL DESIGN FEATURES .......................................................... 14 2.1 LINER AND LEACHATE COLLECTION/REMOVAL SYSTEM (LCRS) ........................................ 14 2.1.1 MINIMIZE CONTACT OF WASTES WITH STANDING WATER DURING OPERATIONS ................................ 14 2.1.2 MINIMIZE CONTACT OF WASTES WITH STANDING WATER AFTER CLOSURE ........................................ 14 2.1.3 ENSURE COVER INTEGRITY .................................................................................................................. 15 2.2 MIXED WASTE PLACEMENT ............................................................................................................... 16 2.2.1 ENSURE COVER INTEGRITY .................................................................................................................. 17 2.2.2 ENSURE STRUCTURAL STABILITY ......................................................................................................... 17 2.3 COVER ........................................................................................................................................................ 18 2.3.1 MINIMIZE INFILTRATION ...................................................................................................................... 18 2.3.2 REDUCE EXPOSURE .............................................................................................................................. 20 2.3.3 ENSURE COVER INTEGRITY .................................................................................................................. 20 2.3.4 ENSURE STRUCTURAL STABILITY ......................................................................................................... 22 2.4 DRAINAGE SYSTEMS ............................................................................................................................. 24 2.4.1 PROVIDE SITE DRAINAGE ..................................................................................................................... 24 2.4.2 ENSURE DITCH INTEGRITY ................................................................................................................... 25 2.5 BUFFER ZONE........................................................................................................................................... 25 2.5.1 PROVIDE SITE MONITORING ................................................................................................................. 25 3.0 PERTINENT CHARACTERISTICS OF THE PRINCIPAL DESIGN FEATURES ............................... 26 3.1 LINER .......................................................................................................................................................... 26 3.1.1 FOUNDATION AND CLAY LINER ................................................................................................................. 27 3.1.2 SYNTHETIC LINER SYSTEM .................................................................................................................... 28 3.1.3 SUMP LEACHATE REMOVAL POINT ....................................................................................................... 29 3.2 WASTE PLACEMENT .............................................................................................................................. 29 3.2.1 MIXED WASTE PLACEMENT ................................................................................................................. 29 3.2.2 OVERSIZED DEBRIS LIFT BACKFILL ....................................................................................................... 30 3.3 COVER ........................................................................................................................................................ 30 3.3.1 RADON BARRIER .................................................................................................................................. 31 3.3.2 HDPE LINER AND GEOTEXTILE ............................................................................................................ 31 3.3.3 LOWER FILTER ZONE “TYPE B” FILTER ................................................................................................ 31 3.3.4 SACRIFICIAL SOIL ................................................................................................................................. 31 3.3.5 UPPER FILTER ZONE “TYPE A” FILTER ................................................................................................. 32 3.3.6 EROSION BARRIER ................................................................................................................................ 32 3.4 DRAINAGE SYSTEMS ............................................................................................................................. 32 3.5 BUFFER ZONE........................................................................................................................................... 32 4.0 PROJECTED PERFORMANCE OF THE PRINCIPAL DESIGN FEATURES ..................................... 33 4.1 LINER AND LEACHATE COLLECTION/REMOVAL SYSTEM (LCRS) ........................................ 33 4.1.1 MINIMIZE CONTACT OF WASTES WITH STANDING WATER DURING OPERATIONS ................................ 33 4.1.2 MINIMIZE CONTACT OF WASTES WITH STANDING WATER AFTER CLOSURE ........................................ 34 4.1.3 ENSURE COVER INTEGRITY .................................................................................................................. 37 4.2 MIXED WASTE PLACEMENT ............................................................................................................... 37 4.2.1 ENSURE COVER INTEGRITY .................................................................................................................. 37 4.2.2 ENSURE STRUCTURAL STABILITY ......................................................................................................... 38 4.3 COVER ........................................................................................................................................................ 39 4.3.1 MINIMIZE INFILTRATION ...................................................................................................................... 39 4.3.2 REDUCE EXPOSURE .............................................................................................................................. 48 EnergySolutions Mixed Waste Expansion Project Engineering Justification Report July 18, 2011 Revision 0 Page 3 of 59 4.3.3 ENSURE COVER INTEGRITY .................................................................................................................. 49 4.3.4 ENSURE STRUCTURAL STABILITY ......................................................................................................... 53 4.4 DRAINAGE SYSTEMS ............................................................................................................................. 56 4.4.1 PROVIDE SITE DRAINAGE ..................................................................................................................... 56 4.4.2 ENSURE DITCH INTEGRITY ................................................................................................................... 58 4.5 BUFFER ZONE........................................................................................................................................... 59 4.5.1 PROVIDE SITE MONITORING ................................................................................................................. 59 EnergySolutions Mixed Waste Expansion Project Engineering Justification Report July 18, 2011 Revision 0 Page 4 of 59 1.0 INTRODUCTION EnergySolutions is requesting Utah Division of Solid and Hazardous Waste (DSHW) approval of a Class III modification to its State-issued Part B Permit that will finalize design specifications to define the embankment top of waste at the Mixed Waste embankment and permit northern expansion into two new sumps: sumps 11 and 12. This Expansion Project Engineering Justification Report has been prepared to summarize design criteria, embankment design features, and projected performance of the expanded Mixed Waste embankment. This Expansion Project Engineering Justification Report is based on the prior Mixed Waste Embankment Engineering Justification, revision 2, October 30, 2001 and has been updated with new analyses as needed to incorporate the revised waste column height and northern expansion. In a letter dated March 5, 2003, the Utah Division of Radiation Control concurred with the elements of the Mixed Waste cover design. EnergySolutions’ disposal facility follows an above-grade landfill design. The embankment is constructed using primarily materials native to the Clive region. Engineered features of the embankment have been based upon regulations and guidance promulgated by the State of Utah, Nuclear Regulatory Commission (NRC), and Environmental Protection Agency (EPA), as well as EnergySolutions’ past experience at this location. The Mixed Waste embankment liner and cover systems incorporate synthetic materials and engineering elements in a manner consistent with “Joint NRC-EPA Guidance on a Conceptual Design Approach for Commercial Mixed Waste Low-Level Radioactive and Hazardous Waste Disposal Facilities” (NRC/EPA, 1987). The NRC/EPA guidance (page 5) provides two criteria for minimizing contact of waste with water. The first criterion calls for siting the embankment so that wastes will be placed above the elevation of the highest water table fluctuation and above drainage layers where leachate will collect. As discussed in “EnergySolutions Mixed Waste Cell Infiltration and Transport Modeling,” Section 6.2.4 (Whetstone, November 22, 2000), the distance from the bottom of the waste (i.e., including the liner system) to the top of the aquifer is 18.6 feet. Extending the length of the embankment to the north does not change this distance. As such, this criterion is met. EnergySolutions’ mixed waste embankment is constructed of below-grade sumps; waste is placed within these sumps at elevations below that of the top of the perimeter berm. Please refer to Section 2.1.2 for design criteria applied to minimize contact of wastes with standing water following closure. Projected performance of the embankment to minimize contact of wastes with standing water following closure is discussed in Section 4.1.2. It should be noted that the NRC/EPA document is intended to provide “…a conceptual design approach that meets EPA’s regulations… and NRC’s requirements… The concepts proposed in this document are presented as general guidance… (NRC/EPA, 1987, page 1).” Accordingly, the conceptual design does not carry the force of regulation. One element of the NRC/EPA conceptual design is not incorporated in EnergySolutions’ Mixed Waste embankment design: drainage layers within the cover system. The NRC/EPA guidance for layers within the cover system calls for a secondary drainage layer beneath the HDPE liner and compacted low-permeability clay layer. Presumably, this design might allow secondary capture and diversion of water that may infiltrate the HDPE liner and associated (upper) compacted clay layer. However, this design is unlikely to perform as intended for two reasons. First, because infiltration through the HDPE liner and compacted clay layer is extremely slow, the “buried” secondary drainage layer would not accumulate water fast enough to drain. Accordingly, infiltration may be delayed slightly by the additional thickness of the second drainage layer, but would not be reduced in magnitude. Second, there are serious constructability EnergySolutions Mixed Waste Expansion Project Engineering Justification Report July 18, 2011 Revision 0 Page 5 of 59 concerns raised by the concept of placing a compacted clay layer, particularly to EnergySolutions’ low permeability criteria of 5 x 10-8 cm/sec, over a drainage layer. Internal erosion between these layers would likely limit or eliminate the effectiveness of both layers in meeting the intended function. In fact, it is unlikely that an effective filter layer could be designed to meet the internal erosion and piping criteria for drainage layers provided in Section 2.7.2.1.1 of NUREG/CR-5041, Vol. 1. EnergySolutions’ cover design incorporates a secondary drainage layer, placed above the HDPE liner in order to reduce potential infiltration at the source. As demonstrated in the infiltration and transport modeling report (Whetstone, November 22, 2000 and EnergySolutions, 2011 provided as Appendix C to this document), EnergySolutions’ extended embankment design meets the performance standards for groundwater protection, even though no credit is taken in the model for the significant reductions in infiltration attributable to the HDPE layer in the cover. See also Section 4.3.1 for projected performance of the embankment in limiting infiltration. The general design requirements for the licensing of a radioactive waste disposal facility are set forth in the Utah Administrative Code (UAC), Rule R313-25, administered by the DRC. Rule R313-25-24 outlines six design requirements for near-surface land disposal of radioactive waste as follows: 1. “Site design features shall be directed toward long-term isolation and avoidance of the need for continuing active maintenance after closure. 2. The disposal site design and operation shall be compatible with the disposal site closure and stabilization plan and lead to disposal site closure that provides reasonable assurance that the performance objectives will be met. 3. The disposal site shall be designed to complement and improve, where appropriate, the ability of the disposal site’s natural characteristics to assure that the performance objectives will be met. 4. Covers shall be designed to minimize, to the extent practicable, water infiltration, to direct percolating or surface water away from the disposed waste, and to resist degradation by surface geologic processes and biotic activity. 5. Surface features shall direct surface water drainage away from disposal units at velocities and gradients which will not result in erosion that will require ongoing active maintenance in the future. 6. The disposal site shall be designed to minimize to the extent practicable the contact of standing water with waste during disposal, and the contact of percolating or standing water with wastes after disposal.” R313-25-22 requires that the facility shall be sited, designed, used, operated, and closed to achieve long-term stability of the disposal site without the need for ongoing active maintenance. Radiation protection standards are set forth in R313-25-19, R313-15-301 and R313-15-302. Where UAC design criteria set forth specific criteria, the facility has been designed to meet that specific criteria. However, the general criteria that the facility design must “achieve long-term stability... to eliminate, to the extent practicable, the need for ongoing active maintenance of the disposal site after closure,” requires a determination of the meaning of “long-term.” The EPA and the NRC, in setting design criteria for disposal facilities for uranium mill tailings and 11e.(2) byproduct material, have addressed the issue of long-term stability. Both agencies have adopted a standard that requires that the facility be designed for 1,000 years, whenever reasonably EnergySolutions Mixed Waste Expansion Project Engineering Justification Report July 18, 2011 Revision 0 Page 6 of 59 achievable, but in any case for a minimum of 200 years. EnergySolutions has adopted this standard to determine the design criteria for long-term stability. The extended Mixed Waste embankment falls within overlapping regulatory jurisdictions for groundwater protection: DSHW is the lead agency for hazardous constituents, while DRC with the Utah Division of Water Quality (DWQ) regulate radionuclides. Specifically, EnergySolutions’ State-issued Part B Permit requires, at Module VI, Condition VI.D.3, that the facility must monitor for and meet groundwater protection standards for hazardous constituents for 30 years following facility closure. This permit condition is based on EPA regulations at 40 CFR 264.117(a)(1). EnergySolutions’ Ground Water Quality Discharge Permit, at Condition I.D.1, requires that ground water protection levels (GWPLs) for radionuclides from the Mixed Waste embankment be met for 500 years. This 500-year standard for radionuclides is consistent with EnergySolutions’ LARW and Class A embankments. EnergySolutions has demonstrated, through infiltration and groundwater transport modeling of the Mixed Waste embankment (Whetstone, November 22, 2000), that this standard will be met (see also Section 4.3.1.1 below). Further, an internal analysis, later verified by Whetstone, illustrates this standard will continue to be met by the extended footprint of the Mixed Waste embankment (Appendix C). The Whetstone assessment is focused on the fate and transport of radionuclides. EnergySolutions’ Ground Water Quality Discharge Permit, at Condition I.D.1, requires a performance standard of 200 years for heavy metals for the LARW and Class A embankments; but does not regulate this aspect of the Mixed Waste embankment. Accordingly, modeling for metals has not specifically been performed for the Mixed Waste embankment. Nonetheless, previous modeling efforts for the LARW and Class A embankments provide evidence that metals will not exceed the GWPLs within 200 years (see Whetstone, July 19, 2000). EnergySolutions’ internal assessment illustrates that this conditions remains unchanged for the revised geometry (Appendix C). This conclusion is based on two aspects of these modeling efforts: infiltration rate and source term for hazardous constituents. Based upon a review of previous infiltration modeling performed for the site, the Mixed Waste embankment has the lowest infiltration rate of any of EnergySolutions’ disposal embankments. Accordingly, there is less water available in the Mixed Waste embankment to transport hazardous constituents. In addition, Whetstone modeled transport of metals assuming a source term of 100% heavy metal, based on density (Whetstone, July 19, 2000, Section 8). Therefore, hazardous heavy metals can be received at essentially any concentration without exceeding ground water protection levels at 200 years. The following discussion of design features, their pertinent characteristics, and projected performance deviates from the outline provided in NUREG-1199, “Standard Format and Content of a License Application for a Low-Level Radioactive Waste Disposal Facility.” To aid in review, Table 1 summarizes the outline proposed by NUREG-1199 with cross-references to sections of this document that address the functional requirements in question. Table 1 is not intended to be an exhaustive cross-reference, as the functional requirements outlined by NUREG-1199 may be affected by a number of required functions or complementary aspects of the critical design features. EnergySolutions Mixed Waste Expansion Project Engineering Justification Report July 18, 2011 Revision 0 Page 7 of 59 Table 1 NUREG-1199 Cross-Reference NUREG-1199 Functional Requirement Addressed in Section(s) Water Infiltration Design: 2.3.1 Performance: 4.3.1 Disposal Unit Cover Integrity Design: 2.1.2; 2.2.1; 2.3.3 Performance: 4.1.2; 4.2.1; 4.3.3 Structural Stability Design: 2.2.2; 2.3.4 Performance: 4.2.2; 4.3.4 Contact With Standing Water Design: 2.1.1; 2.4.1 Performance 4.1.1; 4.4.1 Site Drainage Design: 2.4.1 Performance: 4.4.1 Site Closure and Stabilization Design: 2.3 Performance: 4.3 Long-Term Maintenance Design: 2.3.3; 2.4 Performance: 4.3.3; 4.4 Inadvertent Intruder Barrier Design: 2.3.3 Performance: 4.3.3 Occupational Exposure See Section 7.1 of EnergySolutions’ June 20, 2005 LARW License Renewal Application Site Monitoring Design: 2.5.1 Performance: 4.5.1 Buffer Zone Design: 2.5.1 Performance: 4.5.1 The discussions of embankment design and performance following in Sections 2 through 4 are organized around the information summarized in Tables 2 through 4. Table 2 summarizes design criteria of the principal design features for the Mixed Waste embankment, as well as the normal, abnormal, and accident conditions evaluated against each design criteria. Table 3 provides material and construction specifications for the principal design features for the Mixed Waste embankment. Table 4 summarizes performance analyses prepared for appropriate normal, abnormal, and accident conditions for the Mixed Waste embankment. Throughout, the principal design features are discussed beginning at the base of the Mixed Waste embankment, working to the top of the cover system then to the drainage system and the buffer zone around the completed embankment. Each major subsection is addressed in the same order as the tables (i.e., the complementary aspect of a design feature introduced in Section 2.3.1 is reviewed for projected performance in Section 4.3.1). 1.1 REFERENCES A number of relevant documents, including reports previously submitted within the approval process for this and/or other EnergySolutions facilities, are incorporated by reference rather than attached as appendices:  AGEC, October 19, 1998. “Closure Cap Stability and Settlement Estimate Mounding - Mixed Waste Disposal Facility.”  AGEC, July 29, 1999. “Response: Division of Solid and Hazardous Waste Mixed Waste Disposal Facility Mounding.” EnergySolutions Mixed Waste Expansion Project Engineering Justification Report July 18, 2011 Revision 0 Page 8 of 59  AGRA, June 1, 2000. “Evaluation of Settlement of Compressible Debris Lifts, LARW Embankments.”  AMEC, October 4, 2000. “Letter Report: Allowable Differential Settlement and Distortion of Liner and Cover Materials.” (Appendix I-1 of the Class A/B/C Amendment Application dated December 13, 2000)  AMEC, November 8, 2000. “Settlement Evaluation: Proposed LLRW and Mixed Waste Embankments.” (Appendix I-2 of the Class A/B/C Amendment Application dated December 13, 2000)Badu-Tweneboah, K., Tisinger, L.G., Giroud, J.P., and Smith, B.S., 1999. “Assessment of the Long-Term Performance of Polyethylene Geomembranes and Containers in a Low-Level Radioactive Waste Disposal Landfill.” Geosynthetics ’99 Conference Proceedings, pp. 1055-1070.  Bonaparte, R., J.P. Giroud, B.A. Gross, 1989. “Rates of Leakage Through Landfill Liners.” Geosynthetics ’89 Conference Proceedings, vol. 2, pp. 18-29.  Cedergren, H.R., Seepage, Drainage and Flow Nets, second edition, John Wiley and Sons, New York, NY, pp. 178-182 (1977)  DOE, 1984. “Final Environmental Impact Statement: Remedial Actions at the Former Vitro Chemical Company Site.”  DOE, 1992. “Vegetation Growth Patterns on Six Rock-Covered UMTRA Project Disposal Cells.” (UMTRA – DOE/AL 400677.0000)  EnergySolutions, December 15, 2010. “LLRW and 11e.(2) CQA/QC Manual” Revision 25d.  Envirocare of Utah, Inc., Mixed Waste Embankment Engineering Justification Report, Revision 2, October 30, 2001.  Envirocare of Utah, Inc. “State-issued Part B Permit Approval Application,” March 30, 1990.  Envirocare of Utah, Inc., “RCRA Plan Approval” (RCRA Permit), November 11, 1990.  Envirocare of Utah, Inc. “Class A/B/C Amendment Application,” December 13, 2000.  Envirocare of Utah, Inc. “Application For Renewal, Radioactive Materials License Number UT2300249,” Revision 6, March 16, 1998.  Montgomery Watson, February 5, 1998. “Review of Cover Design for LARW Cell.”  Montgomery Watson, March 1, 2000. “LARW Cover Frost Penetration.”  Mines Group, November 14, 2000. “Technical Report for the Mixed Waste Facility Cover Design, Clive, Utah.”  National Oceanic and Atmospheric Administration (NOAA). Atlas 2, Volume VI.  NRC/EPA, 1987. “Joint NRC-EPA Guidance on a Conceptual Design Approach for Commercial Mixed Waste Low-Level Radioactive and Hazardous Waste Disposal Facilities.”  Schroeder, P.R., Aziz, N.M., Lloyd, C.M., and Zappi, P.A. The Hydrologic Evaluation of Landfill Performance (HELP) computer model: User’s Guide for Version 3, EPA/600/R- 94/168A; US EPA Office of Research and Development, Washington, D.C. (1994) EnergySolutions Mixed Waste Expansion Project Engineering Justification Report July 18, 2011 Revision 0 Page 9 of 59  Seed, H.B. “Earthquake Resistant Design of Earth Dams,” in Proceedings, Symposium on Seismic Design of Dams, ASCE, New York (1983)  Seed and Idriss, “Ground Motions and Soil Liquefaction During Earthquakes,” Earthquake Engineering Research Institute, Berkeley, CA (1982)  Sherard, J.L., L.P. Dunnigan, 1985. “Filters and Leakage Control in Embankment Dams and Impoundments” ASCE National Convention Proceedings, Denver Colorado.  SWCA, Inc., November 2, 2000. “Assessment of Vegetative Impacts on LLRW.” (Appendix K-2 of the Class A/B/C Amendment Application dated December 13, 2000)  US Army Corps of Engineers, September 30, 1986 (original) April 30, 1993 (change 1). “Manual EM1110-2-1091: Engineering and Design - Seepage Analysis and Control for Dams.”  U.S. Army Engineer Waterways Experiment Station, “Recommendations to the NRC for Review Criteria for Alternative Methods of Low-Level Radioactive Waste Disposal,” Vol.1, NUREG/CR-5041, December 1987.  U.S. Environmental Protection Agency, “Proposed Guide for Industrial Waste Management,” EPA530-R-99-001, June 1999.  U.S. Environmental Protection Agency, “Guide to Technical Resources for the Design of Landfill Disposal Facilities,” EPA/625/6-88/018, December 1988.  U.S. Nuclear Regulatory Commission, “Methodologies for Evaluating Long-Term Stabilization Designs for Uranium Mill Tailings Impoundments,” (NUREG/CF-4620)  U.S. Nuclear Regulatory Commission, “Final (Standard Format and Content of a License Application for a Low-Level Radioactive Waste Disposal Facility,” (NUREG-1199, USNRC, January 1991).  U.S. Nuclear Regulatory Commission, “Design of Erosion Protection for Long-Term Stabilization,” Draft Report for Comment (NUREG-1623, USNRC, February 1999).  Western Regional Climate Center, Desert Research Institute, Reno, Nevada. November 1, 2000. Minimum Temperature Return Rates data provided to Envirocare (Appendix O-3 of the Class A/B/C Amendment Application dated December 13, 2000)  Whetstone Associates, Inc., July 19, 2000. “Revised Envirocare of Utah Western LARW Cell Infiltration and Transport Modeling.”  Whetstone Associates, October 20, 2000. “Sensitivity Analysis of Vegetated Class A, B, &C Cell Cover” (Appendix K-1 of the Class A/B/C Amendment Application dated December 13, 2000)  Whetstone Associates, November 7, 2000. “Infiltration Through Lower Radon Barrier, Class A, B, &C Cell Cover” (Appendix K-4 of the Class A/B/C Amendment Application dated December 13, 2000)  Whetstone Associate, Inc., November 22, 2000. “Envirocare of Utah Mixed Waste Cell Infiltration and Transport Modeling.” 1.2 APPENDICES The following documents contain new engineering analyses of Mixed Waste embankment design features and their performance: EnergySolutions Mixed Waste Expansion Project Engineering Justification Report July 18, 2011 Revision 0 Page 10 of 59 Appendix A: Clive Total Facility Ditch Flow Calculations Appendix B: Revised Drawing Set: 11009, Rev. 0 Appendix C: Impacts of proposed revisions to the Mixed-Waste Disposal Cell Geometry on Groundwater Compliance Appendix D: AMEC Geotechnical Analysis EnergySolutions Mixed Waste Expansion Project Engineering Justification Report July 18, 2011 Revision 0 Page 11 of 59 Table 2 Design Criteria of the Principal Design Features: Mixed Waste Embankment Table 2 Design Criteria of the Principal Design Features: Mixed Waste Embankment Principal Design Feature Required Function Complementary Aspects Design Criteria Design Criteria Justification Conditions July 18, 2011 Revision 0 Page 1 of 3 Liner and Leachate Collection/ Removal System (LCRS) Minimize contact of wastes with standing water Minimize contact of wastes with standing water during operations Meets requirements of 40 CFR 264.301 (c)(3) Minimum Technical Requirements under RCRA; enables collection and removal of standing water (leachate) that may accumulate in the embankment. normal Constructed per design specification abnormal Inspection/removal pipe clog accident Inspection/removal pipe damage Minimize contact of wastes with standing water after closure Liner permeability cover permeability Inflow into embankment < outflow out of embankment. normal HDPE layers retain design permeability over time; stress cracking occurs within HDPE layers due to natural aging abnormal Cover HDPE increases in permeability faster than the LCRS (in general and specifically due to biointrusion); quality of contact between HDPE and clay is compromised over time accident No reasonable scenario Ensure cover integrity Mitigate differential settlement Maximum allowable distortion in cover = 0.02 AMEC report dated October 4, 2000 normal Settlement completed during operations abnormal One area to cover height with adjacent area less than 25 feet high accident Not required per NUREG-1199 Mixed Waste Placement Ensure cover integrity Mitigate differential settlement Maximum allowable distortion in cover = 0.02 AMEC report dated October 4, 2000 normal All primary and portion of secondary settlement in soil layers completed during construction. abnormal Allow creep of compressible waste and additional secondary settlement of soils. Compressible waste area bounded by incompressible waste forms. accident Not required per NUREG-1199 Ensure structural stability Maintain slope stability Static safety factor 1.5 Pseudo-static Safety Factor > 1.0 (seismic coefficient > 50% of the maximum bedrock acceleration) Pseudo-static Safety Factor > 1.3 (475 year recurrence interval) Seismic safety factor 1.2 (Liquefaction) State of Utah Statutes and Administrative Rules for Dam Safety, Rule R655-11-5 and -6 “Guide to Technical Resources for the Design of Landfill Disposal Facilities,” EPA/625/6- 88/018 normal Static conditions abnormal Ground acceleration due to an earthquake. Liquefaction of foundation soils beneath the embankment accident Not required per NUREG-1199 Cover Minimize infiltration Minimize infiltration Average Infiltration 0.072 inches/year (0.183 cm/year) top slope 0.038 inches/year (0.096 cm/year) side slope HELP model parameter that achieved performance based standards. Whetstone Associates, Inc., “Mixed Waste Infiltration and Transport Modeling”, dated November 22, 2000. EnergySolutions, Inc., “Impacts of Proposed Revisions to the Mixed-Waste Disposal Cell Geometry on Groundwater Compliance”, dated April 20, 2011. normal Average annual precipitation (7.92 ") abnormal All abnormal conditions related to the Complementary Aspects of "Encourage Runoff", "Desiccation", "Frost Penetration", and "Biointrusion". accident Not required per NUREG-1199 Encourage runoff Maintain positive drainage; Maximum design velocity within drainage layer > calculated drainage velocities; Do not allow water accumulation Drainage (flow) needs to be maintained under all conditions normal 25 yr. 24 hr. event (1.9 inches) abnormal PMP (1-hour = 6.1 inches) accident Downstream blockage Prevent desiccation No desiccation cracking in Radon Barrier Clay Maintain radon barrier permeability to ensure infiltration design criteria is attained normal Historic weather patterns abnormal Drought accident Not required per NUREG-1199 Table 2 Design Criteria of the Principal Design Features: Mixed Waste Embankment Principal Design Feature Required Function Complementary Aspects Design Criteria Design Criteria Justification Conditions July 18, 2011 Revision 0 Page 2 of 3 Cover Limit frost penetration Thickness of rock/filter/sacrificial soil zones maximum depth of frost Maintain radon barrier permeability to ensure infiltration design criteria is attained normal Historic weather patterns Minimize infiltration abnormal Monthly average minimum temperatures, 500 year return frequency accident Not required per NUREG-1199 Limit biointrusion Biointrusion shall be discouraged and shall not cause increased infiltration Ensure infiltration design criteria is attained normal Desert plant growth (shallow rooted) abnormal Desert plant growth (deep rooted) combined with degraded geomembrane accident Not required per NUREG-1199 Reduce Exposures Surface dose rates 100 mrem TEDE R313-15-301 normal Low to moderate gamma emitters abnormal High concentration gamma emitter at top of waste accident Not required per NUREG-1199 Ensure Cover Integrity Mitigate Differential Settlement Maximum Allowable Distortion = 0.02 AMEC report dated October 4, 2000 normal All primary and portion of secondary settlement in soil layers completed during construction. abnormal Allow creep of compressible waste and additional secondary settlement of soils. Compressible waste area bounded by incompressible waste forms. accident Not required per NUREG-1199 Prevent Internal Erosion Water velocity < 3 ft/sec on Radon Barrier Clay NUREG/CR-4620 normal 100 yr. 24 hr. event (2.4 inches) abnormal PMP (1-hour = 6.1 inches) accident Not required per NUREG-1199 Prevent Piping: D15(filter)/D85(soil) 5 AND D50(filter)/D50(soil) 25 Prevent Upward Migration of Fines D15(Lower Layer)/D85(Upper Layer) 4 Reduce plugging of lower filter layer. Cedergren, H.R., (1977), "Seepage, Drainage, and Flow Nets" second edition, John Wiley & Sons, New York, pp. 178-182. DOE, 1989. Technical Approach Document, Revision II, UMTRA-DOE/Al 050425.0002, pp. 82-83 normal Performance calculations are developed for saturated conditions within dams. Conditions at EnergySolutions are much less severe. US DOE ratios have been developed for abnormal saturated conditions within an UMTRA embankment. abnormal accident Material Stability / Endure Weathering, External Erosion 1000 year life NUREG-1623 normal Historic weather patterns abnormal PMP (1-hour = 6.1 inches) accident Not required per NUREG-1199 Ensure Structural Stability Settlement Long Term Cover Drainage (No Slope Reversal) Minimize Ponding normal Evenly distributed weight loading abnormal Abnormal conditions assessed for the Principle Design Feature – Mixed Waste Placement, Required Function – Ensure Cover Integrity. accident Not required per NUREG-1199 Maximum Total Settlement 15% of Embankment Height (6.24 feet) Highway embankments and major waste storage embankments have settled up to 15% of their height and performed adequately normal Evenly distributed weight loading abnormal Concrete column accident Not required per NUREG-1199 Maintain Slope Stability Static Safety Factor 1.5 Pseudo-static Safety Factor > 1.0 (seismic coefficient > 50% of the maximum bedrock acceleration) Pseudo-static Safety Factor > 1.3 (475 year recurrence interval) State of Utah Statutes and Administrative Rules for Dam Safety, Rule R655-11-5 and -6 “Guide to Technical Resources for the Design of Landfill Disposal Facilities,” EPA/625/6- 88/018 normal Static Conditions 100 year, 6-hour rainfall event abnormal Earthquake and/or saturated conditions (associated with the PMP) within the embankment accident Accidental blockage of a single drainage component Table 2 Design Criteria of the Principal Design Features: Mixed Waste Embankment Principal Design Feature Required Function Complementary Aspects Design Criteria Design Criteria Justification Conditions July 18, 2011 Revision 0 Page 3 of 3 Drainage Systems Provide Site Drainage Facilitate flow away from the embankment Depth of water < depth of ditch. Promote free flowing conditions. Normal condition freeboard: one foot around the embankment and > ½ foot downstream Minimize potential infiltration into the waste. normal 25 yr. 24 hr. event (1.9 inches) abnormal 100 yr. 24 hr. event (2.4 inches) accident Downstream blockage Minimize Infiltration under flood conditions Water depth < 5.6 feet above ground surface (grade elevation). Calculated from geometry so that surface water will not pond above toe of waste. normal 100 year flood (3,802 cfs) abnormal PMF (48,500 cfs) accident Downstream blockage Ensure Ditch Integrity Prevent Internal Erosion Velocity < 3 ft/sec on Clay NUREG/CR-4620 normal 25 yr. 24 hr. event (1.9 inches) abnormal 100 yr. 24 hr. event (2.4 inches) accident Not required per NUREG-1199 Buffer Zone Provide Site Monitoring Not applicable Sized adequate for monitoring and corrective measures Compliance monitoring normal No releases abnormal Contaminant releases accident Not required per NUREG-1199 EnergySolutions Mixed Waste Expansion Project Engineering Justification Report July 18, 2011 Revision 0 Page 12 of 59 Table 3 Pertinent Characteristics of the Principal Design Features: Mixed Waste Embankment Table 3 Pertinent Characteristics of the Principal Design Features: Mixed Waste Embankment Principal Design Feature Principal Design Element Pertinent Characteristics References July 18, 2011 Revision 0 Page 1 of 4 Liner and Leachate Collection/Removal System Clay Liner Base, Under Entire Embankment 3 foot thick clay liner Compacted to at least 95% of a standard proctor Moisture between optimum and 5.0 percentage points over optimum Permeability < 1 x 10-7 cm/sec Clay Material Requirements: CL or ML Unified Soil Classification 10 < plasticity index < 25 30 < liquid limit < 50 Thickness = Drawing 11009-C02, Revision 0 All specifications in Attachment II-9, Construction QA/QC Manual (specification # in parentheses) Compaction and Moisture (41) Permeability (42) Clay Material Requirements (29) Synthetic Liner design throughout each sump except for sump 3H:1V side slope at edge of the embankment From top of the clay liner up: Secondary 60 mil HDPE liner Secondary drainage net Primary 60 mil HDPE liner Primary drainage net Non-woven Geotextile fabric Two feet protective soil cover Tertiary 80 mil HDPE liner Tertiary drainage net Non-woven Geotextile fabric Two feet protective soil cover Drawing 11009-C02 for layer sequencing All specifications in Attachment II-9, Construction QA/QC Manual (specification # in parentheses) Geosynthetics (Appendix 3) Soil protective cover (121) Synthetic Liner design for sump 3H:1V side slope at edge of the embankment From top of the clay liner up: Secondary 60 mil HDPE liner Secondary drainage net Primary 60 mil HDPE liner Primary drainage net Non-woven Geotextile fabric Tertiary 80 mil HDPE liner Tertiary drainage net Non-woven Geotextile fabric Two feet protective soil cover Drawing 11009-C02 for layer sequencing All specifications in Attachment II-9, Construction QA/QC Manual (specification # in parentheses) Geosynthetics (Appendix 3) Soil protective cover (121) Waste Placement Bulk Waste Placement Waste lift thickness < 12 inches Compacted to at least 90% of a standard proctor Moisture Content between 2% and 3 percentage points above optimum LLRW and 11e.(2) CQA/QC Manual, Work Element – Waste Placement Table 3 Pertinent Characteristics of the Principal Design Features: Mixed Waste Embankment Principal Design Feature Principal Design Element Pertinent Characteristics References July 18, 2011 Revision 0 Page 2 of 4 Waste Placement Oversized Debris and Large Debris Waste Placement Containers and large debris placed to minimize entrapped air (pockets within the pour that CLSM cannot enter) Associated container debris (drum lid, etc.) shall be placed to minimize entrapped air (pockets within the pour CLSM cannot enter) CLSM Flowability Requirements: CLSM (Control Low Strength Material) slump of at least 8 inches or efflux flow time of < 26 seconds Density of at least 100 lbs/ft^3 CLSM Material Requirements: Cement weight per cubic yard: > 50 lbs Pozzolan weight per cubic yard: < 375 lbs Aggregate Particle Size: 100% passing the 3/8” sieve 60% passing the #8 sieve Max. of 30% passing the #100 sieve LLRW and 11e.(2) CQA/QC Manual, Work Element – Waste Placement CLSM material characteristics described in LLRW and 11e.(2) CQA/QC Manual, Table 2 – Material Specifications for Portland Cement CLSM and Table 3 – Material Specifications for Fly Ash CLSM Cover Clay Radon Barrier 2 foot thick clay radon barrier Compacted to 95% of a standard proctor Moisture between optimum and 5.0 percentage points over optimum Permeability less than or equal to 5 x 10-8 cm/sec Clay Material Requirements: CL or ML Unified Soil Classification At least 85% fines (<0.075 mm) 10 < plasticity index < 25 30 < liquid limit < 50 Top Slope: 2% Side Slope: 20% Drawings 11009-W03 Rev. 0 and 11009-W05 Rev.0 All specifications in Attachment II-9, Construction QA/QC Manual (specification # in parentheses) Compaction and Moisture (154) Fines, plasticity index, and liquid limit (134) HDPE Liner and Geotextile 12 oz. Non-woven geotextile 60 mil textured HDPE Drawing 11009-W05 Rev.0 All specifications in Attachment II-9, Construction QA/QC Manual (specification # in parentheses) Geosynthetics (Appendix 3) Table 3 Pertinent Characteristics of the Principal Design Features: Mixed Waste Embankment Principal Design Feature Principal Design Element Pertinent Characteristics References July 18, 2011 Revision 0 Page 3 of 4 Cover Lower Filter Zone Type B Filter 6 inch thick layer meeting gradation ratios compared with sacrificial soil Rock Scoring Test > 50 Permeability 3.5 cm/sec Drawing 11009-W05 Rev.0 All specifications in Attachment II-9, Construction QA/QC Manual (specification # in parentheses) Rock Scoring (171) Permeability (173) Gradation (174) Sacrificial Soil 12 inch thick layer meeting gradation ratios compared with Type A and Type B filter Drawing 11009-W05 Rev.0 All specifications in Attachment II-9, Construction QA/QC Manual (specification # in parentheses) Gradation (174) Upper Filter Zone Type A Filter 6 inch thick layer meeting gradation ratios compared with sacrificial soil Rock Scoring Test > 50 No permeability specification Drawing 11009-W05 Rev.0 All specifications in Attachment II-9, Construction QA/QC Manual (specification # in parentheses) Rock Scoring (171) Permeability (173) Gradation (174) Table 3 Pertinent Characteristics of the Principal Design Features: Mixed Waste Embankment Principal Design Feature Principal Design Element Pertinent Characteristics References July 18, 2011 Revision 0 Page 4 of 4 Cover Erosion Barrier 18 inches thick Rock Scoring Test > 50 Top Cover (Type B riprap): D100 4.5 inches D50 1.25 inches D10 0.75 inch D5 No. 200 Sieve (~ 0.075 mm) Side Cover (Type A riprap): D100 16 inch D90 12 inch D50 4.5 inch D10 2 inch D5 No. 200 Sieve (~ 0.075 mm) Drawing 11009-W05 Rev.0 All specifications in Attachment II-9, Construction QA/QC Manual (specification # in parentheses) Rock Scoring (171) Gradation (182) Drainage Systems Drainage Ditches 3 feet deep "V" shaped with 5:1 (H:V) side slopes 6 inches of Type A filter material 12 inches of Type A riprap material Drawing 11009-W04 Rev.0 See Type A filter and Type A riprap, above Buffer Zone Buffer Zone Minimum 94 feet from toe of waste to fence Minimum 300 feet from toe of waste to EnergySolutions property boundary 100 feet from toe of waste to Vitro property line Drawing 11009-U01 Rev.0 Section 3.5 of this EJR EnergySolutions Mixed Waste Expansion Project Engineering Justification Report July 18, 2011 Revision 0 Page 13 of 59 Table 4 Projected Performance of the Principal Design Features: Mixed Waste Embankment Table 4 Projected Performance of the Principal Design Features: Mixed Waste Embankment Principal Design Feature Required Function Complementary Aspects Design Criteria Projected Performance Performance Reference Safety Factor July 18, 2011 Revision 0 Page 1 of 5 Liner Minimize contact of waste with standing water Minimize contact of wastes with standing water during operations Meets requirements of 40 CFR 264.301(c)(3) Design meets or exceeds requirements of 40 CFR 264.301(c)(3) RCRA Permit, Module V RCRA Permit, Attachment II-9 RCRA Permit Plan Approval Application, Appendix U Not Applicable Minimize contact of wastes with standing water after closure Liner Permeability Cover Permeability Calculated leakage rate of liner / cover: Normal Conditions: 4.76 x 10-10 / 2.86 x 10-10 m3/sec (pinholes) 1.10 x 10-9 / 6.03 x 10-10 m3/sec (cracks) Abnormal Conditions: 8.85 x 10-9 / 1.98 x 10-9 m3/sec (pinholes) 5.18 x 10-9 / 1.60 x 10-9 m3/sec (cracks) Biointrusion Head Analysis: 8.85 x 10-9 / 3.25 x 10-9 m3/sec (pinholes) 5.18 x 10-9 / 2.06 x 10-9 m3/sec (cracks) Biointrusion Infiltration Analysis: 1.73 x 10-10 / 6.2 x 10-11 m/sec Appendix F Whetstone Associates dated September 13, 2001 See Text Normal: 1.67 / 1.82 Abnormal: 4.47 / 3.24 Biointrusion Infiltration: 2.79 Ensure Cover Integrity Mitigate Differential Settlement Maximum Allowable Distortion in Cover = 0.02 Conservative normal maximum distortion = 0.001 Conservative abnormal maximum distortion = 0.007 AGRA Compressible Debris Report dated June 1, 2000 AMEC Settlement Evaluation dated November 8, 2000 (Section 3.5 and Figure 3) Normal = 16.50 Abnormal = 2.86 Mixed Waste Placement Ensure Cover integrity Mitigate Differential Settlement Maximum Allowable Distortion in Cover = 0.02 Normal = 0.004 Abnormal = 0.005 Mines Group Report dated November 14, 2000: Section 2.8 AGEC Stability and Settlement Report dated October 19, 1998 AGRA Compressible Debris report dated June 1, 2000 Normal: 5.00 Abnormal: 4.00 Table 4 Projected Performance of the Principal Design Features: Mixed Waste Embankment Principal Design Feature Required Function Complementary Aspects Design Criteria Projected Performance Performance Reference Safety Factor July 18, 2011 Revision 0 Page 2 of 5 Mixed Waste Placement Ensure Structural Stability Maintain Slope Stability Static Safety Factor 1.5 Pseudo-static Safety Factor > 1.0 (Seismic coefficient > 50% of the maximum bedrock acceleration) Seismic Safety Factor 1.2 (Liquifaction) Static Safety Factor 1.8 Seismic Safety Factor Seismic Safety Factor under liquefaction > 1.4 AGEC Stability Reports dated October 19, 1998 and July 29, 1999 Mines Group Report dated November 14, 2000: Section 2.7 Appendix C of State-issued Part B Plan Approval dated March 20, 1990 AMEC Report dated July 14, 2011 Static = 1.8 (exceeds design criteria of 1.5) Pseudo-static = 1.1 (exceeds design criteria of 1.0) Seismic (liquefaction) = 1.4 (Shallow Depth) Seismic (liquefaction = 1.6 (Deep Depth) Cover Minimize Infiltration Minimize Infiltration Average infiltration 0.072 inches/year (0.183 cm/year) top slope 0.038 inches/year (0.096 cm/year) side slope Infiltration meets performance criteria of transport to monitoring wells within 500 years. Whetstone Associates Inc., “Mixed Waste Infiltration and Transport Modeling” dated November 22, 2000 EnergySolutions, Inc., “Impacts of Proposed Revisions to the Mixed- Waste Disposal Cell Geometry on Groundwater Compliance”, dated April 20, 2011 Not applicable Encourage Runoff Maintain positive drainage; Maximum design velocity within drainage layer > drainage velocities; Do not allow water accumulation Cover minimum design slope = 2%. Maximum theoretical velocities: 2.30 x 10-3 ft/sec (top slope) 2.30 x 10-2 ft/sec (side slope) Maximum drainage velocities: 9.5 x 10-4 ft/sec (top slope) 8.7 x 10-4 ft/sec (side slope) Mines Group Report dated November 14, 2000 Envirocare, 2001 Sections 4.3.1.5, 4.3.3.2, and 4.3.4.1 Top Slope: 2.42 Side Slope: 26.35 Prevent Desiccation No desiccation cracking in Radon Barrier Clay UNSAT-H modeling establishes that the steady- state moisture content of the clay radon barrier will remain constant through all conditions throughout the life of the embankment. Whetstone Associates Inc., “Mixed Waste Infiltration and Transport Modeling” Dated November 22, 2000 Not Applicable Limit Frost Penetration Thickness of rock/filter/sacrificial soil zones maximum depth of frost Top Slope = 3.4 feet Side Slopes = 3.2 feet (Calculated with temperature database lower than 500 year return frequency low temperatures) Montgomery Watson Reports dated February 5, 1998 and March 1, 2000 Mines Group Report dated November 14, 2000: Section 2.5 Top > 1.03 Sides > 1.09 (abnormal condition) Table 4 Projected Performance of the Principal Design Features: Mixed Waste Embankment Principal Design Feature Required Function Complementary Aspects Design Criteria Projected Performance Performance Reference Safety Factor July 18, 2011 Revision 0 Page 3 of 5 Cover Minimize Infiltration Limit Biointrusion Biointrusion shall be discouraged and shall not cause increased infiltration Vegetation causes very small increases in average infiltration. Conservative modeling without a geomembrane maintains a cumulative average annual infiltration less than 0.072 inches/year. SWCA, Inc., dated November 1, 2000 Whetstone Associates, dated November 2, 2000 Whetstone Associates, dated September 13, 2001 See Text Normal = NA Abnormal = 1.50 Compounded Abnormal: 1.01 Reduce Exposure Surface Dose Rates 100 mrem TEDE Worst case of 3 mrem/year through cover using an 11 curie source at the top of waste. Grove Engineering, MicroShield, Version 8.03 computer software Worst case abnormal: 33.34 Ensure Cover Integrity Mitigate Differential Settlement Maximum Allowable Distortion = 0.02 Normal = 0.004 Abnormal = 0.005 Mines Group Report dated November 14, 2000: Section 2.8 AGEC Stability and Settlement Report dated October 19, 1998 AGRA Compressible Debris Report dated June 1, 2000 Normal = 5.00 Abnormal = 4.00 Prevent Internal Erosion Water velocity < 3 ft/sec on Radon Barrier Clay Interstitial Velocities at Radon Barrier/Filter Zone Interface: Top Slope = 9.7 x 10-3 ft/sec Side Slope = 9.7 x 10-2 ft/sec Envirocare, 2001 Top = 307.91 Side = 30.79 (all conditions) Prevent Piping: Met through material specifications Prevent Upward Migration of Fines D15(Lower Layer) / D85(Upper Layer) 4 Upper filter layer D15 / Type A riprap D85 (side slope)= 22/280 = 0.079 Upper filter layer D15 / Type B riprap D85 (top slope)= 22/76 = 0.29 Gradation on Drawing 11009-W05 Rev.0 See Text Piping NA 10.00 and 17.86 Upward Migration: 50.63/13.79 (side slope/top slope) Material Stability / External Erosion 1000 year life Design Rip Rap D50: Top Slope = 1.25 inches Side Slopes = 4.5 inches Mines Group Report dated November 14, 2000 Drawing 11009-W05 Rev.0 Envirocare, 2001 Top = 2.50 Side = 1.50 (all conditions) Depth of rock: 2.23 to 25.00 Material Stability / External Erosion 1000 year life Weighted average quality scoring for specific gravity, absorption, sodium soundness, and L.A. abrasion. Reject rock with quality scoring < 50 CQA/QC Manual, Appendix II-A NUREG-1623 Not applicable Table 4 Projected Performance of the Principal Design Features: Mixed Waste Embankment Principal Design Feature Required Function Complementary Aspects Design Criteria Projected Performance Performance Reference Safety Factor July 18, 2011 Revision 0 Page 4 of 5 Ensure Structural Stability Settlement Long Term Cover Drainage (No Slope Reversal) Since the cover is 2%, distortions would need to exceed 0.02 before slope reversal would arise. See Waste Placement/Ensure Structural Integrity Section 4.2.1. Drawing 11009-W01 Normal = 5.00 Abnormal = 4.00 Cover Maximum Total Settlement 15% of Embankment Height (6.3 feet) Normal Condition Maximum = 16 inches Abnormal Condition Maximum = 18.5 inches AGEC Stability Report dated July 29, 1999 AMEC, 2000 See Text Normal = 4.69 Abnormal = 4.05 Maintain Slope Stability Static Safety Factor 1.5 Pseudo-static Safety Factor > 1.0 (Seismic coefficient > 50% of the maximum bedrock acceleration) Pseudo Safety Factor > 1.3 (475 year recurrence interval) Minimum Static Safety Factor 2.14 Infinite Slope Seepage Safety Factor 1.87 Pseudo-static Safety Factor = 1.07 (5,000 year recurrence interval) Pseudo-static Safety Factor = 1.78 (475 year recurrence interval) Pseudo-static Safety Factor = 1.07 (seismic coefficient > 50% of the maximum bedrock acceleration) Conservative normal saturated Static Safety Factor = 1.88 PMP and Filter Layer Blockage: Safety Factor = 1.77 AGEC Stability reports dated October 19, 1998 and July 29, 1999 Mines Group Report dated November 14, 2000: Section 2.7 Mines Group Letter report dated October 18, 2001 Static = 214 (exceeds design criteria of 1.5) Pseudo-static = 1.07 (exceeds design criteria of 1.0) Pseudo-static = 1.78 (exceeds design criteria of 1.3) Saturated; Normal = 1.87 (exceeds design criteria of 1.5) Conservative pseudo-static = 1.00 (meets design criteria of 1.0) Accident Condition = 1.77 (exceeds design criteria of 1.5) Table 4 Projected Performance of the Principal Design Features: Mixed Waste Embankment Principal Design Feature Required Function Complementary Aspects Design Criteria Projected Performance Performance Reference Safety Factor July 18, 2011 Revision 0 Page 5 of 5 Drainage System Provide Site Drainage Facilitate flow away from the embankment Depth of water < depth of ditch. Promote free flowing conditions Normal condition freeboard: > one (1) foot around the landfill > ½ foot downstream Design ditch height = 4 feet. Max height of water during normal event = 1.74 feet in western ditch adjacent to the MW landfill; 1.4 feet of freeboard remaining. Max height of water during abnormal event = 1.81 feet in western ditch adjacent to the MW landfill; 1.34 feet freeboard remaining. Observed damage or blockage fixed as soon as possible during operations and institutional controls period. EnergySolutions, Inc., “Drainage Ditch Flow Calculations – Mixed Waste Landfill Cell”, dated June 16, 2011 (Appendix A to this document) MW Landfill: Normal SF = 1.25 Abnormal SF = 2.20 Downstream: Normal SF > 1.11 Abnormal SF = 1.06 Minimize Infiltration under flood conditions Water depth < 5.6 feet above ground surface (grade elevation) Maximum depth of PMF is approximately one foot across the site. Water depth under abnormal conditions may reach one (1) foot. Water depth under accident conditions may reach two (2) feet. HEC 1 and HEC 2 Modeling, Appendix KK or LARW License Renewal Application dated March 16, 1998 Abnormal SF: 5.60 Accident SF: 5.60 Ensure Ditch Integrity Prevent Internal Erosion Velocity < 3 ft/sec on Clay Interstitial velocity at the Clay / Rock interface 2.4 x 10-3 ft/sec Envirocare, 2000 1250 (all conditions) Buffer Zone Provide Site Monitoring NA Sized adequate for monitoring and corrective measures The infiltration and Transport Modeling has shown that no contaminants will reach the monitoring wells (located 40 feet from the edge of waste, within the buffer zone boundary of 94 feet) within 100 years. Whetstone Associates, Inc., “Mixed Waste Infiltration and Transport Modeling” dated November 22, 2000. EnergySolutions, Inc., “Impacts of Proposed Revisions to the Mixed- Waste Disposal Cell Geometry on Groundwater Compliance”, dated April 20, 2011 Not applicable EnergySolutions Mixed Waste Expansion Project Engineering Justification Report July 18, 2011 Revision 0 Page 14 of 59 2.0 DESIGN CRITERIA OF THE PRINCIPAL DESIGN FEATURES The principal objectives of the disposal facility design are to provide long-term isolation of disposed waste, minimize the need for continued active maintenance after site closure, and augment the site’s natural characteristics in order to protect public health and safety. EnergySolutions has designed the disposal facility to effectively control any radioactive release for up to 1,000 years. Because of the difficulties in predicting an accurate active lifetime for man- made materials such as geotextiles, the following analyses generally focus on the long-term properties of clay and rock layers in the embankment cover and liner. Considering the presence of geotextiles in the cover and liner system, these analyses are conservative assessments of performance. Accordingly, the principal design features include those elements of the completed embankment that impact long-term performance of the facility. 2.1 LINER AND LEACHATE COLLECTION/REMOVAL SYSTEM (LCRS) The liner and leachate collection/removal system (LCRS) perform the required engineering functions of minimizing contact of wastes with standing water and ensuring cover integrity. In addition to these functions, the LCRS performs the operational function of collecting leachate and detecting leaks through the different layers of the liner (see Section 3.1.2 for a description of the synthetic layers within the liner system). 2.1.1 MINIMIZE CONTACT OF WASTES WITH STANDING WATER DURING OPERATIONS EPA requires that the minimum technical requirements specified at 40 CFR 264.301(c)(3) be met for leachate collection and removal systems. In addition, NRC requires at 10 CFR 61.51(a)(6) that the disposal site “…be designed to minimize to the extent practicable… the contact of water with waste during disposal…” Both criteria are met by application of EPA’s requirements. These requirements are met during operations at the facility by active management of the LCRS. EnergySolutions is required by its State-issued Part B Permit (Module V, Condition V.D.6) to inspect, measure the depth of leachate, and remove leachate each day that the facility is in operation if the depth of leachate is greater than one foot. This depth of water corresponds to the thickness of the drainage layer in the bottom of each sump (see drawing 11009-C01). Between the drainage layer and waste is a soil layer with a minimum thickness of two feet. Therefore, leachate removal for depths up to one foot ensures that standing water will not be in contact with waste during operations and during the 30-year RCRA post-closure monitoring period. Design Criteria: The LCRS shall meet the requirements of 40 CFR 264.301(c)(3). Design Criteria Justification: These are regulatory requirements under RCRA for hazardous waste disposal that enable the inspection, collection, and removal of standing water that may accumulate within the embankment. Accordingly, regulatory requirements for radioactive waste disposal during operations are also met. Conditions Evaluated: The normal condition evaluates LCRS performance for the system constructed in accordance with EnergySolutions’ design specifications. Under abnormal conditions, the inspection/removal pipes from the LCRS sumps to the surface may become clogged. Under accident conditions, the surface extension of the inspection/removal pipes may be damaged or broken due to a collision with heavy equipment. 2.1.2 MINIMIZE CONTACT OF WASTES WITH STANDING WATER AFTER CLOSURE The LCRS is evaluated in terms of its likely effects on cell drainage, or lack thereof, following closure. “Closure” in this sense is considered to begin at year 31 following the completion of cover; since RCRA requires monitoring and removal of leachate for 30 years. Cell drainage after EnergySolutions Mixed Waste Expansion Project Engineering Justification Report July 18, 2011 Revision 0 Page 15 of 59 closure is important to prevent the accumulation of water within the embankment, a condition referred to as “bathtubbing. This section applies to cell drainage only. Overall site drainage under flood conditions is discussed in Sections 2.4.1.2 and 4.4.1.2 below; performance of the embankment cover to limit infiltration (a critical factor in minimizing water available to come into contact with wastes) is discussed in Sections 2.3.1 and 4.3.1 below. The LCRS is considered to be a potential barrier to drainage from the embankment because it incorporates HDPE liners of equal permeability to that of the cover. Also, there are three layers of HDPE liner in the LCRS, compared to a single layer in the cover. Accordingly, if water should enter the embankment following closure, the feature that facilitates minimization of contact of wastes with standing water during operations (the LCRS) may increase the potential for contact of wastes with standing water after closure. The cover and LCRS must be demonstrated to: (a) retain their as-constructed characteristics regarding permeability; (b) degrade (increase in permeability) at parallel rates; or (c) differentially degrade so that the effective permeability of the liner remains greater than or equal to the effective permeability of the cover. Geomembrane degradation mechanisms within an engineered landfill similar to the Mixed Waste Embankment were researched and discussed in Badu-Tweneboah (1999). Degradation mechanisms discussed include the actions of chemicals, oxygen, microorganisms, heat, UV radiation, radioactivity, biota, age of geomembrane, and mechanical stresses. The conclusions of this research and analysis was that, under the conditions present within an engineered landfill, long-term stress cracking due to aging is the only feasible geomembrane degradation mechanism. Design Criteria: Permeability of the liner shall be greater than or equal to that of the cover. Design Criteria Justification: By designing the liner to be equally or more permeable than the cover, the embankment system is assured of maintaining inflow through the cover less than or equal to outflow from the bottom of the liner. If the liner was less permeable than the cover (inflow greater than outflow), water could accumulate within the embankment, creating a possible increased hazard under seismic conditions. Conditions Evaluated: The normal condition evaluates liner performance with the complete cover system performing as constructed to limit infiltration. The LCRS remains in place as a potential barrier to drainage from the embankment. Permeability characteristics of the HDPE layers within the cover and LCRS remain constant over time. A second normal condition considers the natural effects of aging (long-term stress cracking) upon the HDPE layers within the cover and the LCRS. The abnormal condition evaluates the feasibility of phenomena that may degrade the cover, and thereby increasing its permeability, at a faster rate than similar conditions would affect the permeability of the LCRS. Biointrusion was specifically evaluated as a potential mechanism to differentially degrade the cover system. Additionally, the abnormal condition considered the potential for the quality of contact between the HDPE and the low-permeability clay within each system (cover and LCRS) to degrade over time. Abnormal condition analyses were performed both for differential degradation and long-term stress cracking of the cover system and the LCRS. The LCRS is considered a potential barrier to drainage from the embankment. Accordingly, there is not a reasonable scenario that would lead to the accidental failure of passive drainage layers within the LCRS following closure. 2.1.3 ENSURE COVER INTEGRITY Cover integrity has been evaluated as a function of the complementary aspect of mitigating differential settlement within the liner. Total settlement criteria and performance for the embankment, including the liner and native soils beneath the liner, are discussed in Sections 2.3.4.1 and 4.3.4.1. EnergySolutions Mixed Waste Expansion Project Engineering Justification Report July 18, 2011 Revision 0 Page 16 of 59 Design Criteria: The maximum allowable distortion in the cover is 0.02. “Distortion” is a dimensionless ratio of differential settlement divided by the length over which the differential settlement occurs. Design Criteria Justification: The allowable distortion value for the cover was developed by reviewing published tensile “beam tests,” which measure the amount of deflection of a clay beam at which tensile cracking of the beam was first observed. The EnergySolutions cover soils were compared to the published tensile strain values based on similarities in clay content, moisture content at placement, density and plasticity index. It was assumed that permeability of the clay cover would be compromised should such tensile cracks initiate within the cover. The “tensile beam” tests are considered to present a conservative assessment of the maximum allowable distortion, since representing the clay cover by an unsupported simple beam is in itself a very conservative assumption. The constructed embankment cover is subject to normal loading, which tends to reduce the potential for cracking (AMEC, October 4, 2000). This report recommends using a conservatively selected value of 0.02 as the maximum distortion for design. Distortion is relevant only in terms of effects on the cover system, as the liner is designed to drain following closure. Accordingly, should differential settlement lead to increased permeability of the liner following closure, performance of the disposal system would not be compromised. Differential settlement is further discussed below in terms of waste placement (Sections 2.2.1 and 4.2.1), and the cover system (Sections 2.3.3.1 and 4.3.3.1). Conditions Evaluated: The normal condition is that primary consolidation and settlement of the lower layers of the embankment will occur during construction, prior to completion of the final cover. The cut and cover nature of the operation will preclude dramatic differences in waste column height and, accordingly, in settlement within the active cell. The abnormal condition considers possible effects of having a section of the embankment completed to cover height with an adjacent area of waste placement less than 25 feet high. In other words, one section of the embankment would have maximum weight loading on all layers of the embankment, liner, and foundation soils while the adjacent section would have minimum loading. The “low” height of 25 feet was chosen because this is the maximum calculated height of the embankment before preconsolidation stress is exceeded; in excess of this thickness, primary consolidation (settlement) begins to occur in the lowest layers of the embankment. This condition represents the maximum potential differential settlement for the liner. An accident condition is not required for differential settlement, per section 3.2 of NUREG-1199. 2.2 MIXED WASTE PLACEMENT Mixed Waste may take a variety of physical forms, including soil or soil-like material, compressible debris, incompressible debris, and monolithic forms in the size and shape of filled containers such as drums or boxes. In accordance with Module V, condition V.C.22, waste placement construction and testing activities are controlled by the LLRW and 11e.(2) CQA/QC Manual. Since the initial Mixed Waste Embankment engineering Justification Report (EJR) was prepared in 2001, a new waste treatment process known as Macro Vaults has been permitted and implemented. Macro Vaults consist of hazardous debris and a proprietary concrete-based flowable grout known as Macro Mix which encapsulates and fills voids within each vault. Macro Mix is based on Controlled Low-Strength Material (CLSM) flowability criteria, but with admixtures that ensure it has lower permeability and higher compressive strength than standard CLSM. Macro Vaults are constructed within CLSM pyramids. Accordingly, Macro Vaults perform equivalent or better than CLSM in terms of embankment stability. EnergySolutions Mixed Waste Expansion Project Engineering Justification Report July 18, 2011 Revision 0 Page 17 of 59 Mixed Waste placement performs the required functions of ensuring cover integrity and ensuring structural stability of the embankment. 2.2.1 ENSURE COVER INTEGRITY Cover integrity has been evaluated as a function of the complementary aspect of differential settlement due to differing physical properties of the waste material throughout the embankment. Design Criteria: The maximum allowable distortion in the cover is 0.02. “Distortion” is a dimensionless ratio of differential settlement divided by the length over which the differential settlement occurs. Design Criteria Justification: Please refer to the discussion provided in section 2.1.3 above. Conditions Evaluated: The normal condition is that all primary as well as part of the secondary settlement of the embankment foundation, liner, and contents will occur during construction and through the 100-year institutional monitoring period. The abnormal condition considers possible effects of delayed creep of compressible waste; as well as additional secondary settlement of soils after the 100-year institutional monitoring period within a soil/debris lift corridor between two incompressible CLSM pyramids. This provides the worst case condition for differential settlement within the embankment. The CLSM pyramids represent the most stable (incompressible) forms within the embankment and the soil/debris lift corridor consists of waste soil dispersed with the most compressible debris (paper, tyvek, etc). An accident condition is not required for differential settlement, per section 3.2 of NUREG-1199. 2.2.2 ENSURE STRUCTURAL STABILITY Structural stability has been evaluated in terms of slope stability within the layers that comprise the embankment contents. Design Criteria: The embankment must meet global stability requirements for a Sliding Safety factor of 1.5 under static conditions. Under seismic conditions, the embankment must exceed a Sliding Safety factor of 1.0 utilizing pseudo-static coefficients that are at least 50% of the maximum peak bedrock acceleration, or a Sliding Safety factor of 1.3 utilizing a pseudo-static coefficient with a 475 year recurrence interval (10 percent probability of exceedance in 50 years). Furthermore, a minimum Sliding Safety factor of 1.2 must be attained for a post earthquake liquefaction event. Design Criteria Justification: These minimum factors of safety and design methods for static and seismic conditions are found in the State of Utah Statutes and Administrative Rules for Dam Safety, rules R655-11-5 and R655-11-6. These minimum recommended factors of safety are based on reviewing case histories of embankment dams founded on non-liquefiable clay foundations or bedrock, which demonstrated adequate performance under seismic conditions (Seed, 1983, pp. 41-64). The design criteria for a pseudo-static coefficient with a 475 year recurrence interval was provided as an acceptable slope stability factor in the EPA document “Guide to Technical Resources for the Design of Landfill Disposal Facilities,” EPA/625/6- 88/018, December 1988. Conditions Evaluated: The normal condition considers the performance of the embankment under static conditions. The abnormal condition calculates the safety factor inherent to the embankment design against the expected peak ground acceleration due to an earthquake that might affect the site. Further assessments have analyzed the potential liquefaction of foundation soils beneath the embankment. Analyses of reduced structural stability associated with accidents are not required per NUREG- 1199, Section 3.2. EnergySolutions Mixed Waste Expansion Project Engineering Justification Report July 18, 2011 Revision 0 Page 18 of 59 2.3 COVER The cover is the most complex principal design feature of the Mixed Waste embankment, consisting of five layers of clay, soil and rock. Furthermore, the cover also contains a High Density Polyethylene (HDPE) geosynthetic layer in accordance with guidance issued by EPA and the NRC (see Section 3.3.2 of this Design Justification Report). The cover performs the required functions of minimizing infiltration, reducing radiation exposure, ensuring cover integrity, and ensuring structural stability. 2.3.1 MINIMIZE INFILTRATION Minimizing infiltration is critical to ensuring that groundwater contamination is minimized and to ensuring that contact of wastes with standing water is minimized to the extent practicable. Since no credit is given for HDPE layers after 30 years and the infiltration analysis was completed for 500 years, the HDPE layer was ignored in the infiltration modeling for the embankment (no credit was given for its existence and expected performance in minimizing infiltration). The required function of minimizing infiltration is evaluated via five complementary aspects: minimize infiltration, encourage runoff, prevent desiccation, limit frost penetration, and limit biointrusion. 2.3.1.1 Minimize Infiltration Design Criteria: Average infiltration into the disposal embankment shall be less than or equal to 0.072 inches per year (0.183 cm/year) for the top slopes and less than or equal to 0.038 inches per year (0.096 cm/year) for the side slopes. Design Criteria Justification: Infiltration was modeled using the Hydrologic Evaluation of Landfill Performance (HELP) computer model (Schroeder et al, 1994). The maximum average infiltration rate of 0.072 inches per year was conservatively calculated for a cover system without an HDPE geomembrane. At this conservative maximum average infiltration rate (0.072 inches per year), PATHRAE modeling of the fate and transport of hazardous constituents within the waste disposed demonstrates that Ground Water Protection Levels will not be exceeded for at least 500 years for radiological constituents (Whetstone, 2000 – Section 8). Conditions Evaluated: The normal precipitation condition was generated using the HELP model’s synthetic precipitation generator to stochastically generate 100 years of daily precipitation data. This 100-year synthetic data set provided a mean precipitation of 7.92 inches/year, compared to a long-term mean precipitation for the site calculated at 7.85 inches/year (based on 50 years of data from Dugway, Utah, scaled to Clive using 7 years of Clive data). Please refer to section 3.2.3 of the November 22, 2000, Whetstone Associates, Inc. report. The abnormal condition considers increased infiltration due to inadequate runoff from extreme weather events as well as damage to the radon barrier clay due to desiccation, frost penetration, or biointrusion. Evaluation of an accident condition is not required for water infiltration, per section 3.2 of NUREG-1199. 2.3.1.2 Encourage Runoff Design Criteria: Three design criteria are applied to the surface drainage system for the embankment: (1) the surface slope must be adequate to maintain positive drainage; (2) the maximum calculated design velocity within the drainage layer must be greater than the predicted maximum drainage velocity for extreme storm events; and (3) accumulation of water on the surface of the embankment must not occur. Design Criteria Justification: These design criteria will ensure that runoff of precipitation that falls on the surface of the completed embankment will be maintained and maximized under EnergySolutions Mixed Waste Expansion Project Engineering Justification Report July 18, 2011 Revision 0 Page 19 of 59 expected as well as extreme environmental conditions. By maximizing runoff, the design minimizes the volume of precipitation available to infiltrate into the embankment. Conditions Evaluated: The normal condition for runoff is the 25-year, 24-hour storm event of 1.9 inches of precipitation (NOAA Atlas 2, Volume VI, Figure 28). The abnormal condition evaluates impacts of the Probable Maximum Precipitation, a one-hour storm of 6.1 inches (NOAA Atlas 2, Volume VI, Figure 30). The accident condition evaluates effects on runoff due to downstream blockage potentially caused by plant growth on the embankment surface or piping of fines into filter layers. 2.3.1.3 Prevent Desiccation Design Criteria: There will be no desiccation cracking of the radon barrier clay. Design Criteria Justification: The radon barrier clay is the primary infiltration barrier. If this barrier should be compromised, performance of the embankment may be reduced. Conditions Evaluated: The normal condition for desiccation considers performance under historic weather patterns of precipitation and evaporation. The abnormal condition evaluates effects of a prolonged drought on moisture content of the radon barrier clay. Evaluation of an accident condition for desiccation is not addressed in section 3.2 of NUREG- 1199. There is not a credible accident scenario that would cause desiccation of the radon barrier clay in excess of the evaluated abnormal condition. 2.3.1.4 Limit Frost Penetration Design Criteria: The thickness of rock erosion barrier, sacrificial soil, and filter zone materials will exceed the maximum projected depth of frost. Design Criteria Justification: The radon barrier clay is the primary infiltration barrier. If this barrier should be compromised by the effects of freeze/thaw cycles, performance of the embankment may be reduced. Conditions Evaluated: The normal condition for frost penetration considers performance under historic temperature patterns. The abnormal condition evaluates the effects of an extreme freeze (the 500-year freeze event). Evaluation of an accident condition for frost penetration is not addressed in section 3.2 of NUREG-1199. There is not a credible accident scenario that would cause frost penetration of the radon barrier clay in excess of the evaluated abnormal condition. 2.3.1.5 Limit Biointrusion Design Criteria: Biointrusion shall be discouraged and shall not cause the cumulative average infiltration over the design life of the embankment to increase above the base case modeled in the November 22, 2000, Whetstone Associates, Inc., “Mixed Waste Cell Infiltration & Transport Modeling.” Design Criteria Justification: The radon barrier clay is the primary infiltration barrier. If this barrier should be compromised, performance of the embankment may be reduced. While it may not be possible to totally prevent establishment of vegetation on the cover following the 100-year period of institutional controls, the cover design must discourage plant growth and accommodate indigenous species growth without increasing the cumulative average infiltration above the base case modeled in the Infiltration & Transport Modeling. EnergySolutions Mixed Waste Expansion Project Engineering Justification Report July 18, 2011 Revision 0 Page 20 of 59 Conditions Evaluated: The normal condition for biointrusion evaluates the effects of shallow- rooted, indigenous plant species that may become established on the completed embankment following the 100-year period of institutional controls. During the 100-year period of institutional controls, vegetation will be removed as part of post-closure monitoring and maintenance. The abnormal condition evaluates the effects of deep-rooted, indigenous plant species that may become established on the completed embankment following the 100-year period of institutional controls. A compounded abnormal condition evaluates the effects of deep-rooted, indigenous plant species on the cover with a completely degraded HDPE geomembrane layer. Evaluation of an accident condition for biointrusion is not addressed in section 3.2 of NUREG- 1199. There is not a credible accident scenario that would cause biointrusion of the radon barrier clay in excess of the evaluated abnormal condition. 2.3.2 REDUCE EXPOSURE Design Criteria: The dose rate at the surface of the completed embankment shall be less than 100 mrem total effective dose equivalent (TEDE) per year. Design Criteria Justification: This is a regulatory requirement found in UAC R313-15-301. Evaluation of this limit at the surface of the embankment conservatively takes no credit for fences to be installed around the embankment at site closure. Conditions Evaluated: The normal condition will be for wastes placed directly beneath the embankment cover to have gamma source concentrations much less than the DOT limits on package activity for unshielded packaging. The abnormal condition considers effects of having a gamma source with a total activity of 11 curies of Co-60 at the top of the waste column. This activity was selected from DOT limits on package activity at 49CFR173.431 and the table of A1 and A2 values for radionuclides at 49CFR173.435. The A2 value of 10.8 curie for Co-60 was conservatively rounded up. The A2 value represents an activity limit for DOT Type A packages; materials with higher activity would require special transportation equipment, such as shielded casks, etc. Evaluation of an accident condition for reducing exposure to the general public is not addressed in section 3.2 of NUREG-1199. There is not a credible accident scenario that would cause exposure to the general public in excess of the evaluated abnormal condition. 2.3.3 ENSURE COVER INTEGRITY Long-term cover integrity is evaluated in terms of differential settlement, internal erosion within and between the layers that make up the cover, and material stability/resistance to weathering. 2.3.3.1 Mitigate Differential Settlement Design Criteria: The maximum allowable distortion in the cover is 0.02. “Distortion” is a dimensionless ratio of differential settlement divided by the length over which the differential settlement occurs. Design Criteria Justification: Please refer to the discussion provided in section 2.1.3 above. Conditions Evaluated: The normal condition is that all primary as well as part of the secondary settlement of the embankment foundation, liner, and contents will occur during construction and through the 100-year institutional monitoring period. The abnormal condition considers possible effects of delayed creep of compressible waste; as well as additional secondary settlement of soils after the 100-year institutional monitoring period within a soil/debris lift corridor between two incompressible CLSM pyramids. EnergySolutions Mixed Waste Expansion Project Engineering Justification Report July 18, 2011 Revision 0 Page 21 of 59 An accident condition is not required for differential settlement, per section 3.2 of NUREG-1199. 2.3.3.2 Prevent Internal Erosion Two design criteria are related to internal erosion of the cover materials: erosion of the radon barrier clay due to runoff water velocity on the surface of the clay and erosion of the sacrificial soil layer due to piping of the soil material into the lower (Type B) filter layer and/or upward migration of the soil material into the upper (Type A) filter layer under saturated conditions. Additionally, upward migration of the upper filter layer into the rip-rap erosion barrier layer could potentially erode this filter layer under saturated conditions. In order to maintain the flowability characteristics (permeability) of the lower filter layer, as described in Sections 2.3.1.2 and 4.3.1.2, fines within this layer must be limited. Therefore, it is not necessary that this layer be “well-graded.” In fact, it is best if this layer consisted of a “poorly graded” material. Therefore, coefficients relating to the “well-graded” nature of the material (such as the Uniformity Coefficient, CU, and the Coefficient of Gradation, CG) are not applicable to the design. Design Criteria: Runoff water velocity shall not exceed 3 feet per second on the surface of the radon barrier clay. Also, in order to minimize piping, the particle size specification of the sacrificial soil compared with the Type “B” filter zone material shall meet the following ratios: D15 (filter)/D85 (soil)  5 AND D50 (filter)/D50 (soil)  25 Additionally, to prevent upward migration under saturated conditions, the following criteria must be met: D15(underlying layer)/D85(overlying layer)  4 Design Criteria Justification: NUREG/CR-4620, “Methodologies for Evaluating Long-Term Stabilization Designs of Uranium Mill Tailings Impoundments” provides tables of permissible velocities over different surfaces. The permissible velocity criterion is a velocity that will not erode the underlying material. The erosion potential of the material is determined based on the material properties as well as the degree of compaction that the material has undergone. Table 4.9 of NUREG/CR-4620 provides limiting velocities in cohesive materials. The permissible velocities presented in this table range from 1.05 ft/sec for an uncompacted lean clayey soil to 5.90 for a “very compacted” sandy clay. The radon barrier clay is best described in this table as a very compacted clay. The permissible velocity for this type of clay is 5.41 ft/sec. Therefore, the specified design criteria of a velocity < 3 ft/sec is conservative. Internal erosion, or piping, was evaluated based on procedures developed for saturated embankment dams. Filter criteria were originally developed by evaluating the gradation limits between dissimilar materials so that the voids of the finer material cannot migrate into the voids of the underlying coarse material (thereby creating the potential for internal erosion). See Cedergren, 1977, Section 5.2. The US Department of Energy provided filter requirements pertaining to potential upward migration of finer material within dissimilar layers of an embankment cover system. The criteria listed above is for soil group 3 materials with fines contents ( No. 4 sieve) of 15 percent or less. This criteria is included on pages 82-83 of the Technical Approach Document, Revision II, 1989, UMTRA-DOE/AL 050425.0002. Conditions Evaluated: The normal condition evaluated for internal erosion is the 100-year, 24- hour storm event of 2.4 inches of precipitation (NOAA Atlas 2, Volume VI, Figure 30). EnergySolutions Mixed Waste Expansion Project Engineering Justification Report July 18, 2011 Revision 0 Page 22 of 59 The abnormal condition evaluates impacts of the Probable Maximum Precipitation (one-hour storm of 6.1 inches) as the worst-case erosion event that could occur over the 500 year design life of the embankment. Appendix KK to EnergySolutions’ LARW License Renewal Application (March 16, 1998) develops Probable Maximum Precipitation depths for local storms of one to six hours duration. The one-hour event was selected to maximize velocity of precipitation and, accordingly, flow through the cover drainage system. For the piping analysis, the ratios provided above are the required conditions given by the US Army Corps of Engineers to assure that movement of particles from the finer soil layer into the underlying coarser filter layer will not occur. These conditions were developed for saturated conditions within dam structures and therefore provide an extreme abnormal condition for this embankment. These equations are performance related and are not associated with any conditions other than the abnormal saturated condition. Similarly, the ratio for upward migration of fines is provided by the US Department of Energy as a general design criteria for filters under abnormal saturated conditions. Evaluation of an accident condition for internal erosion is not addressed in section 3.2 of NUREG-1199. There is not a credible accident scenario that would cause internal erosion in excess of the evaluated abnormal condition. 2.3.3.3 Material Stability/External Erosion Design Criteria: The rock erosion barrier is designed to have internal stability and endure weathering/external erosion for a minimum of 1,000 years. Design Criteria Justification: This design criteria has been applied from NUREG-1623, “Design of Erosion Protection for Long-Term Stabilization.” A 1,000-year minimum design life ensures that material degradation of the erosion barrier will not reduce embankment performance. Conditions Evaluated: The normal condition evaluates historic weather data regarding maximum wind and water velocities that may impact the erosion barrier surface. The abnormal condition evaluates impacts of the Probable Maximum Precipitation (one-hour storm of 6.1 inches) as the worst-case erosion event that could occur over the design life of the embankment. Appendix KK to EnergySolutions’ LARW License Renewal Application (March 16, 1998) develops Probable Maximum Precipitation depths for local storms of one to six hours duration. The one-hour event was selected to maximize velocity of precipitation and, accordingly, flow through the cover drainage system. Analyses of increased cover erosion resulting from accidents are not required per section 3.2 of NUREG-1199. 2.3.4 ENSURE STRUCTURAL STABILITY The required function of ensuring structural stability is evaluated in terms of the complementary aspects of (1) total settlement of the completed embankment and (2) slope stability. 2.3.4.1 Settlement Design Criteria: Total settlement of the embankment shall not compromise the drainage capability of the cover; i.e., shall not cause slope reversal. Also, the maximum total settlement shall be less than or equal to 15% of the embankment height, or 6.24 feet. This is based on the elevation difference between the top of clay liner and top of temporary cover, as the waste column is the embankment component most susceptible to settlement. Elevation difference is measured at the crest of the embankment from design drawing series 11009. Design Criteria Justification: If embankment settlement should cause the slope of the top of the embankment to be flattened or reversed (i.e., the elevation of the centerline of the embankment EnergySolutions Mixed Waste Expansion Project Engineering Justification Report July 18, 2011 Revision 0 Page 23 of 59 were lower than an area to either side), drainage off of the top of the embankment would be compromised and infiltration may increase. The maximum total settlement to be used for design was based on reviewing the total settlement that other “earthen” embankments with demonstrated satisfactory performance have undergone. Highway embankments (similar in height to the EnergySolutions embankment) located on the soft clay deposits in the Salt Lake valley typically settle from 12 to 18 percent of their height (average 15 percent) during construction. These embankments have performed adequately in supporting pavements and bridge abutments. Conditions Evaluated: Under normal conditions, weight loading (from the cover, waste, and backfill) will be uniformly distributed with loads maximized at the center of the embankment and gradually decreasing to either side. The design criteria of Long Term Cover Drainage is directly related to the maximum distortion attained from the differential settlement analysis relating to mixed waste placement. Therefore, the abnormal condition for Long Term Cover Drainage is the same as provided in Section 2.2.1 and 2.3.3.1. The abnormal condition for total settlement evaluates a column of extreme loading within the center of the embankment. Such a condition might be caused by placement of a column of extremely dense waste forms such as large metal components or solid concrete. Analyses of increased settlement resulting from accidents are not required per section 3.2 of NUREG-1199. 2.3.4.2 Maintain Slope Stability Design Criteria: The embankment must meet global stability requirements for a Sliding Safety factor of 1.5 under static conditions. Under seismic conditions, the embankment must exceed a Sliding Safety factor of 1.0 utilizing pseudo-static coefficients that are at least 50% of the maximum peak bedrock acceleration, or a Sliding Safety factor of 1.3 utilizing a pseudo-static coefficient with a 475 year recurrence interval (10 percent probability of exceedance in 50 years). Design Criteria Justification: These minimum factors of safety and design methods for static and seismic conditions are found in the State of Utah Statutes and Administrative Rules for Dam Safety, rules R655-11-5 and R655-11-6. These minimum recommended factors of safety are based on reviewing case histories of embankment dams founded on non-liquefiable clay foundations or bedrock, which demonstrated adequate performance under seismic conditions (Seed, 1983, pp. 41-64). The design criteria for a pseudo-static coefficient with a 475 year recurrence interval was provided as an acceptable slope stability factor in the EPA document “Guide to Technical Resources for the Design of Landfill Disposal Facilities,” EPA/625/6- 88/018, December 1988. Conditions Evaluated: The normal condition considers the performance of the embankment under static conditions. Additionally, the normal condition for the infinite slope/seepage condition analysis is the 100-year, 6-hour rainfall event. Two abnormal conditions have been evaluated. The first evaluation compares the calculated safety factor inherent to the embankment design against the expected peak ground acceleration due to an earthquake that might affect the site. Saturated conditions within the cover of the embankment resulting from the Probable Maximum Precipitation (PMP) are evaluated as a second abnormal condition. Analyses of reduced structural stability associated with accidents are not required per NUREG- 1199, Section 3.2. However, under the infinite slope/seepage condition analysis, the accidental blockage of a single drainage component has been assessed. EnergySolutions Mixed Waste Expansion Project Engineering Justification Report July 18, 2011 Revision 0 Page 24 of 59 2.4 DRAINAGE SYSTEMS The drainage systems perform the required functions of providing site drainage and ensuring structural stability. In contrast to the embankment, which is designed for a 500-year lifetime, the drainage ditch system is only operational during the active life of the facility. This yields a design life of approximately 25 years for the drainage ditch system. Due to this difference in design life of the two systems, different conditions have been evaluated for each system to more accurately reflect conditions at the site over the appropriate design life. 2.4.1 PROVIDE SITE DRAINAGE Site drainage is considered in terms of two complementary aspects: (1) facilitating flow of precipitation away from the embankment; and (2) minimizing infiltration under flood conditions. 2.4.1.1 Facilitate Flow of Precipitation Away from Embankment Design Criteria: During operations, storm water shall remain within the drainage ditch system with a normal precipitation event freeboard of one (1) foot around the Mixed Waste embankment and 0.5 foot in the downstream collection area. During the abnormal precipitation event, the drainage ditch system shall contain all of the run-off with no overflow. In addition, the drainage ditch system shall be of sufficient slope to allow drainage away from the embankment. Design Criteria Justification: These criteria will promote the collection of precipitation as well as promote flow away from the embankment, thus minimizing standing water adjacent to the embankment; thereby minimizing potential infiltration into the waste. Conditions Evaluated: The normal condition evaluates impacts of the 25-year, 24-hour storm event for the site of 1.9 inches of rain (NOAA Atlas 2, Volume VI, Figure 28). The 25-year storm event has been selected to represent the probable worst-case precipitation event that may be encountered during active site operations. The abnormal condition evaluates impacts of the 100-year, 24-hour storm event for the site of 2.4 inches of rain (NOAA Atlas 2, Volume VI, Figure 30). The 100-year storm event has been selected as a sensitivity case to represent the worst-case precipitation event that may be reasonably expected during active site operations. Appendix A to this document provides a complete analysis of the designed ditch capacity against the amount of water produced by the storm events discussed above. The accident condition evaluates impacts of downstream blockage of the drainage ditch system. 2.4.1.2 Minimize Infiltration Under Flood Conditions Design Criteria: The water depth under a flood condition shall remain less than 5.6 feet above the ground elevation. Design Criteria Justification: This design criteria ensures that surface water due to flooding is not accumulating directly above the toe of waste in the embankment. The cover over the waste is 5.5 feet thick and is placed at a slope of 5:1 (H:V). Using this as a basis, geometry yields a vertical cover height of 5.6 feet above the clay liner at the toe of waste. Therefore, water would need to amass to a height of 5.6 feet above the clay liner at the toe of waste before it would accumulate directly above the waste material. Drawing 11009-W04 shows that the liner is at ground level at the toe of waste. Therefore, flooding would need to reach a height of 5.6 feet above ground level before it would accumulate vertically above the toe of waste. The embankment is designed so that general site flooding must overfill the drainage ditch and partially submerge the embankment before water accumulates directly above waste. Conditions Evaluated: The normal design condition evaluates performance under a 100-year flood of 3,802 cubic feet per second (cfs). EnergySolutions Mixed Waste Expansion Project Engineering Justification Report July 18, 2011 Revision 0 Page 25 of 59 The abnormal design condition evaluates performance in response to the Probable Maximum Flood (PMF) of 48,500 cfs. Appendix KK to EnergySolutions’ LARW License Renewal Application (March 16, 1998) develops both the 100-year flood and the PMF for the watershed encompassing EnergySolutions’ Clive site. The accident condition evaluates impacts of downstream blockage of the drainage ditch system. 2.4.2 ENSURE DITCH INTEGRITY Ditch Integrity is evaluated in terms of the ability of the drainage ditch to prevent internal erosion of the soils beneath the rock erosion barrier. Design Criteria: Runoff water velocity shall not exceed 3 feet per second on the surface of the clay below the centerline of the ditch. Design Criteria Justification: NUREG/CR-4620, “Methodologies for Evaluating Long-Term Stabilization Designs of Uranium Mill Tailings Impoundments” provides tables of permissible velocities over different surfaces. The permissible velocity criterion is a velocity that will not erode the underlying material. The erosion potential of the material is determined based on the material properties as well as the degree of compaction that the material has undergone. Table 4.9 of NUREG/CR-4620 provides limiting velocities in cohesive materials. The permissible velocities presented in this table range from 1.05 ft/sec for an uncompacted lean clayey soil to 5.90 ft/sec for a “very compact” sandy clay. The drainage ditch subgrade is comparable to a “compact clay” within this table. The permissible velocity for this type of clay is 3.94 ft/sec. Therefore, the specified design criteria of a velocity < 3 ft/sec is conservative. Conditions Evaluated: The normal design condition evaluates performance under the 25-year, 24-hour storm event of 1.9 inches of precipitation (NOAA Atlas 2, Volume VI, Figure 28). The abnormal condition evaluates performance under the 100 year, 24-hour storm event of 2.4 inches as the worst-case event (NOAA Atlas 2, Volume VI, Figure 30). Analyses of the effects of accidents on the drainage ditch integrity are not required per section 3.2 of NUREG-1199. 2.5 BUFFER ZONE The buffer zone performs the required function of providing an area for site monitoring. 2.5.1 PROVIDE SITE MONITORING Design Criteria: The buffer zone shall be sized adequately to allow site monitoring as well as corrective measures. Design Criteria Justification: Site monitoring is required during the 100-year period of institutional control to confirm performance of the disposal facility. Should unacceptable migration of radionuclides be identified, adequate area must be available for implementation of corrective measures. Conditions Evaluated: The normal design condition for the buffer zone includes site monitoring activities with no unacceptable releases from the embankment. The abnormal design condition assesses adequacy of the buffer zone for responding to hypothetical contaminant release. Analyses of the effects of accidents on the buffer zone are not required per section 3.2 of NUREG-1199. EnergySolutions Mixed Waste Expansion Project Engineering Justification Report July 18, 2011 Revision 0 Page 26 of 59 3.0 PERTINENT CHARACTERISTICS OF THE PRINCIPAL DESIGN FEATURES This section describes the pertinent characteristics and construction of the principal design features. The Mixed Waste embankment liner design was approved by DSHW as part of EnergySolutions’ initial State-issued Part B permit, drawing set 9401. Subsequently, the approved cover design, drawing set 0017, was added to the permit. As of July 2011, Mixed Waste embankment drawing sets number 9401 and 0017 and the Mixed Waste CQA/QC Manual (work elements applicable to liner construction) are part of the currently approved State-issued Part B permit. Upon approval of the embankment expansion, drawing sets 9401 and 0017 will be replaced by drawing set 11009. EnergySolutions must formally request a modification to the State-issued Part B Permit and receive DSHW approval to construct each phase of liner in the Mixed Waste embankment. EnergySolutions’ request for liner expansion in the Mixed Waste embankment includes specifications (Condition V.C.2.b.i), a liner CQA/QC Manual (Condition V.C.2.b.ii), and a historical data review (Conditions V.C.2.b.iii and V.C.2.b.iv) in order to construct a specific group of sumps. After DSHW “approval to construct,” the new liner is constructed in accordance with the approved design drawings and the approved CQA/QC Manual. After construction has been completed, EnergySolutions prepares a detailed as-built report. The as-built report is certified by a Utah professional engineer and submitted to DSHW. After review and approval of the as-built report, the DSHW issues formal “approval to use” the new liner. For waste placement in the Mixed Waste embankment, DSHW has transferred primary regulatory authority to DRC (Condition V.C.22). To ensure that Mixed Waste embankment waste placement is performed to specification and in accordance with the design drawings, inspections are performed in accordance with the requirements of the LLRW and 11e.(2) CQA/QC Manual, Work Element – Waste Placement (LLRW CQA/QC Manual; the currently approved version is dated December 15, 2010, revision 25d). Only the Waste Placement requirements from the LLRW CQA/QC Manual are applicable in the Mixed Waste embankment. For final cover construction in the Mixed Waste embankment, DSHW has primary regulatory authority over design, construction and approval of the final cover. In 2001, DSHW completed its regulatory review as well as a sixty day public comment period for the Mixed Waste final cover design. In a letter dated March 5, 2003 DRC concurred that the design meets infiltration and engineering stability performance requirements for the radioactive isotopes present in the waste disposed of in this embankment. EnergySolutions must formally request, as a Permit modification, and receive DSHW approval to construct each phase of final cover in the Mixed Waste embankment. Because the basic design has previously been approved, and the design modifications currently requested do not substantially alter the basic elements of the design, this updated Engineering Justification Report is submitted together with a Class III modification for the initial cover construction project at the Mixed Waste embankment. The Mixed Waste CQA/QC Manual and the design drawings (set 11009) for the Mixed Waste embankment liner, and any changes therein, must be reviewed and approved by DSHW before implementation. Final cover design drawings (set 11009) are provided as Attachment B to this report. Table 3, “Pertinent Characteristics of the Principal Design Features: Mixed Waste Embankment” summarizes construction specifications for each principal design feature discussed below. 3.1 LINER The Mixed Waste embankment liner is a multi-layered system consisting of a clay liner, three HDPE liners, two leak detection systems and a leachate removal system. The bottom of the liner system for the Mixed Waste embankment starts with a prepared foundation overlain by a three- EnergySolutions Mixed Waste Expansion Project Engineering Justification Report July 18, 2011 Revision 0 Page 27 of 59 foot thick layer of 1x10-7 cm/sec permeability clay in accordance with 40CFR264.301(c)(1)(i)(B). The clay liner is overlain by a synthetic liner system consisting of three HDPE layers and three synthetic drainage layers. The HDPE liners are protected from puncture during disposal operation by two-foot thick soil protective layers within the liner system. This design exceeds RCRA requirements at 40CFR264.301(c), which specify a minimum of two geomembrane layers in the liner system. The liner in each sump is slightly sloped to the Sump Leachate Removal Point (SLRP) in order to aid water management within the embankment during active waste placement operations (see drawing set 11009). 3.1.1 FOUNDATION AND CLAY LINER The following construction activities are performed during construction of the embankment clay liner. 1. Existing terrain is excavated to a depth of approximately 7-8 feet with this overburden stockpiled for future use in liner construction, capping the embankment, or as fill material. 2. The cell foundation is prepared from in-situ soils to meet design, grade, and compaction specifications. Specifications and inspection activities for foundation preparation are detailed in the Mixed Waste CQA/QC Manual (Work Element: Foundation Preparation). 3. Clay liner construction methods are approved by the satisfactory construction of a clay liner test pad, as detailed in the Mixed Waste CQA/QC Manual (Work Element: Clay Liner Test Pad). The equipment and procedures used for the test pad are reviewed and approved by a professional engineer qualified to certify such soil considerations, with concurrence by the Construction Quality Assurance Officer (CQAO). The test pad method is then submitted to the DSHW. 4. Clay liner borrow materials are sampled and tested to verify their physical characteristics (i.e., 85% fines < 0.075 mm; plasticity index range 10 to 25; liquid limit range 30 to 50) in accordance with the testing procedures and frequencies specified in the Mixed Waste CQA/QC Manual (Work Element: Clay Liner Material Specifications). These characteristics are summarized in Table 3 of this Engineering Justification Report. Once CQA/QC testing is complete and approved, the clay liner borrow materials become clay liner materials approved for clay liner construction. Borrow materials that fail testing may be re-worked or may be discarded and replaced with materials meeting the criteria. 5. The approved clay liner materials are then placed in lifts and compacted to at least 95% of a Standard Proctor, at a moisture content between optimum and 5 percentage points above optimum. Inspection and testing performed on the placed clay liner is described in the Mixed Waste CQA/QC Manual (Work Element: Clay Liner Placement). 6. A number of CQA/QC specifications are applied to protect the approved clay liner against damage. These include drying prevention, seasonal limitations on liner construction to protect against winter weather extremes, and minimization of heavy equipment travel on completed liner (Work Element: Clay Liner Placement; Specifications: Liner Drying Prevention, Frozen Material, Spring Start-Up, and Unsuitable Material). 7. The final surface of the clay liner is carefully prepared in accordance with the requirements outlined in the Mixed Waste CQA/QC Manual (Work Element: HDPE Liner, Specification: Liner Surface Preparation). The final surface is smooth drum rolled and picked clean of rocks larger than ½-inch in size. The effort spent to prepare the final surface provides a smooth, level surface for the deployment of the initial HDPE layer. EnergySolutions Mixed Waste Expansion Project Engineering Justification Report July 18, 2011 Revision 0 Page 28 of 59 3.1.2 SYNTHETIC LINER SYSTEM The following construction activities are required for construction of the embankment synthetic liner system throughout each sump except for the sump 3H:1V side slope located at the edge of the embankment. 1. The clay liner final surface is overlain by the secondary 60 mil HDPE. The secondary 60 mil HDPE is stored, placed, and welded in accordance with the requirements outlined in the Mixed Waste CQA/QC Manual (Work Element: HDPE Liner). The installed secondary 60 mil HDPE layer forms an impermeable barrier throughout the entire sump area. 2. The secondary 60 mil HDPE is overlain by the secondary drainage net. The secondary drainage net is stored, placed, and welded in accordance with the requirements outlined in the Mixed Waste CQA/QC Manual (Work Element: Drainage Net). The installed secondary drainage net form a drainage layer throughout the entire footprint of each sump. The secondary drainage layer forms the lower or secondary leak detection system under the primary HDPE liner in each sump. 3. The secondary drainage net is overlain by the primary 60 mil HDPE liner. The primary 60 mil HDPE is stored, placed, and welded in accordance with the requirements outlined in the Mixed Waste CQA/QC Manual (Work Element: HDPE Placement). The installed primary 60 mil HDPE layer forms the primary impermeable barrier throughout the entire sump area. 4. The primary 60 mil HDPE is overlain by the primary drainage net and a non-woven geotextile fabric. The primary drainage net and geotextile fabric are stored, placed, and welded in accordance with the requirements outlined in the Mixed Waste CQA/QC Manual (Work Element: Drainage Net and Work Element: Geotextile). The installed primary drainage net and geotextile fabric form a drainage layer throughout the entire footprint of each sump. The geotextile fabric serves as a separation layer between the drainage net and the lower protective soil cover. The primary drainage layer forms the upper or primary leak detection system under the tertiary HDPE liner in each sump. 5. The primary drainage layer is overlain by a two foot soil protective cover. The two foot soil protective cover is placed in accordance with the requirements outlined in the Mixed Waste CQA/QC Manual (Work Element: Soil Protective Cover). The installed soil protective cover is placed throughout the entire sump area. The soil protective cover is placed to provide a soil barrier to protect the underlying HDPE liners from puncture. 6. The protective soil cover is overlain by the tertiary 80 mil HDPE liner. The tertiary 80 mil HDPE is stored, placed, and welded in accordance with the requirements outlined in the Mixed Waste CQA/QC Manual (Work Element: HDPE Liner). The installed tertiary 80 mil HDPE layer forms the upper impermeable barrier throughout the entire sump area. 7. The tertiary 80 mil HDPE is overlain by the tertiary drainage net and a non-woven geotextile fabric. The tertiary drainage net and geotextile fabric are stored, placed, and welded in accordance with the requirements outlined in the Mixed Waste CQA/QC Manual (Work Element: Drainage Net and Work Element: Geotextile). The installed tertiary drainage net and geotextile fabric form the primary drainage layer throughout the entire footprint of each sump. The geotextile fabric serves as a separation layer between the drainage net and the upper protective soil cover. The tertiary drainage layer forms the leachate removal system over the tertiary HDPE liner in each sump. 8. The tertiary drainage layer is overlain by a two foot soil protective cover. The two foot soil protective cover is placed in accordance with the requirements outlined in the Mixed Waste CQA/QC Manual (Work Element: Soil Protective Cover). The installed soil protective cover EnergySolutions Mixed Waste Expansion Project Engineering Justification Report July 18, 2011 Revision 0 Page 29 of 59 is placed throughout the entire sump area. The soil protective cover is placed to provide a soil barrier to protect the underlying HDPE liners from puncture. The same construction activities are required for construction of the embankment synthetic liner system for the sump 3H:1V side slope located at the edge of the embankment with the following exception: the lower protective soil cover layer detailed in item 5 above is not constructed. The lower protective soil cover is phased out at the toe of the liner 3H:1V side slope. This transition is depicted on drawing 11009-W04. 3.1.3 SUMP LEACHATE REMOVAL POINT The liner in each sump is slightly sloped to the Sump Leachate Removal Point (SLRP) in order to aid water management within the embankment during active waste placement operations (see drawing set 11009 in Appendix B). The slope in each sump is a minimum of 2% throughout the sump floor sloped to the SLRP. The secondary SLRP forms the secondary leak detection liquid removal point under the primary HDPE liner in each sump. The primary SLRP forms the primary leak detection liquid removal point under the tertiary HDPE liner in each sump. The tertiary SLRP forms the leachate removal point above the tertiary HDPE liner in each sump. From the bottom up, each sump has a secondary SLRP, a primary SLRP and a tertiary SLRP. Each SLRP consists of a perforated PVC leachate collection system located in a one-foot thick granular fill (drainage gravel). The PVC pipe is sloped to a 10-inch diameter HDPE pipe located at the low point of each SLRP. The 10-inch diameter HDPE pipe extends from the SLRP low point up the 3H:1V side slope and extends out of the liner to the pipe stand (see Appendix B). During active waste placement the depth of water in each SLRP is monitored daily through the HDPE pipe. If liquid is detected in a SLRP, with a depth greater than one-foot, then the leachate is removed from the SLRP. This activity is performed as part of the daily inspection procedures described in Attachment II-3 of the State-issued Part B Permit. 3.2 WASTE PLACEMENT No regulatory guidelines are provided for waste placement. However, the techniques utilized must conform to the design criteria provided in Section 2.2 of this Design Justification Report. Mixed waste is generally disposed in one of two forms: bulk soil lifts or oversized debris lifts for large objects and waste within containers. Macro Vaults are a subset of oversized debris lifts. For waste placement in the Mixed Waste embankment, DSHW has transferred primary regulatory authority to DRC (Condition V.C.22). To ensure that Mixed Waste embankment waste placement is performed to specification and in accordance with the design drawings, inspections are performed in accordance with the requirements of the LLRW and 11e.(2) CQA/QC Manual, Work Element – Waste Placement (LLRW CQA/QC Manual; the currently approved version is dated December 15, 2010, revision 25d). Only the Waste Placement requirements from the LLRW CQA/QC Manual are applicable in the Mixed Waste embankment. At this time, Work Element – Waste Placement with Compactor and Work Element – Containerized Waste Facility Waste Placement are not applicable to the Mixed Waste Embankment. 3.2.1 MIXED WASTE PLACEMENT The following description of waste placement in the Mixed Waste embankment provides the primary controls utilized during waste placement. These engineering controls prepare a stable engineered fill that will provide a suitable foundation for the final cover. Following acceptance and unloading, bulk waste packages are emptied and spread into bulk waste lifts that are twelve inches thick or less. After spreading, the bulk waste is compacted to at least 90% of a standard proctor. The moisture content of each bulk waste lift is controlled to between 2% and 3 percentage points over optimum. EnergySolutions Mixed Waste Expansion Project Engineering Justification Report July 18, 2011 Revision 0 Page 30 of 59 After the bulk waste lift is compacted, the density and moisture content of the bulk waste is tested in accordance with the LLRW CQA/QC Manual, Work Element - Waste Placement. Quality Control Inspectors document the testing and approval of each bulk waste lift. Following acceptance and unloading, oversized debris waste packages are placed in order to minimize the volume of void spaces between containers. Containers and large debris are placed to minimize entrapped air (pockets within the pour that CLSM cannot enter) in each oversized debris lift. Associated container debris such as container lids or other incidental debris is placed in the pour in such a manner to minimize entrapped air pockets within the pour. 3.2.2 OVERSIZED DEBRIS LIFT BACKFILL Once oversized debris containers or large debris are placed in the oversized debris lift, backfilling will be conducted by placing free-flowing CLSM meeting the specifications summarized in Table 2 or 3 of the LLRW CQA/QC Manual over the waste packages. The flowability of the CLSM is controlled to ensure adequate filling of the voids within the oversized debris pour. The CLSM shall have a slump of at least 8 inches or an efflux test flow time of less than or equal to 26 seconds. The oversized debris and the CLSM properties are defined in the LLRW CQA/QC Manual, Work Element - Waste Placement. Backfilling is done by pouring CLSM over the packages in the oversized debris pour. A standard concrete mixing truck is used to deliver and pour CLSM in each oversized debris pour. As the CLSM is poured over waste packages, the flowability of the CLSM is tested using the procedures and frequencies in the LLRW CQA/QC Manual, Work Element - Waste Placement. The Quality Control Inspectors test the CLSM for flowability, density and temperature. The Quality Control Inspectors document each oversized debris pour and observe the adequate filling of the void spaces within the pour. 3.3 COVER The Mixed Waste embankment cover is a multi-layer system consisting of a radon barrier, an HDPE layer, lower filter zone, sacrificial soil, upper filter zone and erosion barrier. Table 3 provides material specifications for each layer of the cover. See also Appendix B to this report. As part of the current Permit modification request to revise cover design and authorize the first cover construction project, revisions to Attachment II-9, Construction QA/QC Manual, have been proposed. These revisions provide specifications, quality control, and quality assurance for the work elements associated with building cover over the Mixed Waste embankment. Construction test methods and frequencies for earthwork, such as the clay radon barrier, filter zone, sacrificial soil, and erosion barrier, are consistent with those used in the LLRW CQA/QC Manual. Test methods and frequencies for geomembrane components of the cover system are similarly consistent with those for liner geomembrane in the current Attachment II-9. Once waste placement has reached the design elevation, a “temporary cover” of clean native soil will be placed to establish a non-contaminated surface on which to build radon barrier. Then radon barrier is constructed. The radon barrier is overlain with a 60 mil HDPE layer. This composite infiltration barrier provides an equivalent barrier to the composite clay-HDPE barrier at the base of the liner system. The permeability of the cover radon barrier is lower than the clay liner to minimize the potential for “bathtubbing” within the Mixed Waste embankment. Geotextile is placed on top of the HDPE to protect the HDPE from damage and to provide a non-stick surface for the overlying layers. A lower (“Type B”) filter zone, consisting of small and medium aggregate layers, and a frost protection layer (the sacrificial soil), are both placed over the radon barrier. The upper (“Type EnergySolutions Mixed Waste Expansion Project Engineering Justification Report July 18, 2011 Revision 0 Page 31 of 59 A”) filter zone and erosion barrier are the final layers of the embankment cover. As-built thickness and slope of each layer is confirmed prior to construction of the next layer of the cover. 3.3.1 RADON BARRIER The top of the completed waste zone is graded to meet the slopes specified in the engineering drawings (Appendix B). The slope grades of the embankment are maintained by survey inspection and approved by QA/QC personnel prior to the placement of radon barrier. The Division of Solid and Hazardous Waste is notified that waste placement has ceased for a section of the embankment and that cover construction will begin for that section. Radon barrier clay construction methods are approved by the satisfactory construction of a radon barrier test pad, as provided in the Mixed Waste CQA/QC Manual (Work Element: Radon Barrier Test Pad). The equipment, supervisory personnel, and procedures used for the test pad are reviewed and approved by a professional engineer qualified to certify such soil considerations. 3.3.1.1 5 x 10-8 cm/sec Permeability Clay 1. Soil borrow materials are sampled and tested to verify their physical characteristics (i.e., 85% fines < 0.075 mm; plasticity index range 10 to 25; liquid limit range 30 to 50) in accordance with the requirements outlined in the Mixed Waste CQA/QC Manual (Work Element: Radon Barrier Borrow Material). These characteristics are summarized in Table 3. Once CQA/QC testing is complete and approved, the radon barrier borrow materials become radon barrier materials approved for radon barrier construction. Borrow materials that fail testing may be re-worked or may be discarded and replaced with materials meeting the criteria. 2. The approved radon barrier materials are then placed in lifts and compacted to meet design criteria. Inspection, testing, and surveys performed on the placed radon barrier are described in the Mixed Waste CQA/QC Manual (Work Element: Radon Barrier Placement). 3. A number of CQA/QC specifications are applied to protect approved radon barrier against damage. These include drying prevention, snow removal, cold weather placement, spring start-up, and contamination prevention. 3.3.2 HDPE LINER AND GEOTEXTILE In accordance with joint guidance issued by NRC and EPA for mixed waste disposal embankments (NRC/EPA, 1987), EnergySolutions has incorporated an HDPE liner and geotextile into the mixed waste cover design. The geotextile is placed on top of the HDPE to protect the HDPE from damage and to provide a non-stick surface for the overlying layers. Test methods and frequencies are consistent with those applied to liner construction. 3.3.3 LOWER FILTER ZONE “TYPE B” FILTER The lower (“Type B”) filter zone is placed directly over the geotextile. Specifications for thickness, gradation, and durability are found in Appendix B of this Engineering Justification Report) and summarized in Table 3. The lower filter zone material is placed and spread ahead of construction equipment in order to minimize travel directly on the HDPE and geotextile surface. Filter zone material is handled in a manner to prevent concentration of finer materials in localized areas. Inspections and testing performed on the placed lower filter zone are described in the revised CQA/QC Manual (Attachment II-9). 3.3.4 SACRIFICIAL SOIL Sacrificial soil is placed as a freeze/thaw barrier above the lower filter zone. Specifications for thickness and gradation are found in drawing 11009-W05, Rev. 0 (in Appendix B of this Engineering Justification Report) and summarized in Table 3. Sacrificial soil is placed and spread ahead of construction equipment in order to minimize potential impact to the completed HDPE EnergySolutions Mixed Waste Expansion Project Engineering Justification Report July 18, 2011 Revision 0 Page 32 of 59 liner and radon barrier. Sacrificial soil is handled in a manner to prevent concentration of finer materials in localized areas. Inspection, testing, and surveys performed on the placed sacrificial soil are described in the Mixed Waste CQA/QC Manual. The Mixed Waste embankment will have sacrificial soil placed on the side slopes as well as the top slopes. 3.3.5 UPPER FILTER ZONE “TYPE A” FILTER The upper (“Type A”) filter zone is placed over the sacrificial soil. This layer consists of poorly graded aggregates of less than 6 inch size, with a D70 of 3 inches. This layer serves a similar purpose to the lower (“Type B”) filter zone, serving as a protective layer for the sacrificial soil and providing a transitional gradation between the sacrificial soil and rip-rap erosion barrier. Specifications for thickness, gradation, and durability are found in drawing 11009-W05, Rev. 0 (in Appendix B of this Engineering Justification Report) and summarized in Table 3. Filter zone material is handled in a manner to prevent concentration of finer materials in localized areas. Inspection, testing, and surveys performed on the placed upper filter zone are described in the Mixed Waste CQA/QC Manual. 3.3.6 EROSION BARRIER The top layer of the cover is the erosion barrier. Erosion barrier is constructed of large, durable rock meeting the specifications provided in drawing 11009-W05, Rev. 0 (in Appendix B of this Engineering Justification Report) and summarized in Table 3. Gradation of erosion barrier for the top slopes of the embankment (“Type B Rip-rap”) is smaller than that for the side slopes (“Type A Rip-rap”) due to the generally flat slope of the top compared to the sides. Inspection, testing, and surveys performed on the placed erosion barrier are described in the Mixed Waste CQA/QC Manual. 3.4 DRAINAGE SYSTEMS Systems for the control of precipitation and surface water runon/runoff during operations are described in Section 4.4 below. Following completion of the radon barrier cover for sections of the embankment, runoff berms are removed and replaced with rock-lined drainage ditches. Drainage ditches are constructed buttressing the final cover system of the embankment as depicted in drawing 11009-W08, Rev. 0 (in Appendix B of this Engineering Justification Report). Detail “E” of drawing 11009-W08 shows the transition from the cover system to the drainage ditch. The drainage ditch is constructed of six-inches of Type A Filter Zone rock overlain by 12- inches of Type A RipRap. Inspection, testing, and surveys performed on the drainage ditches are described in the Mixed Waste CQA/QC Manual. 3.5 BUFFER ZONE The minimum buffer zone width of 94 feet has been derived from interpretation of several regulatory references. Utah’s Water Quality Rules state: “The distance to the compliance monitoring points must be as close as practicable to the point of discharge” (R317-6-6.9A). The location of the monitoring wells, therefore, is determined by the cell geometry and other related cell configurations. The monitoring wells are located approximately 90 feet away from the edge of waste placement in the Mixed Waste embankment. The final closure fence, therefore, was located on the outside of the monitoring well location (pads for the monitoring wells are approximately 3-feet wide). Section 4.3.6 of NUREG 1200 states “An acceptable buffer zone shall be a minimum of 30 meters wide around the entire facility.” EnergySolutions has incorporated this criteria at its current LARW and Class A facilities. EnergySolutions’ property boundary is at a distance of at least 100 feet from the limits of waste disposal on the northwest corner of the Mixed Waste cell (i.e., distance to the Vitro property owned by DOE) and at least 300 feet in all other directions. EnergySolutions Mixed Waste Expansion Project Engineering Justification Report July 18, 2011 Revision 0 Page 33 of 59 Reviewers will note that the northwest corner of the expanded Mixed Waste embankment is of irregular shape in order to preserve the minimum distance of 100 feet to the Vitro property. 4.0 PROJECTED PERFORMANCE OF THE PRINCIPAL DESIGN FEATURES EnergySolutions has designed the facility to meet or exceed the performance standards established by regulatory authority. Various engineering evaluations performed on the design confirm that it meets or exceeds the design criteria. Engineering evaluations using the design specifications summarized in Section 3 (Pertinent Characteristics) have been performed for the normal, abnormal, and accident (if appropriate) conditions described in Section 2 (Design Criteria). Table 4, “Projected Performance of the Principal Design Features: Mixed Waste Embankment,” summarizes the projected performance of each design criteria with respect to the normal, abnormal, and accident (as appropriate) conditions. If applicable, a safety factor has also been applied to the projected performance, relating the projected performance to the design criteria. 4.1 LINER AND LEACHATE COLLECTION/REMOVAL SYSTEM (LCRS) 4.1.1 MINIMIZE CONTACT OF WASTES WITH STANDING WATER DURING OPERATIONS Projected Performance – Normal Conditions: Performance of this criteria is met by successful construction in accordance with a design that complies with the minimum technical requirements at 40 CFR 264.301(c)(3). Table 5 below summarizes these requirements and EnergySolutions’ corresponding construction specifications. Table 5 LCRS Minimum Technical Requirements EPA requirement 40 CFR reference EnergySolutions specification EnergySolutions reference Bottom slope  1% 264.(c)(3)(i) Minimum slope of LCRS = 1% State-issued Part B Permit, Module 5, Condition V.C.15 Granular drainage materials with hydraulic conductivity  1x10-2 cm/sec 264.(c)(3)(ii) Granular drainage materials shall have an in-place hydraulic conductivity  1x10-2 cm/sec State-issued Part B Permit, Mixed Waste CQA/QC Plan, specification 106 Granular drainage materials  12 inches thick 264.(c)(3)(ii) Thickness of granular fill shall be a minimum of one foot (12 inches) State-issued Part B Permit, Mixed Waste CQA/QC Plan, specification 107 Synthetic or geonet drainage materials with transmissivity of  3x10-5 m2/sec 264.(c)(3)(ii) All LCRS layers shall have an in-situ hydraulic transmissivity of  5 x 10-4 m2/sec. State-issued Part B Permit, Module V, Condition V.C.16 Constructed of materials that are chemically resistant to the waste and leachate; and of sufficient strength and thickness to prevent collapse under pressures exerted by the waste, cover, and equipment. 264.(c)(3)(iii) HDPE liner with a minimal nominal thickness of 60 mils. State-issued Part B Permit, Module V, Condition V.C.10 State-issued Part B Part B Plan Approval Application, Appendix U Designed and operated to minimize clogging 264.(c)(3)(iv) A filter fabric shall be placed between protective soil layers and drainage nets. Granular fill shall be clean rock, with no more than 10% passing State-issued Part B Permit, Module V, Condition V.C.17 State-issued Part B Permit, Mixed Waste CQA/QC EnergySolutions Mixed Waste Expansion Project Engineering Justification Report July 18, 2011 Revision 0 Page 34 of 59 the number 40 sieve (i.e., minimize fines) Plan, specification 103 Constructed with sumps of sufficient size to collect and remove liquids and prevent liquids from backing up into the drainage layer. 264.(c)(3)(v) Sumps shall be adequately located and designed to efficiently collect and provide for removal of leachate. State-issued Part B Permit, Module V, Condition V.C.18 Projected Performance – Abnormal Conditions: The abnormal condition evaluation considers effects of clogging of the inspection/removal pipes used to access the LCRS sumps. The LCRS is an operational, actively managed system that does not need to demonstrate long-term stability under passive management. Accordingly, this operational scenario is repairable (by extracting the material that clogs the pipe) and the long-term performance of the embankment is not affected. Further, EnergySolutions is required by its State-issued Part B Permit, Module V, Condition V.D.6, to inspect the LCRS once each operating day. Accordingly, the design criteria is met. Projected Performance – Accident Conditions: The operational accident condition is heavy equipment collision with the leachate inspection/removal pipe where it extends to the surface. In this event, EnergySolutions would be required under its State-issued Part B Permit to repair the damage to the LCRS so that the required daily inspection and leachate removal activities may resume. Any repair would be required to maintain the minimum technical requirements for the LCRS. Accordingly, the design criteria are met. Performance References: EnergySolutions, State-issued Part B Permit Approval Application, Appendix U EnergySolutions, State-issued Part B Permit, Attachment II-9, Construction QA/QC Manual EnergySolutions, State-issued Part B Permit, Module V Safety Factor: Conformance with the minimum technical requirements at 40 CFR 264.201(c)(3) is a pass/fail test; accordingly, a safety factor is not applicable to this design criteria. 4.1.2 MINIMIZE CONTACT OF WASTES WITH STANDING WATER AFTER CLOSURE Projected Performance – Normal Conditions: As long as the permeability of the liner is greater than or equal to the permeability of the cover, a steady state situation will be reached where the influent in through the cover will be less than or equal to effluent out through the liner. HDPE layers can be assigned an initial permeability (using the HELP model default value) of 2 x 10-13 cm/sec. Under normal conditions, HDPE geomembranes of this type may be expected to retain a substantial degree of their initial integrity for as much as 500 years after closure (see e.g., Badu- Tweneboah et al, 1999). The potential for differential degradation of the liner relative to the cover is addressed under abnormal conditions below. EnergySolutions provided calculated leakage rates for the cover and LCRS as constructed to the design specifications and also analyzes potential effects of long-term stress cracking of the geomembrane materials in an October, 2001 report entitled, “Mixed Waste Embankment Liner Leakage Rate Analysis” (Envirocare, 2001). These calculations are based on semi-empirical equations developed by J.P. Giroud (1997). These equations have been developed to calculate the rate of liquid migration through degraded geomembrane liners underlain by compacted clays. Assuming some degree of degradation and equal head on both the cover and liner, the calculated leakage rate through a single two millimeter (mm) diameter hole for the cover under normal conditions is 2.86 x 10-10 m3/sec. Under the same normal conditions, the calculated leakage rate for the liner is 4.76 x 10-10 m3/sec. Note that the assumption of equal, constant head upon the cover as well as the liner is conservative, because the cover will be subject to hydraulic head only EnergySolutions Mixed Waste Expansion Project Engineering Justification Report July 18, 2011 Revision 0 Page 35 of 59 during and for relatively short periods of time following precipitation events. For much of the year, the cover will be dry. So long as the degradation rate of the cover and liner is the same, this ratio of leakage rates will be maintained. Accordingly, any infiltrating moisture that reaches the liner will be able to move through it and out of the embankment at least as quickly as moisture enters the embankment through the cover. Therefore, the embankment will remain drained and “bathtubbing” will not occur. The effects on the cover system and the LCRS associated with long-term stress cracking were also evaluated in Envirocare, 2001. The calculated leakage rate associated with a 50 mm wide infinite length crack in the cover under normal conditions is 6.03 x 10-10 m2/sec. Under the same normal conditions, the calculated leakage rate for the liner is 1.10 x 10-9 m2/sec. Long-term stress cracking is not dependant on environmental factors; it is a property of the HDPE material. Therefore, since both the cover and liner are subject to equal differential settlement stresses (see Sections 4.1.3 and 4.3.3 below), similar magnitudes of stress cracking are expected in both geomembrane systems (liner and cover). Therefore, under normal conditions, the leakage rate through the LCRS is greater than the leakage rate through the cover geomembrane/clay system and the design criteria are met. Projected Performance – Abnormal Conditions: The abnormal condition associated with this design criteria is the possibility of differential degradation of the cover HDPE and/or clay radon barrier layers as compared to the LCRS HDPE and/or clay layers. In considering potential degradation mechanisms, it is noted that the HDPE layers will be in similar long-term environments in several respects: buried to a depth that will be isolated from the effects of surface environmental factors such as freeze/thaw cycles or ultraviolet radiation (see e.g., Sections 4.3.1.3 and 4.3.1.4 below); in anaerobic environments; underlain by a compacted clay layer. Of critical consideration, however, in assessing the potential for differential degradation are the differences in the long-term environment of the cover HDPE compared to the LCRS. To the extent that water may enter the embankment through the cover, it will percolate through the emplaced waste and potentially accumulate hazardous and radioactive contamination. This creates harsher chemical and radiological leachate in contact with the LCRS compared to the rainwater that contacts the cover. If this water should accumulate on the LCRS, there would also be hydraulic head present that would act to encourage drainage. Accordingly, the LCRS will be in a harsher chemical and physical environment than the HDPE in the cover. Envirocare, 2001 evaluates the different abnormal scenarios that could potentially manifest themselves within the cover system and the LCRS. These scenarios include the potential for poor geomembrane/clay contact within the systems (considered unlikely due to strict Quality Control in the preparation of the clay surface and installation of the HDPE layer) and potential effects attributed to biointrusion of the cover geomembrane (determined by Badu-Tweneboah (1999) to be insignificant through a literature review and expert opinion). For pinhole degradation, under worst-case conditions of the cover geomembrane in poor contact with the underlying compacted clay and the liner geomembrane in good contact with the underlying compacted clay, the cover would need to degrade a minimum of four-and-one-half times more severely than the liner for the effective permeabilities (liner leakage rates) to be equal. For long-term stress cracking, this same worst-case condition calculation resulted in the cover needing to degrade a minimum of three times more severely than the liner for the effective permeabilities to be equal. From an analysis of environmental effects on the system, the only factor that could potentially differentially degrade the cover HDPE and/or clay radon barrier layers over the LCRS HDPE and/or clay layers is biointrusion of plant roots through these cover layers. The potential for biointrusion to adversely affect the cover system was presented in Whetstone Associates, Inc. EnergySolutions Mixed Waste Expansion Project Engineering Justification Report July 18, 2011 Revision 0 Page 36 of 59 Technical Memorandum entitled, “Effects of Greasewood Root Penetration on the Mixed Waste Cell Cover” Whetstone, 2001) and described in Section 4.3.1.5 of this Engineering Justification Report. Parameters derived in the Whetstone Associates technical memorandum were incorporated into the liner leakage rate analyses provided in Envirocare, 2001. Safety factors were calculated for differential degradation of the cover system with respect to the LCRS. The abnormal effects of biointrusion were examined in two separate evaluations: (1) the maximum head calculated in the Whetstone Associates technical memorandum was assumed to be constant on the cover system; all other parameters remained the same as the normal conditions above, and (2) the maximum average annual infiltration rate (calculated for a fully degraded geomembrane) was compared to the effective permeability of the LCRS. For the condition of maximum head on the cover system as a result of biointrusion, under worst- case conditions of the cover geomembrane in poor contact with the underlying compacted clay and the liner geomembrane in good contact with the underlying compacted clay, the cover system would need to degrade a minimum of two-and-one-half times more than the LCRS before the effective permeabilities would be equal and “bathtubbing” could present a problem. The maximum average annual infiltration through the cover system resulting from biointrusion was calculated by Whetstone Associates as 0.0770 inches/year (6.2 x 10-11 m/sec). Based upon normal degradation of the liner geomembrane and assuming good geomembrane/clay contact, the effective permeability of the LCRS was calculated as 1.73 x 10-10 m/sec (note that poor geomembrane/clay contact yields a larger effective permeability; accordingly, the assumption of good contact is conservative in this case). Therefore, flow through the LCRS is greater than flow through the cover system and the design criteria is met under the abnormal condition of biointrusion. To the extent that HDPE may be susceptible to degrade under long-term embankment conditions, the liner will allow drainage of water faster than the cover. Thus, the design criteria is met. Projected Performance – Accident Conditions: No appropriate accident conditions exist for this design criteria. Performance References: Badu-Tweneboah, K., Tisinger, L.G., Giroud, J.P., and Smith, B.S., 1999. “Assessment of the Long-Term Performance of Polyethylene Geomembranes and Containers in a Low-Level Radioactive Waste Disposal Landfill.” Geosynthetics ’99 Conference Proceedings, pp. 1055- 1070. Envirocare of Utah, Inc., October 30, 2001. “Mixed Waste Embankment Liner Leakage Rate Analysis.” Giroud, J.P., 1997. “Equations for Calculating the Rate of Liquid Migration Through Composite Liners Due to Geomembrane Defects,” Geosynthetics International, 4 (3-4), pp. 335- 348. Section 4.3.1, Complementary Aspects “Prevent Desiccation,” “Limit Frost Penetration,” and “Prevent Biointrusion” Sections 4.1.3 and 4.3.3 of this Engineering Justification Report. Whetstone Associates, Inc., September 13, 2001. Technical Memorandum, “Effects of Greasewood Root Penetration on the Mixed Waste Cell Cover.” Safety Factor: The factor of safety associated with the normal conditions for this design criteria are calculated as the ratio of effective permeability between the LCRS and the cover as constructed to design specifications: 4.76 x 10-10 m3/sec / 2.86 x 10-10 m3/sec = 1.67 for pinhole degradation and 1.1 x 10-9/6.03 x 10-10 = 1.82 for long-term stress cracking. EnergySolutions Mixed Waste Expansion Project Engineering Justification Report July 18, 2011 Revision 0 Page 37 of 59 Under worst-case abnormal conditions (case 4 in Envirocare, 2001, “Mixed Waste Embankment Liner Leakage Rate Analysis”), the factor of safety associated with dissimilar geomembrane/clay contact parameters is 8.85 x 10-9 m3/sec / 1.98 x 10-9 m3/sec = 4.47 for pinhole degradation and 5.18 x 10-9/1.60 x 10-9 = 3.24 for long-term stress cracking. For the abnormal condition of biointrusion degrading the cover system, minimum factors of safety associated with the calculated maximum head are 8.85 x 10-9 m3/sec / 3.25 x 10-9 m3/sec = 2.72 for pinhole degradation and 5.18 x 10-9/2.06 x 10-9 = 2.51 for long-term stress cracking. The minimum safety factor associated with the calculated average annual infiltration rate due to biointrusion is 1.73 x 10-10 m/sec / 6.2 x 10-11 m/sec = 2.79. 4.1.3 ENSURE COVER INTEGRITY Projected Performance – Normal Conditions: Secondary foundation settlements were included as part of the analysis for compressible debris within the LARW embankment completed by AGRA in a report dated June 1, 2000. This analysis is conservative with respect to the Mixed Waste embankment since the LARW embankment has a larger footprint and is taller. Section 4.6 and Figure 15 of the AGRA report calculates maximum secondary settlements of 8-inches after 500 years. Examining Figure 15 of the AGRA report, this secondary settlement is spread over a distance of approximately 550 feet from the toe of the embankment to the point of maximum settlement. This yields a distortion of 0.001 after 500 years under normal conditions. This distortion is within the design criteria of 0.02. Projected Performance – Abnormal Conditions: The abnormal construction condition of an area of the embankment completely covered adjacent to an area 25 feet high was evaluated for the LLRW (B/C) Embankment in a “Settlement Evaluation” AMEC report dated November 8, 2000. The analysis is explained in Section 3.2 on page 9 and in Figure 3 of the AMEC report. This report was completed for the larger (and taller) LLRW (B/C) Embankment and is therefore a conservative assessment of the potential settlements of the Mixed Waste embankment. This analysis used a 3:1 (H:V) construction slope and calculates a maximum differential settlement of approximately eight (8) inches over the 100 foot internal slope area (distortion of approximately 0.007, which is less than the design criteria of 0.02). Projected Performance – Accident Conditions: No appropriate accident conditions exist for this design criteria. Performance References: AGRA, June 1, 2000. “Evaluation of Settlement of Compressible Debris Lifts, LARW Embankments.” AMEC, November 8, 2000. “Settlement Evaluation: Proposed LLRW and Mixed Waste Embankments.” (Appendix I-2 of the Class A/B/C Amendment Application dated December 13, 2000) Safety Factor: For normal conditions, the safety factor is calculated from the worst case distortion, between the toe of waste and the shoulder. This safety factor is calculated as follows: 0.02 / 0.001 = 16.50. The safety factor under abnormal conditions is 0.02 / 0.007 = 2.86. 4.2 MIXED WASTE PLACEMENT 4.2.1 ENSURE COVER INTEGRITY Projected Performance – Normal Conditions: The Mines Group report projected a conservative normal analysis assuming conservative normal conditions (estimated settlements are assumed to occur after cover completion). Under a true normal analysis, differential settlement after cover completion is expected to be unnoticeable. This statement may be made because, under normal conditions, primary consolidation of the lower waste layers will be completed prior EnergySolutions Mixed Waste Expansion Project Engineering Justification Report July 18, 2011 Revision 0 Page 38 of 59 to construction of the cover and strict construction specifications that govern the placement of waste (compaction, CLSM pours, etc.) form a stable embankment. Section 2.8 of the Mines Group report explains the finite element model that was utilized and provides estimated settlement data based upon the full height of waste and six (6) feet of cover (actual design is a 5.5 foot cover). Differential settlement is expected to be approximately 12-inches over the top slope of the embankment (233 feet). This yields a distortion of approximately 0.004. The AGEC, 1998, settlement report calculated similar settlements of 10-12 inches between the shoulder and the crest of the embankment. Therefore, the design criteria is met under normal conditions. Projected Performance – Abnormal Conditions: In a report dated June 1, 2000, AGRA Earth & Environmental, Inc., provided an analysis of settlements associated with compressible debris lifts within the LARW embankment. This analysis provides a conservative basis for the Mixed Waste embankment since the LARW embankment has a higher waste height, a thicker cover, and a much larger footprint; while waste placement specifications are the same for both embankments. The AGRA report performed a differential settlement calculation on the abnormal case of compressible debris lifts “sandwiched” between two incompressible CLSM pyramids. The results of this analysis are provided in Figure 14 and summarized in Table 7 of the AGRA report. For 10% compressible debris, the maximum differential settlement was approximately 0.005. Therefore, the design criteria is met under abnormal conditions. Projected Performance – Accident Conditions: No appropriate accident conditions exist for this design criteria. Performance References: AGEC, October 19, 1998. “Closure Cap Stability and Settlement Estimate Mounding - Mixed Waste Disposal Facility.” The Mines Group, November 14, 2000. “Technical Report for the Mixed Waste Facility Cover Design.” AGRA, June 1, 2000. “Evaluation of Settlement of Compressible Debris Lifts, LARW Embankments.” Safety Factor: The normal conditions safety factor is calculated as follows: 0.02/0.004 = 5.00. The abnormal condition safety factor is 0.02/0.005 = 4.00. 4.2.2 ENSURE STRUCTURAL STABILITY A detailed seismic stability and deformation analysis was completed for the Mixed Waste embankment in a 1998 AGEC stability and settlement report with further explanations and confirmation in a 1999 AGEC addendum report. Furthermore, the Mines Group also provided a stability analysis in Section 2.7 of their report. The AGEC reports both assumed a cover consisting of six (6) feet of compacted clay, a flexible membrane liner, 0.5 foot of filter and drainage materials, and 1.5 feet of rock erosion barrier. These reports were performed to justify an increase in embankment height proposal that was being considered at that time. The 1998 report examines both a four (4) foot and an eight (8) foot height increase compared to the height originally permitted for the embankment (at the shoulder) and the 1999 report refines the analysis to a five (5) foot height increase (the actual height increase later approved by DSHW). The Mines Group report provides similar results to the AGEC analyses, thereby verifying the results. This work has been updated by AMEC, July 14, 2011 “Report of Geotechnical Evaluation, EnergySolutions Clive Facility, Mixed Waste Embankment Expansion” (provided as Appendix D to this report). AMEC, 2011 evaluates the waste height and embankment footprint proposed in EnergySolutions drawing series 11009. EnergySolutions Mixed Waste Expansion Project Engineering Justification Report July 18, 2011 Revision 0 Page 39 of 59 Projected Performance – Normal Conditions: AMEC, 2011 evaluated four failure scenarios and reports a minimum factor of safety as 1.8 (section 3.3.1). Therefore, the design criteria (safety factor > 1.5) is met under all analyses. Projected Performance – Abnormal Conditions: AMEC, 2011 evaluated seismic stability using updated seismic design parameters developed in 2005. The minimum calculated factor of safety was 1.1 (section 3.3.2). Probable post-earthquake embankment deformations were found to be less than 1 inch (section 3.3.3). The liquefaction analysis provided in Appendix C of the State-issued Part B Plan Approval Application dated March 30, 1990 has been reviewed on several occasions (AGEC, 1999, and the Mines Group reports, among others) and is still valid for conditions at the site. This analysis utilizes the techniques presented by Seed and Idriss (1982) to calculate a factor of safety associated with liquefaction of the foundation soils beneath the embankment. The factor of safety under the main portion of the embankment were calculated at 1.4 for the shallow depth (25 feet) and 1.6 for the deep depth (55 feet) using a conservative seismic acceleration of 0.37g. AMEC, 2011 determined that “…the probability of liquefaction with depth would be considered to be quite low based on age of the deposits alone” (section 2.2.2). Liquefaction of the waste material is not a concern since saturation of the waste material will not occur (see the discussion under “Allow Cell Drainage” in Section 4.1.1 above). Projected Performance – Accident Conditions: No appropriate accident conditions exist for this design criteria. Performance References: AGEC, October 19, 1998. “Closure Cap Stability and Settlement Estimate Mounding - Mixed Waste Disposal Facility.” AGEC, July 29, 1999. “Response: Division of Solid and Hazardous Waste Mixed Waste Disposal Facility Mounding.” AMEC, July 14, 2011. “Report of Geotechnical Evaluation, EnergySolutions Clive Facility, Mixed Waste Embankment Expansion.” The Mines Group, November 14, 2000. “Technical Report for the Mixed Waste Facility Cover Design.” Envirocare, March 30, 1990. “RCRA State-issued Part B Plan Approval Application,” Appendix C. Safety Factor: The minimum static factor of safety was calculated to be 1.8. Pseudo-static factor of safety was calculated to be 1.1. Seismic safety factors associated with liquefaction were calculated at 1.4 for shallow depths and 1.6 for deep depths. 4.3 COVER 4.3.1 MINIMIZE INFILTRATION 4.3.1.1 Minimize Infiltration Projected Performance – Normal Conditions: The following discussion of infiltration modeling does not take credit for the presence of the HDPE layer in the cover. This assumption has been made to incorporate a factor of safety in the performance assessment for groundwater contamination; and because of the difficulties in quantifying likely performance of HDPE over hundreds of years. Discounting of the HDPE layer is a conservative assumption in terms of the groundwater model, as infiltration and potential impact to the groundwater is then overstated. Analyses of the projected performance of HDPE layers in the cover and LCRS, and their interrelationship, are presented in section 4.1.2. EnergySolutions Mixed Waste Expansion Project Engineering Justification Report July 18, 2011 Revision 0 Page 40 of 59 Infiltration modeling was performed based upon precipitation data for the last 50 years at Dugway. The Dugway data was correlated to site-specific data generated at the time the model was produced. The Dugway data, scaled to EnergySolutions’ historical data, yielded a long-term average annual precipitation value of 7.85 inches. Application of the HELP model’s synthetic weather generator returned an average annual precipitation of 7.92 inches. The synthetic data set was applied for infiltration modeling. Refer to Whetstone Associates, Inc. November 22, 2000, “Mixed Waste Cell Infiltration & Transport Modeling,” Section 3.2 for a complete discussion of weather data input to infiltration and transport modeling. Using this precipitation data, HELP infiltration modeling arrived at an average predicted infiltration rate of 0.072 cm/sec for the top slope and 0.038 cm/sec for the side slopes (with run- on from the top slope). These values were then used as inputs to the PATHRAE transport modeling to demonstrate that performance criteria for ground water protection levels at the monitoring wells are met at 500 years. EnergySolutions performed an internal analysis of Whetstone’s results as applied to the revised Mixed Waste geometry (EnergySolutions, 2011) and concluded that under current waste acceptance criteria and associated disposal limits ground water protection levels at monitoring wells are still met at 500 years. This internal analysis was reviewed by Whetstone for validity and concurrence. Further assurance that this infiltration value will be met is related to many factors. The most important factor relating to minimizing infiltration is the permeability of the radon barrier clay (5 x 10-8 cm/sec). Engineering controls are provided in the revised CQA/QC Manual. The revised CQA/QC Manual is consistent with the existing LLRW and 11e.(2) CQA/QC Manual. Therefore, at construction and under normal conditions the projected performance of the cover to minimize infiltration meets or exceeds the design criteria. Projected Performance – Abnormal Conditions: Infiltration performance under abnormal conditions requires that positive drainage off of the embankment be maintained and that infiltration not increase due to the effects discussed under the complementary aspects of desiccation, frost penetration, and biointrusion. The discussions in Sections 4.3.1.2 through 4.3.1.5 provide projected performance for each of these subjects. Based upon the analyses performed, the projected performance of the cover to minimize infiltration will meet the design criteria for all abnormal conditions. Projected Performance – Accident Conditions: No appropriate accident conditions exist for this design criteria. Performance References: EnergySolutions, April 20, 2011. “Impacts of Proposed Revisions to the Mixed Waste Disposal Cell Geometry on Groundwater Compliance.” EnergySolutions, December 15, 2010. LLRW and 11e.(2) Construction Quality Assurance/Quality Control (CQA/QC) Manual, revision 25d Sections 4.3.1.2, 4.3.1.3, 4.3.1.4, and 4.3.1.5 of this Engineering Justification Report. Whetstone Associates, Inc., November 22, 2000. “Mixed Waste Cell Infiltration and Transport Modeling.” Safety Factor: A safety factor is not applicable to this complementary aspect. 4.3.1.2 Encourage Runoff Projected Performance – Normal Conditions: The design for the top slope of the cover provides a minimum of 2% slope away from the crest of the embankment and side slopes of 20%. EnergySolutions Mixed Waste Expansion Project Engineering Justification Report July 18, 2011 Revision 0 Page 41 of 59 See Drawing 11009-W01, Rev. 0 (Appendix B). Long-term stability and maintenance of the design slopes for maintaining positive drainage is evaluated in Section 4.3.4.1 below. The projected performance for the design criteria relating to not allowing water accumulation is analyzed in terms of settlement in Section 4.3.4.1 (for both normal and abnormal conditions). Normal conditions for this required function and design criteria relating to allowable velocities within the drainage layer were not evaluated because performance is bounded by the abnormal condition analysis. Projected Performance – Abnormal Conditions: An important consideration of this required function is the maximum allowable velocity within the drainage layer. Infiltration and transport modeling (Whetstone, 2000) show that the majority of the drainage within the cover occurs in the lower (Type B) filter layer, below the sacrificial soil and above the radon barrier clay. The modeling report also provides a hydraulic conductivity associated with this filter layer of 3.5 cm/sec (0.115 ft/sec). A maximum potential velocity through this layer may then be calculated by multiplying this hydraulic conductivity by the slope of the embankment. This yields maximum achievable velocities of 2.30 x 10-3 ft/sec for the top slope and 2.30 x 10-2 ft/sec for the side slope. Mixed Waste rock cover calculations performed as part of a previous Mixed Waste Engineering Justification Report (EnergySolutions, 2001) evaluate the one-hour PMP rainfall intensity at 40.93 inches/hour (9.5 x 10-4 ft/sec) for the top slope and 37.66 inches/hr (8.7 x 10-4 ft/sec) for the side slope. Under the worst possible scenario, the rainfall intensity will equal the maximum flow velocity and would reach the lower filter layer at this same rate. Using this scenario, the lower filter zone is designed to exceed the volume flow associated with the worst case scenario related to the one-hour PMP. Therefore, flow will not back up in the lower filter layer and the design criteria is attained. A sensitivity analysis has been performed to assess potential effects of native plants that may become established on the surface of the embankment. Roots associated with native plants may be considered a concern if they should cause a blockage in drainage layers of the cover system, reducing the effectiveness of runoff. The sensitivity analysis concluded that potential blockage of drainage layers is more than compensated for by increased evapotranspiration due to plant communities. This analysis is discussed further in Section 4.3.1.5. Projected Performance – Accident Conditions: Potential blockage of the lower filter layer due to migration of either the sacrificial soil or the clay radon barrier materials is evaluated in section 4.3.3.2. The piping calculations provided in section 4.3.3.2 provide evidence that minimal migration of the sacrificial soil will occur. Additionally, the extremely low flow velocities at the filter/clay interface prevent erosion, and thereby migration, of the radon barrier clay materials. Therefore, minimal to no blockage of the lower filter layer is projected to occur due to migration of particles from the soil and/or clay layers. Performance References: The Mines Group, November 14, 2000. “Technical Report for the Mixed Waste Facility Cover Design.” Envirocare of Utah, Inc., March 9, 2001. “Mixed Waste Rock Cover Design Calculations.” Sections 4.3.1.5, 4.3.3.2, and 4.3.4.1 of this Engineering Justification Report. Safety Factor: No safety factor is associated with the water accumulation design criteria. For water velocity, the safety factor can be calculated as the ratio between the allowable maximum velocity (associated with the hydraulic conductivity) and the maximum possible velocity EnergySolutions Mixed Waste Expansion Project Engineering Justification Report July 18, 2011 Revision 0 Page 42 of 59 associated with the one-hour PMP. This yields safety factors of 2.30 x 10-3 / 9.5 x 10-4 = 2.42 for the top slope and 2.3 x 10-2 / 8.7 x 10-4 = 26.35 for the side slope. 4.3.1.3 Prevent Desiccation The critical concern for desiccation of radon barrier clay is during construction, when the cover is exposed to the elements. Following completion of the HDPE and geotextile, lower filter zone, sacrificial soil, upper filter zone, and erosion barrier, the radon barrier clay is isolated from the elements. Please refer to Section 3.3.1.1 above for a discussion of protective measures applied during construction. Note that the following analysis takes no credit for HDPE overlying the radon barrier clay. Projected Performance – Normal Conditions: Moisture content modeling has been performed for the cover and embankment system using the UNSAT-H model (see section 4 Whetstone, 2000). This modeling establishes that steady-state moisture content for the clay layers of the cover remain relatively constant at approximately 0.42 by volume (see Section 4.6.1 of the Whetstone report). This steady-state moisture content is comparable to the saturated moisture content of 0.43 for the upper foot of radon barrier. The steady-state moisture content of the radon barrier can be compared against the projected moisture content at which desiccation may begin. Moisture content likely to lead to desiccation cracking can be derived from the plastic limit for a soil (ASTM D4318). The plastic limit is a laboratory-derived measurement of the moisture content at which a soil begins to crack, or desiccate. EnergySolutions’ clay borrow sources for radon barrier construction have an average moisture content of 18.6 by weight at the plastic limit (90 data points from January through November 2000). This converts to a moisture content at which cracking begins of approximately 22% by volume; or roughly half the steady-state moisture content of the radon barrier clay of 42% by volume. Projected Performance – Abnormal Conditions: No matter the length or severity of drought, there is no credible evaporative mechanism to dry out the radon barrier, and moisture content of the radon barrier will remain constant for the life of the embankment. Potential evapotranspiration effects of plant life on moisture content within the layers of the cover system are discussed in Section 4.3.1.5 below. Two aspects of the cover design contribute to maintenance of moisture content in the radon barrier clays at a steady-state condition: 1. Moisture that enters the system is designed to run off of the embankment cover at the interface between the lower filter zone and the surface of the radon barrier. Runoff at this interface provides a re-wetting mechanism for radon barrier clays, should they fall below optimum moisture content. 2. The field capacity of the lower filter zone is over an order of magnitude less than that of the radon barrier (see Table 7 of the Whetstone report). Accordingly, moisture in the system will preferentially migrate to the radon barrier clay. The difference in field capacity confirms the effectiveness of the lower filter zone as a capillary break, as the lower filter zone will not be able to pull moisture from the radon barrier clay for transport to the surface of the cover. Projected Performance – Accident Conditions: No appropriate accident conditions exist for this design criteria. Performance References: Whetstone Associate, Inc., November 22, 2000. “EnergySolutions Mixed Waste Cell Infiltration and Transport Modeling.” Sections 3.3.1.1 and 4.3.1.5 of this Engineering Justification Report. EnergySolutions Mixed Waste Expansion Project Engineering Justification Report July 18, 2011 Revision 0 Page 43 of 59 Safety Factor: The design criteria of “no desiccation cracking in radon barrier clay” is met. A safety factor can be calculated as the steady-state moisture content divided by the moisture content at which desiccation can begin: 0.42 / 0.22 = 1.91. This safety factor applies to abnormal as well as normal conditions, as the abnormal condition evaluation establishes that there is no credible mechanism to dry out the radon barrier. 4.3.1.4 Limit Frost Penetration Projected Performance – Normal Conditions: Normal conditions for this required function and design criteria were not assessed because the performance is bounded by the abnormal conditions analysis. Projected Performance – Abnormal Conditions: Three frost penetration analyses have been completed to assess frost penetration upon the embankments at EnergySolutions. Two of these analyses were completed by Montgomery Watson for the LARW and Class A Disposal embankments. The rock armor (upper and lower filter layers, sacrificial soil, and erosion barrier rip rap) of the proposed Mixed Waste embankment cover is identical to the LARW embankment in the top slope area and identical to the entire Class A Disposal embankment cover. The first analysis performed (Montgomery Watson, 1998) assessed frost penetration in the top slope area of the cover with a sacrificial soil layer, and in the side slope without a sacrificial soil layer. The second analysis (Montgomery Watson, 2000) examined the additional effects of a sacrificial soil layer within the side slopes. Slightly different results were observed and expected for the top and side slopes because the erosion protection rock is larger on the side slope. The third analysis was performed by the Mines Group specifically for the proposed Mixed Waste embankment cover top slope area. The latter independent analysis compares favorably with the previous analyses, thereby confirming the frost penetration results. Temperature data for the Montgomery Watson analyses was generated based on the lowest recorded high and low temperature on each day throughout the freezing season (October through April) over the 47 years of data available at the time from Dugway, Utah. The modeled data set is lower than the 500 year return rate data provided by the Western Regional Climate Center. Table 6, “Minimum Average Monthly Temperatures” compares the 500 year return rate minimum average monthly temperatures to the calculated average monthly temperatures utilized by Montgomery Watson in their frost penetration analyses. Table 6 Minimum Average Monthly Temperatures Month 500 year return average minimum temperature (F) Modeled average minimum temperature (F) October 26.53 20.81 November 13.64 4.80 December -0.06 -6.61 January -7.81 -13.00 February 1.00 -6.00 March 19.38 10.16 April 27.29 19.77 EnergySolutions Mixed Waste Expansion Project Engineering Justification Report July 18, 2011 Revision 0 Page 44 of 59 The modeled average temperatures are lower than the projected 500 year return average minimum temperatures throughout the freezing season. Therefore, the frost penetration modeling performed by Montgomery Watson provides conservative estimates of the abnormal condition frost depths. The Montgomery Watson reports calculate frost depths of 3.4 feet for the top slope area and 3.2 feet for the side slope area with the sacrificial soil layer, as designed. These frost penetration depths are less than the rock/filter/sacrificial soil design depths of 3.5 feet. The Mines Group analysis yielded a comparable frost depth of 3.28 feet for the top slope area. Additionally, the Mines Group took the analysis an extra step and included a finite element analysis of the cover to account for the complexities arising through the addition of a third layer (lower filter layer) with different thermal characteristics from the sacrificial soil layer. The finite element analysis lowered the frost depth estimation slightly to 3.25 feet. The Montgomery Watson analysis is the most conservative and will be used to ascertain the performance of the Mixed Waste embankment rock armor to shield the radon barrier from the effects of frost. Since, according to these calculations, the frost penetration depth does not reach the surface of the clay radon barrier, degradation of this layer will not occur as a result of freeze/thaw processes. Therefore, the projected performance meets the design criteria for frost penetration under normal and abnormal conditions. Projected Performance – Accident Conditions: No appropriate accident conditions exist for this design criteria. Performance References: Montgomery Watson, February 5, 1998. “Review of Cover Design for LARW Cell.” Montgomery Watson, March 1, 2000. “LARW Cover Frost Penetration.” Minimum Temperature Return Rates data provided November 1, 2000. Western Regional Climate Center, Desert Research Institute, Reno, Nevada. (Appendix O-3 of the Class A/B/C Amendment Application dated December 13, 2000) The Mines Group, November 14, 2000. “Technical Report for the Mixed Waste Facility Cover Design.” Safety Factor: The safety factor associated with frost penetration is the ratio of the design criteria depth (3.5 feet) to the projected frost depth. Since the temperature data utilized in this analysis is more conservative than the design criteria abnormal condition, the projected frost depth is conservative and the safety factor will be greater than calculated. Minimum safety factors are 3.5 / 3.4 = 1.03 for the top slope area and 3.5 / 3.2 = 1.09 for the side slope area. 4.3.1.5 Limit Biointrusion Projected Performance – Normal Conditions: The completed embankment cover is expected to deter establishment of deep-rooted plant communities, based on the following considerations. 1. The required density of the radon barrier clay may provide some resistance to root intrusion compared to the native soil deposits. This is discussed in the report, “Assessment of Vegetation Impacts on LLRW,” SWCA, 2000. The revised CQA/QC Manual requires that the radon barrier clay be compacted to a minimum of 95% of a standard proctor; however, construction methods for the 5 x 10-8 cm/sec permeability radon barrier effectively require meeting 100% of a standard proctor. It is not possible to quantify the degree of resistance to root intrusion provided by the density of the surface of the radon barrier. However, under normal conditions, it is assumed that the compacted surface of the radon barrier would provide and maintain a relatively high degree of resistance to root penetration; and therefore preclude significant root intrusion into the radon barrier. EnergySolutions Mixed Waste Expansion Project Engineering Justification Report July 18, 2011 Revision 0 Page 45 of 59 2. The HDPE geomembrane layer provides an additional layer of resistance to root infiltration. A literature review and expert opinions presented by Badu-Tweneboah, et. al. (1999), found that biointrusion is unlikely to infiltrate an intact geomembrane in a cover system similar to EnergySolutions’ proposed cover system. Further, roots generally will find more nutrients above the geomembrane and will be less likely to attempt to penetrate the geomembrane; opting for lateral pathways in the soil above the geomembrane. Badu-Tweneboah also reported that their literature review found no instances of roots enlarging existing geomembrane defects. 3. The DOE report “Vegetation Growth Patterns on Six Rock Covered UMTRA Project Disposal Cells (DOE AL-400677.0000, 1992)” found isolated, sparse vegetation was observed on the Vitro embankment cover at the Clive facility. In this report, vegetation was observed only in areas of the cover that had significant infilling of the fines in the rock cover. The Vitro embankment cover design consists of one (1) foot of rip rap on a six inch sand loam base material over the radon barrier. The Mixed Waste cover design doubles the minimum rock thickness to two (2) feet (1.5 feet of rock erosion barrier and 0.5 feet of upper “Type A” filter zone) above soil-like materials. Accordingly, infilling of fines in the Mixed Waste cover should be significantly delayed compared to the limited infilling observed on the Vitro cover. For the normal conditions presented herein, shallow-rooted plants are defined as plants with a root depth of 3.5 feet or less beneath the completed embankment surface. At this depth, the compacted clay radon barrier surface would not become impacted and the infiltration results previously reported by Whetstone Associates, Inc. (November 22, 2000) are applicable. See Section 4.3.1.1 for a discussion of this infiltration modeling. Projected Performance – Abnormal Conditions: The presence of vegetation on the cover may be controlled during the post-closure period of institutional controls through physical removal or application of herbicides. However, it is possible that native vegetation, including deep-rooted species, may become established on areas of the cover after the 100-year period of institutional control. The following discussion summarizes information provided in the SWCA report, analyzing possible effects of vegetation establishment on embankment covers at the Clive site. Section 3.0 of the SWCA report establishes that black greasewood (Sarcobatus vermiculatus) is the plant most likely to have deep tap roots in western Tooele County; accordingly, the following analysis has focused on this species. Black greasewood may have tap roots with a probable maximum effective depth of 11.8 feet (Section 2.4 of the SWCA report); a field evaluation of individual specimens on the Clive site found tap roots extending to 11 and 11.5 feet; with fine roots extending as deep as 13 feet beneath the surface. If black greasewood were established on the surface of the embankment, this would be deep enough to theoretically penetrate the rock and soil layers of the cover into the radon barrier. A soils literature review has identified, however, that black greasewood is not the dominant species on range sites that may be comparable to that of the infilled erosion barrier (Section 3.2 of the SWCA report) Accordingly, black greasewood might not become established on an infilled embankment cover. However, it cannot be definitively concluded that the soil type expected on the embankment surface as a result of infilling of voids in the erosion barrier would exclude greasewood establishment (Section 4.0 of the SWCA report). Therefore, the abnormal condition evaluation assumes that a black greasewood community becomes established on the cover. The following evaluation was performed to conservatively estimate potential impacts on embankment performance of a significant black greasewood population. A calculation sheet utilizing the following analysis upon the B/C embankment was previously provided as Appendix K-3 to the B/C Amendment Application dated December 13, 2000. EnergySolutions Mixed Waste Expansion Project Engineering Justification Report July 18, 2011 Revision 0 Page 46 of 59 1. Consider that a complete black greasewood population is fully established on year 101 (first year after the end of the maintenance period). That is, within one year after institutional controls end, the vegetation on the cover reaches the late successional stage currently present in undisturbed vegetation around the Clive facility. 2. Late successional vegetation coverage and species distribution was developed as follows. The native vegetation at the site has a 10% ground cover (Vitro Embankment Final Environmental Impact Statement – FEIS). Of the native vegetation, 35% of the plants are black greasewood. (Section 2.2 of the SWCA report). Each black greasewood plant is assumed to have two tap roots. Section 2.4 of the SWCA report discusses the possibility of “several” tap roots per plant; however, excavations at the site as reported in Section 3.3 of the SWCA report did not find multiple tap roots. Each black greasewood tap root has a diameter of 1.5 cm (the SWCA report, Section 3.3 discusses finding mature tap roots in field pits ranging from 0.7 to 1.5 cm in diameter). Finally, the average life of each black greasewood population is assumed to be 100 years (Section 2.3 of the SWCA report). With the first population instantaneously present at year 101 after final closure, a total of four populations of black greasewood plants on the final cover are evaluated. 3. For a typical area of the LLRW (or Mixed Waste) cover, 10% of that area is assumed to be covered by vegetated ground cover. Of the vegetated area, 35% represent black greasewood plants and the number of black greasewood plants was determined within that area. Each plant was assumed to have two tap roots, each with a diameter of 1.5 cm. That area was multiplied by four to conservatively account for multiple populations. Finally, the affected area was divided by the typical area under evaluation and converted to a percentage area impacted. This results in a calculated impact to 0.00683% of the typical area evaluated due to black greasewood tap roots. 4. The percentage area impacted was then used to perform a sensitivity analysis in the HELP model completed for the Mixed Waste embankment to evaluate the effect on infiltration through the Mixed Waste cover. This analysis was completed by Whetstone Associates in “Effects of Greasewood Root Penetration on the Mixed Waste Cell Cover,” September 13, 2001 (Whetstone, 2001). Two scenarios were modeled in this analysis: (a) the HDPE geomembrane remained intact, and (b) the HDPE geomembrane was fully degraded and non- existent (note that this case is a compounded abnormal scenario). (a) HDPE geomembrane intact (Model Run TVL) This sensitivity analysis modeled the HDPE geomembrane explicitly with a defect density of 3,504 one cm2 holes/acre (calculated from the percent impact found in item 3 above) and conservatively modeled the clay radon barrier as a barrier soil with a permeability of 5 x 10-6 cm/sec (increased two orders of magnitude from design characteristic). Degraded permeability of 5 x 10-6 cm/sec for the radon barrier over the entire embankment is not reasonably expected as a result of tap root penetration; however, this value was conservatively selected to demonstrate that degradation of the radon barrier will not reduce embankment performance. Results from this analysis yield an average annual infiltration rate of 0.0480 inches/year (0.122 cm/year). Since the previous infiltration calculations (Whetstone; November 22, 2000) were conservatively evaluated without an HDPE geomembrane there are no comparative performance values; however, this rate is well below the design criteria of 0.072 inches/year. (b) Fully degraded HDPE geomembrane (Model Run TV) This sensitivity analysis modeled the radon barrier as an “equivalent geomembrane barrier layer” having an effective saturated hydraulic conductivity value of 5 x 10-8 cm/sec, and containing a network of circular defects (wherein a discrete defect is EnergySolutions Mixed Waste Expansion Project Engineering Justification Report July 18, 2011 Revision 0 Page 47 of 59 assigned to correspond to each taproot). Each taproot was assumed to be 5.5 feet deep; i.e., to fully penetrate the radon barrier. Results from this analysis yield an average annual infiltration rate of 0.0770 inches/year (0.196 cm/year). This annual infiltration rate is greater than the design criteria infiltration rate of 0.072 inches/year; however, it is unreasonable to assume the membrane would become fully degraded due to the effects of vegetation prior to the end of the 100 year maintenance period, since institutional controls will be applied to minimize vegetation growth. Since the calculated vegetated cover annual infiltration rate is slightly higher than the non-vegetated cover annual infiltration rate, it is reasonable to assume that the annual average infiltration rate during the maintenance period could be conservatively modeled at 0.0480 inches/year (from scenario (a) above). Therefore, conservatively assuming that the geomembrane is completely degraded and that a complete black greasewood population is fully established at year 101, the average annual infiltration over the life of the embankment may be easily calculated:  in/year 0.071year 500 in/year 0.077years 400in/year 0480.0years 100  Therefore, under this compounded abnormal situation, with conservative assumptions, the cumulative average annual infiltration is below the design criteria. The following factors in the black greasewood evaluation strongly suggest that this abnormal condition evaluation is conservative. It will likely take a number of years following the end of institutional controls for late successional vegetation communities to become established on the Mixed Waste cover. The number of vegetation cycles on the Mixed Waste cover is conservative, as anecdotal information indicates that individual black greasewood plants may have a life span well in excess of 100 years. The assumption that late successional vegetation on the Mixed Waste cover will be established to a level equivalent to the native vegetation and distribution currently present is conservative, as the soil type approximated by an infilled rock erosion barrier is not typically dominated by black greasewood. Furthermore, the assumption that the geomembrane would be completely degraded is conservative, as supported by the research of Badu-Tweneboah, et. al. (1999) which found that HDPE geomembranes within an engineered embankment are expected to maintain a substantial degree of their initial integrity for as much as 500 years after closure. The abnormal condition evaluation has considered each tap root to be an open channel that does not heal during the life of the radon barrier. In reality, the tap root will consume water through evapotranspiration throughout the plant’s life. The sensitivity analysis of the tap root as an open channel is conservative in that the root will take a certain amount of time to degrade. Further, the radon barrier clays can reasonably be expected to perform some degree of “self-healing” or infilling of voids left as a taproot decays; however, the HELP sensitivity analysis assumes that each tap root instantly becomes a totally permeable void in the radon barrier. Further, the HELP sensitivity analysis assumes that the complete amount of degradation present at year 500 is instantaneously present as soon as the cover is completed; this approach overestimates potential negative effects. Projected Performance – Accident Conditions: No appropriate accident conditions exist for this design criteria. Performance References: Badu-Tweneboah, K., Tisinger, L.G., Giroud, J.P., and Smith, B.S., 1999. “Assessment of the Long-Term Performance of a Polyethylene Geomembrane and Containers in a Low-Level Radioactive Waste Disposal Landfill,” in Proceedings, Geosynthetics ’99, Boston, MA, April 28- 30, 1999. EnergySolutions Mixed Waste Expansion Project Engineering Justification Report July 18, 2011 Revision 0 Page 48 of 59 DOE, 1992. “Vegetation Growth Patterns on Six Rock-Covered UMTRA Project Disposal Cells.” (UMTRA – DOE/AL 400677.0000) Envirocare of Utah, Inc., November 1, 2000. “Vegetation Impact Calculation.” (Appendix K- 3 of the Class A/B/C Amendment Application dated December 13, 2000) SWCA, Inc., November 2, 2000. “Assessment of Vegetative Impacts on LLRW.” (Appendix K-2 of the Class A/B/C Amendment Application dated December 13, 2000) Whetstone Associates, Inc., November 22, 2000. “EnergySolutions Mixed Waste Cell Infiltration and Transport Modeling.” Whetstone Associates, Inc., September 13, 2001. Technical Memorandum, “Effects of Greasewood Root Penetration on the Mixed Waste Cell Cover.” Safety Factor: Under normal conditions, infiltration is not changed from previously reported values in Section 4.3.1.1. A safety factor is not applicable under this situation. Safety factors for abnormal conditions may be calculated as the ratio of the design criteria cumulative average annual infiltration (0.072 inches/year) to the calculated cumulative average annual infiltration values for the abnormal and compounded abnormal conditions. This yields safety factors of 0.072/0.048 = 1.50 for the abnormal condition with a geomembrane and 0.072/0.071 = 1.01 for the compounded abnormal condition without a geomembrane. 4.3.2 REDUCE EXPOSURE Projected Performance – Normal Conditions: Normal conditions for this required function and design criteria were not assessed because the performance is bounded by the abnormal conditions analysis. Projected Performance – Abnormal Conditions: The potential external dose rates from gamma radiation was evaluated using the Microshield computer code. Mircoshield is a model developed by Grove Engineering specifically to analyze shielding and estimate exposures from gamma radiation. A worst case scenario was developed using the input parameters of a 55-gallon drum composed of 11 curies of Co-60 placed on its side at the top of waste, just below the cover. The cover was assumed to have a total depth of 6.5 feet consisting of: 1. One foot of temporary cover; 2. One foot of 1E-6 radon barrier (note that the Mixed Waste cover design has two feet of 5E-8 radon barrier; the difference does not materially affect density of the radon barrier clays and therefore does not materially affect the analysis results); 3. One foot of 5E-8 radon barrier; 4. 0.5 feet of filter layer; 5. One foot of sacrificial soil; 6. 0.5 feet of filter layer; and, 7. 1.5 feet of rip rap. The calculation for the scenario described above projected a contact dose rate on top of the completed cover of 3.75 E-4 mR/hr. Multiplied over an entire year, this yields a dose rate of approximately 3 mrem. The deep dose equivalent (DDE) at the surface of the cover is well below the 100 mrem total effective dose equivalent (TEDE) even assuming that some of the TEDE was available for committed effective dose equivalent (CEDE). The Microshield output file was submitted under cover letter CD11-0123 on May 2, 2011 as Figure 1 to the Class A West License Amendment Request. EnergySolutions Mixed Waste Expansion Project Engineering Justification Report July 18, 2011 Revision 0 Page 49 of 59 Projected Performance – Accident Conditions: No appropriate accident conditions exist for this design criteria. Performance References: EnergySolutions, May 2, 2011. “License Amendment Request: Class A West Embankment,” (Submitted under cover letter CD11-0123). Safety Factor: The safety factor associated with this required function of the cover is the ratio of the design criteria and the computer program output dose rate. This yields a factor of safety of 33.34 for the abnormal condition assessed. 4.3.3 ENSURE COVER INTEGRITY 4.3.3.1 Mitigate Differential Settlement Differential settlement within the cover is directly related to the waste placement strategies employed within the embankment. Differential settlement within the layers of the cover itself was not considered to be a major design issue, as the layers of the cover system are constructed to narrow engineering specifications. For these reasons, please refer to the waste placement discussion of section 4.2.1. 4.3.3.2 Prevent Internal Erosion Projected Performance – Normal Conditions: Rock Cover Design Calculations for the Mixed Waste embankment were provided as part of the earlier Mixed Waste Engineering Justification Report (Envirocare, 2001). In addition to other calculations related to the rock cover design, these calculations provide an analysis of the interstitial velocities associated with the clay/rock interface. These calculations take no credit for the presence of HDPE liner and geotextile between the clay and rock. This analysis uses the slopes and dimensions of the embankment (see Appendix B) and the hydraulic conductivity of the Type B Filter (from the Whetstone November 22, 2000, report) to calculate a maximum interstitial velocity at the interface. Maximum calculated interstitial flow velocities are 9.7 x 10-3 ft/sec on the top slope and 9.7 x 10-2 ft/sec on the side slopes. These velocities are maximum possible velocities at the interface and are not dependent on the amount of water flow. These velocities are both orders of magnitude below the design criteria velocity (3 ft/sec). Therefore, neither significant erosion of the radon barrier clay nor migration of fines between layers will occur. Piping calculations have been assessed for the abnormal saturated condition. This condition bounds the normal conditions; therefore, a normal condition analysis is not necessary. Projected Performance – Abnormal Conditions: Abnormal conditions are not applicable for the internal water velocity calculations because the calculated interstitial velocity at the clay/rock interface is a maximum theoretical velocity. Any further water will flow in areas above the interface and will not cause erosion of the clay layer. Internal erosion related to upward migration of finer material within dissimilar layers of the embankment cover has been evaluated using the assessment included in the Filter Requirements and Design section of the DOE Technical Approach Document. Table 4.5 of the DOE document describes criteria for filter design based upon percent fines (material  a No. 4 sieve) within the filter material. The document is unclear which parameter is necessary from each layer; instead, the document simply provides the following ratio for filter design (for fines less than 15 percent): D15/D85 ≤ 4 From an examination of the situation, it appears that this equation is referring to the D15 of the smaller graded material and the D85 of the larger graded material. EnergySolutions Mixed Waste Expansion Project Engineering Justification Report July 18, 2011 Revision 0 Page 50 of 59 Examining the interfaces present within EnergySolutions’ proposed cover design, this equation could be applied to the sacrificial soil/upper (Type A) filter interface and the upper (Type A) filter/rip-rap erosion barrier interface. The only other interfaces present within the proposed cover involve the HDPE geomembrane for which this analysis is irrelevant. In order to account for differing gradations between filter and soil materials from different borrow sources, evaluation of specific materials against the above calculations is required. Please refer to Drawing 11009-W05 in Appendix B. Test frequency for evaluating gradation of the Type A filter zone and sacrificial soil are provided in the revised CQA/QC Manual. Therefore, upward migration of the underlying layers will not occur due to material specifications and quality assurance/quality control measures. Utilizing the gradations provided in Drawing 11009-W05 in Appendix B, (summarized in Table 3) and plotting on a grain size distribution plot, the following parameters are obtained for the other layers of interest: Layer D15 (mm) D85 (mm) Upper (Type A) Filter 22 ~110 Type A Rip-rap ~55 ~280 Type B Rip-rap ~22 ~76 For the upper filter layer/Type A rip-rap interface (side slopes), the ratio is: 22/280 = 0.079 For the upper filter layer/Type B rip-rap interface (top slopes), the ratio is: 22/76 = 0.29 Therefore, all interface ratios are within the design criteria tolerances provided by the DOE. As noted above, the technical guidance document is unclear which parameter is necessary from each layer. Therefore, this same analysis may be performed using the D15 from the larger graded material and the D85 from the smaller graded material. For the upper filter layer/Type A rip-rap interface (side slopes), the ratio is: 55/110 = 0.50 For the upper filter layer/Type B rip-rap interface (top slopes), the ratio is: 22/110 = 0.20 Again, all interface ratios are within the design criteria. EnergySolutions Mixed Waste Expansion Project Engineering Justification Report July 18, 2011 Revision 0 Page 51 of 59 Projected Performance – Accident Conditions: No appropriate accident conditions exist for this design criteria. Performance References: Cedergren, H. R., 1977. Seepage, Drainage and Flow Nets, second edition, John Wiley and Sons, New York, NY, pp 178-182. Envirocare of Utah, Inc., March 9, 2001. “Rock Cover Design Calculations.” Sherard, J.L., L.P. Dunnigan, 1985. “Filters and Leakage Control in Embankment Dams and Impoundments” ASCE National Convention Proceedings, Denver Colorado. US Army Corps of Engineers, 30 September 1986 (original) 30 April 1993 (change 1). “Manual EM1110-2-1091: Engineering and Design - Seepage Analysis and Control for Dams.” DOE, December, 1989. “Technical Approach Document, Revision II,” UMTRA-DOE/AL 050425.0002. EnergySolutions, Inc., Drawing Series 11009 (Appendix B). Whetstone Associates , Inc., November 22, 2000. “Mixed Waste Cell Infiltration and Transport Modeling.” Safety Factor: The safety factor of the internal water velocity over the radon barrier clay is the ratio of the calculated interstitial velocities to the design criteria (minimal erosion) velocity. Accordingly, for the top slope, the safety factor is 3 / 9.7 x 10-3 = 307.91 and for the side slope the safety factor is 3 / 9.7 x 10-2 = 30.79. Safety factors for piping are not applicable. The design criteria is met through material specifications and ensured through quality assurance/quality control measures. Safety factors for upward migration of fines is the design criteria for the calculations (4) over the calculated ratios for each interface with the exception of the sacrificial soil/upper filter layer interface which will be met through material specifications and ensured through quality assurance/quality control measures. The factor of safety for the upper filter zone/Type A rip-rap (side slope) interface is 4/0.079 ≈ 50.63. The factor of safety for the upper filter zone/Type B rip- rap (top slope) interface is 4/0.29 ≈ 13.79. 4.3.3.3 Material Stability/External Erosion Projected Performance – Normal Conditions: The basis of the design calculations is a 1000 year life span considering all conditions, both normal and abnormal. Therefore, the normal conditions are bounded by the abnormal condition analyses below. Projected Performance – Abnormal Conditions: Rock Cover Design Calculations based on NUREG-1623 presented as part of the earlier Mixed Waste Engineering Justification Report (Envirocare, 2001) provide an analysis of the minimum average rip-rap rock size (D50) that the embankment should use for a 1000-year minimum life span. These calculations account for effects of the one-hour probable maximum precipitation (PMP) including erosion velocities that will be attained over the embankment from this design event. This analysis concludes that, for angular rock, the average rock size (D50) for the top slope area needs to be at least 0.33 inches and D50 for the side slopes needs to be at least 2.13 inches. Applying correction factors for rounded rock, the D50 for the top slope area needs to be at least 0.50 inches and D50 for the side slope areas needs to be at least 3.0 inches. Embankment specifications (Drawing 11009-W05, Rev. 0, in Appendix B of this Engineering Justification Report) call for a top slope (Type “B” Rip Rap) D50 of 1.25 inches and a side slope (Type “A” Rip Rap) D50 of 4.5 inches. Both of these design values exceed the design criteria for rock stability for both angular and rounded rock. EnergySolutions Mixed Waste Expansion Project Engineering Justification Report July 18, 2011 Revision 0 Page 52 of 59 Section 2.6 of the Mines Group Report also provides an analysis of the “stable particle size diameter” and the associated “depth of scour” required to achieve a stable rock armor formation. The analyses from this report focused on the side slopes of the embankment. The report used four different methods to evaluate the required parameters. From these analyses, the stable particle diameter ranged from 1.10 inches (27.89 mm) to 1.96 inches (49.89 mm) with an average diameter of 1.50 inches (38 mm). The depth of scour is the minimum depth of rock that must be placed in order to form a stable rock armor. In the Mines Group analysis, the calculated depth of scour ranged from 0.06 to 0.67 feet. The design Rip Rap thickness is 1.5 feet. Therefore, stability of the Rip Rap layer will be maintained. NUREG-1623 also provides criteria to assess the suitability of rock to be used as protective cover based on laboratory tests that determine the physical characteristics of the rock. The reference states that the rock should be screened for about three-to-five durability test methods to classify the rock as being of poor, fair, or good quality. For non-critical areas including top and side slopes of embankments, it is recommended that a rock quality score less than 50 be rejected. EnergySolutions currently applies these rock scoring criteria in construction of the Class A embankment cover (as provided in the LLRW and 11e.(2) CQA/QC Manual). Specific rock quality criteria are found in the CQA/QC Manual, Work Element: Filter Zone; Specifications: Quality of Rock and Quality Assurance Sampling; as well as Work Element: Rock Erosion Barrier; Specifications: Quality of Rock and Quality Assurance Sampling. Similar language is provided in the revised Mixed Waste CQA/QC Manual. The following four durability tests will be performed on the rock: Specific Gravity – ASTM C-128 Absorption (%) – ASTM C-127 Sodium Soundness (%) – ASTM C-88 L. A. Abrasion (%) – ASTM C-131 & ASTM C-535 Therefore, the design criteria is met through material specifications and ensured through quality assurance/quality control measures. Projected Performance – Accident Conditions: No appropriate accident conditions exist for this design criteria. Performance References: The Mines Group, November 14, 2000. “Technical Report for the Mixed Waste Facility Cover Design.” Envirocare of Utah, Inc., March 9, 2001. “Rock Cover Design Calculations.” NUREG-1623, February, 1999. “Design of Erosion Protection for Long-Term Stabilization”, draft report for comment. EnergySolutions, December 15, 2010. LLRW and 11e.(2) Construction Quality Assurance/Quality Control (CQA/QC) Manual, revision 25d Safety Factor: The safety factor associated with the rip-rap sizing aspect of this design criteria is calculated as the ratio of the design rock D50 to the calculated minimum acceptable rock D50. Utilizing the more conservative parameters calculated as part of a Mixed Waste Engineering Justification Report in 2001 (Envirocare, 2001) for rounded rock, safety factors of 1.25 / 0.5 = 2.50 for the top slope and 4.5 / 3.0 = 1.5 for the side slopes are attained. The safety factor associated with the depth of the rock layer is the design depth divided by the calculated stable depth of scour. This ranges from 1.5/0.67 = 2.23 to 1.5/0.06 = 25.00. EnergySolutions Mixed Waste Expansion Project Engineering Justification Report July 18, 2011 Revision 0 Page 53 of 59 A safety factor is not appropriate for the rock quality scoring aspect of this design criteria. 4.3.4 ENSURE STRUCTURAL STABILITY 4.3.4.1 Settlement Projected Performance – Normal Conditions: The normal conditions associated with the design criteria of Long Term Cover Drainage are bounded by the abnormal conditions analysis. The total expected settlement for the Mixed Waste embankment is estimated in AMEC, 2011 to be approximately 16 inches at the center of the embankment. This calculated settlement is well below the design criteria of 6.24 feet. Projected Performance – Abnormal Conditions: For cover drainage to cease, the slope of the embankment (2%) would have to be overcome through differential settlement. One method of assessing slope reversal is to evaluate distortion calculations as the slope between areas of greater and lesser settlement. Examining the differential settlement analyses described in Section 4.2.1 above, the maximum abnormal distortion is 0.005. This distortion is significantly less than the minimum design slope of 2% (0.02). Therefore, the design criteria is met for long term cover drainage under abnormal conditions. A second confirmation that slope reversal will not occur can be reached using total settlement analysis. Drawing 11009-W01 shows that there is approximately 5 feet of drop between control points at the crest of the embankment and the embankment shoulder. The maximum total settlement reported above is approximately 1.25 feet. This is considerably less than the 5 foot elevation difference between the crest of the embankment and the shoulder. Accordingly, even if maximum total settlement occurred at the crest, the slope of the cover would be reduced but not entirely flattened or reversed. Total settlement involving the abnormal condition of one extremely heavy column (concrete column) within the embankment was examined in the AMEC Settlement Evaluation for the LLRW (B/C) Embankment dated November 8, 2000. The analysis, provided in Figure 4 and summarized in Table 5 of the AMEC report, shows that this abnormal situation would increase the total settlement of the embankment by only 2 to 2.5 inches. Adding this increased settlement to the worst-case settlement calculated for the Mixed Waste embankment (16 inches) yields an abnormal total settlement of 18.5 inches. This is well below the design criteria of 6.24 feet and therefore meets the design criteria for this abnormal condition. Projected Performance – Accident Conditions: No appropriate accident conditions exist for this design criteria. Performance References: AGEC, October 19, 1998. “Closure Cap Stability and Settlement Estimate Mounding - Mixed Waste Disposal Facility.” The Mines Group, November 14, 2000. “Technical Report for the Mixed Waste Facility Cover Design.” AMEC, November 8, 2000.” “Settlement Evaluation: Proposed LLRW and Mixed Waste Embankments.” (Appendix I-2 of the Class A/B/C Amendment Application dated December 13, 2000) Safety Factor: Since the cover slope is 2%, the safety factors associated with Long Term Cover Drainage is equivalent to the safety factors associated with the differential settlement analysis in Section 4.2.1 (normal = 5.00; abnormal = 4.00). EnergySolutions Mixed Waste Expansion Project Engineering Justification Report July 18, 2011 Revision 0 Page 54 of 59 For the maximum total settlement, a safety factor may be calculated for both the normal and the abnormal conditions by assessing the ratio of the design criteria settlement (6.24 feet = 75 inches) to the actual projected settlements. Therefore, the safety factor for the normal condition is 75 / 16 = 4.69 and the safety factor for the abnormal condition is 75 / 18.5 = 4.05. 4.3.4.2 Maintain Slope Stability A detailed seismic stability and deformation analysis was completed for the Mixed Waste embankment in a 1998 AGEC stability and settlement report with further explanations and confirmation in a 1999 AGEC addendum report. Furthermore, the Mines Group also provided a stability analysis in Section 2.7 of their report (Mines Group, 2000). The AGEC reports both assumed a cover consisting of six (6) feet of compacted clay, a flexible membrane liner, 0.5 foot of filter and drainage materials, and 1.5 feet of rock erosion barrier. These reports were performed to justify an increase in embankment height proposal that was being considered at that time. The 1998 report examines both a four (4) foot and an eight (8) foot height increase compared to the height originally permitted for the embankment (at the shoulder) and the 1999 report refines the analysis to a five (5) foot height increase (the actual height increase approved by DSHW). The Mines Group (2000) report incorporated the additional HDPE and drainage net layers into their analysis and provided similar results to the AGEC analyses, thereby verifying the results. The Mines Group (2000) report is the only one of the three reports that expands the analysis to include safety factors within the waste pile and at the liner interface within the cover. Projected Performance – Normal Conditions: The 1998 AGEC stability and settlement report calculated static factors of safety of 2.7 and 2.5 for the full height of the embankment at corresponding height increases of four (4) and eight (8) feet respectively. The 1999 report further refined the analysis and calculated a static factor of safety of 2.54 for the actual height of the embankment with the approved height increase of five feet. The Mines Group (2000) report calculated a static factor of safety of 2.28 through the waste column. Therefore, the design criteria (safety factor > 1.5) was met under all analyses. The Mines Group (2000) report also calculated the slope stability between a drainage net and the textured HDPE geomembrane within the cover system. This analysis resulted in a calculated safety factor of 2.14. Additionally, in a technical letter report dated October 18, 2001, the Mines Group assessed the slipping potential for other interfaces within the cover system. Other interfaces examined include the textured HDPE/Radon clay barrier interface, the textured HDPE/non-woven geotextile interface, and the non-woven geotextile/lower (Type B) filter interface. In each instance it was determined that the interface analyzed in the 2000 report provided a conservative estimate of slipping potential within the embankment cover system. All of the interfaces examined in the 2001 report yielded larger factors of safety than the interface analyzed in the 2000 report. In their 2001 report, the Mines Group also analyzed an infinite slope/seepage condition utilizing the conservative normal condition 100-year, 6-hour rainfall event. Results from this analysis yielded a safety factor against slipping of 1.87. Projected Performance – Abnormal Conditions: The referenced reports utilize an array of seismic coefficients to analyze the stability of the embankment. From past analyses of seismic conditions at the site (see Section 3.4.2 of the LARW License Renewal Application dated March 16, 1998 for a thorough review of site seismology), the maximum bedrock acceleration has been conservatively assessed at 0.37g. The 1998 AGEC analysis calculated safety factors of 1.05 and 1.07 using a seismic coefficient of 0.25g. This seismic coefficient corresponds to the 5,000 year recurrence interval and is much greater than 50% of the maximum bedrock acceleration (0.185g). The 1999 AGEC report provides seismic safety factors of 1.78 for a 475 year recurrence interval (0.08g) and 1.07 for a 5,000 year recurrence interval (0.25g). The Mines Group (2000) analysis utilized a seismic coefficient of 0.185g (50% of the maximum bedrock acceleration) and EnergySolutions Mixed Waste Expansion Project Engineering Justification Report July 18, 2011 Revision 0 Page 55 of 59 calculated a safety factor of 1.16 through the waste column. Therefore, the performance of the Mixed Waste embankment meets both stability abnormal design criteria (safety factor > 1.0 for 50% of the maximum bedrock acceleration and > 1.3 for a 475 year recurrence interval). The Mines Group (2000) report also calculated a factor of safety for the interface between a drainage net and the textured HDPE geomembrane under seismic conditions. This calculated safety factor is 1.07. As explained above, other interfaces in the cover system were examined in the 2001 Mines Group report. All other interfaces yielded higher calculated factors of safety than the original interface examined in the 2000 report. The Mines Group (2000) report also provided an infinite slope analysis to simulate saturated conditions within the cover materials. The minimum safety factor calculated through this analysis was 1.88 at a saturation depth of 2.0 feet (the depth of the Rip Rap and upper filter layers). A further analysis of saturated conditions was conducted with results presented in the 2001 Mines Group report. Additionally, the safety factor related to a pseudo-static acceleration equal to one- half of the maximum acceleration (0.185g) was calculated for the properties of the HDPE geomembrane. Results from this analysis predicted a factor of safety of 1.00 against slipping. This factor of safety meets the design criteria for this scenario. Furthermore, based upon the maximum magnitude of the nearest capable fault (Puddle Valley, magnitude 6.6; see Appendix J of EnergySolutions’ License Renewal Application dated March 16, 1998), a more realistic pseudo-static ground acceleration would be between 0.1g and 0.15g (October 22, 2001 conversation between Tim Orton and Kenneth Myers, P.E.; the MINES Group). Accordingly, the predicted factor of safety is based on conservative assumptions; under actual situations, a factor of safety greater than one is likely. Therefore, design criteria were met or exceeded under all normal, abnormal, and accident conditions. Projected Performance – Accident Conditions: The Mines Group (2001) also examined the effects of the abnormal PMP event coinciding with the accidental filter blockage condition. This analysis yielded a calculated safety factor of 1.77. Performance References: AGEC, October 19, 1998. “Closure Cap Stability and Settlement Estimate Mounding - Mixed Waste Disposal Facility.” AGEC, July 29, 2999. “Response: Division of Solid and Hazardous Waste Mixed Waste Disposal Facility Mounding.” The Mines Group, November 14, 2000. “Technical Report for the Mixed Waste Facility Cover Design.” The Mines Group, October 18, 2001. “Round 2 Interrogatories on Proposed Revisions to Mixed Waste Embankment Cover; Engineering Justification Report (Rev.1 July 25, 2001) Response to Interrogatory MW 1/2, Attachment I, Item 1.” Safety Factor: The minimum static factor of safety under normal conditions was calculated to be 2.14. The normal condition infinite slope/seepage condition analysis yielded a factor of safety of 1.87. Pseudo-static factors of safety were calculated as: 1.07 for a seismic coefficient of 50% of the maximum bedrock acceleration; 1.07 for a seismic coefficient associated with a 5,000 year recurrence interval; and 1.78 for a seismic coefficient associated with a 475 year recurrence interval. A conservative normal saturated condition compounded by seismic forces yielded a safety factor of 1.00. Compounding the abnormal and accidental conditions for the infinite slope/seepage condition resulted in a calculated safety factor of 1.77. EnergySolutions Mixed Waste Expansion Project Engineering Justification Report July 18, 2011 Revision 0 Page 56 of 59 4.4 DRAINAGE SYSTEMS 4.4.1 PROVIDE SITE DRAINAGE 4.4.1.1 Facilitate flow away from the embankment Projected Performance – Normal Conditions: Calculations are provided in Appendix A that use simple geometry, the slope of the ditches, and Manning’s formula to arrive at design flow velocities and storage capacity of the drainage ditch system surrounding the Mixed Waste embankment as well as downstream drainage ditch systems surrounding the 11e.(2) embankment. Table 7, below, provides the drainage flows associated with the normal storm event (25-year, 24- hour; 1.9-inches) and abnormal storm event (100-year; 2.4-inches) for all ditches designed for the expanded Mixed Waste embankment (see Appendix A). Table 7 Ditch Flow Freeboards – Expanded Mixed Waste Ditch Normal Condition Abnormal Condition Depth Runoff in Ditch (ft) Freeboard (ft) Depth Runoff in Ditch (ft) Freeboard Eastern Ditch 1.60 1.40 1.66 1.34 Southern Ditch 1.75 1.25 1.82 1.18 Western Ditch 1.74 1.26 1.81 1.19 Northern Ditch 0.98 2.02 1.02 1.98 During the normal storm event, water would rise in the southern ditch to a maximum depth of 1.75 feet, leaving 1.25 feet of freeboard in the ditch above the water level. This maximum storage amount would occur approximately fifteen minutes into the 24-hour event and would quickly subside to lower water levels within the ditch. Therefore, the ditch is adequately designed to contain the normal storm event with more than two feet of freeboard. Appendix A provides downstream drainage ditch storage capacity calculations for the southern and western ditches of the 11e.(2) embankment. Section 6.2 of Appendix A illustrates that these two ditches are the limiting factors for site-wide drainage. Table 8 below illustrates the drainage flows associated with the normal storm event (25-year, 24-hour; 1.9-inches) and abnormal storm event (100-year; 2.4-inches) for the southern and western 11e.(2) ditches. Table 8 Ditch Flow Freeboards – 11e.(2) Ditch Normal Condition Abnormal Condition Depth Runoff in Ditch (ft) Freeboard (ft) Depth Runoff in Ditch (ft) Freeboard Western 11e.(2) Ditch 3.44 0.56 3.57 0.43 Southern 11e.(2) Ditch 3.61 0.39 3.75 0.25 As illustrated in Table 8 (see Appendix A), water will rise in these ditches to a maximum depth of approximately 3.61 feet, leaving approximately 0.39 feet of freeboard. EnergySolutions Mixed Waste Expansion Project Engineering Justification Report July 18, 2011 Revision 0 Page 57 of 59 Projected Performance – Abnormal Conditions: Drainage flow calculations around the Mixed Waste embankment associated with the abnormal storm event are presented in Table 7 above and in Appendix A, attached. Under the abnormal storm event (100-year, 24 hour; 2.4-inches), the ditches will fill to a maximum depth of 1.82 feet, leaving approximately 1.18 feet of freeboard. This maximum storage amount would occur approximately fifteen minutes into the 24-hour event and would quickly subside to lower water levels within the ditch. Therefore, the ditch is adequately designed to contain runoff associated with the abnormal storm event. Downstream calculations in Appendix A project maximum ditch flow depths of 3.75 feet in the ditches surrounding the 11e.(2) embankment. Therefore, the site drainage ditches are adequately designed to contain the runoff from the abnormal storm event. Projected Performance – Accident Conditions: A downstream blockage in the drainage ditch would lead to a localized flood situation in that section of the ditch. Once the water level reaches the outside berm height, water would disperse away from the embankment as overland flow. Please refer to the discussion of projected performance under flood conditions provided in Section 4.4.1.2 below. Performance References: EnergySolutions, July 5, 2011. “Clive Facility Total Ditch Flow Calculations, revision 0.” (Appendix A) Safety Factor: Safety factors have been calculated for both the drainage ditch system surrounding the Mixed Waste embankment and the downstream 11e.(2) ditch system. For the normal condition, the safety factors are calculated as the ratio of projected freeboard to the design criteria for freeboard. For the normal event, the design criteria is a freeboard of at least one (1) foot in the ditches surrounding the Mixed Waste embankment; the calculated, minimum freeboard adjacent to the Mixed Waste embankment during the normal event is 1.25 feet; therefore, the safety factor is 1.25/1 = 1.25. Downstream, in the 11e.(2) drainage ditch system, the design criteria is that the ditch will be able to contain the flow; therefore, for the four foot ditch, the factor of safety is 4.00/3.61 = 1.11. For the abnormal event, the design criteria is that the ditch be able to contain the flow; no freeboard is necessary. The calculated flow during the abnormal event within the Mixed Waste drainage ditch system is 1.82 feet and downstream in the 11e.(2) drainage ditch system is 3.75 feet. Therefore, since the ditch is four (4) feet deep, the safety factor associated with the Mixed Waste ditch system is 4.00/1.82 = 2.20. Downstream, in the 11e.(2) drainage system, the safety factor is calculated as 4.00/3.75 = 1.06. 4.4.1.2 Minimize Infiltration Under Flood Conditions Projected Performance – Normal Conditions: Performance related to normal conditions for the complementary aspect of minimizing infiltration under flood conditions have not been analyzed because the performance is bounded by the abnormal conditions analysis. Projected Performance – Abnormal Conditions: The HEC 1 and HEC 2 Modeling analysis provided by Bingham Environmental (presented in Appendix KK of the LARW License Renewal Application of March 16, 1998) develops the Probable Maximum Flood (PMF) for the watershed encompassing the Clive site. This analysis calculates depth of the PMF across the site at approximately one-foot above grade (ground elevation); the depth of the 100-year flood will be considerably less. Since the toe of waste is at ground elevation and the ditch is below ground elevation, the abnormal condition flood would fill the ditch and surrounding area to a vertical depth of one-foot up the side of the embankment. This depth is less than the design criteria depth of 5.6 feet. EnergySolutions Mixed Waste Expansion Project Engineering Justification Report July 18, 2011 Revision 0 Page 58 of 59 Therefore, the abnormal flood event will not cause water to accumulate above the waste and the drainage system is adequately designed to minimize infiltration of water through the waste under both normal and abnormal conditions. Projected Performance – Accident Conditions: The HEC-1 and HEC-2 modeling referenced above calculates a maximum depth of flood during the PMF of approximately one-foot above grade (ground elevation). The ditch is below grade; however, the inspection road is constructed to a height one-foot above grade (see Drawing 11009-W04, Rev. 0 in Appendix B). Under an accident condition, the entire ditch to the height of the inspection road could be infilled with silt. This would, in effect, elevate the ground surface at the edge of the embankment by one foot compared to local native grade. Accordingly, the PMF would not encroach directly upon the embankment under these conditions; the infilled ditches and inspection road would remove floodwaters to a horizontal distance of 58 feet from the embankment. Thus, infilling of drainage ditches would improve protection of the embankment from PMF conditions. All drainage ditches downstream of the Mixed Waste embankment have the same four-foot deep “V” ditch design as the Mixed Waste embankment ditches. Furthermore, the Mixed Waste embankment has higher base elevation ditches than the downstream ditches because the entire ditch system (and native grade of the site) slopes to the south and west (see Drawing 11009-W01, Rev. 0 in Appendix B). Therefore, since the downstream ditch systems have a lower base elevation and the same design, complete siltation of downstream ditches in the site drainage network will promote less accumulation of water within the Mixed Waste ditch system than the discussion above. For an accident flooding condition, the analysis of the Mixed Waste drainage ditch system alone is the limiting case. Performance References: Bingham Environmental, November 26, 1996. “HEC-1 and HEC-2 Analysis LARW Application for License Renewal EnergySolutions Disposal Facility Clive, Utah.” (Appendix KK to License Renewal Application dated March 16, 1998). Safety Factor: The safety factor relating to the abnormal and accident conditions is calculated as the ratio of the maximum design height that the water could attain to the actual PMF maximum water height above the clay liner. For the abnormal condition, the safety factor is 5.6 feet / 1 foot = 5.60. For the accident condition of the drainage ditch and road completely silted over, the safety factor can also be calculated as 5.6/1 = 5.6. 4.4.2 ENSURE DITCH INTEGRITY Projected Performance – Normal Conditions: Perimeter ditch calculations (Envirocare, 2001) provide an analysis of the interstitial velocities associated with the clay/rock interface. The calculations use the slope of the ditches and the gradation parameters of the Type A Filter rock to obtain a maximum interstitial velocity at the interface. Calculated maximum interstitial flow velocities are 2.4 x 10-3 ft/sec and 1.3 x 10-3 ft/sec for each section of the perimeter ditch, depending on the slopes associated with each section. These velocities are maximum possible velocities at the interface and are not dependent on the amount of water flow. These velocities are both orders of magnitude below the design criteria velocity at which erosion may occur (3 ft/sec). Therefore, significant erosion of the ditch clay surface will not occur. Projected Performance – Abnormal Conditions: Abnormal conditions are not applicable for the internal water velocity calculations because the calculated interstitial velocity at the clay/rock interface is a maximum velocity. Any further water will flow in areas above the interface and will not affect erosion of the clay layer. Durability of the riprap rock cover (rock scoring criteria) within the perimeter ditches is not a concern since the ditches will only be operational during the activity life of the facility. EnergySolutions Mixed Waste Expansion Project Engineering Justification Report July 18, 2011 Revision 0 Page 59 of 59 Additionally, during this time regular inspections will enable detection and corrective action, should deterioration of the rock occur. Projected Performance – Accident Conditions: No appropriate accident conditions exist for this design criteria. Performance References: The Mines Group, November 14, 2000. “Technical Report for the Mixed Waste Facility Cover Design, Clive, Utah.” Envirocare of Utah, Inc., March 8, 2001. “Perimeter Ditch Calculations.” Safety Factor: The safety factor of the internal water velocity over the clay within the ditch is the ratio of the calculated interstitial velocities to the design criteria (minimal erosion) velocity. Therefore, the safety factor is the ratio of the design criteria maximum velocity (3 ft/sec) to the maximum calculated interstitial velocity (2.4 x 10-3 ft/sec). This factor of safety is at least 1250 for all conditions. 4.5 BUFFER ZONE 4.5.1 PROVIDE SITE MONITORING Projected Performance – Normal Conditions: Under the normal condition of no releases, the monitoring network within the buffer zone will not be necessary and the design of the system will be adequate. Projected Performance – Abnormal Conditions: The Groundwater Infiltration and Transport modeling shows that no contaminants will reach the monitoring wells within 500 years. The groundwater monitoring wells are located 90 feet from the edge of waste, within the boundary of the buffer zone (94 feet). If contaminants are detected at the monitoring wells within the 100- year monitoring period, remediation measures could be easily accommodated due to the extremely slow linear velocity of the groundwater (2.74 ft/year, calculated in Section 7.2.4 of the Infiltration and Transport Modeling report). In addition, EnergySolutions’ property boundary is at least 100 feet from the edge of waste on the northwest corner of the Mixed Waste cell (i.e., distance to the Vitro property owned by DOE) and at least 300 feet in all other directions. This allows adequate space as well as time for implementation of remedial measures. Projected Performance – Accident Conditions: No appropriate accident conditions exist for this design criteria. Performance References: Whetstone Associate, Inc., November 22, 2000. “EnergySolutions Mixed Waste Cell Infiltration and Transport Modeling.” Safety Factor: A safety factor is not applicable to this Principal Design Feature. Appendix A Ditch Flow Calculations CLIVE FACILITY DRAINAGE DITCH FLOW CALCULATIONS MIXED WASTE LANDFILL CELL July 5, 2011 For Utah Division of Solid and Hazardous Waste 195 North 1950 West Salt Lake City, UT 84114-4880 EnergySolutions, LLC 423 West 300 South, Suite 200 Salt Lake City, UT 84101 July 5, 2011 MWLC/Clive Ditch Flow Calculations Page 2 of 34 1.0 INTRODUCTION The following calculations are completed to determine the adequacy of the Clive facility ditch systems to contain runoff associated with both normal and abnormal precipitation events that could occur during operations. This assessment was performed specifically for the expansion of the Mixed Waste Landfill Cell (MWLC) to add sumps 11A, 11B, 12A, and 12B. Calculations have been made to address flows from the Mixed Waste drainage area through the MWLC ditch system as well as flows from the entire Clive drainage area through the 11e.(2) ditch system to the outlet into the desert. After operations cease, EnergySolutions will take no credit for the remaining ditch systems. As currently planned, drainage from completed portions of all covers will be directed throughout the ditch systems to an outlet in the southwestern corner of the site. At this point, the water is dispersed into the desert south of the facility. A simple depiction of the drainage plan is provided in Figure 1. Figure 1. Simple schematic of the site with general drainage flows (not to scale) 1115’ 11e.(2) Class A West 25 6 8 . 5 ’ 17 7 5 ’ 2259.9’ 2250’ Vitro LARW 26 5 0 ’ 1 8 7 0 ’ 1310’ MW 863.2 1 9 1 8 . 4 ’ 2260.1’ 25 6 8 . 6 ’ Figure 1 also provides details on the length/width geometry of each of the embankments that are part of this drainage system. With the exception of the Vitro embankment and the MWLC, the dimensions presented in Figure 1 are the waste limit dimensions for each embankment. The stated dimensions of the Vitro Embankment are for the entire run-off area. The dimensions for the MWLC are the ditch centerline dimensions and represent a worst-case rectangle for the footprint of the embankment (ignoring the design ‘jog’ in the northwest corner). Four separate dimensions have been given for the Class A West embankment as its design dimensions are slightly different for each side. Water from all embankments will flow through the 11e.(2) drainage ditches before reaching the drainage system outlet. The outlet channel is much larger than the ditches feeding it; therefore, the performance requirement of the entire system will depend on the performance characteristics of the 11e.(2) drainage ditches. 2.0 FLOW VELOCITIES To begin the performance assessment of the MWLC and 11e.(2) drainage ditches, the peak flow velocities for the ditches must be calculated. These flow velocities are based upon the flow area and slope of the ditches. For this analysis, all ditches of concern have triangular geometry: the MWLC ditches are 3-feet deep and 30-feet wide; the 11e.(2) ditches are 4-feet deep by 40-feet wide (5H:1V side slopes). This geometry is the minimum requirement for the ditches and thereby provides the minimum (most conservative) cross-sectional flow area within the ditches. Drawing 11009-W02 shows design dimensions for the MWLC ditches. Table 1 provides the corner elevations from drawing 11009-W02 and the results of the slope calculations for each side of the MWLC. All slopes (foot of drop/foot of length) are between 1.5E-3 and 1.6E-3. Table 1. MWLC Ditch Slope Evaluation Corner Ditch Invert Elevation Side Length (ft) Drop in Elevation (ft) Slope (ft/ft) NE 4275.70 East 1918.4 2.98 1.55E-03 SE 4272.72 South 863.2 1.34 1.55E-03 SW 4271.38 West 1919.9 3.00 1.56E-03 NW 4274.38 North 829.7 1.32 1.59E-03 Slopes for the 11e.(2) ditch system may be discerned from the ditch centerline elevations provided in Drawing 9420-4. For the 11e.(2) ditch system, the following slopes are calculated based on ditch centerline drop in elevation across the ditch centerline length July 5, 2011 MWLC/Clive Ditch Flow Calculations Page 3 of 34 (note that the dimensions of the ditch centerline are the edge of waste dimensions provided in Figure 1 plus 42.5 feet in all directions): North/South Lengths: 1.1 feet / 2335 feet = 4.71 x 10-4 foot/foot East/West Lengths: 0.9 feet / 1860 feet = 4.84 x 10-4 foot/foot Based on these slopes, and using Manning’s Formula, the maximum flow rate for each ditch length may be calculated. Manning’s Formula is: 2/13/2486.1 SARnQ where, Q = flow in cubic feet per second n = Manning’s Coefficient of Roughness (= 0.035 for ditches with earth, stone, and weeds) A = cross-sectional area of flow (ft2) R = hydraulic radius; area of flow divided by wetted perimeter (WP) (ft) S = slope (ft/ft) Since the side slopes are 5:1, the water in the ditch, at the surface, will extend five times the depth (d) in each direction. Therefore, the cross-section will be a triangle with a base of 2(5d) and a height of d. Therefore, the cross-sectional area will be ½ x 2(5d)d = 5d2. Furthermore, a single side of the wetted perimeter is the hypotenuse of the right triangle created by the depth, d, and the surface, 5d. Therefore, the wetted perimeter is 2 x (d2 + 25d2)½ = 2(26) ½d. Then, the hydraulic radius, R, is A/WP = 5d2/(2(26) ½d) ~ 0.49d. The literature value for the Manning’s Coefficient of Roughness for ditches with earth, stone, and weeds (0.035) may be found in several references; the particular reference used for this analysis was “Environmental Engineering Reference Manual for the PE Exam”, by Michael R. Lindeburg, PE, 2001, Professional Publications, Inc. This value may alternatively be calculated based on the diameter of rocks in the ditch. An equation has been derived by Abt, et. al. in 1988 (“Development of Riprap Design Criteria by Riprap Testing in Flumes: Phase II,” NUREG/CR-4651). This equation only constitutes effects to Manning’s Coefficient of Roughness due to the size of the rock within the ditch. The formula is as follows: n = 0.0456 * (D50*S)0.159 July 5, 2011 MWLC/Clive Ditch Flow Calculations Page 4 of 34 July 5, 2011 MWLC/Clive Ditch Flow Calculations Page 5 of 34 The design of the ditch consists of a six inch thick Type A filter layer placed on the ground surface within the ditch and one foot of Type A RipRap overlying this filter layer. Utilizing the Abt equation above, and noting that the D50 of the Type A Filter Rock within the drainage ditches is 40 mm (1.57 inches), the Coefficient of Roughness based on the filter rock is calculated as: n = 0.0186 for the north and south ditches and n = 0.0168 for the east and west ditches. Comparatively, the D50 of the Type A RipRap is 4.5 inches. Therefore, the Coefficient of Roughness based on the RipRap rock may be calculated as: n = 0.0220 for the north and south ditches and n = 0.0200 for the east and west ditches. Therefore, the literature value for the Manning’s Coefficient of Roughness provides a conservative estimate of the flow of water in the ditches. Tables 2 and 3 on the next page display the calculated flow rates of the MWLC and 11e.(2) ditch systems using Manning’s formula. The peak flows that each of the ditch systems is able to manage is highlighted in bold. Table 2. Ditch Flow Rates for the CAW Drainage Ditches East (S = 0.15%) South (S = 0.15%) West (S = 0.16%) North (S = 0.16%) Height of water in Ditch (ft) Flow area in Ditch A (ft2) Wetted Perimeter WP (ft) Hydraulic Radius R=A/WP Flow Rate Q (ft3/sec) Flow Rate Q (ft3/min) Flow Rate Q (ft3/sec) Flow Rate Q (ft3/min) Flow Rate Q (ft3/sec) Flow Rate Q (ft3/min) Flow Rate Q (ft3/sec) Flow Rate Q (ft3/min) 0.5 1.25 5.10 0.25 0.82 49.03 0.81 48.86 0.82 49.17 0.82 49.47 1.0 5.00 10.20 0.49 5.19 311.33 5.17 310.24 5.20 312.24 5.23 314.10 1.5 11.25 15.30 0.74 15.30 917.90 15.25 914.70 15.34 920.59 15.43 926.06 2.0 20.00 20.40 0.98 32.95 1976.80 32.83 1969.93 33.04 1982.61 33.24 1994.38 2.5 31.25 25.50 1.23 59.74 3584.19 59.53 3571.71 59.91 3594.70 60.27 3616.06 3.0 45.00 30.59 1.47 97.14 5828.28 96.80 5808.00 97.42 5845.38 98.00 5880.11 Table 3. Ditch Flow Rates for the 11e.(2) Drainage Ditches North/South (S = 0.05%) East/West (S = 0.05%) Height of water in Ditch (ft) Flow area in Ditch A (ft2) Wetted Perimeter WP (ft) Hydraulic Radius R=A/WP Flow Rate Q (ft3/sec) Flow Rate Q (ft3/min) Flow Rate Q (ft3/sec) Flow Rate Q (ft3/min) 0.5 1.25 5.10 0.25 0.45 27.07 0.46 27.44 1.0 5.00 10.20 0.49 2.86 171.89 2.90 174.21 1.5 11.25 15.30 0.74 8.45 506.80 8.56 513.63 2.0 20.00 20.40 0.98 18.19 1,091.46 18.44 1,106.16 2.5 31.25 25.50 1.23 32.98 1,978.95 33.43 2,005.61 3.0 45.00 30.59 1.47 53.63 3,217.98 54.36 3,261.34 3.5 61.25 35.69 1.72 80.90 4,854.10 81.99 4,919.49 4.0 80.00 40.79 1.96 115.51 6,930.33 117.06 7,023.70 July 5, 2011 MWLC/Clive Ditch Flow Calculations Page 6 of 34 3.0 STORM EVENTS The performance of the drainage ditches to contain runoff is only important during the active life of the facility (approximately 25 years). Upon closure, the drainage ditches will either be removed or become silted in to allow sheet flow across the site over the natural grade of the area. Therefore, a reasonable maximum normal storm event over the active life of the ditches is the 25 year, 24 hour storm event (1.9 inches). A reasonable abnormal event during the active life of the ditches is the 100 year, 24 hour storm event (2.4 inches). Both of these storm events are depicted in the isopluvial maps of NOAA Atlas 2, Volume VI (1973; see web sight www.wrcc.dri.edu/pcpnfreq.html). These maps contain 6 and 24 hour events with return frequencies of 100 and 25 years. Region specific equations to calculate storm distributions are also provided in the text accompanying these maps. The rainfall amount at one hour during the 100- and 25-year events may be calculated using the equations provided in the text of NOAA Atlas 2. For the region of Utah that Clive is located in (region 2), the equation is:     hr-24 hr-6hr-60.7890.322hr-1 The variables (6-hr) and (24-hr) are the precipitation amounts read from the isopluvial maps. Empirical equations have been developed for the 15-min, 30-min, 2-hour, and 3-hour events. These equations are based upon the previously derived 1-hour and 6-hour events: 15-min = 0.57 x (1-hr) 30-min = 0.79 x (1-hr) 2-hr = 0.299 x (6-hr) + 0.701 x (1-hr) 3-hr = 0.526 x (6-hr) + 0.474 x (1-hr) The 12-hour distribution may be easily found using graphical methods, based upon the 6- hr and 24-hr events, described in the NOAA text. Using the equations and methods described above, the storm distributions shown in Table 4 may be obtained. Over the short active life span of the drainage ditches, it would not be reasonable to assume larger storm events such as the Probable Maximum Precipitation (PMP). These larger storm events are more appropriately utilized in the longer life elements of the embankment design such as the rock cover over the embankment. July 5, 2011 MWLC/Clive Ditch Flow Calculations Page 7 of 34 Table 4. Storm Distributions Time (minutes) Normal Event (25 Year Storm) (inches) Abnormal Event (100 Year Storm) (inches) 15 0.65 0.73 30 0.90 1.00 60 1.14 1.27 120 1.21 1.40 180 1.27 1.50 360 1.40 1.70 720 1.65 2.05 1440 1.90 2.40 4.0 DRAINAGE AREA As mentioned previously, with the exception of the Vitro embankment and the MWLC, the dimensions presented in Figure 1 are the waste limit dimensions for each embankment. The stated dimensions for the Vitro embankment are for the entire run-off area and the dimensions for the MWLC are the ditch centerline dimensions (from drawing 11009-W02). For the 11e.(2) embankment, the distance between the waste limits and the centerline of the ditch is 42.5 feet (8.5 feet of cover times 5 for a 5:1 side slope). For the LARW embankment, the distance between the waste limits and the centerline of the ditch varies between 15 and 35 feet, but a more conservative 35 feet is used in the area calculation. For the Class A West embankment, the distance between the waste limits and the centerline of the ditch is a 15.3 feet (see Drawing 10014-C03). Further, for all embankments except Vitro, the drainage area conservatively extends another 45.6 feet beyond the centerline of the ditch to the outer edge of the inspection road (see drawing 10014-C03). Using the information described above, the actual drainage dimensions and areas for each embankment are provided in Table 5. Note that using the outer edge of the inspection road provides a conservatively large drainage area for these calculations and the distance is much larger than anticipated for the MWLC, which is described in drawing 11009-W04. Note also that the previous MWLC drainage area was 1,664,744.64 square feet. July 5, 2011 MWLC/Clive Ditch Flow Calculations Page 8 of 34 Table 5. Drainage Areas Embankment Length (E-W) (ft) Width (N-S) (ft) Drainage Area (ft2) Class A West 2,381.8 2,690.35 6,407,875.63 Vitro 1,310 2,650 3,471,500.00 LARW 1,276.2 2,031.2 2,592,217.44 11e.(2) 2,426.2 1,951.2 4,734,001.44 MW 954.4 2,009.6 1,917,962.24 Summing these drainage areas, the total drainage area is 19,123,556.75 square feet. Run-off Coefficient, C = 0.5 (for earth with stone surface). Thus, the Site Weighted Total Drainage Area = (19,123,556.75)(0.5) = 9,561,778.38 ft2 The run-off coefficient has been estimated based upon a worst-case review of literature values for similar surfaces (see “Environmental Engineering Reference Manual for the PE Exam”, by Michael R. Lindeburg, PE, 2001, Professional Publications, Inc. The value of 0.5 provides a conservative estimation for drainage from the embankments at the Clive facility. The Cover Test Cell (CTC) is a simulation of the designed embankment cover. The CTC has been providing run-off data for nine years. Calculated run-off data from the CTC combined with precipitation data from the site weather station provides an observed run-off coefficient for the embankment cover design. The data for the nine years of operation are shown in Table 6. Table 6. CTC Run-Off Data Year: 2002 2003 2004 2005 2006 2007 2008 2009 2010 Run-off (in/yr): 0.112 0.000 0.727 1.341 0.838 0.335 0.000 0.112 0.009 Precip (in/yr): 5.75 7.46 9.06 10.16 7.39 8.29 3.20 8.12 9.00 Run-off Coefficient: 0.019 0.000 0.080 0.132 0.113 0.040 0.000 0.014 0.001 Disregarding the two years that no run-off was observed (2003 and 2008), the average annual run-off coefficient is calculated at 0.057. Therefore, the literature value run-off coefficient of 0.5 used in these calculations provides conservative drainage results. July 5, 2011 MWLC/Clive Ditch Flow Calculations Page 9 of 34 5.0 DITCH VOLUME EQUATIONS To obtain a realistic volume, the geometry and slope of the ditches must be reviewed together. This is necessary because the ditches are sloped so that the height of water in each ditch will increase as you progress down slope within the ditch. The calculations of ditch volume require an understanding of the geometry within each ditch. To illustrate the geometry, Figure 2 provides a cross-section view of a ditch with the geometric features described below highlighted. Figure 2. Ditch Cross-Section (1) (2) A1 A2 hf H LS L The following parameters are depicted in Figure 2 and explained further below: H = height of water in the ditch at the lowest point of the ditch L = length of the ditch LS = length of ditch times slope of ditch = height of water in the pyramid section of the ditch (see below) hf = height of water in the frustum section of the ditch (see below) A1 = triangular plane of the frustum section of the ditch (see below) A2 = trapezoidal plane of the frustum section of the ditch (see below) To calculate the volume of each ditch section, the ditch must be separated into two solid geometric figures, as depicted in Figure 2. (1) A three-sided pyramid created by visualizing a zero-slope plane that bisects the ditch such that the plane rests upon the ditch centerline at the upper end of the slope. This, when extended across the length of the ditch, creates a pyramid below the plane that has a triangular base on the down slope side of the ditch with a water height equal to the length of the ditch multiplied by the slope. (2) The volume above this plane is a frustum of a second pyramid with the upper end of the slope consisting of a triangular area and the lower end of the slope a trapezoid formed from the visualized plane mentioned above up to the height of the ditch. July 5, 2011 MWLC/Clive Ditch Flow Calculations Page 10 of 34 The volume of each section of the ditch may be calculated by first calculating these two separate volumes and adding them together. Using geometry and algebra, the volume within any ditch may be calculated from three factors: the length of the ditch (L), the height of water in the ditch at the low point of the ditch (H), and the slope of the ditch (S). The derivations of the required formula’s follow: (1) Pyramid Section Volume of pyramid, Vpyramid = 1/3 (base area) (length) The height of water at the base of the pyramid (lowest point of the ditch) is: h = LS The base area, Abase = ½ (width) h Since all of the ditches have 5:1 slopes on both sides, the width of water within the ditch is simply 2 x 5 x h = 10h = 10LS. Therefore, Abase = ½ (10LS) LS = 5(LS)2; and Vpyramid = 1/3 (5(LS)2) L = 5/3(L3S2). Note in the case that the ditch height, H, is lower than the triangle height, h, then length of water up the ditch, L may be represented as L = H/S, and Vpyramid = 5/3(H/S)3S2 = 5/3(H3/S) (2) Frustum Section Volume of frustum,LAAAA3/1V 2121frustum where A1 and A2 are the areas of the two planes at the top and bottom of the frustum as depicted in Figure 2 (A1 is the area of the triangle on the upslope end of the ditch and A2 is the area of the trapezoid on the downslope end of the ditch). Since the base height of water in the frustum at the downslope end is LS (the height of water in the pyramid section), the height of water in the frustum, hf, may be correlated to the height of water in the ditch at the downstream end, H, using the following equation: hf = H – LS A1 = triangle = ½ (width)hf = ½ (10hf)hf = 5(H – LS)2. July 5, 2011 MWLC/Clive Ditch Flow Calculations Page 11 of 34 July 5, 2011 MWLC/Clive Ditch Flow Calculations Page 12 of 34 A2 = trapezoid = ½ (Wbottom + Wtop)hf Wbottom and Wtop are the widths of the triangular ditch at the bottom and top of the trapezoid. From the geometry of the ditch: Wbottom = width of pyramid section = 10LS and Wtop = 10H Therefore, A2 = ½ (10LS + 10H)(H – LS) = 5(H + LS)(H – LS); and Vfrustum = 1/3 L {5(H – LS)2 + 5(H + LS)(H – LS) + [5(H – LS)2(5(H + LS)(H – LS))]½}. Upstream Storage Some account must be made for water that backflows up into upslope ditch sections. In general, this backflow will not exceed the pyramid section of the upslope ditch. Furthermore, the upslope ditch will have a different slope from the down slope ditch; this slope will be designated S2. The pyramid volume for the upslope ditch section uses the same formula derived for the down slope section; however, the length that liquid travels up the ditch into this upslope area (L2) is slightly different: 2 2 S LS-HL Further, Abase for this ditch section is equivalent to A1 from the trapezoid section of the down slope ditch. Therefore,          2 3 2 2 uppyramid,S LS-H3/5S LS-HLS-H53/1V In the event that the height of water in the upslope ditch exceeds the height of the pyramid section, L2 will equal the design length of the upslope ditch and the upslope ditch pyramid section will be completely full: Vpyramid,up = 5/3(L23S22). Furthermore, an additional volume within the upslope ditch frustum section should also be accounted for. The height of water in the upslope frustum section, hf, is calculated as follows: hf = H – LS – L2S2 and the other calculations are the same as above to give: A1,up = 5(H – LS – L2S2)2 Wbottom,up = 10L2S2 Wtop,up = 10(H – LS) A2,up = 5(H – LS + L2S2)(H – LS – L2S2) Vfrustum,up may then be calculated using these areas and the frustum volume equation provided previously. Total Storage The total storage volume is the sum of all the appropriate individual ditch volumes: Vtotal = Vpyramid + Vfrustum + Vpyramid,up + Vfrustum,up These equations have been used to define ditch storage volume in the calculations that follow. 6.0 DRAINAGE CALCULATIONS 6.1 MWLC Ditches From design drawing 11009-W02, the ditches around the MWLC are highest at the northeast corner and flow south-west or west-south to the discharge point in the southwest corner. Half of the flow from the MWLC will be directed through the northern and western drainage ditches; the other half will be directed through the eastern and southern drainage ditches. Individual ditches will have different drainage areas associated with them. Using design drawing 11009-W02 as a basis, an approximation of the amount of drainage area for each ditch may be calculated. The northing and easting points for the edge of waste may be used to approximate the rectangular edge of waste dimensions as 1821.8 feet by 766.4 feet (yielding an approximate area of 1,396,227.52 ft2). The triangular portion in the northern quadrant of the MWLC has an area of ½(157.5+225.7)(766.4) = 146,842.24 ft2. Assuming each triangular section is equal and each trapezoidal section is equal, the surface area of the triangular sections (north and south) is approximately 10.5% of the total surface area and the surface area of the trapezoidal sections (east and west) is approximately 39.5% of the total surface area. Using these approximations as a basis, along with the total MWLC drainage July 5, 2011 MWLC/Clive Ditch Flow Calculations Page 13 of 34 area of 1,917,962.24 ft2, the drainage areas associated with each ditch are as follows: East Ditch = 757,595.08 ft2 South Ditch = 757,595.08 + 201,386.04 = 958,981.12 ft2 West Ditch = 958,981.12 ft2 North Ditch = 201,386.04 ft2 These drainage area values are used in the drainage calculations. The calculations that follow perform a simple mass balance over each ditch: Flow into the ditch – Flow out of the ditch = Accumulated Storage The accumulated flow into the ditch is calculated by multiplying the accumulated rainfall by the drainage area associated with that particular ditch. The flow out of the ditch (volume of water discharged) is calculated by multiplying the flow rate at a specific depth (as calculated in Section 2.0) by the elapsed time of rainfall. The volume of each ditch at a specified depth (H) is calculated using the equations derived in Section 5.0 of this report. The volume associated with this depth may be compared to the required storage volume calculated by subtracting the available discharge from the accumulated flow into the ditch. Iterations based on the depth of water in the ditch may be made to equate these two volumes, providing a maximum depth of flow within the ditch for a particular storm event. 6.1.1. Eastern MWLC Ditch NORMAL STORM EVENT The weighted drainage area (using the Run-Off Coefficient described in Section 4.0) for the eastern MWLC ditch is 378,797.54 ft2. From drawing 11009-W02, the eastern MWLC ditch length is 1918.4 feet. For the worst-case normal storm event, an iterative method is used to equate the required storage with the available storage volume at a specific water depth within the eastern MWLC ditch. This depth was found to be 1.60 feet at the lowest portion of the ditch (SE corner). Using this depth and the slope of the eastern MWLC ditch (1.55E-3, see Table 1), the discharge flow rate was found to be approximately 1,093 ft3/min. The storage volume at this height is approximately 4,395 ft3 and does not even fill the pyramid portion of the ditch. Table 7a provides a summary of the calculations. July 5, 2011 MWLC/Clive Ditch Flow Calculations Page 14 of 34 Table 7a. MWLC Eastern Ditch Normal Storm Event Drainage Flows Ditch flow at 1.60 foot depth Lapsed Time (min) Accum. Rainfall (in) Accum. Flow (ft3) Available Discharge (ft3) Required Storage (ft3) 15 0.65 20,438 16,397 4,042 30 0.90 28,327 32,793 None 60 1.14 35,857 65,587 None 120 1.21 38,349 131,174 None 180 1.27 40,242 196,761 None 360 1.40 44,193 393,522 None 720 1.65 52,085 4,207,285 None 1440 1.90 59,976 8,414,571 None These calculations demonstrate that during the worst-case normal condition 25-year, 24-hour storm event (1.9 inches of precipitation), the maximum volume retained in storage within the MWLC eastern ditch is approximately 4,042 ft3. This maximum volume occurs approximately 15-minutes into the storm event and decreases rapidly. This volume equates to a depth of water at the deepest portion of the ditch (SE Corner) of approximately 1.60 feet, leaving approximately 1.40 feet of freeboard. ABNORMAL STORM EVENT For the abnormal storm event, as above, an iterative method is used to equate the required storage with the available storage volume at a specific waster depth within the eastern MWLC ditch. This depth was found to be 1.66 feet at the lowest portion of the ditch (SE corner). Using this depth and the slope of the eastern MWLC ditch (1.55E-3, see Table 1), the discharge flow rate was found to be approximately 1,206 ft3/min. The storage volume at this height is approximately 4,908 ft3 and does not even fill the pyramid portion of the ditch. Table 7b provides a summary of the calculations. July 5, 2011 MWLC/Clive Ditch Flow Calculations Page 15 of 34 Table 7b. MWLC Eastern Ditch Abnormal Storm Event Drainage Flows Ditch flow at 1.66 foot depth Lapsed Time (min) Accum. Rainfall (in) Accum. Flow (ft3) Available Discharge (ft3) Required Storage (ft3) 15 0.65 22,889 18,088 4,800 30 0.90 31,723 36,176 None 60 1.14 40,155 72,352 None 120 1.21 44,194 144,705 None 180 1.27 47,260 217,057 None 360 1.40 53,663 434,114 None 720 1.65 64,711 4,207,285 None 1440 1.90 75,760 8,414,571 None These calculations demonstrate that during the abnormal condition 100- year, 24-hour storm event (2.4 inches of precipitation), the maximum volume retained in storage within the MWLC eastern ditch is approximately 4,800 ft3. This maximum volume occurs approximately 15-minutes into the storm event and decreases rapidly. This volume equates to a depth of water at the deepest portion of the ditch (SE Corner) of approximately 1.66 feet, leaving approximately 1.34 feet of freeboard. 6.1.2. Southern MWLC Ditch NORMAL STORM EVENT The weighted drainage area (using the Run-Off Coefficient described in Section 4.0) for the southern MWLC ditch is 479,490.56 ft2. From drawing 11009-W02, the southern MWLC ditch length is 863.2 feet. For the worst-case normal storm event, an iterative method is used to equate the required storage with the available storage volume at a specific water depth within the southern MWLC ditch. This depth was found to be 1.75 feet at the lowest portion of the ditch (SW corner). Using this depth and the slope of the southern MWLC ditch (1.55E-3, see Table 1), the discharge flow rate was found to be approximately 1,388 ft3/min. The storage volume at this height is approximately 5,312 ft3. Furthermore, small amounts of water will also backflow into the eastern MWLC ditch, creating a total available volume of approximately 5,386 ft3 at this depth. Table 8a provides a summary of the calculations. July 5, 2011 MWLC/Clive Ditch Flow Calculations Page 16 of 34 Table 8a. MWLC Southern Ditch Normal Storm Event Drainage Flows Ditch flow at 1.75 foot depth Lapsed Time (min) Accum. Rainfall (in) Accum. Flow (ft3) Available Discharge (ft3) Required Storage (ft3) 15 0.65 25,871 20,816 5,055 30 0.90 35,857 41,632 None 60 1.14 45,388 83,264 None 120 1.21 48,544 166,528 None 180 1.27 50,939 249,792 None 360 1.40 55,941 499,584 None 720 1.65 65,930 4,205,911 None 1440 1.90 75,919 8,411,822 None These calculations demonstrate that during the worst-case normal condition 25-year, 24-hour storm event (1.9 inches of precipitation), the maximum volume retained in storage within the MWLC southern ditch is approximately 5,055 ft3. This maximum volume occurs approximately 15-minutes into the storm event and decreases rapidly. This volume equates to a depth of water at the deepest portion of the ditch (SW Corner) of approximately 1.75 feet, leaving approximately 1.25 feet of freeboard. ABNORMAL STORM EVENT For the abnormal storm event, as above, an iterative method is used to equate the required storage with the available storage volume at a specific waster depth within the southern MWLC ditch. This depth was found to be 1.82 feet at the lowest portion of the ditch (SW corner). Using this depth and the slope of the southern MWLC ditch (1.55E-3, see Table 1), the discharge flow rate was found to be approximately 1,541 ft3/min. The storage volume at this height is approximately 5,947 ft3. Furthermore, small amounts of water will also backflow into the eastern MWLC ditch, creating a total available volume of approximately 6,066 ft3 at this depth. Table 8b provides a summary of the calculations. July 5, 2011 MWLC/Clive Ditch Flow Calculations Page 17 of 34 Table 8b. MWLC Southern Ditch Abnormal Storm Event Drainage Flows Ditch flow at 1.82 foot depth Lapsed Time (min) Accum. Rainfall (in) Accum. Flow (ft3) Available Discharge (ft3) Required Storage (ft3) 15 0.65 28,973 23,111 5,862 30 0.90 40,155 46,222 None 60 1.14 50,829 92,444 None 120 1.21 55,942 184,888 None 180 1.27 59,823 277,332 None 360 1.40 67,928 554,665 None 720 1.65 81,913 4,205,911 None 1440 1.90 95,898 8,411,822 None These calculations demonstrate that during the abnormal condition 100- year, 24-hour storm event (2.4 inches of precipitation), the maximum volume retained in storage within the MWLC eastern ditch is approximately 5,862 ft3. This maximum volume occurs approximately 15-minutes into the storm event and decreases rapidly. This volume equates to a depth of water at the deepest portion of the ditch (SE Corner) of approximately 1.82 feet, leaving approximately 1.18 feet of freeboard. 6.1.3. Western MWLC Ditch NORMAL STORM EVENT The weighted drainage area (using the Run-Off Coefficient described in Section 4.0) for the western MWLC ditch is 479,490.56 ft2. From drawing 11009-W02, the western MWLC ditch length is 1919.9 feet (1,559.6’ + 360..’). For the worst-case normal storm event, an iterative method is used to equate the required storage with the available storage volume at a specific water depth within the western MWLC ditch. This depth was found to be 1.74 feet at the lowest portion of the ditch (SW corner). Using this depth and the slope of the western MWLC ditch (1.56E-3, see Table 1), the discharge flow rate was found to be approximately 1,371 ft3/min. The storage volume at this height is approximately 5,619 ft3 and does not even fill the pyramid portion of the ditch. Table 9a provides a summary of the calculations. July 5, 2011 MWLC/Clive Ditch Flow Calculations Page 18 of 34 Table 9a. MWLC Western Ditch Normal Storm Event Drainage Flows Ditch flow at 1.74 foot depth Lapsed Time (min) Accum. Rainfall (in) Accum. Flow (ft3) Available Discharge (ft3) Required Storage (ft3) 15 0.65 25,871 20,568 5,304 30 0.90 35,857 41,135 None 60 1.14 45,388 82,271 None 120 1.21 48,544 164,541 None 180 1.27 50,939 246,812 None 360 1.40 55,941 493,624 None 720 1.65 65,930 4,219,731 None 1440 1.90 75,919 8,439,462 None These calculations demonstrate that during the worst-case normal condition 25-year, 24-hour storm event (1.9 inches of precipitation), the maximum volume retained in storage within the MWLC western ditch is approximately 5,304 ft3. This maximum volume occurs approximately 15-minutes into the storm event and decreases rapidly. This volume equates to a depth of water at the deepest portion of the ditch (SW Corner) of approximately 1.74 feet, leaving approximately 1.26 feet of freeboard. ABNORMAL STORM EVENT For the abnormal storm event, as above, an iterative method is used to equate the required storage with the available storage volume at a specific waster depth within the western MWLC ditch. This depth was found to be 1.81 feet at the lowest portion of the ditch (SW corner). Using this depth and the slope of the western MWLC ditch (1.56E-3, see Table 1), the discharge flow rate was found to be approximately 1,523 ft3/min. The storage volume at this height is approximately 6,325 ft3 and does not even fill the pyramid portion of the ditch. Table 9b provides a summary of the calculations. July 5, 2011 MWLC/Clive Ditch Flow Calculations Page 19 of 34 Table 9b. MWLC Western Ditch Abnormal Storm Event Drainage Flows Ditch flow at 1.81 foot depth Lapsed Time (min) Accum. Rainfall (in) Accum. Flow (ft3) Available Discharge (ft3) Required Storage (ft3) 15 0.65 28,973 22,849 6,124 30 0.90 40,155 45,698 None 60 1.14 50,829 91,395 None 120 1.21 55,942 182,790 None 180 1.27 59,823 274,185 None 360 1.40 67,928 548,371 None 720 1.65 81,913 4,219,731 None 1440 1.90 95,898 8,439,462 None These calculations demonstrate that during the abnormal condition 100- year, 24-hour storm event (2.4 inches of precipitation), the maximum volume retained in storage within the MWLC western ditch is approximately 6,124 ft3. This maximum volume occurs approximately 15-minutes into the storm event and decreases rapidly. This volume equates to a depth of water at the deepest portion of the ditch (SW Corner) of approximately 1.81 feet, leaving approximately 1.19 feet of freeboard. 6.1.4. Northern MWLC Ditch NORMAL STORM EVENT The weighted drainage area (using the Run-Off Coefficient described in Section 4.0) for the northern MWLC ditch is 100,693.02 ft2. From drawing 11009-W02, the northern MWLC ditch length is 829.7 feet. For the worst-case normal storm event, an iterative method is used to equate the required storage with the available storage volume at a specific water depth within the northern MWLC ditch. This depth was found to be 0.98 feet at the lowest portion of the ditch (NW corner). Using this depth and the slope of the northern MWLC ditch (1.59E-3, see Table 1), the discharge flow rate was found to be approximately 299 ft3/min. The storage volume at this height is approximately 986 ft3 and does not even fill the pyramid portion of the ditch. Table 10a provides a summary of the calculations. July 5, 2011 MWLC/Clive Ditch Flow Calculations Page 20 of 34 Table 10a. MWLC Northern Ditch Normal Storm Event Drainage Flows Ditch flow at 0.98 foot depth Lapsed Time (min) Accum. Rainfall (in) Accum. Flow (ft3) Available Discharge (ft3) Required Storage (ft3) 15 0.65 5,433 4,490 943 30 0.90 7,530 8,980 None 60 1.14 9,532 17,959 None 120 1.21 10,194 35,918 None 180 1.27 10,697 53,878 None 360 1.40 11,748 107,755 None 720 1.65 13,845 4,257,845 None 1440 1.90 15,943 8,515,690 None These calculations demonstrate that during the worst-case normal condition 25-year, 24-hour storm event (1.9 inches of precipitation), the maximum volume retained in storage within the MWLC northern ditch is approximately 943 ft3. This maximum volume occurs approximately 15- minutes into the storm event and decreases rapidly. This volume equates to a depth of water at the deepest portion of the ditch (NW Corner) of approximately 0.98 feet, leaving approximately 2.02 feet of freeboard. ABNORMAL STORM EVENT For the abnormal storm event, as above, an iterative method is used to equate the required storage with the available storage volume at a specific waster depth within the northern MWLC ditch. This depth was found to be 1.02 feet at the lowest portion of the ditch (NW corner). Using this depth and the slope of the northern MWLC ditch (1.59E-3, see Table 1), the discharge flow rate was found to be approximately 333 ft3/min. The storage volume at this height is approximately 1,112 ft3 and does not even fill the pyramid portion of the ditch. Table 10b provides a summary of the calculations. July 5, 2011 MWLC/Clive Ditch Flow Calculations Page 21 of 34 Table 10b. MWLC Northern Ditch Abnormal Storm Event Drainage Flows Ditch flow at 1.02 foot depth Lapsed Time (min) Accum. Rainfall (in) Accum. Flow (ft3) Available Discharge (ft3) Required Storage (ft3) 15 0.65 6,084 4,995 1,089 30 0.90 8,433 9,991 None 60 1.14 10,674 19,981 None 120 1.21 11,748 39,962 None 180 1.27 12,563 59,943 None 360 1.40 14,265 119,887 None 720 1.65 17,202 4,257,845 None 1440 1.90 20,139 8,515,690 None These calculations demonstrate that during the abnormal condition 100- year, 24-hour storm event (2.4 inches of precipitation), the maximum volume retained in storage within the MWLC northern ditch is approximately 1,089 ft3. This maximum volume occurs approximately 15-minutes into the storm event and decreases rapidly. This volume equates to a depth of water at the deepest portion of the ditch (NW Corner) of approximately 1.02 feet, leaving approximately 1.98 feet of freeboard. 6.2 11e.(2) Ditches (Overall Site Drainage) Similar calculations were performed for the 11e.(2) ditches to ascertain if they could maintain the flow from the entire site during the normal and abnormal storm events. From knowledge of water flows at the site and examination of the general design in Figure 1 of this report, it is evident that each ditch only retains a portion of the water generated throughout the site. From this assessment, the drainage area associated with the 11e.(2) western ditch constitutes half of the completed 11e.(2) drainage area plus the Class A West (CAW) drainage area. Similarly, the 11e.(2) south ditch will manage waters associated with half of the completed 11e.(2) drainage area as well as from the Vitro, LARW, and MW drainage areas. As the western and southern 11e.(2) ditches are limiting, they are the only two ditches necessary to be examined to demonstrate that the ditch system is adequate to maintain site runoff. As described in Section 4.0, the distance between the waste limits (shown in Figure 1) and the centerline of the ditch is 42.5 feet. With this information, the length of the ditch system, at the centerline, around the 11e.(2) embankment is 8,390 feet, 2335 feet for both the northern and southern ditches and 1,860 feet for the eastern and western ditches. During the design storm events water will backflow into the “feeder” ditches from the other embankments around the site. The capacity of each of the ditches is July 5, 2011 MWLC/Clive Ditch Flow Calculations Page 22 of 34 dependent on the geometry of the ditch as described in Section 5.0 of this report. Utilizing these equations, the capacity of the 11e.(2) ditch system alone is approximately 386,331 ft3 when the low end (southwest corner) is at a four-foot depth. Backflow into the CAW ditch system adds another 108,297 ft3 to the capacity; backflow into the LARW embankment adds an additional 96,573 ft3 of capacity; backflow into the MWLC ditch system adds another 14,352 ft3, and backflow into the VITRO ditch system was estimated, assuming slopes within the VITRO ditches, as an additional 20,067 ft3 of capacity. Therefore, considering all potential backflow scenarios, the total storage capacity within the ditch system at the site is approximately 625,619 ft3. The backflow volume calculations provided in this section were performed using the pyramid and frustum equations described in Section 5.0 utilizing the following additional information: CAW North Ditch Length = 2290.5 feet CAW North Ditch Slope = 6.99E-4 CAW South Ditch Length = 2290.7 feet CAW South Ditch Slope = 6.98E-4 CAW East Ditch Length = 2599.2 feet CAW East Ditch Slope = 1.12E-3 CAW West Ditch Length = 2599.1 feet CAW West Ditch Slope = 1.12E-3 LARW North/South Ditch Lengths = 1,185 feet LARW East/West Ditch Length = 1,740 feet LARW West Ditch Slopes = 6.32E-4 LARW South Ditch Slope = 8.44E-4 LARW East Drop in Slope = 1.21E-3 LARW North Drop in Slope = 1.69E-3 VITRO South Ditch Length = 1,270 feet VITRO West Ditch Length = 2,610 feet VITRO South Ditch Slope = 1.57E-3 VITRO West Ditch Slope = 1.15E-3 The LARW information was obtained from the design drawings for the LARW embankment. The VITRO information was conservatively estimated based upon known drainage area lengths and the approximate drop in slope for known embankments running parallel with the respective ditches. The overall storage is conservative because it assumes all embankments are completed to design capacity, including the 11e.(2) embankment. July 5, 2011 MWLC/Clive Ditch Flow Calculations Page 23 of 34 6.2.1. Western 11e.(2) Ditch NORMAL STORM EVENT The weighted drainage area (using the Run-Off Coefficient described in Section 4.0) for the western 11e.(2) ditch includes the CAW drainage area and half of the 11e.(2) drainage area (0.5*(6,407,875.63 + 0.5*(4,734,001.44)) = 4,387,438 ft2). For the worst-case normal storm event, an iterative method is used to equate the required storage with the available storage volume at a specific water depth within the western 11e.(2) ditch. This depth was found to be 3.44 feet at the lowest portion of the ditch (SW corner). Using this depth and the slope of the western 11e.(2) ditch (4.84E-4), the discharge flow rate was found to be approximately 4,698 ft3/min. The storage volume at this height, including backflow into the 11e.(2) north, CAW west, CAW south, and CAW east ditches, is approximately 189,637 ft3. Table 11a provides a summary of the calculations. Table 11a. 11e.(2) Western Ditch Normal Storm Event Drainage Flows Ditch flow at 3.44 foot depth Lapsed Time (min) Accum. Rainfall (in) Accum. Flow (ft3) Available Discharge (ft3) Required Storage (ft3) 15 0.65 236,729 70,467 166,262 30 0.90 328,098 140,934 187,163 60 1.14 415,313 281,868 133,445 120 1.21 444,183 563,736 None 180 1.27 466,101 845,605 None 360 1.40 511,868 1,691,209 None 720 1.65 603,273 2,348,163 None 1440 1.90 694,678 4,696,326 None These calculations demonstrate that during the worst-case normal condition 25-year, 24-hour storm event (1.9 inches of precipitation), the maximum volume retained in storage within the western 11e.(2) ditch system (including backflow) is approximately 187,163 ft3. This maximum volume occurs approximately 30-minutes into the storm event and dissipates over the next hour. This volume equates to a maximum depth of water at the lowest portion of the ditch (SW Corner) of approximately 3.44 feet, leaving approximately 0.56 feet of freeboard. ABNORMAL STORM EVENT For the abnormal storm event, as above, an iterative method is used to equate the required storage with the available storage volume at a specific waster depth within the western 11e.(2) ditch. This depth was found to be 3.57 feet at the lowest portion of the ditch (SW corner). Using this depth July 5, 2011 MWLC/Clive Ditch Flow Calculations Page 24 of 34 and the slope of the western 11e.(2) ditch (4.84E-4), the discharge flow rate was found to be approximately 5,186 ft3/min. The storage volume at this height, including backflow into the 11e.(2) north, CAW west, CAW south, and CAW east ditches, is approximately 212,986 ft3. Table 11b provides a summary of the calculations. Table 11b. 11e.(2) Western Ditch Abnormal Storm Event Drainage Flows Ditch flow at 3.57 foot depth Lapsed Time (min) Accum. Rainfall (in) Accum. Flow (ft3) Available Discharge (ft3) Required Storage (ft3) 15 0.65 265,107 77,794 187,313 30 0.90 367,429 155,588 211,842 60 1.14 465,100 311,176 153,925 120 1.21 511,880 622,351 None 180 1.27 547,395 933,527 None 360 1.40 621,554 1,867,054 None 720 1.65 749,521 2,348,163 None 1440 1.90 877,488 4,696,326 None These calculations demonstrate that during the abnormal condition 100- year, 24-hour storm event (2.4 inches of precipitation), the maximum volume retained in storage within the western 11e.(2) ditch system (including backflow) is approximately 211,842 ft3. This maximum volume occurs approximately 30-minutes into the storm event and dissipates over the next hour. This volume equates to a maximum depth of water at the lowest portion of the ditch (SW Corner) of approximately 3.57 feet, leaving approximately 0.43 feet of freeboard. 6.2.2. Southern 11e.(2) Ditch NORMAL STORM EVENT The weighted drainage area (using the Run-Off Coefficient described in Section 4.0) for the southern 11e.(2) ditch includes the LLRW, MW, and Vitro drainage areas, and half of the 11e.(2) drainage area (0.5*(2,592,217.44 + 1,917,962.24 + 3,471,500.00 + 0.5*(4,734,001.44)) = 5,174,340 ft2). For the worst-case normal storm event, an iterative method is used to equate the required storage with the available storage volume at a specific water depth within the western 11e.(2) ditch. This depth was found to be 3.61 feet at the lowest portion of the ditch (SW corner). Using this depth and the slope of the southern 11e.(2) ditch (4.71E-4), the discharge flow rate was found to be approximately 5,272 ft3/min. The storage volume at this height, including backflow into the 11e.(2) east; LARW north, south, east, and west; Vitro south and west; July 5, 2011 MWLC/Clive Ditch Flow Calculations Page 25 of 34 and MW south, west, and east ditches, is approximately 230,071 ft3. Table 12a provides a summary of the calculations. Table 12a. 11e.(2) Southern Ditch Normal Storm Event Drainage Flows Ditch flow at 3.61 foot depth Lapsed Time (min) Accum. Rainfall (in) Accum. Flow (ft3) Available Discharge (ft3) Required Storage (ft3) 15 0.65 279,187 79,075 200,112 30 0.90 386,943 158,149 228,794 60 1.14 489,801 316,299 173,502 120 1.21 523,849 632,598 None 180 1.27 549,698 948,897 None 360 1.40 603,673 1,897,793 None 720 1.65 711,472 2,316,948 None 1440 1.90 819,271 4,633,896 None These calculations demonstrate that during the worst-case normal condition 25-year, 24-hour storm event (1.9 inches of precipitation), the maximum volume retained in storage within the southern 11e.(2) ditch system (including backflow) is approximately 228,794 ft3. This maximum volume occurs approximately 30-minutes into the storm event and dissipates over the next hour. This volume equates to a maximum depth of water at the lowest portion of the ditch (SW Corner) of approximately 3.61 feet, leaving approximately 0.39 feet of freeboard. ABNORMAL STORM EVENT For the abnormal storm event, as above, an iterative method is used to equate the required storage with the available storage volume at a specific waster depth within the southern 11e.(2) ditch. This depth was found to be 3.75 feet at the lowest portion of the ditch (SW corner). Using this depth and the slope of the southern 11e.(2) ditch (4.71E-4), the discharge flow rate was found to be approximately 5,835 ft3/min. The storage volume at this height, including backflow into the 11e.(2) east; LARW north, south, east, and west; Vitro south and west; and MW south, west, and east ditches, is approximately 261,558 ft3. Table 12b provides a summary of the calculations. July 5, 2011 MWLC/Clive Ditch Flow Calculations Page 26 of 34 Table 12b. 11e.(2) Southern Ditch Abnormal Storm Event Drainage Flows Ditch flow at 3.75 foot depth Lapsed Time (min) Accum. Rainfall (in) Accum. Flow (ft3) Available Discharge (ft3) Required Storage (ft3) 15 0.65 312,655 87,519 225,136 30 0.90 433,329 175,038 258,291 60 1.14 548,518 350,076 198,442 120 1.21 603,687 700,151 None 180 1.27 645,572 1,050,227 None 360 1.40 733,032 2,100,453 None 720 1.65 883,950 2,316,948 None 1440 1.90 1,034,868 4,633,896 None These calculations demonstrate that during the abnormal condition 100- year, 24-hour storm event (2.4 inches of precipitation), the maximum volume retained in storage within the western 11e.(2) ditch system (including backflow) is approximately 258,291 ft3. This maximum volume occurs approximately 30-minutes into the storm event and dissipates over the next hour. This volume equates to a maximum depth of water at the lowest portion of the ditch (SW Corner) of approximately 3.75 feet, leaving approximately 0.25 feet of freeboard. 7.0 PEAK RUN-OFF RATE The rational formula can be used to estimate the peak run-off rates from the embankments and determine if the MWLC and 11e.(2) ditches are designed sufficiently to contain these rates. To complete this analysis, it is first necessary to calculate the maximum length for the travel of water to the discharge point and then determine the time required for water to travel this maximum distance and reach the discharge point. This time of concentration (Tc)is determined from the following formula: Tc = 0.00013 L0.77 S-0.385 where L is the length in feet and S is the slope (foot/foot). 7.1 MWLC The maximum distance for water to travel within the MWLC ditch system is from the northern crest of the embankment (at the point of the northern triangular section), eastward down the top and side slopes to the ditch, and down the eastern and southern ditches to the discharge point in the southwest corner of the MWLC July 5, 2011 MWLC/Clive Ditch Flow Calculations Page 27 of 34 ditch system. The distance that water must travel can be broken down into four discrete sections: 1. East from northern crest to the shoulder of the MWLC; 2. Down the MWLC shoulder to the eastern ditch; 3. Through the eastern MWLC ditch to the southeast corner; and 4. Down the southern MWLC ditch to the southwest corner. The individual Tc’s may be calculated and summed to determine a total time of concentration. These calculations are described in Table 13. Table 13. MWLC Travel Time Calculations Section L (ft) S Tc (hrs) 1 224.9 0.02 0.038 2 206.7 0.20 0.026 3 1491.3 1.55E-3 0.437 4 863.2 1.53E-3 0.290 Total Tc =0.774 Therefore, the time it takes for water to travel the farthest distance within the MWLC watershed is approximately 0.77 hours (~ 46.4 minutes). It is only necessary to estimate the peak runoff flow rates during the abnormal condition, since it is the bounding condition. If the flow rates for the abnormal condition are within tolerance for the ditch system, then the normal condition will also be within tolerance. Extrapolating from the storm intensity data in Section 3.0, the storm intensity at 47.4 minutes is approximately 1.27 inches of rainfall. This equates to rainfall intensity (i) of 0.0273 inches/min or 2.27 x 10-3 feet/min. The rational formula, Q = CiA may now be used to calculate the flow rate from the embankment. As the flow is split from the beginning of this assessment (NE corner), only half of the MWLC drainage area is utilized in this calculation. The weighted drainage area for half of the MWLC is 479,490.56 ft2. Therefore, flow through the MWLC ditch system is calculated as: Q = (0.5)( 2.27 x 10-3)( 479,490.56) = 544.9 cfm From the ditch flow calculations in Section 2.0 of this report, this calculated flow would yield a runoff depth slightly less 1.24 feet in the SW corner outlet. July 5, 2011 MWLC/Clive Ditch Flow Calculations Page 28 of 34 7.2 11e.(2) Embankment – Total Site Drainage The maximum distance for water to travel through the embankment systems is from the same northern crest of the MWLC to the discharge point in the southwest corner of the 11e.(2) embankment ditch. This distance can be broken down into six discrete sections of water flow (the first four being those described above for the MWLC): 1. East from northern crest to the shoulder of the MWLC; 2. Down the MWLC shoulder to the eastern ditch; 3. Through the eastern MWLC ditch to the southeast corner; and 4. Down the southern MWLC ditch to the southwest corner. 5. Across the LARW southern ditch; 6. Through the southern 11e.(2) ditch. The transition areas (areas between embankments) may be ignored in the overall Tc calculations as the distances are very short and the slopes are rather large; therefore, the time spent in these sections will be inconsequential to the overall travel time. The Tc’s for the six sections described above may be calculated and summed to determine a total time of concentration. The Table 14 lists the calculated lengths and travel times for each water flow section and the total travel time for flow through the embankment systems. Table 14. MWLC Travel Time Calculations Section L (ft) S Tc (hrs) 1 224.9 0.02 0.038 2 206.7 0.20 0.026 3 1491.3 1.55E-3 0.437 4 863.2 1.53E-3 0.290 5 1185.0 8.44E-4 0.461 6 2335.0 4.71E-4 0.941 Total Tc =2.209 Therefore, the time for water to travel the farthest distance within the Clive embankments watershed is approximately 2.21 hours (~132.5 minutes). It is only necessary to estimate the peak runoff flow rates during the abnormal condition, since it is the bounding condition. If the flow rates for the abnormal condition are within tolerance for the ditch systems, then the normal condition will also be within tolerance. Extrapolating from the storm intensity data in Section 3.0 of this report, the storm intensity at 132.5 minutes is approximately 1.23 inches of rainfall. This equates to rainfall intensity (i) of 0.0093 inches/min or 7.72 x 10-4 feet/min. The rational formula, Q = CiA may now be used to calculate the individual flow rates from the Clive embankments watershed. The total drainage area for the July 5, 2011 MWLC/Clive Ditch Flow Calculations Page 29 of 34 southern ditch is described in Section 6.2.2 of this report as 5,174,340 ft2. Therefore, flow from the Clive embankment watershed to the southeast corner of the 11e.(2) ditch system is calculated as: Q = (0.5)(7.72 x 10-4)(5,174,340) = 1,996.6 cfm From the ditch flow calculations in Section 2.0 of this report, this calculated flow would yield a runoff depth slightly less 2.51 feet in the SW corner outlet. 8.0 OPERATIONAL DITCHES Prior to final closure of the facility, operational ditches will be constructed around the MWOB to allow drainage from completed portions of the cover. The operational ditches will be smaller than the final design “V” ditches, allowing more room for infrastructure that is already present around the perimeter of the MWLC. Operational ditches are described in Drawings 11009-W07 and 11009-W08. The geometry of the operational ditches is slightly different from the final cover drainage ditches. They will also be “V” ditches, but will have side slopes of 2:1 (H:V) and a design minimum depth of 2.5 feet. This design change alters the volume calculations presented in Sections 2.0 and 5.0 of this report. The slopes and ditch lengths are also altered, as shown in Table 15. The information in Table 15 is directly from drawing 11009-W07. Table 15. MWLC Operational Ditch Slope Evaluation Corner Ditch Invert Elevation Side Length (ft) Drop in Elevation (ft) Slope (ft/ft) NE 4276.9 East 1886.5 2.4 1.27E-03 SE 4274.5 South 832.9 0.8 9.60E-04 SW 4273.7 West 1891.4 2.4 1.27E-03 NW 4276.1 North 800.7 0.8 9.99E-04 With the different geometry of the operational ditch, the cross-sectional area with respect to the depth of water in the ditch is 2d2, the wetted perimeter is 2(5)½d, and the hydraulic radius is d/5½. The operational ditch geometry also changes the pyramid and frustum equations to the following: Vpyramid = 2/3(L3S2) Vfrustum = 2/3 L {(H - LS)2 + (H + LS)(H - LS) + [(H - LS)3(H + LS)]½} July 5, 2011 MWLC/Clive Ditch Flow Calculations Page 30 of 34 2 2 3 2 2 3 uppyramid,SL2/3 or S LS-H3/2V       A1,up = 2(H – LS – L2S2)2 Wbottom,up = 4L2S2 Wtop,up = 4(H – LS) A2,up = 2(H – LS + L2S2)(H – LS – L2S2) Further, the drainage area encompassed by the MWLC and the operational ditches is slightly smaller than the drainage area encompassed by the MWLC with final ditches in place. Assuming 10 feet of drainage beyond the ditches in all directions, the weighted drainage area for the entire area is calculated as ½(832.9 + 10 + 10)(1886.5 + 10 + 10) = 813,026.93 ft2. For this analysis, it will only be necessary to examine the low point of the ditches in the southwest corner (i.e., flow through the southern and western ditches). Each of the ditches will be inundated with flow from half of the overall MWLC drainage area, or 406,513.46 ft2. As operations are only expected for 25-30 years, only the worst- case normal storm event (25-year, 24-hour) was examined. Furthermore, as operations personnel will be present, no freeboard limit will be assessed to the design of these ditches – repairs and adjustments will be employed during or shortly after the event. The only operational restriction is that the design of the ditches be large enough to hold all of the collected precipitation from the worst-case normal storm event. 8.1 MWLC Southern Operational Ditch As described in Section 6.0 of this report, an iterative method is used to equate the required storage with the available storage volume at a specific water depth within the southern operational MWLC ditch. This depth was found to be 2.34 feet at the lowest portion of the ditch (SW corner). Using this depth and the slope of the southern operational MWLC ditch (9.60E-4, see Table 15), the discharge flow rate was found to be approximately 1,024 ft3/min. The storage volume at this height is approximately 6,771 ft3. Furthermore, approximately 1,914 ft3 of water backflows into the eastern operational MWLC ditch, creating a total available ditch volume of approximately 8,685 ft3 at this depth. Table 16 provides a summary of the calculations. July 5, 2011 MWLC/Clive Ditch Flow Calculations Page 31 of 34 Table 16. MWLC Southern Operational Ditch Normal Storm Event Drainage Flows Ditch flow at 2.34 foot depth Lapsed Time (min) Accum. Rainfall (in) Accum. Flow (ft3) Available Discharge (ft3) Required Storage (ft3) 15 0.65 21,934 13,368 8,566 30 0.90 30,400 26,735 3,664 60 1.14 38,480 53,471 None 120 1.21 41,155 106,942 None 180 1.27 43,186 160,413 None 360 1.40 47,427 320,825 None 720 1.65 55,896 1,244,648 None 1440 1.90 64,365 2,489,295 None These calculations demonstrate that during the worst-case normal condition 25- year, 24-hour storm event (1.9 inches of precipitation), the maximum volume retained in storage within the MWLC southern operational ditch is approximately 8,566 ft3. This maximum volume occurs approximately 15-minutes into the storm event and decreases over the next 45 minutes. This volume equates to a depth of water at the deepest portion of the ditch (SW Corner) of approximately 2.34 feet. 8.2 MWLC Western Operational Ditch As described in Section 6.0 of this report, an iterative method is used to equate the required storage with the available storage volume at a specific water depth within the southern operational MWLC ditch. This depth was found to be 2.34 feet at the lowest portion of the ditch (SW corner). Using this depth and the slope of the western operational MWLC ditch (1.27E-3, see Table 15), the discharge flow rate was found to be approximately 1,024 ft3/min. The storage volume at this height is approximately 6,732 ft3. This storage only fills the pyramid section of the ditch; no backflow into upstream ditches will occur. Table 17 provides a summary of the calculations. July 5, 2011 MWLC/Clive Ditch Flow Calculations Page 32 of 34 Table 17. MWLC Western Operational Ditch Normal Storm Event Drainage Flows Ditch flow at 2.34 foot depth Lapsed Time (min) Accum. Rainfall (in) Accum. Flow (ft3) Available Discharge (ft3) Required Storage (ft3) 15 0.65 21,934 15,365 6,569 30 0.90 30,400 30,729 None 60 1.14 38,480 61,459 None 120 1.21 41,155 122,917 None 180 1.27 43,186 184,376 None 360 1.40 47,427 368,752 None 720 1.65 55,896 1,430,579 None 1440 1.90 64,365 2,861,158 None These calculations demonstrate that during the worst-case normal condition 25- year, 24-hour storm event (1.9 inches of precipitation), the maximum volume retained in storage within the MWLC western operational ditch is approximately 6,569 ft3. This maximum volume occurs approximately 15-minutes into the storm event and decreases rapidly. This volume equates to a depth of water at the deepest portion of the ditch (SW Corner) of approximately 2.34 feet. 9.0 CONCLUSIONS The calculations presented in this report demonstrate that the ditches surrounding the MWLC (both final ditches and operational ditches) are adequately designed to contain the flow from the worst-case storm events that may occur at Clive. In addition, the entire ditch system was assessed and demonstrated to be adequate to maintain all flows from completed embankments through the 11e.(2) ditch system to the outlet into the desert. July 5, 2011 MWLC/Clive Ditch Flow Calculations Page 33 of 34 Appendix B Mixed Waste Expansion Design Drawings 1 E D c JJe(2) ','---.. ---\ B A 2 3 ~,.----:---:---:::---~-.----------, ' ',-',:, 2 3 j{ MIXED WASTE EMBANKEMNT LEGEND 800 4- owe. NO. 11009 GOl 11009-LOl 11009-C01 11009 CO2 11009-C07 11009-WOl 11009-W02 11009-W03 11009-W04 11009-W07 11009-W08 11009-UOI 11009-U02 ROAD PROPERTY LINE RAILROAD SECTION LINE PERMITED EMBANKMENTS TO C06 TO W06 TO WOg ENERGYSOLUnONS PROPERTY 800 1600 5 6 WASTE E~1BANKMENT DESCRIPTION TITLE SHEET FACILITY & EMBANKMEI'-lT LAYOUT EMBANKMENT LINER LAYOUT LINER SECTIONS & OET AILS CELL LINER COVER GRADING EMBANKMENT WASTE SURFACE CONTROLS TEMPORARY COVER SURFACE & CLOSURE DITCH CONTROLS WASTE & FINAL COVER -CROSS SECTIONS WASTE & FINAL COVER -SECTIONS & DETAILS OPERATIONAL (TEMPORARY) DITCH PLAN OPERATIONAL (TEMPOARY DITCH SECTIONS & DETAILS EMBANKMENT LOCATION MAP & BUFFER ZONE EMBANKMENT ENVIRONMENTAL MONITORING ENERGYSOLUTIONS CLIVE FACILITY 1-80 EXIT 49 15 70 -fir '----1-1 2_1 _1 5 UTAH VICINITY MAP 6 E D c B '-w z " w z :;;; "" 0 J: Z U w I~ L. 0 Lw Z V1 0 Z W >= U CL :J ir u a: '" 0 W lL 0 B:' >- 0 tD ~ "'W '" '" ,,0 <0 FINAL DRAl¥ING E D c B A 1 RUN-ON CONTROL BERM SEE DETAIL 1 (APPROXIMATE LOCATION) WASTE FOOTPRINT INDIVIDUAL DISPOSAL CELL (SUMP) EMBANKMENT RUN-OFF BERM -----t-----Ili WASTE GRADE __ ~, BREAK LINE MIXED WASTE RESTRICTED AREA BOUNDARY (MAY VARY) WASTE STORAGE (TECHNOLOGIES) BUILDING EVAPORATION POND WASTE ASSAY BUILDING SECTION 32 BOUNDARY 2 / / / 2 I~ l.,p. I;l> / / u i--" o tJj co tJj 3 / / / .--"-"-" 3 ! . L-___ .... __ !',· , I I : , ! j 4 RAIL TO BE REMOVED OR REALIGNED SITE ACCESS ROAD (TYPICAL) SECTION 32 BOUNDARY RUN-ON CONTROL BERM SEE DETAil 1 (APPROXIMATE LOCATION) PROPERTY LI NE ----------(TYPICAL) 4 MIXED WASTE RESTRICTED AREA BOUNDARY (MAY VARY) OPERATIONS BUILDING UNLOADING DOCK TREATMENT BUILDING FIRE PUMP BUILDING MAINTENANCE WELD SHOP 5 j{ 6 CLAY COMPACTED TO 90% OF STANDARD PROCTOR Nt\ TIVE GRADE RUN-ON CONTROL BERM NOT TO SCALE NOTES: 1. DRAWING INCORPORATES INFORMATION ON FORMER DRAWING 9401-6, REV T. 2. CELLS (SUMPS) f f A AND f 2A ARE MODIFIED (SHORTENED) TO PROVIDE A MINIMUM 100 FT BUFFER AREA BETWEEN THE TOE OF WASTE AND THE PROPERTY (VITRO) BOUNDARY. 5 6 E D c ~ FINAL DRAlVING 11009 LO 1 1 E D 743.1 ' c B A 1 I ! Ii I DESIGN NE RIM CORNER N 12,18732 E 15,037,13 EL 427943 I _--l__ l I r -I I I L.J I L ___ .J 1 B A 2 I r --~--. I r--I I L _J t L __ . --' ", "$: J " A 2 1 A r --1 ! r -I f I L.J I 1__ __ .J 9 9A 3 4 5 .---------------1828.0'--------------------------------------------------------------------~ 8 8A 3 I I ---1-" .. J.... " -. , I I " -I 1 I ,. ..J I L. -.J I I. '. __ .J L_. __ ..J 6B 5B 7A 5A 150.0' I t ---t--.--1- 1 r -I I I r--I I I L.J I I l. _I L ___ J L . .J ~A 3A I I RUN-orr CONTROL BERM .--1-1 1 I I I L .J I L __ . . _.J 2B 2i\ RIM CORNER N 10,359,48 \ E 15,013,35 EL 4277,03 I r ----l-.-1 I r "1 I I L.J I L . • ____ J 1 II ........... :::::~ : lA PLAN VIEW-MIXED WASTE EMBANKMENT DESIGN SV RIM CORNER N 10,369,53 E j4,24092 EL 427703 80 o 80 160 NOTE~ 1. DRAWING INCORPORATES INFORMATION ON FORMER DRAWING 9401-6, REV T. 2. DRAWING DEPICTS TOP OF LINER PROTECTIVE COVER, REFER TO DRAWING C07 raR ADDITIONAL DETAIL. 3. REFER TO CONSTRUCTION (PHASE) AS-BUILT REPORTS FOR AS-BUILT INFORMATION. 4. CELLS (SUMPS) 118 & 128 WILL FOLLOW THE SAME CONSTRUCTION PLAN AS CELLS 9B & lOB. CELLS 11 A & 12A Will BE SIMILAR TO 9A & lOA ALTHOUGH SHORTER AS SHOWN. DETAILED CONSTRUCTION PLANS AND SPECIFICATIONS WILL BE SUBMITTED TO THE STATE OF UTAH (DHSW) FOR REVIEW AND APPROVAL PRIOR TO CONSTRUCTION, THESE PLANS WILL CLEARLY DETAIL THE MODIFICATIONS TO CELLS IIA & 12A. 4 5 6 E D 772.5' 6 FINAL DRA'~ING 11009 COl E D C B A 1 2 NOTES: 1. DRAWING INCORPORATES INFORMATION FROM FORtviER DRAWING 9401-6B REV F. 2. ALL SLOPES ARE ~3:1 UNLESS OTHERWISE SHOWN. ' :3 RUB SHEETS SHALL BE 60 MIL HOPE STITCH WELDED TO UNDERLYING GEOMEMBRANES. 4. TENCH CAPS SHALL EXTEND I' (IviIN) BEYOND RUB SHEETS AND BE WELDED (100%) TO PRIII>iARY AND SECONDARY LINERS 5. 10" SLRP PIPES WILL BE EXTENDED DURING COVER CONSTRUCTION. 6. CONCRETE PIPE SUPPORT MAY BE REQUIRED TO BE REMOVED DURING COVER CONSTRUCTION. 7. DRAWING APPLIES ONLY TO PHASE V & VI (CELLS 9A, 9B, lOA & lOB) !\NO FUTURE CELLS 11 A, 11 B, 12A AND 12B. PRIMARY GEOFABRIC PRIMARY GEONET PRIMARY GEOMEMBRANE SECONDARY GEONET SECONOARY GEOMEMBRANE TERTIARY GEOSYNTHETICS LAYERS 3" SCH 80 PVC PERFORATED PiPE (TYP) GRANULAR FILL TERTIARY SLRP \, --\.-. --~. ------ \ PRIIV,ARY & 'L SECONDARY GEOSYNTH EYIC LAYERS CLAY LINER (3' THICK IVdN) l' MIN OF GRANULAR FILL 501 L PROTECTIVE COVER (2' MIN) TERTIARY S LR P CLAY LINER (3' MIN) PRIMARY SLRP \ 2% SLOPE MIN SECONDARY SLRP 2 3 10" SDR 11 HDPE PiPE (TYP) .~" FIELD FABRICATE GEOTEXTILE "SOCK" TERTIARY SLRP PIPE ~ EXTEND TRENCH CAP 5' MIN FROM TOE 2% SLOPE MINIMUM-- EXTEND TRENCH CAP 4- HDPE PIPE BOOT (TYP) ~05 {L'\ EXPLODED E-W SLRP CROSS SECTION \~01 NTS SOIL PROTECTIVE COVER (2' THICK MIN OVER PIPE) 3 4 5 SAND BEDDING AROUND PIPES (TYPICAL) PRIMARY, 60 MIL, TRENCH CAP (SEE NOTES) SECONDARY, 60 MIL, TRENCH CAP (SEE NOTES) 6 CONCRETE PIPE SUPPORT SEE DETAIL@ C06 --..:r----- SIMILAR RUB SHEET (SEE NOTES) PERIMETER BERM r (RUNOFF CONTROL) SAND BEGDING ~ AROUND PIPES ~o(' (TYP) E-W SLRP CROSS SECTION 4-0 4-8 5 GEOSYNTHET!CS ANCHOR TRENCH 6 D FINAL DRA ,~ING 11009 C02 E D c B A 1 TERTIARY GEOTEXTILE PRllviARY GEOTEXTILE PRIMARY GEONET PRIMARY GEOMEMBRANE SECONDARY GEONET SECONDARY GEOMEII>1BRANE TERTIARY LAYERS OF GEOSYNTHETICS PRiMARY & SECONDARY LAYERS OF GEOSYNTHETICS 1 2 3 4 5 6 ~ ____________________________________________________________ ~60' ______ --____ ------__ ------______ --____ ----------------------~ 3" SCH 80 PVC PERFORATED PIPE (TYP) /'U8'Hm 2 SOIL PROTECTIVE COVER (2' 1v1IN) 2% RUB SHEET CLAY LINER 10" SDR 11 HOPE PIPE (TYP) FILL -------------------- I' MIN (TYP) RUB SHEETS N-S EXPLODED SECTION THROUGH SLRP NTS TERTIARY SLRP ~ PRIMARY SLRP ~ SOIL PROTECTIVE COVER (2' THICK MIN) ~===-------=----~~-~-~-------------------- --------------'-----..........,' SECONDARY SLRP 3 ------- SOIL PROTECTIVE COVER l' MIN THICK BETWEEN SLRPS CLAY LINER (3' THICK MIN) N-S CROSS SECTION THROUGH SLRP 4 4- 4 NOTES: 1. DRAWING INCORPORATES INFORlviATION FROM FORMER DRAWING 9401 -6C, REV E 2 DRAWING APPLIES ONLY TO PHASE V & VI CONSTRUCTION (CELLS 9A, 9B, 10A & lOB) AND FUTURE CELLS 11A, 118, 12A AND 12B 3 ALL SLOPES ~31 UNLESS OTHERWISE NOTED 4 RUB SHEETS SHALL BE 60 MIL HDPE STITCH WELDED TO UNDERLYING GEOMEMBRANES. 5 RUB SHEET 6 E D c B I-W Z '" W Z :;, <{ a I z U w :;, lL <{ 0 w z Vl z a w ;;: u "-::J (j' u ce V1 0 W lL 0 lD >-"-In 0 ",-W " I-~C5 <0 FINAL DRAWING 11009 C03 E D c B A 1 10" SDR 11 HOPE PIPE (TYP) 2 2' MIN COVER 3 SOIL PROTECTIVE COVER (2' MIN) 4- ~ TERTIARY GEOTEXTILE ilJ\J ~ TERTiARY GEONET ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~rTE~AAYGroM~BR~E ---PRIMARY GEONET ~~::;~~~~;::'-=~f~.~.=-=-I--T---·-------~----=:;;;;~~~~~~:-:---PRIMARY GEOMEIv1BRANE \.£02 1 SECONDARY GEONET SECONDARY GEOMEIv1BRANE CLAY LINER (3' MIN) FOUNDATION 60 MIL HOPE TRENCH CAPS FULLY WELDED ~2.23' SAND P',PE BEDDING WITHDRAWAL PIPE TRENCH (EXPLODED VIEW) NTS 2 TERTIARY SLRP PIPE PRIMARY SLRP PIPE SECONDARY SLRP PIPE ~ RUNOFF CONTROI_ BERM ~ 3-1_-:.I~ ___ -r SLOPE VARIES 1 I - VARIES (3:1 MAX) CLAY LINER RIM ANCHOR TRENCH (TYP) NTS 3 -j 3' MIN, I' MAX 3' MIN ANCHOR TRENCH 4- @ WITHDRAWAL PIPE 2 0 2 ~,.y 5 ~ 2' MIN COVER OVER PIPE 6 SOIL PROTECTIVE ~COVER -(2' THICK MIN) SECONDARY LAYERS GEOSYNTHETICS TRENCH 4 J 5 NOTES: 1. DRAWING INCORPORATES INFORMATION FROM FORMER DRAWING 9401-6F, REV C. 2. DRAWING APPLIES ONLY TO PHASE V & VI (CELLS 9A, 9B, IDA & lOB) AND FUTURE CELLS l1A, 11 B, 12A AND 12B. 6 E D c B '-z w '" a z w 'l' w if> Z I~ '" &: (/) -l <: f-w °I ~~ (/):::! z o . _W '-> ()~ w-' (/)u ° Ct: W W x Z ~ ::J FINAL DRA'~ING 11009 C04 E D c B A 1 \ 60' I ~50' PIPE 3" SCH 80 pVC PERFORATED PIPE (TYP) ,--------------- R III III I II I II I II III III III w "-o -' (!) PLACE I' MIN GRANULIoR FILL IN SUMP 2 ]" SCH 80 PVC END CAP (TYP) r"~j Ii I 2% SLOPE I~IN--~~~~~~~c==~== I III I III III III III III III III III III III w "-S (!) -L-i---J U }-________ ~58' ----------! TERTIARY SLRP PLAN I STANDARD TEE n II', '/ (3 PLACES) I, ~cr:~ TO 10" ~'--_Li _,_~ L I ') -HDPE PIPE ~ 90' ELBOW 3" SCH 80 PVC PIPE & FITTINGS 10" SOR 11 HOPE PIPE 3 ]" SCH 80 PVC PERFORATED PIPE (TYP) r------ w "-S Vl PLACE l' MIN 4 "" GRANULAR FILL II N IN SUMP II 10" SOR 11 HOPE PipE 60' ~50' PIPE I II ____ 2.:_~::.r.::_~~=_{jt__i=:::}::±====::J \{ I I II I II z II ~ II w "-o -' Vl ~35' PIPE PRIMARY SLRP PLAN W SLRP SUMP PLAN VIEW ~02 NTS I II II II II II FUSION OR EXTRUSION PIPE WELD 10" SDR 11 HOPE PIPE n----l,----/"'---r--w ~~ 5 PLACE i' MIN GRANULAR FILL IN SUMP 3" SCH 80 PVC pERFORATED PipE \ W/ END CAPS (TYP) \ \ ~lO' PIPE 22' ! ,--176' 6 SECONDARY SLRP PLAN 3" SCH 80 PVC TEES INSTALL BACK TO BACK l SEE DETAIL 5 \ r-~~~~--!----4~-~~ £ PIPE JOINT DETAILS PLAN VIEW-NTS 3" SCH 80 PVC VARIES PIPE & FITTINGS \ MATCH GRADES ( " HOPE LINER \ \ (_', '\ ( (TYPICAL) --.-~'~~OTATE TEE TO ~ MATCH GRADE (TYPICAL) (7\ PIPE JOINT SECTION ~_ NTS 1 2 3" SCH 80 PVC PERFORATION PIPE 1/2" THICK HOPE END PLATE EXTRUSION WELDED TO END OF 1 0" PIPE 3 (Cj ~ -3.5 10" SDR 11 HDPE PIPE ALTERNATING 1i; "0 PERFORATIONS (TYP) STAGGER HOLES OPPOSiTE SIDE 3" TO 10" PIPE CONNECTION DETAIL NTS PIPE PERFORATION DETAIL NTS NOTES: 1 DRAWING INCORPORATES INFORMATION FROM FORMER DRAWING 9401-6A, REV E 2. ALL PVC JOINTS TO BE CONNECTED WITH STAINLESS STEEL SCREWS (# 12 x 1"). MINiMUM OF TWO (2) PER JOINT, INSTALLED ON OPPOSITE SIDES OF THE PiPE. 00 NOT USE PVC CEMENT 3. REMOVE ALL CUTIINGS AND TRIMMINGS FROM PIPES. 4. DRAWING APPLIES ONLY TO PH/I.SE V & VI (CELLS 9A, 98, lOA & 10B) AND FUTURE CELLS 11 A, 11 B, 12A AND 12B 4 5 ON -----+----- 6 E D c B ~ ~ ~ S ;2 () «: lL ~ W > ::J r"C ,U ~ (!) z 0 f= ::J -' ~ 0 (!) >-0 a: w ~ Z w z: ~ z l(5 ~ ~ o r is () :. u. «: 0 llL.! Z fD Q z e-U Q :J C2 () Il: V1 OW U. 0 '-Vl z ...J ~ ~ '" w z 0 :r as '" ~ 2 :;J w Vl z w o . '-_W (!) 02: ~ w..J (!)U 0 0:: w w x' Z ~ ::J FINAL DRA,~ING 11009 C05 1 2 E 10" HOPE PIPE TYPE I D /~~?' C : ~"1 c < B A 1 2 3 LOCKING PIN 10" HOPE PIPE PIPE CAP DETAIL NOT TO SCALE 10" HOPE PIPE (TYP) \ \ ~ HOLE DRILLED II~ PVC PIPE AND CAP LOCK TYPE II I I I I 1- I 1 1,5' MIN 10" HOPE PIPE 4 10" PVC ~CAP / LOCKiNG ! ' ~PIN ~ \'LOCK· -l I CAST IN PLACE 12" THICK CONCRETE COLLAR USE 4000 PSI CONCRETE W I TYPE Ii PORTLAND CEMENT COLLAR MAY BE ROUGH CAST WIO FORMS 5 FILLET HOPE LINER 2 EA ST AI NLESS STEEL BANDS @ 3" O,C. PIPE BOOT DETAIL NOT TO SCALE 2 EA STAINLESS STEEL BANDS @ 3" OC. HOPE BOOT \ FILLET WELD \ , \ HOPE LINER J TYP L_L __ J __ J #5 REBAR TOP & BOTTOM 3" MIN CLEARANCE FROM SURFACE k~ PIPE BOOT DETAIL ~~---NO-T-T-O--SC-A-LE-------- ! ~ PIPE SUPPORT DETAIL NOT TO SCALE 3 4- NOTES: I. DRAWING INCORPORAES INFORMATION FROM FORMER DRAWING 9401-60, REV E. 2 DRAWING APPLIES ONLY TO PHASE V & VI (CELLS 9A, 9B, IDA & lOB) AND FUTURE CELLS 11 A, 11 B, 12A AND 12B 5 6 FILLET WELD 6 FINAL DRA1VING OTED 106/17/11 11 11009 C06 E D c B A 1 APPROXllviATE LOCATION OF lEAK DETECTION SUMP 1 2 3 4-5 -~-.------~~- -----:\ -------- !\;-I----~~~~-~=--- II' ----- I I -r----:::---::: -'1 ---~-~ ill. -_ . 1111 -,---__ 1111 ~-. I I I I I 1 ---------_ 1 I II II . -~-r\~ 4fr~--~~==> ;1 --~~==?> 11111 -~ -~- 11111 • -~-- I I j I I f _---------I ----- I I i I -----~ i _--I II I I _-+--- 1111 i _---I I I I --'=-~-.-.-.---' -------- ----~ t ~ "-"-'-"- "-"-~ "-'- /' ,/ / ,/ ,/ ,/ ,/ ~ ,/ ,/ o '01- ,/ / ,/ ,/ ,/ ---/ ------------ ---- __ 2% MIN ~ ----------~----------< /,/ I I I ---- ------...----- INDIVIDUAL CELL PLAN VIEW 20 o 20 2 3 4-0 NOTES: 1. DRAWING INCORPORATES INFORMATION FROM FORMER DRAWING 9401-6E. REV A 2. DRAWING SHOWS THE TYPICAL l' CONTOURS OF THE TOP OF LINER PROTECTIVE COVER OVER THE TERTIARY GEOSYNTH[T1CS FOR A SINGLE SUMP 3. CELLS (SUMPS) 1 i A & 12A ARE SiMilAR. 4 5 6 E D c 6 ~ ~ i::: S ::J G f-<:J -<: z z LL W is :;, -<: 'w xc fr:: ~ > z <:Jr ::J -<: fr::~ (We ,u OJ :;, ~:J w ~ g:' W 0 Ow Qltn 0.::2: f-« W...J :cJ $: ~u --.J ~ 0 0 -' (/) W -' >-x -' (.9 ~ W fr:: U w ~ Z w S FINAL DRA'~ING 11009 C07 E D c - B i- A 1 I 2 I 3 I 4 5 6 ~ 4 + 1 ______________________________________________________________________ 1822.0' _____________________ ---------------------------------------------------~ I~----311.0' --------~1-------------------------11 76.1 '-------------------------------------------------------1---~---334.9' -------I ~ N 12,184.36 N 11,873.39 /:.. CLAY LINER RIM N 10,697.38 -L B \ N V E 15,034.09 VE 15,029.97 WASTE FOOTPRINT E 15,012.73 \ "W03 E 15 \. EL 4279.43 ; EL 4279.02 EL 4277.47 ~ EL NATURAL GRADE EL ~4278. 70 f'\", "3J "'" //, I '" N 12,028.92 WASTE N 10,699.09 / I " E 14,874,52 r 8REAKOVER ~1' E 14,855.24 / '"L::_:2-----j-------~----J5-----------~4308:_~_ I _~// : I " ~ N 11,875,59 =-r / I ~ I I '" E 14,872.48 / N 10,522.07 ! " ! '" EL 4310.52 / I -E 14,854.00 ~\. ____ *-___ --_lI..------J '" I / I EL 4308.74 I U ~ i I "", N 11,806.13 ~Io\ 224.9' / I I " ,~~E 14,645.80 N 10,748.83 / I I I 'EL 4315.60 E 14631.73 / :--;:::.--11 -:57~:~ I -----------------1-~;;-,~ --------~ :3~O~::, ':3':: 'Ii. ,:::'"-: I, N 12,034.41 I // ~I I " I , EL 4310.72 I / I I / N 11,865.66 "'" I , I / E 14,420.89 ' I 737.0' E 14,452,631 I 1 225.5' '" I EL 4310.50 I '" N 12,193.95' ---_ t '" 1 , / ~I I N 10.527.93 I / I ;::; 157,5' E 14,403.49 '" , / ---------I riEL 4308.74 " V ,-----227.6'_ '", I ",. NATURAL GRADE' EL ~4277.9 ~' , , . 7' . E 14,294.63 N 11,769.57 A 9 EL 4279.17 E 14,262.13 N 10,372.4 199.2'--.....{ LEGEND: ______ DESIGN WASTE LIMITS ______ DESIGN WASTE BREAK UNES _ . _ ' _ . _' DESIGN CLAY LINER RIM 80 0 I -;'.'1 80 160 \ 2 EL 4278.87 W03 E 14,243.96 EL 4277.03 1-------------------------------------1397,2'--------------------------------------------------------------------~ NOTES: 1. ELEVATIONS AND DIMENSIONS ARE FOR TOP OF WASTE UNLESS OTHERWISE NOTED. I 3 4-5 NATURAL GRADE EL ~4277. 3 \ 766.5' NATURAL GRADE EL ~4276.4 6 I - c - B o f-W Z x w ~ S2 z « CD :2 w ~ FINAL DRA1~ING A "'B:"DICK t'G."' DUTSON D.BOOTH AS NOTED 106/17/11 F j}, """,,,0 11009 ViTO 1 E D c B A 3 4 5 6 1 2 ~ :4 +-r-________________________________________________________________ 1918.4' ___ ~--------------------------------------------------------------J EL 4275.70 --- N 1 E 1 EL N 11,873.32 TEMPORARY COVER FOOTPRINT N 10,697.33 WASTE F_OOTPRINT _ __ _ ___ r DITCH CENTERLINE E 15,017.83 _ / EL 4277.47 DITCH SLOPE 0.15% ---------------------- N 10,357.36 E 15,015.46 EL 4277.03 DITCH INVERT + NATURAL GRADE EL ~4278.7 If~~-~-~-==~~~~-~~==~~~==~====~~~==~~~-=====~~==~~=~~==~~~~====~~~==~=_c~====~~~==~~~====_~~====~~~==~~==~~~==~=-~-~-=-=c::~~-- 829.7' I I I \ "-~ N 12,029.03 WASTE / E 14,874.63 /-BREAKOVER 1 N 10,699.08 / EL 4311.72 ~ E 14,855.35 ~ ""f --~~~':7;5-9--_____________ ~ ______________ E_L ~3~9~ _ ~ / / / , I i j -I " I. J 7(N 10m,,: ' / I E 14,854,11 I I~ , I EL 4309.74 I Wo~ , N 11 ,806.13 ~I,I / / I I \, E 14,872.59 ~ EL 4311.52 ~I ~I , EL 4314.60 / I / I c:il Iw ~ ~LI13~~~6~0 "\ ~ ~~:~j~:~~_~ / II l~a.o ' I ~ I ,,~ \ -----------------------------~ ~ ~I il I / / " II g I I IN 12,034.52 / ~,·l ~,,: o/! \ \ E 14,452.54 EL 4311.72 / N 11,865.67 " ! I E 14,420.78 " I I I EL 4311.50 I ,I N 12,199.12 I I i-Y EE~44~~~:~~-~: --------------:1------1 ---------N '~5:7_::--" i 1 '11 E 14,403.38 ", II I NATURAL I 1 EL 4309.74 " EL G~~gi7~~~~~~~~~==~~~i=it~~~~~~~~~~====~~====~~~==~~~====~~~==~~~==~~~==~~~~==~~~==~~~====~~~==~~~====~~====~~ EL 4274.38 DITCH INVERT EL 4272.81 EL 4279.03 W03 E 14,238.79 w CL ,0 I...J (I) DITCH INVERT EL 4272.72 863.2' NATURAL I GRADE I EL ~4276~ j I DITCH INVERT JII R RE~E:-:-N:T~ _______________ 360.3' EL 4277.03 ______ DITCH INVERT EL 4271.38 i5~ 184.5' LEGEND: CLOSURE DITCH CENTERLINE TEMPORARY COVER LIMiTS DESIGN WASTE LIMITS 80 80 160 1 2 NOTES: 1. ELEVATIONS ARE FOR TOP OF TEMPORARY COVER UNLESS OTHERWISE NOTED. 2. TEMPORARY COVER IN THIS AREA WILL BE PLACED THICKER THAN i FT TO TRANSITION FROM TOP OF WASTE SURFACE TO A MORE UNIFORM COVER SURFACE. 3. EMBANKMENT CAPACITY FROM THE DESIGN TOP OF PROTECTIVE SOIL COVER (2ND LAYER) TO THE TOP OF WASTE IS CALCULATED TO BE 1,354,092 CY. 3 LARW 1559.6' ---------------------~123 ~ I __ ~--------------II I CLOSURE DITCH TIE-IN WITH ~----+--___ --L Sl LARW DITCH ~ • .1>'7"-"_ 270. 1 0 4 5 6 E D FINAL 11009 W02 1 E D c B A CLAY LINER RIM POINT OF REFERENCE FOR DESIGN SHOULDER HEIGHT (ELEVATION VARIES) 2 GROUNDWATER TABLE PREPAf<ED SUBGRADE 3 4 EAST & WASTE SURFACE TEMPORARY COVER CROSS SECTION 5 RADON BARRIER SOIL PROTECTIVE COVER TERTIARY LINER SYSTEM PROTECTIVE COVER AND SECONDARY SYSTEMS LINER (}a~ j ~ @~1 ~U':J \ WOS SLRP PIPES 2% MIN SLOPE- RADON BARRIER SOIL PROTECTIVE COVER TERTIARY LI NER SYSTEM SOIL PROTECTIVE COVER PRIMARY AND SECONDARY LINER SYSTEMS CLAY LINER CLAY LINER RIM POINT OF REFERENCE FOR DESIGN SHOULDER HEIGHT (ELEVATION VARIES) 1 2 I \ \ TEMPORARY COVER WASTE SURFACE , \ \l'~-. ___ ' I \\ PREPARED SUBGRADE 9' MIN 'T GROUNDWATER TABLE '" CLAY LINER RIM ~ DESIGN LIMITS OF WASTE TYPICAL EAST & WEST -SIDE CROSS SECTION AT SUMP ~01 SCALE: I = 40 WASTE SURFACE PROTECTIVE COVER 157.5' VARIES I g' MIN '--1-GROUNDWATER PREPARED I SUBGRADE ~OI 3 TABLE TERTIARY LINER SYSTEM CLAY LlNER'l PRIMARY AND SECONDARY LINER SYSTEMS SOIL PROTECTIVE COVER TYPIC.AL NORTH & SOUTH-SIDE CROSS SECTION SCALE i -40 4 5 D 6 FINAL (f) (f) o cr~ u~ <{ If-=:J DRA\~ING 11009 W03 E D c B A 1 '7 ---- INSPECTION ROAD (TYP) 12" THICK ROAD BASE COMPACTED TO 95% STANDARD PROCTOR RADON INSPECTION ROAD CENTERLINE MONITORING WELL (TYP) TYPE A RIPRAP TYPE A FILTER SACRIFICIAL SOIL TYPE B FILTER 2 3 CLOSURE DITCH CENTERLINE (INVERT) (42' MIN @ WELLS) 12 oz, NON WOVEN GEOTEXTILE AND 60 MIL HOPE LINER (TEXTURED 80TH SIDES) ACTUAL WASTE LIMITS NOTES) DESIGN LIMITS i OF WASTE 3" MIN 80' MIN 4 43.1' MIN RU NOFF BERM TO BE REMOVED PRIOR TO RADON BARRIER CONSTRUCTION TYPE B & TYPE A FILTERS MERGE 5 TYPE A RIPRAP TYPE A FILTER SACRIFICIAL SOIL TYPE 8 FI L TER COVER 21TS / / LINER GEOSYNTHETICS J ANCHOR TRENCH RUNOFF BERM TO BE REMOVED PRIOR TO RADON BARRIER CONSTRUCTION CLOSURE DITCH CENTERLINE (INVERT) EXTEND SLRP PIPES AS NEEDED TYPE 8 & TYPE A FILTERS MERGE 3' MIN 6 12 oz. NON WOVEN GEOTEXTILE AND 60 MIL HOPE LINER (TEXTURED 80TH SIDES) SOIL PROTECTIVE COVER L ACTUAL LIMITS OF WASTE \ (SEE NOTES) ~ DESIGN LIMITS OF WASTE 32' MIN (42' MIN @ WELLS) INSPECTION ROAD 12" THICK ROAD BASE INSPECTION ROAD CENTERLINE COMPACTED TO 95% ~ STANDARD PROCTOR,p ~ 4-____________ ~~~--~~~~3:-1~~.~------~-~-----~-------------------_ SOIL PROTECTIVE COVER LINER GEOSYNTHETICS I ANCHOR TRENCH TEMPORARY COVER LIMITS CLAY LINER COVER GEOSYNTHETICS ANCHOR TRENCH NOTES: 1, DESIGN LIMIT OF WASTE IS CONTROLLED BY THE HORIZONTAL AND VERTICAL LIMITS or THE CLAY LINER RIM. HOWEVER, THE ACTUAL WASTE LIMIT IS WHERE THE DESIGN WASTE SURFACE AND THE SOIL PROTECTIVE COVER SURFACE INTERSECT (AS SHOWN IN THE SECTIONS ABOVE), SINCE THE SLOPES or THE LINER AND THE THICKNESS OF THE SOIL PROTECTIVE COVER VARY, THE ACTUAL WASTE LIMIT VARIES SLIGHTLY AS WELL. 1 2 3 TYPE A RIPRAP / 43.1' MIN TYPE A FILTER TYPICAL COVER/DITCH DETAIL @ SLRPs SCALE: 1 = 10 4 5 6 E FINAL DRA 1VING 11009 W04 E D c B A 1 6" THICK TYPE A FILTER ZONE ~-. ,-'Co- 6" MIN THICK TYPE B FILTER ZONE 60 MIL HDPE LINER (TEXTURED 80TH SIDES) 12" THICK TEMPORARY --1':t-~J;::;;;;'9::.cc COVER 2 TYPE DETAIL-SIDE SLOPE 12" THICK TYPE A RIP RAP NTS TYPICAL SIDE SLOPE COVER DETAIL TYPE A FILTER ZONE, THICKNESS VARIES, 6" MIN DETAIL-DITCH OUTER SLOPE NTS 1 TYPICAL PERIMETER DITCH COVER DETAIL 2 12" THICK SACRIFICIAL SOIL 12 oz./sy NON-WOVEN GEOTEXTILE 2' OF 5x10-8 CM/SEC RADON BARRIER 3 6" THICK A FILTER 6" MIN THICK TYPE B FILTER ZONE - 60 MIL HOPE LINER (TEXTURED 80TH SIDES) 4 18" THICK TYPE 8 RIPRAP 12" THICK SACRIFICIAL SOIL 1 2 oz./sy NON-WOVEN GEOTEXTILE 2' OF 5x10-8 CM/SEC RADON 8ARRIER 12" THICK TEMPORARY---~~~~~G±SG02i12it2~B2~~~~ COVER 6" MIN THICK TYPE B FILTER ZONE - 60 MIL HOPE LINER (TEXTURED 80TH SIDES) 12" THICK TEMPORARY -~--",,-. COVER 3 DETAIL-TOP SLOPE NTS TYPICAL TOP SLOPE COVER DETAIL 18" THICK TYPE 8 RIPRAP 12" THICK SACRIFICIAL SOIL 12 oz./sy NON-WOVEN GEOTEXTILE 2' OF RADON BARRIER DETAIL-SHOULDER NTS 4 5 5 6 COVER MATERIAL GRADATIONS (ASTM C-136) TYPE A RiP RAP 0100<= 16 INCH 090 <= 12 Ii'iCH D 50 >= 4-1/2 INCH Dl0 >= 2 INCH D 5 > == NO. 200 SIEVE TYPE B RIP RAP D 100<= 4-1/2 INCH 050 >== 1-1/4 INCH D 10 >= 3/4 INCH D 5 > = NO. 200 SIEVE TYPE A FILTER ZONE D 100<= 6 INCH D 70 <= 3 INCH D 50 <= 1.57 INCH (40 mm) D 15 <= .85 INCH (22 mm) 010 >= NO. 10 SIEVE (2mm) D5 >= NO. 200 SIEVE TYPE B FILTER & SACRIFICIAL SOIL TYPE B FILTER & SACRIFICIAL SOIL MATERIAL GRADATIONS ARE DETERMINED BY THE FOLLOWING SPECIFICATION: D1S (MAX) FILTER Dss (MIN) SOIL MUST BE < 5 DsO ( MAX) FILTER D50 (MIN) SOIL MUST BE <= 25 TYPE B FILTER Dl00 <= 1.5 INCH TYPE B FILTER MIN PERMEABILITY == 3.5 em/sec SACRIFICIAL SOIL MIN MOISTURE @ 15 aim == 3.5% TYPE A FILTER & SACRIFICIAL SOIL MATERIAL GRADATIONS SHALL MEET THE FOLLOWING SPECIFICATION: D15 FILTER DS5 son::-MUST BE <= 4 015 SOIL DS5 FILTER MUST BE <= 4 NOTE: ADDITIONAL MATERIAL SPECIFICATIONS RELATED TO COVER CONSTRUCTION ARE LOCATED IN THE CONSTRUCTION QUALITY ASSURANCE/QUALITY CONTROL MANUAL UNDER THE APPLICABLE WORK ELEMENT. 6 E D FINAL DRA,~ING 11009 W05 E D c B A 1 1.5' THICK TYPE A RIPRAP 6" THICK TYPE A FILTER 2 REMOVE RUNOFF CONTROL BERM PRIOR TO RADON l BARRIER CONSTRUCTION 3 4 SLRP CONCRETE COLLAR CONSTRUCTED ON TOP OF TYPE B FILTER ZONE 5 EXTEND SLRP PIPES AS -NEEDED UTILIZING FUSION SLEEVES OR OTHER APPROVED METHOD 6 9~ PIPE CAP I' THICK SACRIFICIAL SOIL 5:1 MAX REMOVE SLRP PIPE COLLAR PRE~OUSLY CONSTRUCTED FOR AFTER TEMPORARY COVER BUT PRIOR TO BARRIER PLACEMENT ---;-DETAIL 6" MIN THICK TYPE B FILTER 120z. NON-WOEN GEOTEXTILE OVER 60 MIL HOPE LINER (TEXTURED BOTH SIDES) 2' THICK RADON (5Xl0-B I' THICK TEMPORARY COVER WASTE SURFACE SOIL PROTECTIVE COVER __ --(~2' THICK I"AYER) TERTIARY LINER [-_______ ~------------- AND S L R P::::---------~ PRIMARY LINER r- AND SLRP L SECONDARY LINER [ AND SLRP 3' THICK CLAY LlNE:~ 1.5' 0.5' SLRP (TYP 3 PLCS.) t '/ \""AC U"IT~ OF WASTE 11-1--I 1\-. I---~. ~~~==-!" -L ________ +-________ ~ __ ~I-l= LI_I-_1 __ 1 __ I_l~ I 3.1' SLRP CONCRETE COLLAR DETAIL NTS 1 2 / /~( / .~~(- ~ ~ANCHOR TRENCH FOR LINER GEOSYNTHETICS DESIGN LIMITS OF WASTE SUMP PIPE EXTENSION SECTION SCALE: 1 = 4 2 EA. STAINLESS STEEL BANDS @ 3" O.C. ~ 8 HOPE BOOT~ ~ CAST -IN-PLACE CONCRETE COLLAR 12" THICK 4000 PSI TYPE II PORTLAND CEMENT FILLET WELD"""\ \ HOPE~ LINER \ TOE OF RADON BARRIER ANCHOR TRENCH FOR COVER GEOSYNTHETICS PIPE BOOT DETAIL WELD ROUGH CAST & ROUCH FINISH PIPE BOOT OET AIL #5 EYPOXY COATED ~ REBAR, CENTERED, 3" MIN CLEARANCE FROM SURFACE I 05' r------:=- 3 NTS 4-5 A & TYPE B FILTER INTERCONNECT IN THIS REGION /10" PVC CAP- / STAINLESS ~ ~_\~ STEEL PIN "'--~ .. . WEATHER RESISTANT.._______ . -KEYED LOCK ~10" HOPE PIPE PIPE CAP DETAIL NTS 6 FINAL f... Z W ;;;: o z w ;;;: "-<t 0 W Z ~ g Lu ... ,-,0. o ii u '" V1 o w u_ 0 DRA l~ING 11009 W06 E D c B A 1 DITCH INV El 4276.9 800.7' OITCH INV EL 4276. i FENCEJ (TYPICAL) 1 6:1 o -1 V! :r: u t: "" 2 RELOCATED RAIL TO B~ONSTRUCTION PRIOR TlO 12B LINER OF CEl / / / --- DESIGN LINER RIM . J<-------) / , / DITCH I / / INV El ~ ~ _ ~_ :-__ =-., __ ----,L--~4_275.7 E ROAD (TYPICAL) SIT 3 1886.5' 4 OPERATIONS BUILDING ---- 5 / OPERATIONAL (TEMP) WOB __ _ ___ ~ DRAINAGE DITCH CENTERtI" _ I ----------/~~ :~l / / OVER LIMITS TEMPORARY C G W02 FOR REFER TO T~~N CONTROLS ----< / / I~;!O I 'I ~ I \ vi I il I I ' u I I~ l 1 ,I I DITCH ENV El 4274.5 TREATMENT d ____ -+-___ BUllOING CENTRAL CONTAINER STORAGE AREA FENCE (TYPICAL) STORAGE (VTD) BUILDING 6 832.9' _L CO~'''~' ______ _ OPERATIONAL (TEMP) DRAINAGE DITCH CENTERLINE i' ~:::, i '. I I MW '. I J_ -'---DITCH SLOPE 0.13%- ~ ; I I EVAPORATION _~ POND -~-~~~- DITCH INV EL 4273.7 LARW CLOSURE LARW DITCH INV EL -4270.1 CUL VERT '-INV EL 4273.0 EVAP_~~~ __ 7~~ _______________________________ __ DITC H CENTERLINE 7' TROL CAe. Wm( , ", RUN ON CON _~:~L~IM~I=TS~~ __ ~~_____________ ~ NOTES' HAUL ROADS AT~~ OPERATIONAL 1 RELO~ATED EXDIST+~G ACCOMMODATE 1 1 . AS NEEDE -BERMS DRAINAGE DITCH. ~08 COVER 100 o 100 200 2 3 4 5 6 FINAL DRAWING E DITCH 't D c B A 1 TEMPORARY COVER TOE 2 .\ I ,I I' DITCH <t I 3 j{ 6' CHAIN LINK FENCE (TEMP CLOSURE FENCE) INV EL 4274.5 ____ ....••... dy CONCRETE LINED DRAINAGE SWALE (FIELD ROUTED) MECHANICAl/MCC ROOM TREATMENT BUILDING DITCH-TREATMENT BUILDING DETAIL TANK CONCRETE CONTAINMENT SCALE: r :: 40' CONCRETE LINED (FIELD ROUTED) It DRAINAGE SWALE ~ DITCH \ ~ I EXIST FENCE ~ f I il 'G)ANK II .. 225 I I I ~ /1 I '~ CDNCRETE LINED I ~ DRAINAGE SWALE~' r (FIELD ROUTED) I I f I j{ TEMPORARY COVER TOE DESIGN LINER RIM WASTE LIMIT 6' CHAIN LINK FENCE (TEMP CLOSURE FENCE) @ DITCH-TANK CONTAINMENT DETAIL "'!!07 SCALE: : ' -80 2 3 6' CHAIN LINK FENCE 4 EXIST _ 1-3' MIN GRADE 1 ~ ~'"J'='I ,- l' TYP J '-1 CLAY BERM 6" MIN TYPE A FILTER MATERIAL 5 HOLD TYPE A RIPRAP BACK FROM DITCH I~--------27.2' ----,L-----l / / I' MIN CLAY (Cl) ~ COMPACTED TO AT LEAST 95% COVER GEOSYNTHETICS STD PROCTOR ANCHOR TRENCH TYPICAL COVER/DITCH SECTION SCALE: I = 10 6 TYPE A FilTER DESIGN WASTE LIMITS TEMPORARY COVER TOE 6' CHAIN LINK FENCE HOLD TYPE A RIP RAP BACK FROM DITCH 3" UNREINFORCED CONCRETE \ EVAP TANK ; CONTAINMENT ~ .... > ~?-r·"J.9' m'·· .. ~ CLAY BERM 1-i+'1'-'~KA1 l' MIN THICK CLAY / (Cl) COMPACTED-..I TO AT LEAST 95% STD PROCTOR 6" MIN TYPE A FilTER MATERIAL /,/ ~ COVER GEOSYNTHETICS ANCHOR TRENCH DITCH/TANK CONTAINMENT SECTION SCALE: 1 = 10 6' CHAIN A FILTER B FilTER WASTE LIMITS TEMPORARY COVER TOE ( LINK FENCEr:-HOLD TYPE A RIPRAP 't C BACK FROM DITCH EXIST 1------27.2' ____ I..,LL ____ ~~~I [GRADE I 1------21.5' TYPE A FILTER MECHANICAL MOe Til ... FIELD DETERMINED ~ I DRAINAGE SWALE--.I 3" UNREINFORCED CONCReTE l' MIN THICK CLAY (Cl) COMPACTED TO AT LEAST 95% STD PROCTOR 4 2% MIN SLOPE 6" MIN TYPE A FILTER MATERIAL ~ COVER GEOSYNTHETICS ANCHOR TRENCH BUILDING SECTION 5 B FilTER DESIGN WASTE LIMIT TEMPORARY COVER TOE 6 E 1 FINAL l~~~WING I G. DUTSON AS 11009 WOS E D c B A 1 LARW DITCH <t I 2 3 MW DITCH if. L-~---------~-184.3' ----------~-_j MW BOUNDARY (RESTRICTED AREA) FENCE EDGE OF DITCH (TYPICAL) 4 j{ EXIST GRADE ELEV VARIES \ +-~-- MW l~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~--~~~.~~~~~~~~~~~~DITCH I FT MIN THICKNESS .4 OF CLAY (CL SPEC) OUTLET Y INV EL I 4273.0 I 30" CORRUGATED HOPE CULVERT (WATER TIGHT) LARW INSPECTION (HAUL) ROAD .\. -'---'---'--'-'-- /' NEW 6' CHAIN LINK / RESTRICTED AREA FENCE \ (FIELD LOCATE) ( ~ APPROXIMATE LIMITS OF I MW EVAPORATION POND DITCH CONNECTION PLAN SCALE: \ ' = 40 MW SW DITCH CORNER INV EL 4273.7 COMPACTED TO AT LEAST 95% STD PROCTOR 5 6" MIN OF TYPE A FI LTER MATERIAL SELECT BACKFILL PLACED IN 12" LOOSE LIFTS & -COMPACTED TO AT LEAST 95% STD PROCTOR 30" CORRUGATED HOPE CULVERT NOTE: 6 + CONSTRUCT DITCH FROM SW CORNER OF MIXED WASTE TO THE INTERCEPT WITH THE LARW DITCH. THEN PLACE 30"¢ CULVERT IN THE BOTTOM OF DITCH ON TOP OF CLAY AND BACKFILL AROUND CULVERT WITH SELECT MATERIAL. CONNECTOR DITCH SECTION SCALE: i' = 8' MW DITCH LARW DITCH <t I 4' WATER LEVEL \ IN LARW DITCH \ BEVEL LARW INSPECTIONi HAUL ROAD MW BOUNDARY r (RESTRICTED AREA) I FENCE EXIST GRADE ~ _ I MW SOUTH DITCH INVERT \ I END -,,~w~ ,,~~_SJ~~ ~··l-~~_(N_Uv_L_VEE_LR_T4_;_7U_3T_~_ET_ 60.0' _~~~~~~_I INV EL -7270. I CULVERT INLET INV EL 4373.2 CONNECTOR DITCH SECTION SCALE: 1 = 20 2 3 4 l' MIN THICK CLAY (CL SPEC) COMPACTED TO AT LEAST 95% STD PROCTOR 5 6 E Di' I c Vl -' ~ ;;: f-w 0 .ltI ~ (I) >-Z t-o S :J ;:: U t-U ..: z w "-w (I) ::E :c " ~ w Z uJ: > ..: !::« :::; co 01-,0 ::E o::::J w ~ 0 (I) W t-• Z t-uW o (I) w> -..: ~::J !; :;:: oU ~ -' o 0 U Vl W CL >-X <:J -a:: ::E ::E w w ~ Z G w -' ~I ..: Z 0 ;:: !g I CL 0 FINAL DRA1¥ING 11009 Wa9 1 E D c B A , 2 Q [j D 1- , = "-~ ~. --~-~ --~ ~/ / CLASS A NORTH", , '~, "'. / / / / CLASS-A~" , / / / 11 e.(2 )\, /~ ". " ./ / I I I I I I L 3 NW WASTE LIMIT: N 12,193.95 E 14,297.10 N 40' 41' 14.351" W 113" 06' 33.354" NW BUFFER LIMIT: N 12,295.23 E 14,198.97\ N 40' 41' 15.334" W 113' 06' 34.651" WEST BUFFER LIMIT 1: N 11.996.05 E 14,193.39 N 40' 41' 12.377" W 113' 06' 34.652" WEST BUFFER LIMIT 2: N 11.777.39 E 14,162.22 N 40' 41' 10.212" W 113' 06' 35.004" / / LAIRW I I / i I I I I 4 RAIL (TYPICAL) I BUILDING OR STRUCTURE ~~ (TYPICAL) ~I I ROAD WEST WASTE LIMIT 1: Nll,994.79 E 14,294.63 N 40' 41' 12.384" W 113' 06' 33.338" WEST WASTE LIMIT 2: N 11,769.57 £ 14,262.13 N 40' 41' 10.153" W 113' 06' 33.705" N£ eUFF£R LIMIT: N 12,283.05 E 15,135.41 N 40' 41' 15.385" W 113' 06' 22.497" NE WASTE LIMIT: N 12,184.36 E 15,034.09 N 40' 41' 14.391" W 113' 06' 23.788" EAST WASTE LIMIT 1: N 11,873.39 E 15,029.97 N 40' 41' 1 1 .31 9" W 113' 06' 23.767" EAST WASTE LIMIT 2: N 10.697.38 £ 15,012.73 N 40' 40' 59.700" W 113' 06' 23.708" SE WASTE LIMIT: N 10,362,52 E 15,010.39 N 40' 40' 56.392" W 113' 06' 23.658" .. -.. -•. -•. - . , -•• -.• -.• -• : -===~SW~8~U~F~FE~R~U~M~IT~: =-;f==1~SW~W:'=A~S~T~E ~L~IM;;'IT~:~~g;: I ~ SE BUFFER ZONE LIMIT: I N 10.261.22 N 10,273.80 N 10,372.49 E 14,142.67 E 14,243.96 N 40' 40' 55.357" N 40' 40' 56.350" W 113' 06' 34.896" W 1',3' 06' 33.605" I E 15,109.69 , __ ~ N 40' 40' 55.4-09" r W 113' 06' 22,346" 2 3 5 5 j{ LEGEND: ------MW WASTE LIMITS ------MW WASTE BREAK LINES ------MW BUFFER ZONE LIMITS _ .. -.. -SECTION BOUNDARIES _______ PROPERTY BOUNDARIES 1/ ///://j MW BuFFER ZONE NOTES: 6 COORDINATES ARE LISTED BOTH IN THE LOCAL "CLIVE" SYSTEM AND AS LATITUDE AND LONGITUDE. 400 0 400 aliI 800 i 6 E FINAL )->-[lJ OJ DRA'~ING 11009 UOl 1 E D c B A 2 IL~ I P~-95SWC ~ I; I I I' ~ \ )\\ \ GW-151 GW-152 ___ -.L-____ .L ___ _ 1-3-30 ,,1-3-50\ / S-12. I I -------& "K-3-~O _q;--/ Gvf-13-0 G~-13j / / / I o ' 1~ o GW-56R ( " / I 1 'y I I I I I I 1 I I I I ~I~ I I ~ I ~ I ! ~ I c-' I I >< I UJ I lARW WASTE I I I ~ I ~ I LlMITS~.~' i 0 I ~ I ~ I I lW~128 : : : lARW WASTE I I BREAK LlNES~: 1 I ; I 1 0 I /A" I I W-64 I / " / "I 3 MIXED WASTE I I ) -----, EVAPORATION POND ~~ / " i I -10 GW-66R i , GWT7bL -=-~-------~ . J B (38 -----' .. , A-10" GW-l05 [!<J 2 1-1-30 1-1-50 1-1-100 3 17 A-37 1ZI S-27 D. 4 RAIL (TYPICAL) PAVED SITE ROAD (TYPICAL) 8-2 1.5 MILES EAST BUILDING OR STRUCTURE (TYPICAL) 5 LEGEND: J{ MW WASTE LIMITS MW WASTE BREAK LINES RUN-ON BERM APPROX. CENTERLINE SECTION BOUNDARIES PROPERTY BOUNDARIES A-XX lZI EXIST. AIR SAMPLING STATION S-yy D. EXIST. SOIL SAMPLING STATION GW-ZZ 0 EXIST. GROUNDWATER MONITORING WELL A-XX III NEW AIR SAMPLING STATION 5-YY A NEW SOIL SAMPLING STAT!ON GW-ZZ III NEW GROUNDWATER MONITORING WELL 200 0 200 WIl.\' I ENVIRONMENTAL MONITORING WELLS TO BE ABANDONED OR RELOCATED GW-130 GW-131 GW-132 1-3-30 1-3-50 1-3-10C 5 400 l 6 E DI c B 6 I-W Z W " '" z 0 <i Z r w u '" LL <{ 0 w z V1 z 0 w r= 'U "-::J Ii' U tt: V1 2 w 0 >->-Q) CD -"-w ~~ <D FINAL DRAWING 11009 U02 Appendix C Review of Expansion Impacts on Groundwater Modeling CLIVE FACILITY IMPACTS OF PROPOSED REVISIONS TO THE MIXED-WASTE DISPOSAL CELL GEOMETRY ON GROUNDWATER COMPLIANCE April 20, 2011 For Utah Division of Radiation Control 195 North 1950 West Salt Lake City, UT 84114-4850 EnergySolutions, LLC 423 West 300 South, Suite 200 Salt Lake City, UT 84101 1 I. PURPOSE EnergySolutions has proposed a revision to the Mixed-Waste disposal cell design originally assessed by Whetstone in 2000 (Whetstone, 2000). Table 1 summarizes the geometry differences that may potentially impact the validity of Whetstone’s initial fate and transport model. As is reflected, the revised Mixed- Waste disposal cell geometry considers an elongated design with a 77,500 ft2 smaller foot-print than originally examined in 2000. This is also reflected in the shorter corresponding top and side slope lengths and smaller waste heights. This memorandum examines impact of the proposed revisions to the Mixed- Waste disposal cell geometry on the validity of the Whetstone’s initial fate and transport assessment. II. BACKGROUND In compliance with requirements of its Groundwater Quality Discharge Permit for its Mixed-Waste disposal cell, EnergySolutions tasked Whetstone Associates to model water infiltration into the disposal cell and any resulting contaminant transport away towards a compliance point (Whetstone, 2000). This assessment was then used to demonstrate to the Utah Division of Radiation Control that any environmental impacts to the groundwater beneath the Mixed-Waste disposal cell will be kept within regulatory-governed tolerable risk levels (as defined by contaminant-specific groundwater protection limits). In a well-understood methodology employed in support of other EnergySolutions’ licensing activities, Whetstone divides its assessment into four phases: 1) The infiltration through the closed Mixed-Waste cell as projected by EPA’s HELP model (Schroeder, 1994); 2) Percolation rates predicted by the HELP model are input into the UNSAT-H model (Fayer, 1990) to predict the moisture content and time of travel through the vadose zone; 3) A dispersive solution for contaminant transport through the vadose zone as determined using the PATHRAE model (Merrell, et al. 1995); and 4) The horizontal migration of contaminant constituents through the aquifer to a point of compliance as modeled using PATHRAE. 2 TABLE 1 DIFFERENCES IN MIXED-WASTE DISPOSAL CELL MODELED PARAMETERS AS MODELED IN 22-Nov-00 AS MODELED IN 15-Apr-11 Disposal Cell Length ft 856 765 Disposal Cell Width ft 1718 1820 Top Slope Length ft 228 224 Maximum waste layer thickness above liner soil ft 39.5 36.0 Waste height at shoulder ft 35 31.5 Average waste height ft 37.3 33.7 Side Slope Length ft 200 157.5 Waste height at shoulder ft 35 31.5 Average waste height ft 17.5 15.8 3 III. IMPACT Impacts of the proposed revisions of the Mixed-Waste disposal cell geometry on the validity of Whetstone’s initial fate and transport study are assessed separately below for the HELP-predicted infiltration, UNSAT-H modeled soil moisture contents, PATHRAE-projected vertical contaminant transport, and the PATHRAE-assessed horizontal contaminant transport. 3.1 Infiltration Whetstone uses EPA’s HELP model to estimate the infiltration of rainwater through the closed Mixed- Waste cell cover. Once site-specific meteorological and climatological conditions are defined, the HELP model uses an internally-calculated “Time of Concentration” as the amount of time precipitation is in contact with surface soils (making infiltration available). As is reflected in Schroeder’s equation 33, the Time of Concentration is calculated from the steady-state rainfall intensity, steady-state infiltration rate, slope length, slope angle, and Manning’s roughness coefficient (Schroeder, 1994). As is self-evident, a decrease in concentration time, “results in less infiltration because less time is available for infiltration to occur.” (Schroeder, 1990, pg 38). Using this theory, the impact to the Time of Concentration from changes to slope angle and slope length is defined as, ݐ௥௨௡ ൌݐ଴ ൤ቀ௅೙೐ೢ ௅బ ቁଶ ቀ ௌబ ௌ೙೐ೢቁ൨ ଵ ଷൗ (1) where: trun = Revised Time of Concentration, or runoff travel time (minutes). t0 = Initial Time of Concentration, or runoff travel time (minutes). Lnew = Revised slope length (ft) L0 = Initial slope length (ft) Snew = Revised slope angle (dimensionless) S0 = Initial slope angle (dimensionless) 4 Infiltration results, presented in Table 2, illustrate that the revised geometry results in reduced Times of Concentration of precipitation falling on both the Top and Side Slopes of the Mixed-Waste disposal cell. In review of the Top Slope assessment, a 1 percent reduction in Time of Concentration results in a correspondingly-small decrease in infiltration. Since the amount of modeled-precipitation is not being revised as part of the proposed geometry, a reduction in infiltration into the cover system is reflected in an increased projected water runoff (from 0.007 in/year to 0.04 in/year). Finally, the projected changes to Times of Concentration result in similar changes in the volume of water migrating through the Mixed Waste, reducing it from 0.072 in/year to 0.071 in/year. The revised geometry results in a 15% reduction in the Time of Concentration for precipitation falling on the Mixed-Waste disposal cell’s Side Slope. This reduction in the time available for precipitation to infiltrate is reflected in the decrease in predicted infiltration into the cover system (from 3.12 in/year to 2.66 in/year) and increase in precipitation runoff (from 0.007 in/year to 0.47 in/year). Finally, the amount of water migrating through the disposal cell’s Side Slope and mixe-waste is reduced from 0.026 in/year to 0.022 in/year. The Whetstone model also considers the impact of water laterally draining out from the Top Slope’s filter layers onto the Side Slope. Whetstone accounts for this additional water by calculating an effective increase in the Mixed-Waste disposal cell’s Side Slope length, which is increased by the ratio of Top Slope filter layer drainage to Side Slope infiltration. Reductions in the lateral water drainage resulting from the proposed geometry within the Top Slope’s filter layers to the Side Slope, result in a reduced effective Side Slope length of 343 feet (from 430 ft). This reduction in effective Side Slope length results in a corresponding smaller precipitation Time of Concentration (14%), than is originally modeled. Reductions in the Time of Concentration and the effective Side Slope length reduces the amount of infiltration into the cover system from 3.12 in/year to 2.66 in/year. Finally, the amount of water migrating through the Mixed-Waste Side Slope is reduced from 0.038 in/year to 0.033 in/year. 3.2 Soil Moisture Whetstone uses PNL’s one-dimensional finite-difference UNSAT-H model to estimate the long-term, steady-state moisture content in the waste, liner, and vadose zone (which numerically calculates solutions to a modified form of Richard’s equation), (Fayer, 1990). While not considered as accurate as the UNSAT-H model methodology, the impacts of the proposed geometric changes to the vadose soil’s steady-state moisture content have been approximated using methodology developed by Merrell, et al. (Merrell, et al. 1995). 5 TABLE 2 INFILTRATION IMPACTS FROM ADJUSTED WASTE CELL GEOMETRY AS MODELED IN 22-Nov-00 AS MODELED IN 15-Apr-11 TOP SLOPE Change to Time of Concentration (trun / t0) 0.99 Precipitation in/yr 7.92 7.92 Runoff in/yr 0.007 0.04 Evaporation in/yr 4.69 4.69 Top layer infiltration in/yr 3.22 3.18 Lateral Drainage from Drainage Layer in/yr 3.15 3.11 Percolation/Leakage through Radon Barrier in/yr 0.072 0.071 Percolation/Leakage through Clay Liner in/yr 0.072 0.071 SLIDE SLOPE (without run-on) Change to Time of Concentration (trun / t0) 0.85 Precipitation in/yr 7.92 7.92 Runoff in/yr 0.007 0.47 Evaporation in/yr 4.79 4.79 Top layer infiltration in/yr 3.13 2.66 Lateral Drainage from Drainage Layer in/yr 3.1 2.64 Percolation/Leakage through Radon Barrier in/yr 0.026 0.022 Percolation/Leakage through Clay Liner in/yr 0.026 0.022 SLIDE SLOPE (with run-on) Change to Time of Concentration (trun / t0) 0.86 Precipitation in/yr 7.92 7.92 Runoff in/yr 0.007 0.47 Evaporation in/yr 4.79 4.79 Top layer infiltration in/yr 3.13 2.66 Lateral Drainage from Drainage Layer in/yr 3.089 2.63 Percolation/Leakage through Radon Barrier in/yr 0.038 0.033 Percolation/Leakage through Clay Liner in/yr 0.038 0.033 6 Sൌܵ௥൅ሺ1െܵ௥ሻቂ௉ ௄೓ቃௌேை (2) where: S = Fraction of Saturation (unitless) Sr = Residual Saturation Fraction (unitless) P = Annual Percolation (m/yr) Kh = Vadose zone saturated hydraulic conductivity (m/yr) SNO = Soil Index Using Merrell’s equation, effective soil index numbers of 0.0974 and 0.0937 are calculated to represent Whetstone’s original UNSAT-H analysis. As reflected in Table 3, these effective soil indexes can then be used, in conjunction with the revised percolation rates, vadose zone effective saturated hydraulic conductivity, and vadose zone residual saturations to estimate new fractions of saturation (0.375 for vadose soils beneath the Top Slope and 0.363 for vadose soils beneath the Side Slopes). 3.3 Vertical Contaminant Transport Whetstone uses the HELP-predicted infiltration and UNSAT-H-predicted fractions of saturation as input into the PATHRAE-RAD model to assess the vertical transport of leached contaminant from the Mixed- Waste disposal cell downward to the aquifer. As illustrated in Table 4, the revised fractions of saturation and infiltration rates result in slight delays in infiltrated water travel through the vadose zone (e.g., an increase of 5 years beneath the Top Slope and 156 years beneath the Side Slope). These decreases in vertical travel velocities become more pronounced, as illustrated in Table 5, when retarded nuclide transport is considered. While the proposed changes to the Mixed-Waste disposal cell geometries do not result in appreciable differences in the peak water table concentrations beneath the Top Slope, the arrivals of the peaks are delayed. More pronounced decreases in peak water table concentrations of approximately 14% are projected for contaminants transported to the water table from beneath the Mixed Waste disposal cell’s Side Slope. Additionally, vertical transport beneath the Side Slope is delayed by an average of 12 years. Most significantly, the arrival of the 41Ca peak concentration of 200,000 Ci/m3 at the water table below the Side Slope is delayed by 18 years. 7 TABLE 3 VADOSE ZONE SOIL MOISTURE IMPACTS FROM ADJUSTED WASTE CELL GEOMETRY AS MODELED IN 22-Nov-00 AS MODELED IN 15-Apr-11 Top Slope Residual Saturation Fraction 3.58E-02 3.58E-02 Soil Index 9.74E-02 9.74E-02 Infiltration Rate m/yr 1.83E-03 1.81E-03 Vertical Zone Saturated Hydraulic Conductivity m/yr 83.4 83.4 Vadose Fraction of Saturation 0.375 0.375 Side Slope Residual Saturation Fraction 3.58E-02 3.58E-02 Soil Index 9.37E-02 9.37E-02 Infiltration Rate m/yr 9.65E-04 8.34E-04 Vertical Zone Saturated Hydraulic Conductivity m/yr 83.4 83.4 Vadose Fraction of Saturation 0.368 0.363 8 TABLE 4 VADOSE ZONE TRANSPORT IMPACTS FROM ADJUSTED WASTE CELL GEOMETRY AS MODELED IN 22-Nov-00 AS MODELED IN 15-Apr-11 Top Slope Residual Saturation Fraction 3.58E-02 3.58E-02 Infiltration Rate m/yr 1.83E-03 1.81E-03 Vertical Zone Saturated Hydraulic Conductivity m/yr 83.4 83.4 Bulk Waste Density kg/m3 1,800 1,800 Vadose Soil Density kg/m3 1,553 1,553 Vadose Thickness m 7.4 7.4 Vadose Volumetric Water Content 0.137 0.137 Fraction of Saturation 0.375 0.375 Vertical Water Velocity m/yr 1.33E-02 1.32E-02 Vertical Water Travel Time from Waste to Aquifer yr 556 561 Side Slope Residual Saturation Fraction 3.58E-02 3.58E-02 Infiltration Rate m/yr 9.65E-04 8.34E-04 Vertical Zone Saturated Hydraulic Conductivity m/yr 83.4 83.4 Bulk Waste Density kg/m3 1,800 1,800 Vadose Soil Density kg/m3 1,553 1,553 Vadose Thickness m 7.4 7.4 Vadose Volumetric Water Content 0.135 0.135 Fraction of Saturation 0.368 0.363 Vertical Water Velocity m/yr 0.0071 6.17E-03 Vertical Water Travel Time yr 1,042 1,199 9 TABLE 5 VADOSE ZONE RETARDED TRANSPORT IMPACTS FROM ADJUSTED WASTE CELL GEOMETRY 22-Nov-00 234Bk 41Ca 249Cf 36Cl Top Slope Vadose Kd 1.00E-03 0.05 1.00E-03 2.50E-03 Vadose Retardation 1.01E+00 1.57E+00 1.01E+00 1.03E+00 Contaminant Travel Time to Water Table (yr) 562 871 562 571 Contaminant Peak Water Table Concentration (Ci/m3) 9.56E-09 2.22E+05 1.59E-08 3.54E-05 Year of Peak Water Table Concentration (yr) 603 957 591 618 Side Slope Vadose Kd 1.00E-03 0.05 1.00E-03 2.50E-03 Vadose Retardation 1.01E+00 1.57E+00 1.01E+00 1.03E+00 Contaminant Travel Time to Water Table (yr) 1,054 1,633 1,054 1,071 Contaminant Peak Water Table Concentration (Ci/m3) 7.80E-09 2.30E+05 6.40E-09 3.70E-05 Year of Peak Water Table Concentration (yr) 1,096 1,762 1,056 1,131 15-Apr-11 Top Slope Vadose Kd 1.00E-03 0.05 1.00E-03 2.50E-03 Vadose Retardation 1.01E+00 1.57E+00 1.01E+00 1.03E+00 Contaminant Travel Time to Water Table (yr) 567 879 567 577 Contaminant Peak Water Table Concentration (Ci/m3) 9.45E-09 2.19E+05 1.57E-08 3.50E-05 Year of Peak Water Table Concentration (yr) 609 967 596 624 Side Slope Vadose Kd 1.00E-03 0.05 1.00E-03 2.50E-03 Vadose Retardation 1.01E+00 1.57E+00 1.01E+00 1.03E+00 Contaminant Travel Time to Water Table (yr) 1,212 1,879 1,212 1,232 Contaminant Peak Water Table Concentration (Ci/m3) 6.74E-09 1.99E+05 5.53E-09 3.20E-05 Year of Peak Water Table Concentration (yr) 1,107 1,780 1,066 1,142 10 3.4 Horizontal Contaminant Transport Whetstone uses a second PATHRAE-RAD assessment to model the horizontal aquifer transport of contaminants arriving at the water table beneath the Mixed-Waste disposal cell to a compliance point down-gradient of the cell. As illustrated in Table 6, the proposed revisions in the Mixed-Waste disposal cell result in negligible impact to the horizontal transport phase of Whetstone’s model (assuming the distance from the Mixed Waste disposal cell to the point of compliance remains unchanged). Water beneath the Top Slope of the Mixed-Waste disposal cell arrives at the point of compliance in 88 years. Conversely, water beneath the Side Slope of the Mixed-Waste disposal cell arrives at the point of compliance in 15 years. These travel times are conservatively based on the shortest pathway from the disposal cell to the compliance point. As are reflected in Table 7, contaminants transported from the Top Slope regions of the Mixed-Waste disposal cell are projected to arrive at the compliance point between 6 to 10 years later than projected with the original cell geometry. Of more dramatic impact, the compliance point arrival of contaminants leached from the Side Slope region of the Mixed-Waste disposal cell are delayed by 220 to 700 years under the proposed new geometry. IV. CONCLUSIONS In summary, proposed revisions to the geometry of the Mixed Waste disposal cell results in delays in the transport of contaminants from the waste to the water table and then to the compliance well. Furthermore, compliance point contaminant concentrations for waste leached from the Side Slope are lower than those originally calculated by Whetstone. However, no appreciable compliance point differences are projected for the permit-limiting Top Slope concentrations. Because of this, it is concluded that the revised Mixed-Waste disposal cell geometry does not result in any increases in compliance well concentrations. Furthermore, no subsequent revisions are required to the existing Radioactive Material License waste acceptance criteria and associated disposal limits, as a result of the revised Mixed-Waste disposal cell geometry. Finally, because compliance point concentrations of contaminants traveling from the Mixed-Waste disposal cell’s Side Slope are reduced by approximately 14%, the revised Mixed Waste cell geometry provides an added buffer of safety for the environment and EnergySolutions’ demonstration of compliance with permitted groundwater protection limits. 11 TABLE 6 AQUIFER IMPACTS FROM ADJUSTED WASTE CELL GEOMETRY AS MODELED IN 22-Nov-00 AS MODELED IN 15-Apr-11 Top Slope Aquifer Density kg/m3 1,553 1,553 Aquifer Saturated Porosity 0.29 0.29 Aquifer hydraulic conductivity cm/sec 7.67E-04 7.67E-04 Hydraulic Gradient ft/ft 6.80E-04 6.80E-04 Aquifer Linear Velocity m/yr 8.34E-01 8.34E-01 Distance to compliance well m 73.2 73.2 Water Travel time to Well yr 88 88 Side Slope Aquifer Density kg/m3 1,553 1,553 Aquifer Saturated Porosity 0.29 0.29 Aquifer hydraulic conductivity cm/sec 7.67E-04 7.67E-04 Hydraulic Gradient ft/ft 6.80E-04 6.80E-04 Aquifer Linear Velocity m/yr 8.34E-01 8.34E-01 Distance to compliance well m 12.2 12.2 Water Travel time to Well yr 15 15 12 TABLE 7 COMPLIANCE WELL IMPACTS FROM ADJUSTED WASTE CELL GEOMETRY 234Bk 41Ca 249Cf 36Cl 22-Nov-00 Top Slope Year that GWPL are Exceeded at Compliance Point 500 640 500 500 Year of Peak Compliance Point Concentration 692 1,094 679 709 Side Slope Year that GWPL are Exceeded at Compliance Point 780 1,080 845 775 Year of Peak Compliance Point Concentration 795 1,103 860 790 15-Apr-11 Top Slope Year that GWPL are Exceeded at Compliance Point 506 650 506 506 Year of Peak Compliance Point Concentration 697 1,104 685 715 Side Slope Year that GWPL are Exceeded at Compliance Point 1,107 1,780 1,066 1,142 Year of Peak Compliance Point Concentration 1,121 1,803 1,081 1,157 13 REFERENCE Fayer, M.J., 1990. “UNSAT-H version 2.0: Unsaturated Soil Water and Heat Flow Model,” PNL-6779, Battelle Memorial Institute, April 1990. Merrell, G.B., Rogers, V.C., and Chan T.K., 1995. “The PATHRAE-RAD Performance Assessment Code for the Land Disposal of Radioactive Wastes,” RAE-9500/2-1, Rogers & Associates Engineering Corporation report, March 1995. Schroeder, 1994. “The Hydrologic Evaluation of Landfill Performance (HELP) Model: Engineering Documentation for Version 3,” EPA/600/R-94/168b, U.S. Environmental Protection Agency Office of Research and Development, Washington, D.C., September 1994. Whetstone, 2000. “Envirocare of Utah – Mixed Waste Cell Infiltration and Transport Modeling.” Whetstone Associates, Inc report to Envirocare of Utah, November 22, 2000. 13 REFERENCE Fayer, M.J., 1990. “UNSAT-H version 2.0: Unsaturated Soil Water and Heat Flow Model,” PNL-6779, Battelle Memorial Institute, April 1990. Merrell, G.B., Rogers, V.C., and Chan T.K., 1995. “The PATHRAE-RAD Performance Assessment Code for the Land Disposal of Radioactive Wastes,” RAE-9500/2-1, Rogers & Associates Engineering Corporation report, March 1995. Schroeder, 1994. “The Hydrologic Evaluation of Landfill Performance (HELP) Model: Engineering Documentation for Version 3,” EPA/600/R-94/168b, U.S. Environmental Protection Agency Office of Research and Development, Washington, D.C., September 1994. Whetstone, 2000. “Envirocare of Utah – Mixed Waste Cell Infiltration and Transport Modeling.” Whetstone Associates, Inc report to Envirocare of Utah, November 22, 2000. Appendix D Geotechnical Analysis REPORT OF GEOTECHNICAL EVALUATION ENERGY SOLUTIONS CLIVE FACILITY MIXED WASTE EMBANKMENT EXPANSION CLIVE, TOOLE COUNTY, UTAH Submitted to: EnergySolutions, Inc. 423 West 300 South, Suite 200 Salt Lake City, Utah 84101 Submitted by AMEC Earth & Environmental, Inc. Salt Lake City, Utah July 14, 2011 Job No. 10-817-05290 Page ii TABLE OF CONTENTS Page EXECUTIVE SUMMARY ................................................................................................. IV 1. INTRODUCTION ............................................................................................................... 1 1.1 OBJECTIVES ........................................................................................................ 1 2. SITE CHARACTERIZATION DATA .................................................................................. 2 2.1 SEISMIC DESIGN CRITERIA ............................................................................... 2 2.1.1 General ...................................................................................................... 2 2.2 SITE CONDITIONS ............................................................................................... 3 2.2.1 Background................................................................................................ 3 2.2.2 Subsurface Conditions ............................................................................... 4 2.2.3 Groundwater .............................................................................................. 5 2.3 EMBANKMENT DESIGN CRITERIA ..................................................................... 6 2.3.1 Existing Embankment Geometry ............................................................... 6 2.3.2 Proposed Mixed Waste Embankment Expansion Geometry ..................... 6 2.3.3 Geotechnical Design Values ...................................................................... 6 3. CALCULATIONS ............................................................................................................... 7 3.1 GENERAL ............................................................................................................. 7 3.2 ENGINEERING DESIGN PARAMETERS ............................................................. 8 3.3 STABILITY CALCULATIONS .............................................................................. 10 3.3.1 Embankment Static Stability .................................................................... 10 3.3.2 Embankment Seismic Stability ................................................................ 10 3.3.3 Probable Embankment Deformations ...................................................... 11 3.3.4 Sensitivity Analyses ................................................................................. 11 3.4 SETTLEMENTS ANALYSIS ................................................................................ 11 3.4.1 General .................................................................................................... 11 3.4.2 Foundation Settlements ........................................................................... 11 3.4.3 Time Rate of Foundation Settlement ....................................................... 13 4. CONCLUSIONS .............................................................................................................. 14 5. LIMITATIONS .................................................................................................................. 14 REFERENCES ........................................................................................................................... 16 List of Figures Figure 1 Regional Setting Figure 2 Location Map Figure 3 Exploration Location Map Figure 4 Generalized Foundation Conditions Based on CPT List of Appendices Appendix A Seismic Hazard (ref AMEC 12/13/2005) Quaternary Fault Reports From USGS Website Appendix B CPT Logs Appendix C Slope Stability Analyses Appendix D Settlement Analysis EnergySolutions, Inc. Geotechnical Report Job No. 10-817-05290, Phase II Mixed Waste Embankment July 14, 2011 Page iii EXECUTIVE SUMMARY Included herein is a geotechnical report for an investigation that evaluated the geotechnical potential for expanding the footprint and increasing the height of the Mixed Waste Embankment at the EnergySolutions facility near Clive, Utah. The Mixed Waste Embankment was the subject of a geotechnical evaluation by The Mines Group, Inc. in late 2000. In general the existing embankment design is depicted on drawings titled Design Drawings for the Mixed Waste Embankment Cover, drawings 0017-01 through 0017-08; each stamp dated April 4, 2002. AMEC has completed geotechnical studies for the adjacent Low Activity Radioactive Waste (hereinafter LARW) and Class A Embankments which culminated in a 2005 study that reviewed previous reports to obtain and summarize basic geotechnical engineering design parameters, evaluated previous and current seismic design criteria and included an updated seismic hazard analysis. A key element presented in AMEC’s 2005 study included an updated seismic hazard analysis. The seismic hazard analysis indicated that the deterministic maximum considered earthquake for the site is a magnitude M 6.8 earthquake on the Skull Valley fault at less than 30 km, yielding an “average” acceleration of 0.24g for the bedrock site conditions. The probabilistic peak horizontal acceleration of 0.24g for the weighted mean hazard curve corresponds to an average recurrence interval of approximately 8,825 years. This bedrock acceleration is amplified by site conditions to a peak horizontal acceleration value of 0.28g. Supplemental field exploration performed for this report confirmed that a generalized soil profile is applicable to the area of the Mixed Waste Embankment. The proposed expansion and height increase are considered minor. Slope stability analyses indicated that embankment stability is primarily governed by the height of the outer 5(H):1(V) side-slopes. Slope stability calculations included with this report continue to support the conclusion that the 5(H):1(v) slope configuration is geotechnically feasible. Foundation settlements of the proposed Mixed Waste Embankment expansion were found to be on the same order as predicted in previous studies. The majority of foundation settlements are anticipated to be complete by the time the final cover is to be placed. EnergySolutions, Inc. Geotechnical Report Job No. 10-817-05290, Ph II Mixed Waste Embankment July 14, 2011 Page 1 1. INTRODUCTION This geotechnical report summarizes our findings regarding the proposed minor expansion of the existing Mixed Waste Embankment at the EnergySolutions Clive Facility near Clive, Utah. The proposed expansion of the Mixed Waste Embankment configuration is depicted on the EnergySolutions, Inc. drawings titled Mixed Waste Embankment: Embankment Waste Surface Controls, DWG No. 11009-W01, dated June 17, 2011; and drawing titled Mixed Waste Embankment: Temporary Cover Surface & Closure Ditch Controls, DWG No. 11009-W02, dated June 17, 2011. EnergySolutions, Inc. is proposing to expand the embankment to the west by one cell and to raise the overall embankment height by approximately 2 feet. In November of 20001 The Mines Group, Inc., (hereinafter TMG) completed a technical report for the design of the Mixed Waste Facility cover. In addition to indentifying the various cover components, the TMG report evaluated stability of the cover and of the overall waste embankment configuration. The TMG report also evaluated potential settlement of the waste embankment. TMG based their stability and settlement analyses on geotechnical parameters previously documented by AMEC (formerly AGRA) for the adjacent Low Activity Radioactive Waste (LARW) Embankment. Since 2000, AMEC has completed several geotechnical studies for the adjacent LARW embankment including a 2005 study2 of the feasibility to increase the height and footprint of the existing Class A Embankment. AMEC’s 2005 study summarized the geotechnical soil parameters relevant to the typical subsurface soil profile and provided an update to the local seismicity of the Clive Facility. Additional geotechnical field investigations were completed to confirm the subsurface stratigraphy and associated engineering properties previously assumed in the 2005 study remain applicable for the current evaluation. For this investigation, two CPT soundings were performed on the south and north boundaries to the Mixed Waste Embankment. The EnergySolutions, Inc. Clive Facility is located within the southeast quarter of Section 32, T1S, R11W (Salt Lake Base and Meridian). The general site location of the Clive Facility is shown on Figure 1, Regional Setting. Figure 2, Location Map, shows the general arrangement of the various embankments at the EnergySolutions, Inc. Clive Facility. The locations of the AMEC’s CPT explorations completed as a part of this 2011 study are shown on Figure 3, Exploration Location Map. 1.1 OBJECTIVES The objectives of this investigation were to geotechnically evaluate the proposed expansion of the Mixed Waste Embankment configuration, considering geotechnical and seismic design considerations for slope stability and settlement. This investigation has utilized the work of AMEC’s 2005 study that summarized the geotechnical design parameters and site specific data 1 The Mines Group, Inc., (2000), Technical Report for the Mixed Waste Facility Cover Design, Clive, Utah, TMG Project Number: 00-17-01. Dated November 14, 2000. 2 AMEC (2005), Report, Combined Embankment Study, Envirocare, Tooele County, Utah, AMEC Job No. 4-817-004769, dated December 13, 2005. EnergySolutions, Inc. Geotechnical Report Job No. 10-817-05290, Ph II Mixed Waste Embankment July 14, 2011 Page 2 developed in our 1999a3 and preceding studies, along with the supplemental subsurface investigations to confirm site characterization within the footprint of the proposed embankment expansion. The objectives of this study were to: • Confirm by use of CPT soundings that the generalized soil profile for the Clive Facility is applicable at the area of the Mixed Waste Embankment. • Evaluate the static and seismic stability of the slightly higher embankment. • Evaluate static embankment settlements of the slightly higher embankment. 2. SITE CHARACTERIZATION DATA 2.1 SEISMIC DESIGN CRITERIA 2.1.1 General The referenced AMEC 2005 study completed an updated detailed seismic hazard analysis for the Clive Facility; a copy of the seismic hazard analysis is presented in Appendix A. The following paragraphs essentially reiterate the general summary that was stated in the referenced 2005 study with minor revisions that were identified by Interrogatory4 review. The deterministic peak horizontal acceleration values for fault earthquake sources within about 70 km of the EnergySolutions, Inc. site are summarized in Appendix A: Table A-2. Probabilistic peak horizontal acceleration values for the background earthquake source within 100 km of the site are shown on Appendix A: Figure A-5. The largest peak acceleration in Appendix A: Table A-2 corresponds to an M 6.6 earthquake generated by the East Cedar Mountains fault. The peak acceleration corresponding to an M 6.8 earthquake generated by one of the Skull Valley faults is nearly as high. The Skull Valley faults are located no closer to the site than 30 km at the ground surface, but the faults dip toward the site, making the attenuation distance less than 30 km. The 84th percentile values are 0.242g and 0.238g, respectively, as calculated by the attenuation relation of Abrahamson and Silva (1997). For comparison, the largest 84th percentile peak accelerations calculated by the Campbell and Bozorgnia (2003) and Pankow and Pechmann (2004) attenuation relations are 0.198g and 0.181g, respectively, for the M 6.8 earthquake on one of the Skull Valley faults. The expected maximum magnitude of 6.8 comes from Wong and Others (2002), but Swan and Others (2004) report an expected maximum magnitude of 6.5 for the same fault. The lower maximum magnitude for the Skull Valley faults gives 84th percentile accelerations of 0.219, 0.168, and 0.154g for the three attenuation relations, as can be seen in Appendix A: Table A-2. 3 AMEC (formerly AGRA) (1999a), Report, Geotechnical Site Characterization, Proposed New LARW Embankment, near Clive, Tooele County, Utah,” AGRA Job No. 9-817-002586, dated October 26, 1999. 4 AMEC (2006), Round 2 Interrogatories and Response, Class A Embankment Height Study, Energy Solutions Facility, Near Clive, Tooele County, Utah, AMEC Job No. 4-817-004769, dated April 28, 2006. EnergySolutions, Inc. Geotechnical Report Job No. 10-817-05290, Ph II Mixed Waste Embankment July 14, 2011 Page 3 The second largest peak acceleration in Appendix A: Table A-2 corresponds to two different earthquakes for the three attenuation relations. A maximum magnitude of 7.0 on the Stansbury fault produces 84th percentile peak accelerations of 0.162 and 0.195g for the Pankow and Pechmann (2004) and Campbell and Bozorgnia (2003) relations, respectively. A maximum magnitude of 6.6 on the Cedar Mountains fault produces an 84th percentile acceleration of 0.242g for the Abrahamson and Silva (1997) relation. Based on this review and update of earthquake ground motion at the EnergySolutions, Inc. site, a conservative, but reasonable deterministic maximum peak horizontal acceleration is 0.24g for rock site conditions. This maximum acceleration exceeds the 0.181g 84th percentile value predicted by the Pankow and Pechmann (2004) attenuation relation for any of the fault sources in the site region, and is approximately equal to the largest maximum 84th percentile value predicted by Campbell and Bozorgnia (2003) and the second largest 84th percentile value predicted by Abrahamson and Silva (1997). The probabilistic peak horizontal acceleration of 0.24g for the weighted mean hazard curve on Appendix A: Figure A-5 corresponds to an average recurrence interval of approximately 8,825 years. The AMEC 2005 study also evaluated whether the foundation soils and embankment either amplify or attenuate this site acceleration. A one-dimensional response analysis was completed using the software program SHAKE2000. As described in the 2005 study a small amplification of the peak horizontal ground acceleration value was calculated. Based on this consideration, it was found that the free field bedrock accelerations of 0.24g may increase up to a value of 0.28g in the free field through the foundation soil. However, the presence of the embankment tends to attenuate the free field ground motions to slightly above 0.25g. The range appropriate for stability analysis was therefore from 0.25g to 0.28g. 2.2 SITE CONDITIONS 2.2.1 Background AMEC completed a geotechnical site characterization for the existing adjacent LARW and Class A Embankments and submitted our findings in a report dated October 26, 1999, which was updated by AMEC in 2005. This site characterization supplemented the previous hydrogeology site characterization by Bingham Engineering, which included soil engineering property tests and shear wave velocity measurements down to 100 feet. As mentioned earlier in this report TMG, 2000 adopted this soil profile and pertinent soil parameters in their technical report for the Mixed Waste Facility Cover Design. In an effort to confirm and augment the engineering properties and stratigraphy selected for use from previous studies, supplemental CPT soundings were completed for this evaluation. The CPT’s were placed adjacent to the existing Mixed Waste Embankment and within the footprint of the proposed northern Mixed Waste expansion. The results of the CPT sounding’s are EnergySolutions, Inc. Geotechnical Report Job No. 10-817-05290, Ph II Mixed Waste Embankment July 14, 2011 Page 4 presented in Appendix B. The locations of the CPT’s are shown on Figure 3, Exploration Location Map. 2.2.2 Subsurface Conditions The subsurface conditions encountered in the supplemental explorations completed for this 2011 study were found to be consistent across the site and similar to the conditions encountered in the previously referenced investigations. A stratigraphic cross section comparing the conditions encountered by six (6) previous CPT soundings from the proposed northern expansion of the Class A Embankment and the two (2) recent CPT soundings for this study is shown on Figure 4, Generalized Foundation Conditions Based on CPT. The conditions observed are also in general agreement with the hydrogeologic cross sections developed by others across Section 32 and presented in Appendix D of EnergySolutions’ (formerly Envirocare) LARW Permit Application previously reviewed5. The general stratigraphic conditions are summarized below in Table 2.1, Subsurface Characterization. The same geologic unit numbers used in the hydrogeologic characterization are used herein. The importance of these findings is that subsurface conditions are sufficiently uniform across the Clive Facility that a single characterization is appropriate for Mixed Waste Embankment and other embankments. Table 2.1 – Subsurface Characterization Unit No. Depth (ft) Soil Type Description 4 0 to 9 +/- Upper Clays Silty Clays, classifying as CL in accordance with the Unified Soil Classification System. Contains some fine silt layers and is generally dry and medium stiff to stiff consistency. Considered to represent the deep Lake Bonneville clays. This material is used as both liner below the embankment and to construct the radon barrier. 3 9 to 26 +/- Silty Sands Dense to medium dense silty sands and silts containing a few thin clay layers. 2 26 to 64 +/- Clays and Silts Interbedded clay and silt layers with a few isolated sand layers up to two feet thick. Sand layers were discontinuous across the site. Clays are generally stiff with a few soft layers. Saturated throughout. 1 64 to max depth Interbedded Sand, Silt and Clay layers A sequence of interbedded silty sand, fine sand and coarse to gravelly sand layers with interbedded clay and silt layers. Increasing sand layers beginning at depths of 50-feet and extending to maximum depth investigated, 100 feet. Dense to very dense sands and stiff clays. 5 See AGRA Letter Report, “Technical Appendix Document Review, New LARW Facility, Envirocare of Utah NW 1/4, Section 32, Near Clive, Utah, AGRA Job No. 9-817-002427, July 15, 1999. EnergySolutions, Inc. Geotechnical Report Job No. 10-817-05290, Ph II Mixed Waste Embankment July 14, 2011 Page 5 As has been described by AMEC for previous studies at the Clive Facility and based on detailed geologic studies completed on other projects within the Basin and Range, we expect that the upper clays (Unit 4) represent the lake-bed clay deposited within the deep Lake Bonneville cycle(s) from about 12,000 to 30,000 years before present. The sequence of silty sands (Unit 3) below the upper clays were either alluvial, colluvial or lacustrine deposits which may have occurred during fluctuations in the Lake Bonneville level or during periods when the lake was not present (similar to current conditions). The lower (Unit 2) silts and clays most likely represent an older period of lacustrine deposition, predating 20,000 years before present and termed as the “Cutler Dam Lake cycle” in the geologic literature. The (Unit 1) sands, silts and clays most likely represent pre-Pleistocene deposits from an Interglacial period. These deposits may date as old as 100,000 to 150,000 years before present. The significance of these probable ages is that numerous earthquakes have occurred during this geologic time period surrounding the site vicinity and the probability of liquefaction with depth would be considered to be quite low based on age of the deposits alone. Based on geologic cross sections developed for the hydrogeologic site conditions, the anticipated depth to bedrock below the site is at least 400 feet. The geology of the surrounding area is described in the Utah Geologic Survey (UGS) Map 166 (Doelling, et al, 1994). This map and the accompanying text should be referenced for more detail than the very general description that follows herein. In general, the bedrock exposed along the Grayback Hills to the north consists of hard, durable limestone of the Triassic Age (180 to 225 million years before present), including the Thaynes, Dinwoody Formations, and volcanoclastic rock (volcanic rock incorporating sediments, some of which contain cobbles; aged about 35 million years before present). These rocks generally form the “basin and range” blocks that have been faulted during the Quaternary (3 million years ago to present). The basin and range faulting created the typical north-south trending mountain ranges filled with thick sequences of sediment in the intervening valleys. From about 10,000 to 30,000 years before present, prehistoric Lake Bonneville covered the entire area. There were numerous lake stages and elevations during this period, along with a few intervening dry periods, similar to conditions today. In a very general manner, the collective “Bonneville” deposits consist of fine sands, silts, and clays along the valley bottoms, and granular sands and gravels deposited along lake benches and spits. 2.2.3 Groundwater EnergySolutions has monitored groundwater at the Mixed Waste Embankment for many years. Their data indicates groundwater is typically measured at an elevation of 4248 to 4250 feet, or at a depth of approximately 28 feet below the adjacent natural ground surface. However, during our analysis, to be consistent with possible worst case conditions, the water level was modeled per EnergySolutions DWG. 0017-04 dated April 2, 2002 and more current drawings that have a note to maintain a minimum of 9 feet separation between the embankment and the water table. EnergySolutions, Inc. Geotechnical Report Job No. 10-817-05290, Ph II Mixed Waste Embankment July 14, 2011 Page 6 2.3 EMBANKMENT DESIGN CRITERIA 2.3.1 Existing Embankment Geometry Based on plans stamp dated April 4, 2002, the EnergySolutions, Inc. existing Mixed Waste Embankment design has a footprint of about 800-feet by 1,600-feet and a maximum height of about 43 feet at the crest. The embankment includes a 5(H):1(V) exterior slope extending 38 feet in height, and a 2 percent top slope. The embankment is to be provided with a protective rock cover, filter layers, and a clay radon barrier that total 5.5-feet thick on the top and side slopes. 2.3.2 Proposed Mixed Waste Embankment Expansion Geometry EnergySolutions, Inc. is considering constructing a waste embankment expansion in the northern direction of the existing embankment design and increasing the height of the mixed waste embankment by approximately 2 feet. The original design cover geometries have not been modified. The new Mixed Waste Embankment is designed with a footprint of about 800-feet (east-west) by 1,900-feet (north-south). The embankment includes a 5(H):1(V) exterior slope extending approximately 38 feet in height, and an approximate 2 percent minimum top slope. The maximum height of the top cover extends up to about 43 feet, given this general geometry. The embankment is provided with a debris free soil layer, clay radon barrier, filter layers, and protective rock cover that total 6.5-feet thick on the top and side slopes. The embankment is also provided with an approximate 7 foot thick base liner system Between the adjacent cells the bottom of the Mixed Waste Embankment is constructed with an undulating surface. Our stability analyses considered these features would afford additional resistance and therefore the bottom was smoothed out from the lowest portion of the waste cell which is located at the toe of the embankment. This approach resulted in an overall height analyzed of approximately 50 feet from the toe of the embankment to the crest of the 5(h):1(v) slope. 2.3.3 Geotechnical Design Values A summary of the geotechnical design criteria used for the existing embankment are presented in a following Table 3.1, Summary of Engineering Properties in Slope Stability Analysis and Table 3.2, Summary of Engineering properties in Settlement Analysis. These soil parameters are based on the geotechnical design values that were described in AMEC’s 2005 study. As previously indicated the AMEC 2005 study summarized design parameters and site specific data that was contained in AMEC 1999a and preceding studies. The 1999a AMEC study evaluated seismic stability, deformations, development of shear strengths for compressible debris, and shear wave velocity data of the embankment materials EnergySolutions, Inc. Geotechnical Report Job No. 10-817-05290, Ph II Mixed Waste Embankment July 14, 2011 Page 7 (for seismic response). Subsequent to that study, additional embankment material types (incompressible debris, controlled low strength material [hereinafter CLSM], containerized waste, oversize debris, large components) were evaluated which generally possessed higher shear strengths. We consider the available characterization to be adequate, but conservative. By conservative, it is meant that the shear strengths used in our calculations envelop the various types of waste placed in the embankments. Less conservative design assumptions could be utilized, however using higher shear strengths may require that limitations be placed on where certain types of waste can be placed within the embankment. We therefore continued to use the lower bound shear strengths to allow flexibility in waste placement and placement methods. The stability calculations utilized an 18 degree friction angle for the LARW debris, which is representative of a very high compressible debris percentage. Field tests indicated that the internal friction angle of compressible debris increased from 24 to 34 degrees as the waste percentage increases from 10 to 40 percent, respectively. However, at higher percentages of waste (greater than 50 percent), the friction angle may approach the 18 degree friction angle value. The 18 degree friction angle value conservatively bounds the lowest available shear strength. Higher shear strength values could be justified, even with the available data; that would lead to higher calculated factors of safety for a given design consideration. However, initial sensitivity and subsequent stability calculations revealed that less conservatism in the shear strength assumptions used in the analysis would not be necessary6. 3. CALCULATIONS 3.1 GENERAL Soil parameters that were summarized in Table 3.1 of the 2005 study for the foundation soil and embankment materials have continued to be used for this update report. To evaluate the Mixed Waste Embankment based on slope stability, the following sets of calculations were completed for the new embankment design height: • Static stability was calculated. • Pseudostatic (seismic) stability was calculated. • “Yield” accelerations (or the yield coefficient was determined) to estimate deformations. • Deformations following a seismic event were calculated using a “Newmark Sliding Block” analysis. 6 Large scale laboratory shear box testing could be completed that would reduce the shear strength conservatism in the analysis. Similarly, the strength of the radon barrier clay and clay liner was conservatively estimated from published values and laboratory testing. Supplemental testing could support higher strength values and further reduce conservatism in the values used. EnergySolutions, Inc. Geotechnical Report Job No. 10-817-05290, Ph II Mixed Waste Embankment July 14, 2011 Page 8 The following sections discuss each of these items in further detail. 3.2 ENGINEERING DESIGN PARAMETERS Drained strength parameters were used in static stability calculations and both drained and undrained parameters were used in seismic stability calculations. Further details and background with regards to the soil parameters are presented in the text and appendices of the 2005 study. The foundation layers used in the slope stability model were based on the site characterization and stratigraphy described in Section 2.2, Site Conditions, of this report. In addition to the material properties defined by previous studies, this evaluation considered the interface shear strength of the liner systems. The embankment consists of three different liner systems defined as follows: GT/GM Interface – The cover liner system consisting of a geotextile (GT) underlain by a high density polyethylene (HDPE) geomembrane (GM) liner sandwiched between a coarse filter layer on top and a low permeable radon barrier on bottom. GT/GN/GM Interface – Tertiary liner system below the waste consisting of a GT underlain by a geonet (GN) underlain by a HDPE GM liner sandwiched between a protective soil layer on the top and bottom. GT/GN/GM/GN/GM Interface – Primary and secondary liner system below the tertiary liner system consisting of, from top to bottom, GT, GN, HDPE GM, GN, and a HDPE GM sandwiched between a protective soil layer on top and a low permeable clay liner on bottom. Conclusive laboratory testing consisting of large scale direct shear tests have not been conducted on these complex liner systems. Assumptions were made on the shear strength parameters of these interfaces and sensitivity analyses were conducted to evaluate the embankment stability with various interface shear strengths. EnergySolutions, Inc. Geotechnical Report Job No. 10-817-05290, Ph II Mixed Waste Embankment July 14, 2011 Page 9 Table 3.1 – Summary of Engineering Properties in Slope Stability Analysis (ref AMEC 12/13/05) Material / Soil Units Unit Weight, (pcf) Angle of Internal Friction, (degrees) Cohesion Intercept, (psf) Basis / Reference Source LARW Embankment Properties Rip Rap (Cover) 135 40 0 Appendix B-2, Table B Clay Cover 123 0 1000 AMEC 1999a, Section 3.2.7 Protective Soil Layer (Debris Free Soil) – silty sand 117.5 38 250 AMEC 1999b7, Figure A-7 Compressible Debris 101 18 130 AMEC 1999b, Figure 9 CLSM 120 0 15200* (equal to 100 psi) Specification calls for minimum of 150 psi Clay Liner 123 0 (28) 1000 (100) Appendix B-2, Table B (AMEC 5/25/99, Figure A-6) GT/GM Interface 60 17 0 Assumed GT/GN/GM Interface 60 15 0 Assumed GT/GN/GM/GN/GM Interface 60 15 0 Assumed Embankment Foundation Properties Drained / Undrained Drained / Undrained Unit 4- Upper Clays 118 29 / 0 0 / 2000 CPT correlations Appendix B-1 (or AMEC 2005, App B-1) and AMEC 1999a Unit 3 - Silty Sands 120 34 0 CPT correlations Appendix B-1 (or AMEC 2005, App B-1) and AMEC 1999a Unit 2 - Clays and Silts 121 29 / 0 1000 / 2000 CPT correlations Appendix B-1 (or AMEC 2005, App B-1) and AMEC 1999a Unit 1 - Interbedded Sand, Silt and Clay 120 29 0 CPT correlations Appendix B-1 (or AMEC 2005, App B-1) and AMEC 1999a * This strength exceeds the strengths of the other materials by a large margin. 7 AMEC (formerly AGRA) (1999b), Task 2 -Summary of Field Strength Tests, Clive Disposal Facility, 75 Miles West of Salt Lake City, Clive, Utah, AGRA Job No. 8-817-002103, dated June 28, 1999. EnergySolutions, Inc. Geotechnical Report Job No. 10-817-05290, Ph II Mixed Waste Embankment July 14, 2011 Page 10 3.3 STABILITY CALCULATIONS 3.3.1 Embankment Static Stability Our slope stability analyses were performed with the computer program SLIDE version 5.077 (Rocscience, 2007), utilizing the Spencer’s Method8 for circular and planar modes of movement. The geometry of the slope stability model and tabulation of the analysis is shown in Appendix C. The strength of the embankment and foundation materials was modeled using both drained and undrained strength parameters. In general, a static factor of safety greater than 1.5 is desired to meet generally accepted geotechnical design criteria (Kramer, p. 431). Stability is calculated by allowing the computer program to search for a critical failure surface. Four failure scenarios or cases were studied for this report: Case 1 – shallow circular failure surfaces within the mixed waste embankment; Case 2 – deep circular failures through the foundation soils, Case 3 – shallow circular failures in the fully saturated cover, and Case 4 – planar failures along the liner interfaces. The minimum factor of safety was at least 1.8 and was from the shallow circular failure in the fully saturated cover, which is within the acceptable range for static stability. Details of the stability analysis, plots of the lowest factor of safety failure surfaces, and a tabulation of the analysis completed are found in Appendix C. 3.3.2 Embankment Seismic Stability Following the static stability calculations, the pseudostatic stability of the Mixed Waste Embankment was calculated for each of the cases identified in the section above. “Pseudostatic” stability is calculated by applying a horizontal coefficient equal to 50 percent of the seismic design acceleration to the embankment (Hynes-Griffin, 1984). This factor may be taken as 50 percent of the 0.28g acceleration. In general, factors of safety greater than or equal to 1.29 are desired when this method of seismic slope stability is utilized (Kramer, p. 436). Again, the Spencer’s Method for circular and planar slip surfaces for each of the three cases was evaluated within the program SLIDE. For pseudostatic stability, though, both drained and undrained foundation soil strength parameters were utilized. Stability was calculated by allowing the computer program to search for a critical failure surface. Plots of the lowest factor of safety failure surfaces are also included in Appendix C. The minimum calculated factor safety was 1.1 and was from planar failures occurring within the liner interface. Due to the low pseudostatic factor of safety, displacement analyses were performed utilizing the Simplified Newmark Method (Newmark, 1965) to evaluate the potential embankment deformation during the maximum seismic event. The embankment deformations are discussed in the following section. 8 The Spencer’s Method of Calculating Slope Stability using the limiting equilibrium method (method of slices) satisfies both force and moment equilibrium. The Bishop’s Method used previously satisfies only force equilibrium and is therefore less rigorous. 9 Actual values discussed by Kramer vary from 1.0 to 1.15. EnergySolutions, Inc. Geotechnical Report Job No. 10-817-05290, Ph II Mixed Waste Embankment July 14, 2011 Page 11 3.3.3 Probable Embankment Deformations The slope stability model described previously in Section 3.3.2, Embankment Seismic Stability, was also used to estimate the potential range of post earthquake deformations of the Mixed Waste Embankment. To estimate the post earthquake deformation, the seismic coefficient (acceleration) required to achieve a factor of safety of unity (i.e. 1.0) is calculated. This value is termed the “yield acceleration” and is utilized in conjunction with a number of published empirical relationships between yield acceleration and potential post earthquake slope deformations. The minimum yield acceleration for the Mixed Waste Embankment was found to be between 0.15g for the planar failures and 0.56g for deep circular failures. The probable earthquake deformations were calculated for each of the three cases studied using the simplified Newmark Sliding Block Analysis. As was determined in the 2005 study, the probable post earthquake embankment deformations were found to be less than 1 inch. The results are presented in Appendix C. These post earthquake deformations are predicted to be quite small and do not represent significant risk to the facility. 3.3.4 Sensitivity Analyses Sensitivity analyses evaluate the variability of slope stability factors of safety due to a range of strength parameters. The interface shear strengths of the three liner systems were assumed and as the static and pseudostatic slope stability evaluations show, have a paramount roll in the slope stability. As shown in Appendix C, Figure 4, the interface friction angle was varied from 0 to 30 degrees for each interface and the factors of safety against planar failures along the interface were calculated. Under the embankment configuration evaluated, the friction angle of the GT/GM, GT/GN/GM and GT/GN/GM/GN/GM interfaces required for an acceptable factor of safety (1.5) were 12 degrees, 8 degrees, and 9 degrees, respectively. These values represent lower bound values and the friction values used in our analyses are based on values presented in the TMG, 2000 report which, exceed the aforementioned friction angles. 3.4 SETTLEMENTS ANALYSIS 3.4.1 General For this report we have only reevaluated the potential foundation settlement of the Embankment in order to show the embankment foundation settlements are expected to be on the same order as predicted in previous studies. 3.4.2 Foundation Settlements The subsurface site characterizations described early in this report provide the information to define material boundaries and soil parameters. Compressibility parameters used in 2005 study, and as described in Table 3.2, were utilized in the calculations. EnergySolutions, Inc. Geotechnical Report Job No. 10-817-05290, Ph II Mixed Waste Embankment July 14, 2011 Page 12 Table 3.2 – Summary of Engineering Properties in Settlement Analysis Material / Soil Units OCR E (psf) Cc Cr Cv e0 Creep Unit 4 – Upper Clays 5.3 200,000 0.08 0.008 1.0 0.68 0.192 Unit 3 – Silty Sands - 400,000 - - - - - Unit 2 – Clays and Silts 1.0 100,000 0.04 0.004 0.80 0.75 0.192 Unit 1 – Interbedded Sand, Silt and Clay - 400,000 - - - - - Settlements of the foundation material were evaluated for elastic or immediate, primary consolidation, and secondary consolidation (creep) deformations using industry standard equations. The elastic settlements were estimated based on the Theory of Elasticity by Timoshenko and Goodier (1951) as follows: ߜ௘ ൌݍ଴ܤԢ ቀଵିఓమ ாೞ ቁቀܫଵ ൅ ଵିଶఓ ଵିଶఓ ܫଶቁ ܫி (Bowles, 1996) Where ݍ଴ ൌ intensity of contact pressure (psf) ܤԢ ൌ least lateral dimension of contributing base area (ft) ܫ௜ ൌ influence factors, which depend on L’/B’, thickness of stratum H, Poisson’s ratio ߤ, and base embedment depth D ܧ௦,ߤൌ elastic soil parameters ߜ௘ ൌ elastic settlement (ft) The thickness of the stratum considered all compressible soil beneath the embankment to bedrock, conservatively assumed to be 500 feet below ground surface. The modulus of elasticity (Es) was calculated as the weighted average of the four soil units that make up the subsurface to bedrock. Primary and secondary (creep) consolidation settlement predictions were based on the theory of one-dimensional consolidation for normally consolidated soils as follows: ߜ௖ ൌ ∑஼೎ ଵା௘బ ܪ݈݋݃ ቀఙᇱ೥೑ ఙᇱ೥బ ቁ (Coduto, 1999) Where ߜ௖ ൌ primary consolidation settlement ܥ௖ ൌ compression index ݁଴ ൌ initial void ratio ܪൌ thickness of the compressible layer ߪԢ௭௙ ൌ final vertical effective stress EnergySolutions, Inc. Geotechnical Report Job No. 10-817-05290, Ph II Mixed Waste Embankment July 14, 2011 Page 13 ߪԢ௭଴ ൌ initial vertical effective stress and ߜ௦ ൌ ܪ௙ܥఈ݈݋݃ ቀ௧మ ௧భቁ (Bowles, 1996) Where ߜ௦ ൌ secondary consolidation settlement ܥఈ ൌ secondary compression index ݐଵ ൌ time at the end of primary consolidation ݐଶ ൌ time at the end of secondary consolidation ܪ௙ ൌ thickness of compressible layer ߪԢ௭଴ ൌ initial vertical effective stress Consolidation settlement occurs as pore water is squeezed out the soil matrix as the material compresses under the induced loads. The subsurface stratigraphy at this site consists of two fine grained layers, the Upper Clays of Unit 4, and the Clays and Silts of Unit 2. The soils comprising Units 1 and 3 are coarser grained in nature and are believed to only exhibit elastic settlement. The Upper Clays of Unit 4 are above the measured ground water table and are therefore unsaturated and can be ignored in the consolidation settlement calculations. The Clays and Silts of Unit 2 lie below design groundwater table and are saturated; all consolidation settlements are assumed to come from this layer. The time required to complete primary consolidation for the adjacent Class A Embankment was evaluated in AMEC’s 2005 report and was not computed in this evaluation as the stratigraphy does not significantly change. The analyses estimated that 95 percent consolidation will be complete within approximately one year as described in the following section. The time required to complete secondary consolidation was assumed to be the life of the facility, 500 years. Settlements were calculated beneath the center of the embankment expansion at the maximum embankment height and maximum induced stress. Elastic settlement of the entire subsurface stratigraphy with an estimated thickness of 500 feet was 12 inches. Primary and secondary consolidation settlements from the 38 foot thick Clay and Silt Unit 2 layer were 3.5 inches and 2 inches, respectively. The total settlement of the embankment was estimated to be approximately 16 inches at the center of the proposed embankment. 3.4.3 Time Rate of Foundation Settlement As was described in AMEC’s 2005 study, we anticipate that the embankment is constructed sufficiently slow that drainage (consolidation) of the foundation layers occurs during construction. If one assumes that the Mixed Waste Embankment was placed all at once our analysis estimated that 95 percent consolidation will be complete within approximately one year. Again, given the Mixed Waste Embankment will receive waste over many years before topping out, this is a worst-case scenario. EnergySolutions, Inc. Geotechnical Report Job No. 10-817-05290, Ph II Mixed Waste Embankment July 14, 2011 Page 14 4. CONCLUSIONS Based on the foregoing discussions, the following conclusions have been made for the proposed Mixed Waste Embankment: • The stability of the proposed embankment is governed primarily by the height of the 5(H):1(V) slope. At a height of slightly above 38 feet, the static and pseudostatic stability of Mixed Waste embankment was found to be acceptable. • Settlement analysis of the currently proposed embankment geometry determined that foundation settlements of the proposed Mixed Waste Embankment were on the same order as predicted in previous studies. The majority of foundation settlements are anticipated to be complete by the time the final cover is to be placed. 5. LIMITATIONS This report was prepared within the scope of generally accepted geotechnical engineering practices under the direction of a licensed engineer. No warranty, express or implied is made as to the conclusions and professional advice included in this report. AMEC Earth & Environmental, Inc. disclaims responsibility and liability for problems that may occur if the recommendations contained herein are not followed. This report was prepared for EnergySolutions, Inc and their design consultants solely for the design and construction of the project described herein. It may not contain sufficient information for other uses or the purposes of other parties. These recommendations should not be extrapolated to other areas or used for other facilities with consulting AMEC Earth & Environmental, Inc. Recommendations herein are based on interpretations of the subsurface conditions concluded from information gained from subsurface explorations. The interpretations may vary horizontally and vertically across the site. EnergySolutions, Inc. Geotechnical Report Job No. 10-817-05290, Ph II Mixed Waste Embankment July 14, 2011 ame We trust that this report adequately provides the design support for the Mixed Waste Embankment height and footprint increase. If you have any questions or comments, please contact the undersigned. Respectfully submitted, ·~~bl. ~ e, PE Pro essional Engineer State of Utah No. 358996 EAB/DW:eab Addressee (4) c: Sean McCandless (1) David Weidinger E.I.T. Justin Hall Professional Engineer Page 15 EnergySolutions, Inc. Geotechnical Report Job No. 10-817-05290, Ph II Mixed Waste Embankment July 14, 2011 Page 16 REFERENCES Black, B.D., et al, “Quaternary Fault and Fold Database and Map of Utah,” Utah Geologic Survey Map 193DM, 2003 (on CD rom). Bowles, J.E., 1996. Foundation Analysis and Design. Fifth Edition. New York: McGraw-Hill Book Company. 816 pp. Bray, R.J., et al, 1998, “Simplified Seismic Design Procedure for Geosynthetic-Lined, Solid Waste Landfills,” Geosynthetics International, Vol. 5, No. 1-2, pp. 203-235. Coduto, D.P., 1999. Geotechnical Engineering Principles and Practices. New Jersey: Prentice- Hall. Doelling, H.H., Solomon, B.J., and Davies, S.F. “Geologic Map of the Grayback Hills Quadrangle, Tooele County, Utah,” Utah Geological Survey, UGS Map 166, dated 1994. Hynes-Griffin, Mary E. and Franklin, Arley G., (1984). Rationalizing the Seismic Coefficient Method. Miscellaneous Paper GL-84-13, Geotechnical Laboratory, Waterways Experiment Station, US Corps of Engineers, Vicksburg, Mississippi. Kavazanjian Jr., E. and Matasovic, N., (1995). Seismic Analysis of Solid Waste Landfills. GeoEnvironment 2000, Acar, Y.B. and Daniel, D.E., Editors, ASCE Geotechnical Special Publications No. 46, New Orleans, pp. 1066-1080. Kavazanjian, E. Jr.; Matasovic, N.; and Caldwell, J., (1998). Seismic Design and Performance Criteria for Landfills. 6th U.S. National Conference on Earthquake Engineering, EERI. Kramer, Steven L., (1996). “Geotechnical Earthquake Engineering”, Prentice-Hall. Newmark, N.M., (1964). “Effects of Earthquakes on Dams and Embankments”, Geotechnique, Vol. 15, pp. 136-160. Rocscience. 2007. Slide Version 5.0 Users Manual. Toronto, Ontario, Canada. Seed, R.B. and Bonaparte, R., (1992). Seismic Analysis and Design of Lined Waste Fills: Current Practice. Proceedings, Conference on Stability and Performance of Slopes and Embankments, Vol. 2, ASCE Geotechnical Special Publications, No. 31, pp. 1521-1545. Timoshenko, S., and Goodier, J.N., (1951), Theory of Elasticity, 2nd ed., McGraw-Hill, New York, 506 pp. EnergySolutions, Inc. Geotechnical Report Job No. 10-817-05290, Ph II Mixed Waste Embankment July 14, 2011 Page 17 Zhang, G., Robertson, P.K., and Brachman, R.W.I., (2002), Estimating Liquefaction Induced Ground Settlements from CPT for Level Ground, Canadian Geotechnical Journal, 39(5): pp 1168 – 1180. ame & ! " # $ % ! & '& Reference: Adapted from AMEC 2005, FIGURE 1 FIGURE 1 REGIONAL SETTING E.lhqu_ Epic ..... rs < 1650-2000<) __ ._.... ... .. __ 0 ...... . ...... -" ..... , ..... "S .,. .... . ~ , MM ~ .. N~ .. f ..,"-ffcmUSGS_UG5 o.t.b ... E~""!rom UniYort.it)r '" U100h _d Un.....,.i1y 01 N ....... ~ ... "" •• PrQjo<:'"" io UTI,j Zone 12 WG5&4 VICINITY MAP EMB'NIQlENT ABE' LBGlNDi • • CLASS II NORTH c 11 .. (2.) , "'" L LOCATION MAP " , " " .... , , , , , , ENERGY SOLUTIONS. INC, ENERGY SOLUTIONS CU\IE FACIUTY MIXED WASTE EMBANKMENT EXPANSION LOCATION MAP amecfJ _10... _ CHEeIIIO IT EM DIm: _ ... ___ II' 1M 7/11'" -~ -EARTH AND ENVIRONMENTAL 108170529F06 A • CPT04-05 LEGEND; S CPTll-01 H'PAOXIIo\TE LOCA1ION OF n£ CONE PENETRATION lEST (VfAR PEARlIIIAED) ENERGY soumONS. INC. ~W EXPLORATION LOCATION WAP 1081705290F05 3 A