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HomeMy WebLinkAboutDRC-2018-006321 - 0901a0688085ca10,..--...--...----7.. ENERGYSOLUTIONS DFC-Zote -OD63ZI June 27, 2018 CD18-0121 Mr. Scott T. Anderson, Director Division of Waste Management and Radiation Control P.O. Box 144880 Salt Lake City, UT 84114-4880 Div of Waste Management and Radiation Control JUN 2 7 2018 Subject: Ground Water Quality Discharge Permit No. UGW450005 (GWQDP): Abandonment of Compliance Monitoring Wells GW-84, GW-85, and GW-86; and Collection Lysimeters CL-W3, CL-W4, and CL-N5 Dear Mr. Anderson: The GWQDP, approved on October 9, 2014, includes the abandomnent of several existing monitoring wells to facilitate the construction of Class A West embankment liner. This letter provides notification that EnergySolutions intends to proceed with abandonment of monitoring wells GW-84, GW-85, and GW-86, three of the wells approved for abandonment in the GWQDP. In accordance with GWQDP Part 1.1.4, compliance monitoring of these wells will continue until their abandonment. All three wells have already been sampled in 2018 during the annual groundwater monitoring event, and all three will be abandoned during the second half of 2018. EnergySolutions will use a current Utah-Licensed well driller to perform the permanent abandonment of wells GW-84, GW-85, and GW-86 in accordance with Utah Administrative Code (UAC) R655-4-14, Abandonment of Wells. Collection lysimeters CL-W3, CL-W4, and CL-N5 will also be abandoned during the second half of 2018 to facilitate the embankment liner construction. The approved Collection Lysimeter Operation, Maintenance, and Closure Plan (Plan) (GWQDP Appendix C, July 27, 2011) requires that closure is accomplished by pressure grouting the lysimeter transfer pipes using a sand, cement, and bentonite slurry mixture. EnergySolutions requests a variance to abandon the three lysimeters according to the Plan without the requirement to pressure grout the transfer pipes. Unlike the other Clive Facility lysimeters, the transfer pipes of CL-W3, CL-W4, and CL-N5 are located completely beneath the footprint of the Class A West embankment. As such, they do not represent preferential pathways for contamination to reach groundwater or the vadose zone outside the embankment boundaries. Abandonment will consist of removing the manholes and standpipes. Transfer pipes will be cut outside of the manhole to prevent breaking the transfer pipes during manhole removal. Prior to backfilling, the end of each transfer pipe will be capped with a water-tight seal. The manhole excavation will be backfilled in accordance with Specification 26 in the current revision of the LLRW and 1le.(2) CQA/QC Manual, i.e., 9-inch maximum uncompacted lifts, compacted to at least 95% of Standard Proctor. The attached engineering evaluation demonstrates that the abandoned lysimeters will not collapse during or subsequent to construction of the Class A West embankment. Prior to the commencement of abandonment work, EnergySolutions will notify the Division of Waste Management and Radiation Control (DWMRC) via e-mail of the field schedule. Notification will be provided at least 7 days prior to the start of field work. EnergySolutions will submit an "As-Plugged" report to DWMRC within 30 days of the completion of the abandonment 299 South Main Street, Suite 1700 • Salt Lake City, Utah 84111 (801) 649-2000 • Fax: (801) 880-2879 • www.energysolutions.com ENERGYSOLUTIONS Mr. Scott Anderson June 27, 2018 CD18-0121 Page 2 of 2 project, as required by GWQDP Part II.M. The report will also include documentation for the abandonment of collection lysimeters CL-W3, CL-W4, and CL-N5. To provide adequate time for planning and scheduling, EnergySolutions requests approval of the Plan variance by July 31, 2018. Should you have any questions regarding this submission please feel free to contact me at (801) 303-0187. Sincerely, Iv Robert W. Sobocinski Groundwater Program Manager Enclosure cc: Charles Bishop (DWMRC) Don Verbica (DWMRC) I cer* under penalty of law that this document and all attachments were prepared under my direction or supervision in accordance with a system designed to assure that qualified personnel properly gather and evaluate the information submitted. Based on my inquiry of the person or persons who manage the system, or those persons directly responsible for gathering the information, the information submitted is, to the best of my knowledge and belief true, accurate, and complete. I am aware that there are significant penalties for submitting false information, including the possibility offine and imprisonment for knowing violations. ENERGYSOLUTIONS To: Robert Sobocinski From: David F. Booth CC: Vern Rogers, File Date: June 27, 2018 Re: Lysimeter Abandonment Pipe Collapse Evaluation I have performed the following evaluation to determine whether or not the 8—inch diameter lysimeter collection pipes for Lysimeters CL-W3, CL-W4 and CL-N5 will collapse if not grouted when abandoned. Problem: Will the 8" diameter schedule 80 PVC lysimeter pipes collapse due to the overlying soil and waste materials, if they are not grouted? Approach: Evaluate CL-W3, as it is the lysimeter collection pipe with the greatest amount of overlying material when the Class A West embankment is completed. Calculate the overburden load in units of pounds per square inch (psi) and compare that value to the collapse pressure rating for 8 inch Schedule 80 PVC pipe. Criteria: Collapse Pressure for Schedule 80 8-inch PVC Pipe = 175 psi (https://www.pvcfittingsonline.com/resource-center/strength-of-pvc-pipe-with-strength-chart/) Collection Pipe Invert Elevation at Manhole (deepest point) = 4258 feet above mean sea level (ft amsl) => Top of Pipe= 4258.67 ft amsl Top of Liner Protective Cover Elevation = 4266 ft amsl Top of Waste = 4340.3 ft amsl, use max waste height although height at pipe location is less Top of Cover = 4346.3 ft amsl Clay Unit Weight = 115 lbs/cubic foot, typical of native clays used for backfill and liner Waste Unit Weight = 100 lbs/cubic foot, estimated value Cover Unit Weight = 125 lbs/cubic foot, conservative average of clay, rock and soil layers Calculations: Backfill/Clay Liner/Liner Protective Cover Thickness and Loading Thickness = 4266 — 4258.67 = 7.33 feet (use 7.5 feet) Loading = 7.5 feet x 115 lbs/cubic feet = 862.5 pounds per square foot (psf) Waste Thickness and Loading Thickness = 4340.3 — 4266 = 74.3 feet Loading = 74.3 feet x 100 lbs/cubic foot = 7,430 psf 299 South Main Street, Suite 1700 • Salt Lake City, Utah 84111 (801) 649-2000 • Fax. (801) 880-2879 • www.energysolutions.com ENERG SOLUTIONS Cover Thickness and Loading Thickness = 4346.3 — 4340.3 = 6 feet Loading = 6 feet x 125 lbs/cubic foot = 750 psf Total Loading = 862.5 + 7,430 + 750 = 9,042.5 psf or 62.8 psi, < 175 psi collapse rating Safety Factor = 175 psi/62.8 psi = 2.8 Conclusions: The 8-inch pipe ability to resist collapse from the overlying materials (buried application) exceeds the calculated overburden pressure, with a safety factor of 2.8. Therefore, there is no need to grout the pipes to prevent collapse. Please contact me if you have any questions. Thanks. David F. Booth, PE Engineering Director 299 South Main Street, Suite 1700 • Salt Lake City, Utah 84111 (801) 649-2000 • Fax: (801) 880-2879 • www energysolutions.com