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Home My WebLink AboutDRC-2012-001472 - 0901a068802dd05c(6/7/2012) Shairose Falahati Nini 05 31 12 trnsmtl interrog response ICTM PDF -*i—— Page 1 1472 DA MINES Denison Mines (USA) Corp 1050 17th Street, Suite 950 Denver, CO 80265 USA Tel 303 628-7798 Fax 303 389-4125 www (denisonmines com May 31, 2012 VIA E-MAIL AND OVERNIGHT DELIVERY Mr Rusty Lundberg Director, Division of Radiation Control Utah Department of Environmental Quality 195 North 1950 West P 0 Box 144850 Salt Lake City, UT 84114^850 Re Radioactive Materials License DRC-04, Response to Utah Division of Radiation Control ("DRC") Round 1 Interrogatory on the March 10, 2010 Revised Infiltration and Contaminant Transport Modeling Report Dear Mr Lundberg This letter transmits Denison Mines (USA) Corp's ("Denison's") responses to DRC's Round 1 Interrogatories for the Revised Infiltration and Contaminant Transport Modeling Report of March 2010, which Denison received on March 28, 2012 Denison's responses to DRC's Round 1 Interrogatories on the White Mesa Mill Reclamation Plan Revision 5 0 be submitted under separate cover 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 Dan Hillslen Ron F Hochstein Harold R Roberts David E Turk Katherine A Weinel Central files N \Reclamation Plan\Rec Plan Rev 5 Resp to Interrog 5 31 12\05 31 12 trnsmtl inlen-og response ICTM ijoc ATTACHMENT A Attachment E-1 – Original laboratory reports and summary tables of hydraulic and geotechnical properties of onsite stockpiled random fill soil material, onsite stockpiled clay soil material, and clay borrow source material from Section 16 Table summarizing hydraulic and geotechnical properties of onsite stockpiled random fill soil material. Retained #200 Passing #200 Solids Density Max Dry Bulk Modified or Standard 85% Compaction Optimum Moisture Hydraulic Cond. Hydraulic Cond. Source Test Hole and Depth Stockpile USCS Material LL PL PI SL % Gravel % Sand % Silt & Clay % Clay from < #200 % Silt % Clay (g/cm3)Density (g/cm3)Proctor Compaction (g/cm3)Content (%) (cm/s) Specificiation Material Description Chen & Associates 1978 TH 2 @ 0‐5 ft ‐‐"Random Fill" 20 17 3 17 ‐42 58 33 39 19 -1.88 SP 1.60 10.8 5.5E‐07 95% SP; 16.4% sandy silt Chen & Associates 1978 TH 5 @ 7.5‐10 ft ‐‐"Random Fill" 33 25 8 25 ‐44 56 21 44 12 ‐1.67 SP 1.42 18.5 8.2E‐08 98% SP; 22.0% calcareous silty clay Chen & Associates 1978 TH 15 @ 1.5‐4.5 ft ‐‐"Random Fill" 36 28 8 17.5 ‐35 65 42 38 27 ‐1.71 SP 1.45 19.0 1.2E‐08 97% SP; 18.0% mod. Calcareous sandy clay Chen & Associates 1978 TH 40 @ 4‐5.5 ft ‐‐"Random Fill" 26 17 9 ‐‐36 64 42 37 27 ‐1.76 SP 1.50 16.2 1.6E‐08 97% SP; 16.4%; sandy clay Chen & Associates 1978 TH 19 @ 0‐3 ft ‐‐"Random Fill" 23 17 6 18 ‐30 70 ‐46 25 ‐1.88 SP 1.60 12.8 3.4E‐08 94% SP; 12.4% sandy clayey silt Chen & Associates 1978 TH 37 @0‐4 ft ‐‐"Random Fill" 23 18 5 ‐‐28 72 ‐47 25 ‐1.90 SP 1.62 11.5 6.1E‐07 93% SP; 11.5% sandy clayey silt Chen & Associates 1978 TH 38 @ 5‐7 ft ‐‐"Random Fill" 29 15 14 14 ‐31 69 ‐45 24 ‐1.78 SP 1.51 16.7 4.0E‐08 92% SP; 17.9% sandy clay Chen & Associates 1978 TH 49 @ 5‐7 ft ‐‐"Random Fill" 25 16 9 ‐‐29 71 ‐46 25 ‐1.77 SP 1.50 15.6 3.2E‐08 95% SP; 13.9% calcareous sandy silt Chen & Associates 1979 TH 80 @ 4.5‐7 ft ‐‐"Random Fill" 39 19 20 ‐‐22 78 ‐51 27 ‐1.67 SP 1.42 NA 7.8E‐07 96% SP; 19.4% calcareous sandy clay Chen & Associates 1979 TH 84 @ 0‐2 ft ‐‐"Random Fill" 18 16 2 ‐‐35 65 ‐42 23 ‐1.88 SP 1.60 NA 4.3E‐06 96% SP; 11.7% sandy silt Chen & Associates 1979 TH 96 @ 8.5‐9.5 ft ‐‐"Random Fill" 32 26 6 ‐‐34 66 ‐43 23 ‐1.60 SP 1.36 NA 1.5E‐06 97% SP; 20.7% calcareous sandy clay Chen & Associates 1979 TH 100 @ 0‐1 ft ‐‐"Random Fill" 17 ‐NP ‐‐56 44 ‐29 15 ‐1.92 SP 1.63 NA 3.7E‐07 98% SP; 9.7% very silty sand Chen & Associates 1979 TH 114 @ 0‐2 ft ‐‐"Random Fill" 22 16 6 ‐‐42 58 ‐38 20 ‐1.89 SP 1.61 NA 5.8E‐07 95% SP; 12.9% sandy, clayey silt Chen & Associates 1979 TH 120 @ 1‐2 ft ‐‐"Random Fill" 25 17 8 ‐‐31 69 ‐45 24 ‐1.82 SP 1.55 NA 1.1E‐07 95% SP; 14.7% sandy, clayey silt Chen & Associates 1979 TH 122 @ 4‐6 ft ‐‐"Random Fill" 25 17 8 ‐‐34 66 ‐43 23 ‐1.81 SP 1.54 NA 4.2E‐07 96% SP; 14.7% sandy, silty clay Chen & Associates 1979 TH 123 @ 1‐3 ft ‐‐"Random Fill" 23 16 7 ‐‐29 71 ‐46 25 ‐1.87 SP 1.59 NA 5.4E‐07 95% SP; 12.6% sandy, clayey silt Geosyntec 2006 ‐RF5 CH "Random Fill" 53 16 37 ‐19 81 ‐53 28 ‐2.03 MP 1.73 NA ‐‐fat clay with sand Geosyntec 2006 ‐RF5 CL "Random Fill" 40 14 26 ‐26 74 ‐48 26 ‐‐ ‐ ‐NA ‐‐lean clay with sand Geosyntec 2006 ‐Mix 3 RF5 ‐"Random Fill"‐‐‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐2.03 MP 1.73 11.2 4.6E‐08 90% MP; 2%> OWC ‐ Geosyntec 2006 ‐Mix 3 RF5 ‐"Random Fill"‐‐‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐3.3E‐08 90% MP; 5%> OWC ‐ Chen & Associates 1987 ‐‐"Random Fill" 22 15 7 ‐52 48 ‐31 17 2.67 1.93 SP 1.64 11.8 ‐‐ ‐ Western Colorado Testing 1999 ‐RF1‐S1 ML "Random Fill" 27 20 7 0 36.9 63.1 ‐41 22 ‐1.83 SP 1.56 13.2 ‐‐clay, silty, sandy, red Western Colorado Testing 1999 ‐RF2‐S1 SM "Random Fill" NP NP NP GC 72.9 27.1 ‐18 10 ‐1.90 SP 1.62 13.2 ‐‐sand, clayey, grvly, brn Western Colorado Testing 1999 ‐RF2‐S2 SM "Random Fill" NP NP NP GC 73.1 26.9 ‐17 9 ‐2.06 SP 1.75 8.8 ‐‐sand, gravely, brown Western Colorado Testing 1999 ‐RF3‐S1 SM "Random Fill"‐NP ‐GC 57.5 42.5 ‐28 15 ‐1.95 SP 1.66 11.3 ‐‐sand, clayey, grvly, brn Western Colorado Testing 1999 ‐RF3‐S2 SM "Random Fill" 28 20 8 GC 53.4 46.6 ‐30 16 ‐1.79 SP 1.52 14.3 ‐‐clay, v sandy, red Western Colorado Testing 1999 ‐RF3‐S3 SM "Random Fill" NP NP ‐GC 69.3 30.7 ‐20 11 ‐2.04 SP 1.73 10.3 ‐‐sand, clayey, grvly, brn Western Colorado Testing 1999 ‐RF4‐S1 SM "Random Fill" 22 19 3 GC 62.6 37.4 ‐24 13 ‐2.04 SP 1.73 9.9 ‐‐sand, clayey, grvly, brn Western Colorado Testing 1999 ‐RF5‐S1 SM "Random Fill" 24 18 6 GC 52.1 47.9 ‐31 17 ‐1.98 SP 1.68 11.3 ‐‐sand, clayey, grvly, brn Western Colorado Testing 1999 ‐RF6‐S1 GC‐GM "Random Fill" 23 16 7 GC 52.7 47.3 ‐31 17 ‐2.03 SP 1.73 9.2 ‐‐sand, clayey, grvly, brn Western Colorado Testing 1999 ‐RF7‐S1 ML "Random Fill" 23 20 3 GC 38.9 61.1 ‐40 21 ‐1.81 SP 1.54 13.9 ‐‐clay, v sandy, silty, rd Western Colorado Testing 1999 ‐2‐1‐W SM "Random Fill" 23 19 4 GC 66.6 33.4 ‐22 12 ‐1.96 SP 1.67 11.6 ‐‐sand, clayey, grvly, brn Western Colorado Testing 1999 ‐2W‐7C SM "Random Fill"‐NP ‐GC 64.8 35.2 ‐23 12 ‐1.97 SP 1.67 10.8 ‐‐sand, silty, gravely, br Western Colorado Testing 1999 ‐3‐1C SM "Random Fill" 26 16 10 GC 55.3 44.7 ‐29 16 ‐1.96 SP 1.67 10.7 ‐‐sand, clayey, grvly, brn AVG OF ALL 32 RF SAMPLES 44 56 36 20 2.67 1.87 1.59 Notes: Compaction tests completed by Chen & Associaciates (1978) were assumed to be based on Standard Proctor since 1979 tests were. Maximum dry densities with gravel represent rock corrected tests results as reported by Western Colorado Testing (1999). Samples without a measured clay fraction assumed that the percent passing the #200 sieve was comprised of 65% silt and 35% clay (based on average of 20% clay). TH=test hole; USCS=Unified Soil Classification System; GC=gravel corrected; LL=liquid limit; PL=plastic limit; PI=plasticity index; SL=shrinkage limit; NP=non plastic; MP=modified Proctor; SP=standard Proctor; OWC=optimum water content Table summarizing hydraulic and geotechnical properties of onsite stockpiled clay soil material. Retained #200 Passing #200 Solids Density Max Dry Bulk Modified or Standard 90% Compaction Optimum Moisture Hydraulic Cond. Hydraulic Cond. Source Test Hole and Depth Stockpile USCS Material LL PL PI SL % Gravel % Sand % Silt & Clay % Clay from < #200 % Silt % Clay (g/cm3)Density (g/cm3)Proctor Compaction (g/cm3)Content (%) (cm/s) Specificiation Material Description Geosyntec 2006 ‐C1 CL "Clay" 34 15 19 ‐‐32 68 ‐‐‐‐ ‐ ‐ ‐ ‐ ‐ ‐sandy lean clay Geosyntec 2006 ‐C1 CL "Clay" 33 15 18 ‐‐24 76 ‐‐‐‐ ‐ ‐ ‐ ‐ ‐ ‐lean clay with sand Geosyntec 2006 ‐C1 CL "Clay" 31 14 17 ‐‐34 66 ‐‐‐‐ ‐ ‐ ‐ ‐ ‐ ‐sandy lean clay Geosyntec 2006 ‐Mix 1 C1 ‐"Clay"‐‐‐‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐2.01 MP 1.81 10.4 4.7E‐07 90% MP; 2%> OWC ‐ Geosyntec 2006 ‐Mix 1 C1 ‐"Clay"‐‐‐‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐2.1E‐08 90% MP; 5%> OWC ‐ Geosyntec 2006 ‐C2 SC "Clay" 32 15 17 ‐‐53 47 ‐‐‐‐ ‐ ‐ ‐ ‐ ‐ ‐clayey fine sand Geosyntec 2006 ‐C2 CL "Clay" 32 14 18 ‐‐40 60 ‐‐‐‐ ‐ ‐ ‐ ‐ ‐ ‐sandy lean clay Geosyntec 2006 ‐C2 CL "Clay" 35 17 18 ‐‐49 51 ‐‐‐‐ ‐ ‐ ‐ ‐ ‐ ‐sandy lean clay Geosyntec 2006 ‐Mix 2 C2 ‐"Clay"‐‐‐‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐2.06 MP 1.85 9.5 5.7E‐07 90% MP; 2%> OWC ‐ Geosyntec 2006 ‐Mix 2 C2 ‐"Clay"‐‐‐‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐3.2E‐08 90% MP; 5%> OWC ‐ Western Colorado Testing 1999 ‐C1‐S1 CL "Clay" 28 16 12 ‐0 35.2 64.8 ‐‐‐‐1.89 SP 1.70 15.1 ‐‐clay, very sandy, silty, red Western Colorado Testing 1999 ‐C2‐S1 SM "Clay" 25 23 2 ‐GC 60.8 39.2 ‐‐‐‐1.99 SP 1.79 10.3 ‐‐sand, clayey, gravely, brown Chen & Associates 1978 TH 12 @ 2‐5 ft ‐‐"Clay" 53 18 35 ‐‐12 88 67 29 59 2.67 1.62 SP 1.46 20.6 6.6E‐08 94% SP; 18.3% weathered claystone Chen & Associates 1978 TH 43 @ 13.5‐16.5 ft ‐‐"Clay" 40 16 24 ‐‐15 85 52 41 44 2.62 1.76 SP 1.58 16.9 2.3E‐08 95% SP; 15.8% claystone Chen & Associates 1979 TH 99 @ 88‐9.5 ft ‐‐"Clay" 40 20 20 ‐‐11 89 ‐‐‐‐1.67 SP 1.50 ‐2.1E‐07 95% SP; 18.5% weathered claystone Chen & Associates 1979 TH 128 @ 6‐7 ft ‐‐"Clay" 41 17 24 ‐‐11 89 ‐‐‐‐1.58 SP 1.42 ‐1.2E‐07 93% SP; 23.9% claystone AVG OF ALL 12 RF SAMPLES 31 69 35 52 2.65 1.82 1.64 Notes: Compaction tests completed by Chen & Associaciates (1978) were assumed to be based on Standard Proctor since 1979 tests were. Maximum dry densities with gravel represent rock corrected tests results as reported by Western Colorado Testing (1999). TH=test hole; USCS=Unified Soil Classification System; GC=gravel corrected; LL=liquid limit; PL=plastic limit; PI=plasticity index; SL=shrinkage limit; MP=modified Proctor; SP=standard Proctor; OWC=optimum water content Table summarizing hydraulic and geotechnical properties of the clay borrow source material from Section 16. Retained #200 Passing #200 Solids Density Max Dry Bulk Modified or Standard 90% Compaction Optimum Moisture Hydraulic Cond. Hydraulic Cond. Source Borning/Test Pit Sample Depth USCS Material LL PL PI % Sand % Silt & Clay % Clay from < #200 % Silt % Clay (g/cm3)Density (g/cm3)Proctor Compaction (g/cm3)Content (%) (cm/s) Specificiation Material Description D'Appolonia 1982 101 0‐5 ft SC‐SM "Clay" 24.0 18.5 5.5 61 39 44 22 17 ‐‐ ‐ ‐ ‐5.2E‐10 1.88 g/cm3; 14.6%; 0‐25 ft ‐ D'Appolonia 1982 " 5‐10 ft CH "Clay" 58.9 24.1 34.8 26 74 35 48 26 ‐‐ ‐ ‐ ‐ ‐ ‐ ‐ D'Appolonia 1982 " 10‐15 ft CH "Clay" 73.0 28.2 44.8 10 90 44 50 40 ‐‐ ‐ ‐ ‐ ‐ ‐ ‐ D'Appolonia 1982 " 15‐20 ft CH "Clay" 103.0 31.2 71.8 7 93 42 54 39 2.59 ‐‐ ‐‐‐ ‐ ‐ D'Appolonia 1982 102 5‐10 ft ML "Clay"‐‐NP ‐‐ ‐‐‐‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ D'Appolonia 1982 " 10‐15 ft ML "Clay"‐‐NP ‐‐ ‐‐‐‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ D'Appolonia 1982 " 15‐20 ft CL "Clay" 20.3 10.2 10.1 ‐‐ ‐‐‐‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ D'Appolonia 1982 103 0‐5 ft SM "Clay" 17.0 14.9 2.1 70 30 40 18 12 2.71 ‐‐ ‐‐1.2E‐09 1.87 g/cm3; 13.3%; 0‐25 ft ‐ D'Appolonia 1982 " 5‐10 ft CH "Clay" 73.8 24.9 48.9 15 85 55 38 47 ‐‐ ‐ ‐ ‐ ‐ ‐ ‐ D'Appolonia 1982 " 10‐15 ft CH "Clay" 59.8 26.6 33.2 13 87 44 49 38 ‐‐ ‐ ‐ ‐ ‐ ‐ ‐ D'Appolonia 1982 " 15‐20 ft CH "Clay" 71.0 21.6 49.4 13 87 43 50 37 ‐‐ ‐ ‐ ‐ ‐ ‐ ‐ D'Appolonia 1982 104 0‐5 ft SM "Clay" 18.4 16.2 2.2 55 45 33 30 15 ‐‐ ‐ ‐ ‐ ‐ ‐ ‐ D'Appolonia 1982 " 5‐10 ft CL "Clay" 31.2 16.5 14.7 30 70 39 43 27 ‐‐ ‐ ‐ ‐ ‐ ‐ ‐ D'Appolonia 1982 " 10‐15 ft ‐"Clay"‐‐‐66 34 50 17 17 ‐‐ ‐ ‐ ‐ ‐ ‐ ‐ D'Appolonia 1982 " 15‐20 ft Cl "Clay" 35.7 11.8 23.9 37 63 51 31 32 ‐‐ ‐ ‐ ‐ ‐ ‐ ‐ D'Appolonia 1982 105 0‐5 ft SM "Clay"‐‐NP 58 42 48 22 20 ‐‐ ‐ ‐ ‐ ‐ ‐ ‐ D'Appolonia 1982 " 5‐10 ft SM "Clay"‐‐NP 65 35 51 17 18 ‐‐ ‐ ‐ ‐ ‐ ‐ ‐ D'Appolonia 1982 " 10‐15 ft SC "Clay" 24.0 12.0 12.0 62 38 55 17 21 ‐‐ ‐ ‐ ‐ ‐ ‐ ‐ D'Appolonia 1982 " 15‐20 ft CH "Clay" 71.0 18.9 52.1 17 83 57 36 47 ‐‐ ‐ ‐ ‐ ‐ ‐ ‐ D'Appolonia 1982 1 ‐CH "Clay" 108.0 25.0 83.0 17 83 52 40 43 ‐1.60 MP 1.44 19.9 ‐‐ ‐ D'Appolonia 1982 2 ‐CH "Clay" 141.2 18.4 122.8 17 83 40 50 33 ‐1.79 MP 1.61 15.0 4.7E‐10 99% MP; 14.7%‐ D'Appolonia 1982 3 ‐CH "Clay" 115.0 23.0 92.0 3 97 57 42 55 2.60 1.62 MP 1.46 20.5 ‐‐ ‐ D'Appolonia 1982 2‐16 65 ft CL "Clay" 32.0 15.8 16.2 ‐‐ ‐‐‐‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ D'Appolonia 1982 " 125 ft CH "Clay" 57.5 25.9 31.6 7 93 54 43 50 ‐‐ ‐ ‐ ‐ ‐ ‐ ‐ D'Appolonia 1982 " 180 ft CH "Clay" 148.5 25.3 123.2 ‐‐ ‐‐‐‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ Advanced Terra Testing 1996 UT‐1 CH "Clay" 103.1 19.9 83.2 ‐‐ ‐‐‐2.39 1.82 MP 1.64 13.9 3.7E‐08 95% MP; OWC ‐ AVG (w/out 0‐5 ft) 29 71 37 35 2.53 1.71 1.54 Notes: For the row summarzing data from Advanced Terra Testing (1996), the solids density for the clay taken from Rogers & Associates (1996). TH=test hole; USCS=Unified Soil Classification System; LL=liquid limit; PL=plastic limit; PI=plasticity index; MP=modified Proctor; SP=standard Proctor; OWC=optimum water content DAPPOLON CONSULTING ENGINEERS INC March 1982 Project No RM786823 Mr Roberts Energy Fuels Nuclear Inc 1515 Arapahoe Street Three Park Central Suite 900 Denver Colorado 80202 Letter Report Section 16 Clay Material Test Data White Mesa Uranium Project Blanding Utah Dear Harold This report presents the results of field investigations and laboratory tests performed on Section 16 clay material The material tested was obtained from borings and test pits made in April 1979 The laboratory tests were performed and the data retained in our files until your recent request for the data Field Investigations The area of investigation is canyon located in Section 16 about three miles south of the mill site Seven borings were drilled as part of the field investigations These borings 100 through 106 are located approximately as shown on Figure The borings were drilled with rig provided by Energy Fuels using the rotary method with air pressure to flush out the cuttings Samples were obtained by sampling the cuttings on five foot intervals Only qualitative information on the subsurface materials is available because of the method of drilling and sampling utilized However the qualitative information and samples obtained are suitable to provide preliminary data on the character of the subsurface materials present Three test pits 13 were excavated to obtain bulk samples for laboratory testing The location of the test pits is shown on Figure Samples from Boring 216 drilled by Energy Fuels in November 1978 were also provided to DAppolonia for testing The location of Boring 216 is shown on Figure 7400 SOUTH ALTON COURT ENGLEW000 CO 80112 TELEPHONE 303/771-3464 TELEX 45-4565 BECKLEY WV CHESTERTON IN CHICAGO IL HOUSTON TX AGUNA NIGUEL CA PITTSBURGH PA WILMINGTON NC BRUSSELS BELGIUM SE KOREA Mr Roberts March 1982 Subsurface Conditions The subsurface conditions in the canyon based on the boring data are shown on Cross Sections AA and BB presented on Figures and respectively The plan locations of these cross sections is shown on Figure As shown on the cross sections the subsurfce consists of surficial layer of red clayey and silty sand about five feet thick The underlying material is mostly red or gray silty clay The consistency of the silty clay layer varies from stiff to hard based on observations of the drillers and rig during drilling lense or layer of very hard silt was noted in Boring 105 This layer appears to be well cemented unit from the cutting samples obtained In Boring 106 the surf icial sand layer was about 20 feet thick and clayey sand layer was also encountered at depth of about 30 feet The laboratory soil classifications for the tested samples are also shown on Cross Sections AA and BB The testing program is discussed in detail in the following section however the testing results indicate that the silty clay layer is mostly CL or CII material with one sample being SM and two ML These test results show the material is basically fine grained soil with varying amount of silt and clay size particles The plasticity characteristics of the material vary from low to high Further discussion of the test results and material characteristics is given below Water in the borings was not noted except for Boring 104 for which depth of about 43 feet was measured This depth is not considered completely reliable since it was measured only one day after drilling and the water level may not have had time to stabilize Laboratory Test Results The laboratory testing program conducted on samples from the borings and test pits included the following types of tests Classification Grain size sieve and hydrometer Atterberg limits Specific gravity XRay Diffraction Cation Exchange Capacity Exchangeable Cat ions Modified Proctor Compaction Density Permeability The results of the classification tests are given on Table The soil classifications given are shown on Cross Sections AA and BB Figures and and were discussed above Mr Roberts March 1982 The cation exchange capacity CEC and exchangeable ions were conducted to evaluate the type of clays present and the chemical effects resulting from contact with the tailings liquid Tests were run on samples from Test Pits and samples and Boring 103 1520 foot depth Soil from each sample was treated by soaking in simulated tailings liquid for 48 hours before testing Both treated and untreated as received samples were tested and the results are presented on Table Results of the testing are summarized as follows The untreated samples indicate pH 11 values between 7.40 and 8.35 with CEC values in the 4556 meq/lOOg range The predominate exchangeable ions are calcium and sodium for Test Pits and and calcium and magnesium for Boring 103 1520 ft The treated samples indicate pH 11 values between 1.70 and 2.35 with CEC values in the 90100 meq/lOOg range The predominate exchangeable ions are hydro gen calcium and magnesium for all the samples These results indicate that exposure to the tailings water causes the pH 11 of the material to decrease the exchangeable hydrogen and magnesium to increase the exchangeable calcium and sodium to decrease the CEC to increase by factor of about two due primarily to the large increase in exchangeable hydrogen The effects of these changes on clay material properties particularly permeability is discussed in the following paragraphs The Xray diffraction tests were run on material from the same three samples as tested for CEC and exchangeable ions The xray diffraction testing was conducted to evaluate the type of clay minerals occurring in the material The results of the testing are given on Table As shown about 50 percent of the material is quartz 25 percent montmorillonite 25 percent illite and minor percentages of other minerals Montmorillonite is an active clay mineral which typically has low coefficient of permeability Illite is also clay mineral but it is typically relatively inactive with somewhat higher coefficient of permeability Modified Proctor compaction tests were conducted on four different samples Test Pits and samples were tested and composite sample from Boring 16 85 to 210 feet depth The results of the modified Proctor tests are given on Table The average maximum dry density measured is 107 pounds per cubic foot and the average optimum water content is 17.5 percent Mr Roberts Marh 1982 Permeability tests were conducted on compacted samples of material from Boring 216 composite 85120 feet Boring 101 composite 025 feet Boring 103 composite 025 feet and Test Pit The tests were conducted in perme ability cells with confining pressure applied around the sample which is encased in rubber membrane differential pressure was applied across the sample and flow of fluid through the sample measured Both distilled water and simulated tailings liquid were used in the tests The tests on Borings 101 and 103 and Test Pit were conducted over period of about five months to assess the effects of tailings liquid on the permeability of the material The tests were conducted with distilled water for about two months to establish saturation and steady state flow Tailings liquid was then introduced to the sample and the test continued for three more months The results of the permeability tests are presented on Table along with other pertinent sample data The material has an average coefficient of germe ability with water of 3.3x10 centimeters per second and 5.lx10 centi meters per second with simulated tailings liquid The test results indicate that the permeability of the material was essentially the same with distilled water and tailings liquid and no degradation of the material was indicated Conclusions and Recommendations Based on the field and laboratory investigations discussed above conclusions which can be made regarding the materials in Section 16 are The material is mostly silty clay CL to CH with slight variation in properties The clay minerals are mostly montmorillonite with some illite The material varies laterally with some layers or lenses of sand and silt The consistency of the material also varies from stiff to hard or very hard The permeability values of the material are very low and longterm permeability tests conducted with simulated tailings liquid indicate little change in permeability with time This result is in good agreement with the results of the CEC exchangeable ion tests and xray diffraction test results The clay material is suitable for use as borrow for use as clay liner or in situ as natural liner layer Recommendations for further assessment of the clay for use as borrow area or in situ clay liner source are Geotechnical borings with split spoon samples to assess the material characteristics more specifically including consistency natural water content and classification DAT OLONL Mr Roberts March 1982 Field permeability tests falling or rising head in the borings to measure the in situ permeability Installation of piezometers to determine the ground water level Additional discussion of the above recommendations can be provided as neces sary depending on your needs VerYtrulYou5L Corwin Oldweiler Project Engineer CEO par DY OWNL TA B L E LA B O R A T O R Y T E S T RE S U L T S OP T I HU H SA M P L E GR A I N SIZ E AN A L Y S I S AT T E R S E E C LI M I T S PR O C T O R VA L U E S BO R I N G DE P T H SA N D SIL T CL A Y LI Q U I D PL A S T I C PL A S T I C I T Y US G S SP E C I F I C DR Y D E N S I T Y WA T E R C O N T E N T TE S T PIT FE E T PE R C E N T PE I C E N T PE R C E N T PE R C E N T PE R C E N T P E R C E N T CL A S S I F I C A T I O N GR A V I T Y PC PE R C E N T lO t 05 61 22 17 24 . 0 1 5 . 5 5. 5 SC S M 51 0 26 45 26 58 . 9 2 4 . 1 3 4 . 8 CM ID I S tO 50 40 73 . 0 2 1 . 2 44 . 8 ml 15 2 0 54 39 10 3 . 0 31 . 2 71 . S CI I 2. 5 9 10 2 5- 1 0 NP ML tO - I S NP ML 15 2 0 20 . 3 10 . 2 1 0 . 1 CL 10 3 05 10 IS 12 17 . 0 1 4 . 9 2. 1 SM 2. 7 1 St o IS 38 47 73 . 8 2 4 . 9 4 1 . 9 CII 10 I S II 49 38 59 . 8 2 6 . 6 3 3 . 2 CI I 15 2 0 13 50 37 71 . 0 2 1 . 6 4 9 . 4 CI I 10 4 05 55 30 IS 18 . 4 1 6 . 2 2. 2 SM St O 30 43 27 31 . 2 1 6 . 5 1 4 . 7 CL 10 I S 66 Il 17 15 2 0 37 31 32 35 . 7 1 1 . 8 2 3 . 9 CL lO S 0- 5 58 22 20 pip Sit 5t O 65 17 IS NP SM 10 I S 62 Il 21 24 . 0 1 2 . 0 1 2 . 0 SC 15 2 0 17 36 47 71 . 0 1 5 . 9 2. 1 CI I Il 40 43 10 8 . 0 25 . 0 1 3 . 0 CI I 99 . 9 19 . 9 Il 50 33 14 1 . 2 11 . 4 12 2 . 8 CI I tI I . 5 15 . 0 3I 42 55 11 5 . 0 23 . 0 9 2 . 0 CI I 2. 6 0 10 1 . 0 20 . 5 21 6 65 32 . 0 I S . S I6 . 2 CL 12 5 43 SO 57 . 5 2 5 . 9 3 1 . 6 CI I IS O 14 8 . 5 25 . 3 12 3 . 0 Gi l C0 M P 0 S j j 8S 2 l O 95 SW - S C CO H P O S J t I SS 2 I O 1 IS 47 35 cl m i 2. 7 2 II 5 . 8 14 . 7 lT h e s e sa m p l e s ar e T e s t PI t 2S a m p l e te s t e d be F o r e so s k j n 1 3S a m p l e te s t e d al t e r so a k I n g 16 ho u r s TABLE CATION EXCHANGE CAPACITY AND EXCHANGEABLE CATION TEST RESULTS UNTREATED SAMPLES TREATED SAMPLES1 TEST PIT TEST PIT BORING TEST PT TEST PIT BORING PARAMETER UNITS 103 22 103 pH 11 8.35 7.40 7.60 2.30 2.35 1.70 Buffer pH NA NA NA 2.28 2.20 2.15 Exchangeable meq/lOOg 56.6 57.6 58.2 Ca meq/lOOg 19.5 21.1 25.8 12.3 13.5 18.7 Mg meq/lOOg 4.3 4.9 15.4 17.0 20.3 17.8 Na meq/lOOg 20.0 28.0 6.5 3.7 6.5 2.6 meq/lOOg 1.2 2.5 0.6 0.8 1.6 0.5 Cation Exchange nieq/lOOg 45 56 48 90 100 98 Capacity CEC gSamples soaked in simulated tailings liquid for 48 hours before testing Represents triplicate results WAU OLONU TABLE XRAY DIFFRACTION SEMIQUANTITATIVE RESULTS SAMPLE QUARTZ ANDESINE MONTMORILLONITE ILILITE MIXED LAYER Test Pit 50%5%1025%1025%510% Test Pit 50%510%1025%1025% 510% Boring 101 50%510%2550%Trace 5% 1520 Depth %J OLONU TA B L E PE R M E A B I L I T Y TE S T R E S U L T S CO E F F I C I E N T S OF PE R M E A B I L I T Y SA M P L E IN I T I A L CO N D I T I O N S WI T H DI S T I L L E D WI T H TA I L I N G S BO R I N G DE P T H DR Y DE N S I T Y WA T E R C O N T E N T WA T E R LI Q U I D TE S T PI T FE E T PC F PE R C E N T CM S E C CM S E c 10 3 02 5 11 6 . 7 13 . 3 1. 2 9. 4 10 1 0 10 1 02 5 11 7 . 5 14 . 6 5. 2 10 1 0 7. 5 10 1 0 11 0 . 7 14 . 7 4. 7 10 1 0 2. 3 10 1 0 21 6 8 5 2 1 0 10 1 15 1. 0 10 1 0 21 6 85 2 1 0 11 0 15 55 10 1 0 Cf 00 .7 -I- -102 JO FIG 8105 KEY PLAN NT.S 0I 3Q40OC 5145 -10 5/ 1- REFERENCE TOPOGRAPHIC MAP OF BLANDING MILLSITESHEETDELTAAERIAL -jSURVEYSINCI2t876 22 ECULCI.E A.%Q SM T- 8-104 16 FIGURE LOCATION OF BORINGS AND SUBSURFACE CROSS SECTIONS 3-SCALE PREPARED FOR ENERGY FUELS NUCLEAA INC DENVER7 COLORADO 2CO 200 FEET ONTOUR TERVAL OFEET JJDIIIMNJ4 SL\ aD .0 aD ZLLJ 30D oz rJ Si to b-flcn en HORIZONTAL SCALE VERTICAL SCALE 20 FEET 5140 LU LU U- 5120 -J LU500 LOOKING NORTH FIGURE THE DEPTH AND THICKNESS OF THE SUBSURFACE STRATA INDICATED ON THE SECTIONS WERE GENERALIZED FROM AND INTERPOLATED BETWEEN THE TEST BORINGS INFORMATION ON ACTUAL SUBSURFACE CONDITIONS EXISTS ONLY AT THE LOCATION OF THE TEST BORINGSANDIT IS POSSIBLE THAT SUBSURFACE CONDITIONS BETWEEN THE TEST BORINGS MAY VARY FROM THOSE INDICATED UNIFIED SOIL CLASSIFICATION SYSTEM FOR PLAN LOCATION OF CROSS SECTION SEE FIGURE VERTICAL EXAGGERATION EQUALS lOX ThJPJP NI ii IXNIL\ BORING 00 INTERSECTION WITH CROSS SECTION BB BORING 102 CH CH 5180 5160 5140 520 500 5080 5060 LU LU LU -j CH 105 5180 560 APPROXIMATE EXISTING GROUND SURFACE CL BORING 06 RED CLAYEY AND SILTY SAND HARD RED AND GRAY SILTY CLAY ao.a 70 STIFF RED AND GRAY SILTY CLAY B.-60 17 B.O.B -40 VERY HARD RED SILT CEMENTED DENSE LIGHT GRAY AND RED CLAYEY SAND O.B.-45 200 200 FEET 20 5080 5060 LEGEND CH LABORATORY SOIL CLASSIFICATION NOTES SUI3SURFACE CROSS SECTION A-A PREPARED FOR ENERGY FUELS NUCLEAR INC DENVER COLORADO cc 9J cc -0 fY L.1c ow I-\J C- CaD 5060 HORIZONTAL SCALE 200 200 FEET 20 VERTICAL SCALE 20 FEET 5060 LOOKING WEST FIGURE THE DEPTH AND THICKNESS OF THE SUBSURFACE STRATA INDICATED ON THE SECTIONS WERE GENERALIZED FROM ANC INTERPOLATED BETWEEN THE TEST BORINGS INFORMATION ON ACTUAL SUBSURFACECONOITIONS EXISTS ONLY AT THE LOCATION OF THE TEST BORINGS AND IT IS POSSIBLE THAT SUBSURFACE CONDITIONS BETWEEN THE TEST BORINGS MAY VARY FROM THOSE INDICATED LEGEND CH LABORATORY SOIL CLASSIFICATION UNIFIED SOIL CLASSIFICATION SYSTEM NOTES FOR PLAN LOCATION OF CROSS SECTION SEE FIGURE VERTICAL EXAGGERATION EQUALS 10 SUBSURFACE CROSS SECTION B-B PREPARED FOR ENERGY FUELS NUCLEARINC DENVER COLORADO 580 560 5140 520 5100 5080 INTERSECTION WITH CROSS ST10N A-A BORING 102 BORING 103 Id IL -J APPROXIMATE EXISTING GROUND SURFACE BORING 04 CL RED CLAYEY AND SILTY SAND CL STIFF RED GRAY SILTY AND CLAY 580 160 40 ILl Id IL 520 Id -J Id500 5050 -47 B.0 55 B.0.b.-46 IZ3 IERCIJLENE 998 SMITH CO PCH PA Soil Sampling and Testing Program White Mesa Mill The purpose of this Soil Sampling and Testing Program is to verify the soil classification gradation and compaction characteristics standard proctor of the stockpiled random fill and clay materials that will be used for cover materials on the tailings cells at the White Mesa Mill Additionally this program will verify the compaction characteristics and gradation of the random fill materials utilized in the platform fill previously placed on Cells and Sampling Sampling will take place on each of six stockpiles of random fill designated RF-i through RF-6 on Exhibit two clay material stockpiles C-i and C-2 on Exhibit and on platform fill areas in Cells total of samples will be taken from the random fill stockpiles Two samples will be taken from the clayS stockpiles and three samples will be taken from the covered areas of the cells Samples will be taken from test pits excavated by backhoe Samples will be taken from depth of feet in stockpiles and from foot depth in cells One backhoe bucket full of material will be taken from the test pit at the specified depth and dumped separately This sample will be quartered and one quarter will be screened to minus rocks over will be removed prior to screening Two five gallon sample buckets will be filled with sample randomly selected from the screened fraction Oversized material remaining after the screening of the sample will be visually classified and then weighed Sample locations will be indicated on site map and sample descriptions will recorded and maintained in the facilitys records total of fourteen samples will be submitted for testing during this program Testing Samples will be packaged and shipped to certified commercial testing laboratory for testing Tests will be run on each sample for standard proctor ASTM D698 particle size analysis ASTM Ci 17 and ASTM Ci36 soil classification ASTM D2487 and plasticity index Atterberg limits ASTM D43 18 SOILTEST.DOC/04/14/99/250 PM 125 120 4- 115 110 105 100 MOISTURE-DENSITY RELATIONSHIP TEST ZAV for Sp 2.65 Water content Test specification ASTM 69891 Procedure Standard Oversize correction applied to each point Elev/ Depth Classification Nat Moist Sp.C LL P1 3/8 in No.200USCSAASHTO N/A 2.65 16.1 ROCK CORRECTED TEST RESULTS UNCORRECTED MATERIAL DESCRIPTION Maximum dry density 122.0 pcf Optimum moisture 11.6 116.1 pcf 13.8 21W Sand clayey grvly brn Project No 804899 Project International Uranium Corporation Location Soil Sample Testing Date 5/3/99 Remarks SUBMITTED BY Client TESTED BY JH Fig No MOISTUREDENSITY RELATIONSHIP TEST WESTERN COLORADO TESTING INC 10 12 14 16 18 20 I- LIQUID AND PLASTIC LIMITS TEST REPORT LIQUID LIMIT 23Sandvetyclayeysisiltyred 19 25.156.9 SM MATERIAL DESCRIPTION LI.PL Pt %40 %200 IJSCS Project No 804899 Client International Uranium Coiporalion Project Soil Sample Testing Source Sample No 2-1-W -_ Remarks Tested By JH Figure 22 LIQUID AND PLASTIC LIMITS TEST REPORT WESTERN COLORADO TESTING INC 124 122 120 -4- 118 116 MOISTURE-DENSITY RELATIONSHIP TEST 114 Water contents Test specification ASTM 69891 Procedure Standard Oversize correction applied to each point Elev/ Depth Classification Nat Moist Sp.G LL P1 3/8 in No.200USCSSAASHTO N/A 2.65 13.4 ROCK CORRECTED TEST RESULTS UNCORRECTED MATERIAL DESCRIPTION Maximum dry density 122.8 pcf Optimum moisture 10.8% 122.8 pcf 10.8 2W7C Sand silty gravely br Project No 804899 Project International Uranium Corporation Location Soil Sample Testing Date 5/3/99 Remarks SUBMITTED BY Client TESTED BY JH Fig No MOISTUREDENSITY RELATIONSHIP TEST WESTERN COLORADO TESTING INC 10 12 14 16 18 PARTICLE SIZE DISTRIBUTION TEST REPORT SAND SILT %CLAY USCS AASHTO P1.LL 15.9 54.5 SM jA-240 SIEVE inches size PERCENT FINER SIEVE number size PERCENT FINER SOIL DESCRIPTION Sand silty gravelytrown 100.0 84.1 100.0 10 80.3 1.5 1010 20 77.0 100.0 40 68.6 3/4 95.7 60 46.4 1/2 91.0 100 36.7 3/8 88.3 200 29.6 GRAIN SIZE REMARK OTestedfly ii-0.344 D30 0.0781 D10 CO EFFICIENT C0 Cu Source Sample No 2W-7C Client International UraniumCoiporation WESTERN COLORADO TESTING4 INC Sail Sample Testing Pro3ect No 804899 Fiaure 39 Ui LL Ui Lii 0. 130 125 .4- 120 4-. CO II -D 115 110 MOISTURE-DENSITY RELATIONSHIP TEST ZAV for Sp 2.65 105 Water content Test specification ASTM 69891 Procedure Standard Oversize correction applied to each ooint Elev/ Depth Classification Nat Moist Sp.G LL RI 3/4 in No.200USCSAASHTO N/A 2.65 9.0 ROCK CORRECTED TEST RESULTS UNCORRECTED MATERIAL DESCRIPTION Maximum dry density 122.4 pcf Optimum moisture 10.7 119.3 pcf 11.8 3iC Sand clayey grvly brn Project No 804899 Project International Uranium Corporation Location Soil Sample Testing Date 5/3/99 Remarks SUBMITTED BY Client TESTED BY JH Fig No MOISTUREDENSITY RELATIONSHIP TEST WESTERN COLORADO TESTING INC 10 12 14 16 18 20 LIQUID AND PLASTIC LIMITS TEST REPORT Dashed line indicates the approximate upper limit boundary for natural soils 6C 50- 40 30 20- 10 %- ML or OL MH orOH 10 30 50 70 90 110 LIQUID LIMIT Sand clayey gravely brocm 26 16 69.510 36.9 SM MATERIAL DESCRIPTION LL PL RI %40 %200 -USCS Project No 804899 Client International Uranium Corporation Project Soil Sample Testing Source Sample No 3-iC Remarks Tested By ill Figure 23 LIQUID AND PLASTIC LIMITS TEST REPORT WESTERN COLORADO TESTING INC 118 116 9- 114 4- Cl 112 110 MOISTURE-DENSITY RELATIONSHIP TEST ZAV for Sp 2.70 108 10 Water content Test specification ASTM 69891 Procedure Standard Oversize correction applied to each ooint Elev/ Depth Classification Nat Moist Sp.G LL P1 No.4 No.200USCSAASHTO N/A 2.70 ROCK CORRECTED TEST RESULTS UNCORRECTED MATERIAL DESCRIPTION Maximum dry density 117.7 pcf Optimum moisture 15.1 117.7 pcf 15.1 ClSi Clay sandy silty rd Project No 804899 Project International Uranium Corporation Location Soil Sample Testing Date 5/3/99 Remarks SUBMITTED BY Client TESTED BY JH Fig No MOISTUREDENSITY RELATIONSHIP TEST WESTERN COLORADO TESTING INC 12 14 16 18 20 22 Co LIQUID AND PLASTIC LIMITS TEST REPORT LIQUID LIMIT Clay vejy sandy silty red 28 16 12 98.3 64.8 MATERIAL DESCRIPTION Li It RI %40 %flO USCS Project No 804899 Client International Uranium Corporation Project Soil Sample Testing Source Sample No Cl-Si Remarks Tested Thy JH Figure 24 LIQUID AND PLASTIC LIMITS TEST REPORT WESTERN COLORADO TESTING INC CL PARTICLE SIZE DISTRIBUTION TEST REPORT %GRAVEL SAND SILT CLAY -I uSCS -I AASHTO PL LL 10 32 CL A-65 28 SIEVE size PERCENT FINER SIEVE number size PERCENT FINER -SOIL DESCRIPTION Clay vezy sandy silty red 1.5 3/4 1/2 3/8 100.0 100.0 1-00.0 100.0 100.0 100.0 100.0 10 20 fl40 60 100 200 100.0 99.9 -99.5 983 96.2 92.3 64.8 REMARKS Tested By JH GRAIN SIZE D30 D10 COEFFICIENTS Cc Cu Source SamyleNo Cl-SI Client International iJranium-Corporalion WESTERN COLORADO TESTING INC Soil Sample Testing Project No 804899 Fioure 41 Lt LU LU 130 125 1- 120 ii 115 110 MOISTURE-DENSITY RELATIONSHIP TEST ZAV for Sp.G 2.65 105 Water content Test specification ASTM 69891 Procedure Standard Oversize correction applied to each point Elev/ Depth Classification Nat Moist Sp.G LL P1 3/4 in No.200USCSAASHTO N/A 2.65 10.3 ROCK CORRECTED TEST RESULTS UNCORRECTED MATERIAL DESCRIPTION Maximum dry density 124.2 pcf Optimum moisture 10.3 120.7 pcf 11.5 C2S1 Sand clayey grvly brn Project No 804899 Prqject International Uranium Corporation Location Soil Sample Testing Date 5/3/99 Remarks SUBMITTED BY Client TESTED BY JH Fig Na MOISTUREDENSITY RELATIONSHIP TEST WESTERN COLORADO TESTING INC 10 12 14 16 18 20 LU LIQUID AND PLASTIC LIMITS TEST REPORT Sand clayey gravely broi 25 23 48.2 26.7 SM MATERIAL DESCRIPTION LI PL P1 %c40 %200 IJSCS Project No 804899 Client International Uranium Corporation Project Soil Sample Testing Source Sample No C2-Sl Remarks Tested By JH Figure 25 LiQUID AND PLASTIC LIMITS TEST REPORT WESTERN COLORADO TESTING INC 50- 40- -- Dashed line indicates the approximate upper limit boundary for natural soils 20- 10 MLorOL 10 MH orOH LIQUID LIMIT 10 110 LU a- PARTICLE SIZE DISTRIBUTION TEST REPORT 31-9 41.4 01 SM A-2-40 23 %3 %GRAVEL %SAND %SILT %CLAY uscs S4ASHTO PL 11 25 SIEVE inches size PERCENT FINER SIEVEl1 size PERCENT FINER SOIL-DESCRIPTION Sand clayey gravely trown 1.5 3/4 1/2 3/8 100.0 100.0 96.6 9kB 90.0 84.9 80.3 10 20 40 60 100 200 68.1 58.0 52.1 48.2 43.8 36.0 263 GRSAJN SIZE -REMARKS OTestedByJHD60 D30 10 2.48 0.0977 COEFFICIENTS Cc Source Sample No C2-S1 Client International Uranium-Corporation WESTERN COLORADO TESTING INC Prt Soil Sample Testing Project No 804899 Flaure 42 .4- -D 114 MOISTURE-DENSITY RELATIONSHIP TEST 104 10 Water content Test specification ASTM 69891 Procedure Standard Oversize correction applied to each ooint Elev/ Depth Classification Nat Moist Sp.C LL P1 No.4 No.200USCSAASHTO N/A 2.65 ROCK CORRECTED TEST RESULTS UNCORRECTED MATERIAL DESCRIPTION Maximum dry density 114.1 pcf Optimum moisture 13.2% 114.1 pcf 13.2% RF1S1 Cloy silty sandy red Project No 804899 Pro-ject International Uranium Corporation Location Soil Sample Testing Date 5/3/99 Remarks SUBMITTED BY Client TESTED BY JH Fig No 12 MOISTUREDENSITY RELATIONSHIP TEST WESTERN COLORADO TESTING INC 112 110 108 106 ZAV for Sp 65 12 14 16 18 20 22 LIQUID AND PLASTIC LIMITS TEST REPORT LIQUID LIMIT 27Claysiltysandyred 20 99A 63.1 ML MATERIAL DESCRIPTION LL PL P1 %40 %C200 USCS Project No 804899 Client International Uranium Corporation Project Soil Sample Testing Source Sample No RF1-Sl Remarks Tested By JR Figure 26 LIQUID AND PLASTIC LIMITS TEST REPORT WESTERN COLORADO TESTING INC PARTICLE SIZE DISTRIBUTION TEST REPORT th -c _L___A....A..ic -_A 100 -i 00 t1 Ui Ui Ui a- Sc---H----- --- 7C-------------4- Sc--H-H----- 4C------.------------ 3c--------s------- 2C -- ic ---- ooioo 10 GRAIN 0.1 SIZE-mm 0.01 0.001 %3 GRAVEL -I SAND %SILT %CLAY uSCS AASHTO P-I. ci 369 ML A401J SIEVE Thebes size PERCENT FINER SIEVE number size PERCENT FINER -SOIL DESCRIPTION O-Claysiltysandyrcd 1.5 314 1/2 3/8 100.0 100.0 100.0 ioo.o 100.0 100.0 100.0 10 20 40 60 100 200 100.0 99.8 99.-S 99 97.6 95.2 63.1 D60 D30 D10 GRAJN.SIZE REMARXS T-estedBy 311 C0 CU COEFFICIENTS oSoutce SampleNo.RF1-S1 Client InternalionaflJranium-Corporation WESTERN COLORADO TESTING INC Project Soil Sample Testing Project No 804899 Fiqure 43 .4- 115 ci 110 100 10 Water content Test specification ASTM 69891 Procedure Standard Oversize correction app1 ied to each point 125 120 MOISTURE-DENSITY RELATIONSHIP TEST 105 ZAV for Sp.G 2.65 12 14 16 18 20 22 EIev/ Depth Classification Nat Moist Sp.G LL P1 3/8 in No.200USCSIAASHTO N/A 2.65 18.0 ROCK CORRECTED TEST RESULTS UNCORRECTED MATERIAL DESCRIPTION Maximum dry density 118.3 pef Optimum moisture 13.2 111.3 pcf 16.1 RF2S1 Sand clayey grvly brn Project No 804899 Project International Uranium Corporation Location Soil Sample Testing Date 5/3/99 Remarks SUBMITTED BY Client TESTED BY JR Fig No 13 MOISTUREDENSITY RELATIONSHIP TEST WESTERN COLORADO TESTING INC LL PARTICLE SIZE DISTRIBUTION TEST REPORT %r GRAVEL SAND SILT CLAY USGS AASHTO PL LL oj 34.8 47.5 SM A-I-b NP NPJ SIEVE size PERCENT FINER SIEVE number size PERCENT FINER SOIL DESCRIPTION Sand sl clayey gravely brown 1.5 3/4 1/2 3/8 100.0 100.0 100.0 931 91.0 83.1 77.5 10 20 4060 100 200 65.2 52.6 44A 38.8 32.9 25.8 17.7 GRPJN SIZE -REMARKS Tested By JHD60 D30 D10 3.42 0.203 COEFFICIENTS C0 Cu Soute Sample No RF2-S1 -CISt International UraniunrCorpocation WESTERN COLORADO TESTING INC Project Soil Sample Testing Project No 804899 Figure 44 135 9- 125 1- 120 MOISTURE-DENSITY RELATIONSHIP TEST 110 Water content Test specification ASTM 69891 Procedure Standard Oversize correction applied to each ooint EIev/ Depth Classification Nat Moist Sp.G LL P1 3/4 in No.200USCSAASHTO N/A 2.65 18.2 ROCK CORRECTED TEST RESULTS UNCORRECTED MATERIAL DESCRIPTION Maximum dry density 128.7 pcf Opt imum moisture 8.8 122.7 pcf 10.8 RF2-S2 Sand gravely brown Project No 804899 Project International Uranium Corporation Location Soil Sample Testing Date 5/3/99 Remarks SUBMITTED BY Client TESTED BY JH Fig No 14 MOISTUREDENSITY RELATIONSHIP TEST WESTERN COLORADO TESTING INC 130 115 ZAV for Sp.C 2.65 10 12 14 16 PARTICLE SIZE DISTRIBUTION TEST REPORT %GRAVEL SAND SILT CLAY USCS AASHTO .PL Ii 30.9 50.5 SM A-2-40 NIH SIEVE size PERCENT FINER SIEVE number size PERCENT FINER Oft DESCRIPTION Sand gravclyirown 1.5 3/4 1/2 3/8 100.0 100.0 100.0 961 94.8 88.4 80.1 10 20 40 60 100 200 69.1 61.1 56.4 .5L7 38.0 24.4 18.6 D30 D10 -GRAiN SIZE REMARKS OTestedByiH1.73 0.190 COEFFICIENTS C0 Cu Source Sample No RF2-S2 GISt International Uranium-Corporation WESTERN COLORADO TESTING tNC Project Soil Same Testing Project No 804899 Fiqure 45 tt Lii El- 130 125 .4- 120 .4- 115 110 105 MOISTURE-DENSITY RELATIONSHIP TEST ZAV for Sp.G 2.65 Water content Test specification ASTM 69891 Procedure Standard Oversize correction applied to each point Elev/ Depth Classification Nat Moist Sp.G LL P1 3/4 in No.200USCSPASHTO N/A 2.65 6.6 ROCK CORRECTED TEST RESULTS UNCORRECTED MATERIAL DESCRIPTION Maximum dry density 121.4 pcf Optimum moisture 11.3 119.2 pcf 12.1 RF3S1 Sand clayey grvly brn Project No 804899 Project International Uranium Corporation Location Soil Sample Testing Date 5/3/99 Remarks SUBMITTED BY Client TESTED BY .N Fig No 15 MOISTUREDENSITY RELATIONSHIP TEST WESTERN COLORADO TESTING INC 10 12 14 16 18 20 2upsojojdumgpopefaJd13N1DNIIS3IOOVUOT03NJ1SM UOPUOthoaUmUtIfluoqnitquaq HfPL gJqpJJ uMoiqAjaisi2oAvpjspuv NOtLdI8OS3O1IOŁI3NIdIN9OŁJ3d WWBZIS NIVŁJO oomog IS-C.tffloNojdhws .N31013d303 ŁI3NIdlN3OŁSd iŁIOd3ŁI.LS31NOI1fl81ŁLLSI3ZIS3131J.Wd 112 110 .4- 108 106 104 MOISTURE-DENSITY RELATIONSHIP TEST LAY or Sp .0 2.65 102 12 Water content Test specification ASTM 69891 Procedure Standard Oversize correcflon applied to each ooint Elev/ Depth Classification Nat Moist Sp.G LL P1 No.4 No.200USCSAASHTO N/A 2.65 ROCK CORRECTED TEST RESULTS UNCORRECTED MATERIAL DESCRIPTION Maximum dry density 11L7 pcf Optimum moisture 14.3 111.7 pef 14.3 RF3S2 Clay sandy red Project No 804899 Project International Uranium Corporation Location Soil Sample Testing Date 5/3/99 Remarks SUBMITTED BY Client TESTED BY JH Fig No 16 MOISTUREDENSITY RELATIONSHIP TEST WESTERN COLORADO TESTING INC 14 16 18 20 22 24 LIQUID AND PLASTIC LIMITS TEST REPORT Clay very sandy red 28 20 69.0 39.0 SM MATERIAL DESCRIPTION LL PL P1 %c40 %200 USCS Project No 804899 Client International Uranium Corporation Project Soil Sample Testing Source Sample No RF3-S2 Remarks Tested By JH Figure 27 LIQUID AND PLASTIC LIMITS TEST REPORT WESTERN COLORADO TESTING INC It Dashed line indicates the approximate___upper limit boundary for natural soils _________________________________50- /i__ 40- lI//I/Ill/I 30 ___________________________ ____20- 10 ___.7 ________ ____________ML c1rOL MHorOH 47 10 30 50 70 90 110 LIQUID LIMIT It Ui Ui It Ui PARTICLE SIZE DISTRIBUTION TEST REPORT to 100 11 II 11111 liii iii 11 it ill liii -H 2C --- IC --___ 200100 10 0.1 0.01 OMOi GRAINSIZE mm 16.3 44.7 %3 %GRAVEL %SAND %SJLT %CLAY USCS AASHTO -FL U. SM A-40 SIEVE inches size PERCENT FINER SIEVE number size PERCENT FINER SOIL UtbUMW1 run Clay vecy sandy red 1.5 3/4 1/2 3/8 100.0 100.0 100.0 JOQ.0 98.7 94.0 90.8 10 20 40 60 100 200 83.7 78.2 73.4 69.0 63.7 45.5 39.0 GRAIN SIZE REMARKS Tested By JH D3 D10 0.222 COEFFICIENTS Cc Cu Source Sample No RF3-S2 Client International UraniumCorporation WESTERN COLORADO TESTING mic Prct Soil SamPle Testing Project No R04899 Ficure 47 135 130 4- C- 125 4.J Co 120 115 110 MOISTURE-DENSITY RELATIONSHIP TEST Water content Test specification ASTM 69891 Procedure Standard Oversize correction applied to each point Elev/ Depth Classification Nat Moist Sp.G LL P1 3/4 in No.200USCSAASHTO N/A 2.65 18.1 ROCK CORRECTED TEST RESULTS UNCORRECTED MATERIAL DESCRIPTION Maximum dry density 127.4 pcf Optimum moisture 10.3 121.3 pcf 12.6 RF3S3 Sand clayey qrvly brn Project No 804899 Project International Uranium Corporation Location Soil Sample Testing Date 5/3/99 Remarks SUBMITTED BY Client TESTED BY JH Fig No 17 MOISTUREDENSITY RELATIONSHIP TEST WESTERN COLORADO TESTING INC 10 12 14 16 18 PARTICLE SIZE DISTRIBUTION TEST REPORT to Ui ElI II 8C 7C- 60----- ------- -- --------- 5C x-------------- 2C 10-------- 200 100 10 GRAIN 0.1 SIZE mm 0.01 0.001 %a %GRAVEL %SAND SILT CLAY IJSCS AASHTO -P-I-JL 01 22.7 53.6 SM A..2-4o jNPJNP SIEVE inches size PERCENT FINER SIEVE number size PERCENT FINER -SOIL DESCRIPTION Sand sI clayey gravely-brown 1.5 3/4 1/2 3/8 100.0 100.0 100.0 97.4 97.4 90.9 86.2 10 20 40 60 100 200 77.3 69.7 64.1 35.8 38.8 30.2 23.7 GRAIN SIZE R-EMARKSC OTested43yJHD60 D30 D10 0323 0.147 COEFFICIENTS Cc Cu Source Sample No RF3-S3 Client InteniationalUranium-Corporation WESTERN COLORADO TESTING INC Project Soil Sample Testing Project No 804899 Fioure 48 135 MOISTURE-DENSITY RELATIONSHIP TEST 110 Water content Test specification ASTM 69891 Procedure Standard Oversize correction applied to each point Elev/ Depth Classification Nat Moist Sp.G LL P1 3/4 in No.200USCSAkSHTO N/A 2.65 7.7 ROCK CORRECTED TEST RESULTS UNCORRECTED MATERIAL DESCRIPTION Maximum dry density 127.2 pcf Optimum moisture 9.9 124.8 pcf 10.7 RF4S1 Sand clayey grvly brn Project No 804899 Project International Uranium Corporation Location Soil Sample Testing Date 5/3/99 Remarks SUBMITTED BY Client TESTED BY JH Fig No 18 MOISTUREDENSITY RELATIONSHIP TEST WESTERN COLORADO TESTING INC 130 .4- 125 Co 120 115 ZAV for Sp.G 2.65 10 12 14 16 CD LIQUID AND PLASTIC LIMITS TEST REPORT LIQUID LIMIT 22Sandclayey gravely brown 19 51.1 25.5 SM MATERIAL DESCRIPTION LL PL P1 %40 %200 USCS Project No 804899 Client International Uranium Corporation Project Soil Sample Testing Source Sample No RF4-S1 Remarks Tested By JH Figure 28 LIQUID AND PLASTIC LIMITS TEST REPORT WESTERN COLORADO TESTING INC PARTICLE SIZE DISTRIBUTION TEST REPORT ___oo Th nnirr LL %SAND %SILT IJSCS AASHTO 91 ----- Sc -- be .S__60 50 -----.- ----- 2C ------ --H ---- oJ_ 200 100 10 0.1 0.01 0.001 -GRAIN SIZE mm 311 GRAVEL -P1 31.8 42.7 SM A-2-40 SIEVE inches size PERCENT FINER SIEVE number size PERCENT FINER SOIL DESCRIPTION 0-Sand clayey gravely brown 1.5 3/4 1/2 3/8 100.0 100.0 100.0 88.1 86.1 81.3 77.7 10 20 40 60 100 W200 68.2 59.6 546 51.1 44.7 33.3 255 GRAIN SIZE REMARKS TestedB ill060 D30 D10 2.11 0.122 COEFFICIENTS C0 Source Sample No RF4-S1 International -Uranium Corporation WESTERN COLORADO TESTING INC Prct Soil Sample Testing Project No 804899 Fioure 49 130 25 4- 120 4J -o 115 110 MOISTURE-DENSITY RELATIONSHIP TEST ZAV for Sp.G 2.65 105 Water content Test specification ASTM 69891 Procedure Standard Oversize correction applied to each coint Elev/ Depth Classification Nat Moist Sp.G LL P1 3/8 in No.200USCSAASHTO N/A%2.65 4.1 ROCK CORRECTED TEST RESULTS UNCORRECTED MATERIAL DESCRIPTION Maximum dry density 123.5 pcf Optimum moisture 11.3 122.2 pcf 11.7 RF5S1 Sand clayey grvly brn Project No 804899 Project International Uranium Corporation Location Soil Sample Testing Date 5/3/99 Remarks SUBMITTED BY Client TESTED BY JH Fig No 19 MOISTUREDENSITY RELATIONSHIP TEST WESTERN COLORADO TESTING INC 10 12 14 16 18 20 LIQUID AND PLASTIC LIMITS TEST REPORT LIQUID LIMIT 24 18Sandclayey gravely brown 74.3 41.6 SM MATERIAL DESCRIPTION LL PL P1 %c40 %200 USCS Project No 804899 Client Jnternational Uranium Corporation Project Soil Sample Testing Source Sample No RF5-S1 Remarks Tested By iii Figure 29 LIQUID AND PLASTIC LIMITS TEST REPORT WESTERN COLORADO TESTING INC PARTICLE SIZE DISTRIBUTION TEST REPORT 100 .5 AflJJ U- LU C- LU 0- sJ- 70- 60---------- 50------H------ 4C------ 30-------m---- 2C- ic ---h1------- 200 100 10 0_I 0.01 0.001 GRAIN SIZE mm %GRAVEL SAND SILT CLAY uSCS AA.SHTO ft 1_i 13.2 45.2 SM jAA0 SIEVE inches size PERCENT FINER SIEVE number size PERCENT FINER SOII DESCRIPTION Sand claycy gravelytrown 1.5 3/4 1/2 3/8 100.0 100.0 100.0 97.2 97.2 93.9 92.1 10 20 40 60 100 -200 868 82.2 783 743 67.8 56.2 4L6 GRAIN SIZE -REMARKS OTcstedlly ii D30 DID -0.176 COEFFICIENTS C0 Source Sample No RF5-S1 International UraniumCorporation WESTERN COLORADO TESTLNG INC Proect Soil Sample Testing II Project No 804899 Fioure 50 130 .4- 120 MOISTURE-DENSITY RELATIONSHIP TEST Water content Test specificotion ASTM 69891 Procedure Standard Oversize correction applied to each point Elev/ Depth Classification Nat Moist Sp.G LL P1 3/4 in No.200USCSAASHTO N/A%2.65 11.7% ROCK CORRECTED TEST RESULTS UNCORRECTED MATERIAL DESCRIPTION Maximum dry density 126.6 pcf Optimum moisture 9.2 122.8 pcf 10.4 RF6S1 Sand clayey grvly brn Project No 804899 Project International Uranium Corporation Location Soil Sample Testing Date 5/3/99 Remarks SUBMITTED BY Client TESTED BY JH Fig.No 20 MOISTUREDENSITY RELATIONSHIP TEST WESTERN COLORADO TESTINC INC 125 115 110 105 ZAV for Sp.C 2.65 10 12 14 16 18 a- LIQUID AND PLASTIC LIMITS TEST REPORT LIQUID LIMIT 23Sandclayey gravely brom 16 30.653.0 GC-GM MATERIAL DESCRIPTION IS PL P1 %c40 %c200 USCS Project No 804899 Client International Uranium Corporation Project Soil Sample Testing Source Sample No RF6-S1 Remarks Tested By ill Figure 30 LIQUID AND PLASTIC LIMITS TEST REPORT WESTERN COLORADO TESTING INC 114 112 110 108 106 104 MOISTURE-DENSITY RELATIONSHIP TEST 10 ZAV for Sp 2.65 Water content Test specification ASTM 69891 Procedure Standard Oversize correction applied to each coint Elev/ Depth Classification Nat Moist Sp.G LL P1 No.4 No.200USCSAASI-ITO N/A 2.65 ROCK CORRECTED TEST RESULTS UNCORRECTED MATERIAL DESCRIPTION Maximum dry density 113.1 pcf Optimum moisture 13.9 113.1 pcf 13.9 RF7S1 Clay sandy silty rd Project No 804899 Project International Uranium Corporation Location Soil Sample Testing Date 5/3/99 Remarks SUBMITTED BY Client TESTED BY JH Fig No 211 MOISTUREDENSITY RELATIONSHIP TEST WESTERN COLORADO TESTING INC 12 14 16 18 20 22 Co 0. LIQUID AND PLASTIC LIMITS TEST REPORT LIQUID LIMIT 23 20Clayveiysandysiltyred 88.6 56.8 ML MATERIAL DESCRIPTION IL PL RI %40 %c200 USCS Project No 804899 Client International Uranium Corporation Project Soil Sample Testing Source Sample No RF7-Sl Remarks Tested By ill Figure 31 LIQUID AND PLASTIC LIMITS TEST REPORT WESTERN COLORADO TESTING INC uJ U- Ui PARTICLE SIZE DISTRIBUTION TEST REPORT %SAND %SILT CLAY USGS AASHTO PL LL 7.1 36.1 IvIL A-40 20 23 SIEVE inches size PERCENT FINER SIEVE number size PERCENT FINER SOIL DESCRIPTION Clay very sandy silty red 1.5 3/4 1/2 3/8 100.0 100.0 100.0 100.0 97.3 95.9 95.0 10 20 40 60 100 200 92.9 92.1 90.9 88.6 86.6 83.7 56.8 GRAIN SIZE REMARKS Tested By ill Drj D10 0.0801 COEFFICIENTS C0 Cu Souze Sample No RF7-S1 Client Jnternalional Uranium Coiporation WESTERN COLORADO TESTING INC Project Soil Sample Testing Project No 804899 Route 52 DENISON MINES (USA) CORP. RESPONSES TO INTERROGATORIES – ROUND 1 FOR RECLAMATION PLAN, REVISION 5.0, MARCH 2012; MAY 31, 2012 TABLE OF CONTENTS INTERROGATORY WHITEMESA RECPLAN REV 5.0; R313-24-4; 10CFR40.31(H); INT 01/1: RESPONSES TO RECLAMATION PLAN REV. 4.0 INTERROGATORIES ........................................... 1 INTERROGATORY WHITEMESA RECPLAN REV 5.0; R313-24-4; 10CFR40, APPENDIX A, CRITERION 4; INT 02/1: ENGINEERING DRAWINGS .......................................................................... 3 INTERROGATORY WHITEMESA RECPLAN Rev. 5.0; R313-24-4; 10CFR40 APPENDIX A CRITERIA 1 AND 4; INT 03/1: CONSTRUCTION QUALITY ASSURANCE/QUALITY CONTROL PLAN, COVER CONSTRUCTABILITY, AND FILTER AND ROCK RIP RAP LAYER CRITERIA AND PLACEMENT ..................................................................................................................................... 6 INTERROGATORY WHITEMESA RECPLAN Rev5.0; R313-24-4; 10CFR40, APPENDIX A, CRITERION 4; INT 04/1: VOID SPACE CRITERIA AND DEBRIS, RUBBLE PLACEMENT AND SOIL/BACKFILL REQUIREMENTS ....................................................................................................... 11 INTERROGATORY WHITEMESA RECPLAN Rev. 5.0 R313-24-4, 10 CFR 40 APPENDIX A; INT 05/1: SEISMIC HAZARD EVALUATION .............................................................................................. 20 INTERROGATORY WHITEMESA RECPLAN REV5.0; R313-24-4; 10CFR40 APPENDIX A, CRITERION 1; INT 06/1: SLOPE STABILITY ........................................................................................ 25 INTERROGATORY WHITEMESA RECPLAN Rev. 5.0; R313-24-4; 10 CFR 40 APPENDIX A, CRITERION 4; INT 07/1: TECHNICAL ANALYSIS - SETTLEMENT AND POTENTIAL FOR COVER SLOPE REVERSAL AND/OR COVER LAYER CRACKING ................................................. 34 INTERROGATORY WHITEMESA RECPLAN Rev5.0 R313-24-4; 10cfr40 APPENDIX A CRITERION 4; INT 08/1: TECHNICAL ANALYSIS –EROSION STABILITY EVALUATION ......... 44 INTERROGATORY WHITEMESA RECPLAN Rev. 5.0; R313-24-4; 10CFR40 APPENDIX A CRITERION 1; INT 09/1: LIQUEFACTION .......................................................................................... 50 INTERROGATORY WHITEMESA RECPLAN 5.0 R313-24-4; 10CFR40 APPENDIX A, CRITERION 6; INT 10/1: TECHNICAL ANALYSES - FROST PENETRATION ANALYSIS ................................ 54 INTERROGATORY WHITE MESA RECPLAN REV 5.0 R313-24-4; 10CFR40 APPENDIX A; INT 11/1: VEGETATION AND BIOINTRUSION EVUALATION AND REVEGETATION PLAN ........... 57 INTERROGATORY WHITEMESA RECPLAN REV 5.0 R313-24-4; 10CFR40 APPENDIX A, CRITERION 6(4); INT 12/1: REPORT RADON BARRIER EFFECTIVENESS .................................... 65 INTERROGATORY WHITEMESA RECPLAN REV 5.0 R313-24-4; 10CFR40, APPENDIX A, CRITERION 6(6); INT 13/1: CONCENTRATIONS OF RADIONUCLIDES OTHER THAN RADIUM IN SOIL ...................................................................................................................................................... 72 INTERROGATORY WHITE MESA RECPLAN REV 5.0 R313-24-4; 10CFR40 APPENDIX A; INT 14/1: COVER TEST SECTION AND TEST PAD MONITORING PROGRAMS ................................... 75 INTERROGATORY WHITEMESA RECPLAN REV 5.0 R313-24-4; 10CFR40, APPENDIX A, CRITERION 9; INT 15/1: FINANCIAL SURETY ARRANGEMENTS.................................................. 86 INTERROGATORY WHITE MESA REC PLAN REV 5.0 R313-15-501; INT 16/1; RADIATION PROTECTION MANUAL ......................................................................................................................... 89 INTERROGATORY WHITE MESA REC PLAN REV 5.0 R313-15-1002; INT 17/1; RELEASE SURVEYS .................................................................................................................................................. 90 INTERROGATORY WHITE MESA REC PLAN REV 5.0 R313-12; INT 18/1: INSPECTION AND QUALITY ASSURANCE .......................................................................................................................... 91 INTERROGATORY WHITE MESA REC PLAN REV 5.0 R313-24; 10 CFR 40.42(J); INT 19/1: REGULATORY GUIDANCE .................................................................................................................... 92 INTERROGATORY WHITE MESA REC PLAN REV 5.0 R313-24,;10 CFR 40 APPENDIX A CRITERION 6(6); INT 20/1: SCOPING, CHARACTERIZATION, AND FINAL SURVEYS ............... 93 ATTACHMENTS ATTACHMENT A Supporting Documentation for Interrogatory 05/1: Site-Specific Probabilistic Seismic Hazard Analysis, White Mesa Uranium Facility, Blanding, Utah ATTACHMENT B Supporting Documentation for Interrogatory 08/1: Updated Probable Maximum Precipitation Calculations ATTACHMENT C Supporting Documentation for Interrogatory 10/1: Updated Frost Penetration Analysis ATTACHMENT D Supporting Documentation for Interrogatory 14/1: Test Section Installation Instructions, Alternative Cover Assessment Program (Benson et. al, 1999). ATTACHMENT E Supporting Documentation for Interrogatory 16/1: Updated Radiation Protection Manual for Reclamation Interrogatory 01/1: R313-24-4; 10CFR40.31(H): Responses to Reclamation Plan Rev. 4.0 Interrogatories Page 1 of 96 INTERROGATORY WHITEMESA RECPLAN REV 5.0; R313-24-4; 10CFR40.31(H); INT 01/1: RESPONSES TO RECLAMATION PLAN REV. 4.0 INTERROGATORIES REGULATORY BASIS: UAC R313-24-4 invokes the following requirement from 10CFR40.31(h): An application for a license to receive, possess, and use source material for uranium or thorium milling or byproduct material, as defined in 10CFR40, at sites formerly associated with such milling shall contain proposed written specifications relating to milling operations and the disposition of the byproduct material to achieve the requirements and objectives set forth in appendix A of 10CFR40. Each application must clearly demonstrate how the requirements and objectives set forth in appendix A of 10CFR40 have been addressed. Failure to clearly demonstrate how the requirements and objectives in Appendix A have been addressed shall be grounds for refusing to accept an application. INTERROGATORY STATEMENT: The Division has reviewed the responses to Reclamation Plan 4.0 and is not asking for additional information at this time; however, the Division reserves the right and may submit comments and/or additional interrogatories following completion of review of the Denison Mines (USA) Corp (DUSA) response document dated December 28, 2011 (DUSA 2011). Response: No response required. BASIS FOR INTERROGATORY: The State transmitted Interrogatory Round 1 following its review and evaluation of Reclamation Plan Rev. 4.0 (o/a September 10, 2010). A meeting was held on October 5, 2010 with DUSA personnel regarding Denison’s plan to prepare and submit a Reclamation Plan Rev. 5.0 incorporating an evapotranspiration cover system. The State prepared and issued Interrogatory Round 1A for the purpose of giving guidance to DUSA on topics that it must address in Reclamation Plan Rev. 5.0 for matters relating to the evapotranspiration cover system. A complete review of DUSA’s December 28, 2011 response to the Round 1 and Round 1A must be performed to ensure that all issues that are still relevant have been adequately addressed. The Division received a letter from Denison Mines (USA) Corp (DUSA ) dated December 28, 2011 (DUSA 2011) that provided responses) to: (i) Round 1 and Round 1A interrogatories that were submitted to DUSA on Rev. 4.0 of the Reclamation Plan Rev. (DUSA 2009) in 2010 (Division 2010); and (ii) Round 1A interrogatories that were submitted to DUSA in 2011 (Division 2011) regarding an alternative cover system design that was proposed by DUSA in 2010 (see DUSA letter dated October 6, 2010 [DUSA 2010]. The December 28, 2011 response document was forwarded to URS Corporation on February 23, 2012 and is currently under review. REFERENCES: Denison Mines (USA) Corp. 2009. Reclamation Plan, White Mesa Mill, Blanding, Utah, Radioactive Materials License No. UT1900479, Revision 4.0, November 2009. Denison Mines (USA) Corp. 2011. Responses to Supplemental Interrogatories – Round 1A for Reclamation Plan, Revision 4.0, November 2009. December 28, 2011. Interrogatory 01/1: R313-24-4; 10CFR40.31(H): Responses to Reclamation Plan Rev. 4.0 Interrogatories Page 2 of 96 Division (Utah Division of Radiation Control) 2010. Denison Mines (USA) Corporation Reclamation Plan, Revision 4.0, November 2009: Interrogatories – Round 1. September 2010 Division (Utah Division of Radiation Control) 2011. Denison Mines (USA) Corporation Reclamation Plan, Revision 4.0, November 2009: Supplemental Interrogatories – Round 1A. April 2011. Interrogatory 02/1: R313-24-4; 10CFR40.Appendix A, Criterion 4: Engineering Drawings Page 3 of 96 INTERROGATORY WHITEMESA RECPLAN REV 5.0; R313-24-4; 10CFR40, APPENDIX A, CRITERION 4; INT 02/1: ENGINEERING DRAWINGS REGULATORY BASIS: UAC R313-24-4 invokes the following requirement from 10CFR40, Appendix A, Criterion 4: “The following site and design criteria must be adhered to whether tailings or wastes are disposed of above or below grade: … (c) Embankment and cover slopes must be relatively flat after final stabilization to minimize erosion potential and to provide conservative factors of safety assuring long-term stability. The broad objective should be to contour final slopes to grades which are as close as possible to those which would be provided if tailings were disposed of below grade; this could, for example, lead to slopes of about 10 horizontal to 1 vertical (10h:1v) or less steep. In general, slopes should not be steeper than about 5h:1v. Where steeper slopes are proposed, reasons why a slope less steep than 5h:1v would be impracticable should be provided, and compensating factors and conditions which make such slopes acceptable should be identified. (d) A full self-sustaining vegetative cover must be established or rock cover employed to reduce wind and water erosion to negligible levels. Where a full vegetative cover is not likely to be self-sustaining due to climatic or other conditions, such as in semi-arid and arid regions, rock cover must be employed on slopes of the impoundment system. The Executive Secretary will consider relaxing this requirement for extremely gentle slopes such as those which may exist on the top of the pile. ….Furthermore, all impoundment surfaces must be contoured to avoid areas of concentrated surface runoff or abrupt or sharp changes in slope gradient. In addition to rock cover on slopes, areas toward which surface runoff might be directed must be well protected with substantial rock cover (rip rap). In addition to providing for stability of the impoundment system itself, overall stability, erosion potential, and geomorphology of surrounding terrain must be evaluated to assure that there are not ongoing or potential processes, such as gully erosion, which would lead to impoundment instability.” NUREG-1620, Section 2.5.3: The assessment of the disposal cell cover design and engineering parameters will be acceptable if it meets the following criteria: (3) Details are presented (including sketches) of the disposal cell cover termination at boundaries, with any considerations for safely accommodating subsurface water flows. (4) A schematic diagram displaying various disposal cell layers and thicknesses is provided. The particle size gradation of the disposal cell bedding layer and the rock layer are established to ensure stability against particle migration during the period of regulatory interest (NRC 1982). INTERROGATORY STATEMENT: Drawing REC-1: Provide design details for Discharge Channel. Drawing REC-3: Provide design details for Discharge Channel. Identify the limits of the proposed Sedimentation Pond. Establish and indicate on the appropriate drawing(s) the location of the main drainage channel. Demonstrate that the Cell 1 embankment and appurtenant apron are designed to remain stable under PMP conditions. Interrogatory 02/1: R313-24-4; 10CFR40.Appendix A, Criterion 4: Engineering Drawings Page 4 of 96 Drawing TRC-2: Correct the location shown by green dashes for the “Approximate limit of compacted cover,” Drawing TRC-4: State where “Filter Layer” is defined. Link Rock Apron A and Rock Apron B to characteristics presented in the table at Detail 1/8. Drawing TRC-5: In Sections A/3 and B/3, indicate the cover thickness to be 9 feet minimum. State the maximum tailings elevation on the North end of each section. Drawing TRC-6: Please explain why the Compacted Cover cannot continue through the entire sections rather that terminating as “wedges”. Drawing TRC-7: Please explain why the Compacted Cover cannot continue through the entire sections rather that terminating as “wedges”. State maximum slope on transitional slopes in Section A/3, B/3, and C/3 to be 5:1. State maximum tailings elevations in each section. Drawing TRC-8: Revise both the Plan and the Elevation of Detail 1/8 to refer to the table provided below rather than stating D50 = 7.4” min. State where “Filter Layer” is defined. Show the “Riprap Filter Layer” on the side slopes of Details 3/5, Detail 4/8, and Detail 5/8 or otherwise resolve the conflict involving “Riprap Filter Layer” that exists between Detail 1/8 and the details cited. State where “Clay Liner” called out in Detail 4/8 is defined. Justify terminating the “Clay Liner” shown in Detail 4/8 at the exterior extreme (of top) of the “Radon Attenuation and Grading Layer”. State the cover thickness shown in Detail 4/8 to be 9 feet minimum. Show the correct maximum tailings elevations in Details 6/8 (presently incorrectly stated) and 7/8 (presently not stated). Response: The final response to this interrogatory will be provided as part of a second response document to be submitted to the Division on August 15, 2012. This is due in part to field investigations, laboratory testing, and analyses that have recently been conducted or will be conducted that may impact the cover design and result in further revisions to the Drawings. The Drawings will be updated to provide design details for the Discharge Channel and identify the limits of the Sedimentation Pond. The Cell 1 embankment and toe are designed to be erosionally stable from peak runoff from the PMP. Erosion protection is to be provided by riprap on the reclaimed slope of the Cell 1 embankment, and by a riprap apron at the toe of the embankment. The erosional stability analyses for the embankment and toe apron are provided in Appendix G of the Updated Tailings Cover Design Report (Appendix D of the Reclamation Plan, Rev. 5.0). Cell 1 will be cleaned of contaminated materials upon reclamation and the materials will be placed in the tailings cells. A portion of the Cell 1 area will be used for permanent disposal of contaminated materials and mill debris. The remaining area of Cell 1 will be breached and converted to a sedimentation basin. The Sedimentation Pond is designed to grade at a 0.1 percent slope northwest towards the Discharge Channel. This area is designed to be erosionally stable from peak runoff from the PMP with topsoil and vegetation. A rock apron is included at the transition between the vegetated surface of the Sedimentation Basin and the bedrock surface at the entrance of the Discharge Channel. Although channeling in this area would not cause erosional issues for the Cell 1 embankment, Denison will revise the grading to include a drainage swale along the center of the Sedimentation Pond area parallel to the toe of the Cell 1 embankment and draining to the west towards the Discharge Channel. Interrogatory 02/1: R313-24-4; 10CFR40.Appendix A, Criterion 4: Engineering Drawings Page 5 of 96 The location of the “approximate limit of compacted cover” may change due to potential revisions to the cover design; however this limit is currently shown correctly on Drawing TRC-2 for the Reclamation Plan, Rev. 5.0 cover design. Additionally, the compacted cover is shown correctly as terminating as “wedges” on Drawings TRC-7 and 8. The compacted cover is the cover layer that will be compacted to 95 percent of standard Proctor dry density. In some areas of Cell 2 and 3, the placed interim cover is thicker than required for the cover design and/or additional interim cover is required to meet grading requirements. As a result, there are areas in Cell 2 and 3 that do not require the compacted cover layer to meet radon emanation requirements. The corresponding radon emanation analyses are provided in Appendix C of the Updated Tailings Cover Design Report (Appendix D of the Reclamation Plan, Rev. 5.0). A note will be added to the drawings to provide additional clarification. Notes will be added to Drawing TRC-4 to clarify details on the filter and aprons are provided on Drawing TRC-8. A minimum cover thickness will be added to Drawing TRC-5 for Sections A/3 and B/3. The maximum tailings elevation will be added to the north end of Sections A/3 and B/3. The maximum transitional slopes will be stated as 10H:1V on Drawings TRC-6 and TRC-7. Drawing TRC-8 will be revised to reference the table for the Plan and Elevation of Detail 1/8. The filter layer and clay liner will be defined on Drawing TRC-8. The riprap filter layer will be added to the Details 3/5, 4/8, and 5/8. The termination of the clay liner will be revised to terminate at the bottom of the radon attenuation and grading layer and a 3- ft berm will be added at the termination location. The minimum cover thickness will be added to Detail 4/8. The maximum tailings elevations will be corrected for Detail 6/8 and will be added to Detail 7/8 BASIS FOR INTERROGATORY: The Licensee should resolve conflicts, clarify ambiguities, and provide missing information to properly document the proposed designs. Upstream of the discharge channel, it appears that drainage from precipitation events would likely create a random main drainage channel location in Cell 1. It is not desirable for this drainage channel to have the northern toe of the Cell 1 dike as a channel wall. Controlling the location of drainage channeling in Cell 1 appears to be important. Without establishing the location of the main drainage channel location, the Cell 1 embankment and appurtenant apron would need to be designed to be stable under PMP drainage channel wall depth and velocities. Note: Drawing TRC-4 shows topsoil and vegetation east of the riprap rock in Cell 1 and bedrock to the west. REFERENCES: NRC 1992. “Preparation of Environmental Reports for Uranium Mills,” Regulatory Guide 3.8, October, 1992. NRC 2003. Standard Review Plan for the Review of a Reclamation Plan for Mill Tailings Sites under Title II of the Uranium Mill Tailings Radiation Control Act of 1978. Washington DC, June 2003. NRC 2008. “Standard Format and Content Of License Applications for Conventional Uranium Mills,” Draft Regulatory Guide DG-3024, Ma, 2008. Interrogatory 03/1: R313-24-4; 10CFR40.Appendix A, Criteria 1 and 4: Construction Quality Assurance/Quality Control Plan, Cover Constructability, and Filter and Rock Riprap Layer Criteria and Placement Page 6 of 96 INTERROGATORY WHITEMESA RECPLAN REV. 5.0; R313-24-4; 10CFR40 APPENDIX A CRITERIA 1 AND 4; INT 03/1: CONSTRUCTION QUALITY ASSURANCE/QUALITY CONTROL PLAN, COVER CONSTRUCTABILITY, AND FILTER AND ROCK RIP RAP LAYER CRITERIA AND PLACEMENT REGULATORY BASIS: UAC R313-24-4 invokes the following requirement from 10CFR40, Appendix A, Criterion 1: “ The general goal or broad objective in siting and design decisions is permanent isolation of tailings and associated contaminants by minimizing disturbance and dispersion by natural forces, and to do so without ongoing maintenance. For practical reasons, specific siting decisions and design standards must involve finite times (e.g., the longevity design standard in Criterion 6)… UAC R313-24-4 invokes the following requirement from 10CFR40, Appendix A, Criterion 4: “The following site and design criteria must be adhered to whether tailings or wastes are disposed of above or below grade: … (c) Embankment and cover slopes must be relatively flat after final stabilization to minimize erosion potential and to provide conservative factors of safety assuring long-term stability. The broad objective should be to contour final slopes to grades which are as close as possible to those which would be provided if tailings were disposed of below grade; this could, for example, lead to slopes of about 10 horizontal to 1 vertical (10h:1v) or less steep. In general, slopes should not be steeper than about 5h:1v. Where steeper slopes are proposed, reasons why a slope less steep than 5h:1v would be impracticable should be provided, and compensating factors and conditions which make such slopes acceptable should be identified. (d) A full self-sustaining vegetative cover must be established or rock cover employed to reduce wind and water erosion to negligible levels. Where a full vegetative cover is not likely to be self-sustaining due to climatic or other conditions, such as in semi-arid and arid regions, rock cover must be employed on slopes of the impoundment system. The Executive Secretary will consider relaxing this requirement for extremely gentle slopes such as those which may exist on the top of the pile. ….Furthermore, all impoundment surfaces must be contoured to avoid areas of concentrated surface runoff or abrupt or sharp changes in slope gradient. In addition to rock cover on slopes, areas toward which surface runoff might be directed must be well protected with substantial rock cover (rip rap). In addition to providing for stability of the impoundment system itself, overall stability, erosion potential, and geomorphology of surrounding terrain must be evaluated to assure that there are not ongoing or potential processes, such as gully erosion, which would lead to impoundment instability.” INTERROGATORY STATEMENT: Refer to Section 5 of Attachment B, Construction Quality Assurance/Quality Control Plan, to the Reclamation Plan, Rev. 5.0: Please provide the following: 1. In Sections 5.3 and 5.4, clarify the nature and characteristics of wastes that would be placed into the reclaimed Cell 1 footprint area within which the 1-foot-thick compacted clay liner would first be installed. Verify whether and state consistently throughout the CQA/CQC Plan whether any uranium mill tailings materials would be placed into the clay-lined Cell 1 footprint area. If no tailings will be placed in the Cell 1 area, then change the name (“Cell 1 Tailings Area”) given in the T.O.C., and Sections 1.1, 5.3, 5.4.2, and 5.6 of the CQA/CQA Plan to “Cell 1 Contaminated Soil and Demolition Debris Disposal Area” or other name as appropriate, and revise the Interrogatory 03/1: R313-24-4; 10CFR40.Appendix A, Criteria 1 and 4: Construction Quality Assurance/Quality Control Plan, Cover Constructability, and Filter and Rock Riprap Layer Criteria and Placement Page 7 of 96 descriptions of waste materials to be placed into the clay-lined Cell 1 area as needed throughout the CQA/CQC Plan to be consistent with the proposed disposal plan. Response 1: No tailings are planned to be disposed of within the footprint of the 1-foot-thick clay liner to be constructed in the reclaimed Cell 1 area. Sections 1.1, 5.3, 5.4.2, and 5.6 of the CQA/CQC Plan will be revised to change the designation of “Cell 1 Tailings Area” to “Cell 1 Disposal Area”. In addition, the designation of “Cell 1 Tailings Area” will be revised to “Cell 1 Disposal Area" in Sections 3.3 and 8.1 of the Technical Specifications and Section 3.2 of the main text of the Reclamation Plan. Sections 5.3.3 and 5.4.2 of the CQA/CQC Plan will be revised to denote that the materials to be placed in the Cell 1 Disposal Area will consist of contaminated materials and mill debris from the mill site decommissioning, and that tailings will not be placed in the Cell 1 Disposal Area. To be consistent with the CQA/CQC Plan, Section 3.2 of the main text of the Reclamation Plan will be revised to clarify that materials to be placed in the Cell 1 Disposal Area will consist of contaminated materials and mill debris from the mill site decommissioning, and that tailings will not be placed in the Cell 1 Disposal Area 2. In Sections 5.6.4 and 5.6.5, provide a detailed justification to support the technical appropriateness and the constructability of the proposed topslope areas of the proposed cover system having such extremely flat slopes (e.g. 0.1 to 0.82 %). Provide information demonstrating that such topslope areas of the cover could be constructed with such shallow inclinations maintained continuously over the long distances that are required based on the currently proposed over design drawings such that no areas of runoff concentration or areas where ponding or could occur would result. Provide information justifying that appropriate required tolerances specified for final grades for ensuring conformance to the proposed extremely flat slope inclinations can be maintained and measured in the field with sufficient accuracy to ensure compliance with the specified slope requirements. Response 2: The proposed top surface cover slopes range from 0.5 to 1 percent, not 0.1 to 0.82 percent as listed in Comment 2. Cover with similar slopes have been permitted and constructed for Uranium Mill Tailings Radiation Control Act (UMTRCA) Title I and II sites including: • Falls City Title I site in Texas (less than 1% cover slopes) • Bluewater Title II site in New Mexico (0.5 – 4% cover slopes) • Conquista Title II site in Texas (0.5 – 1% cover slopes) • Highland Title II site in Wyoming (0.5 – 2% cover slopes) • Panna Maria Title II site in Texas (0.5% cover slopes) • Ray Point Title II site in Texas (0.5 – 1% cover slopes) • Sherwood Title II site in Washington (0.25% cover slopes) • L-Bar Title II site in New Mexico (0.1% cover slopes) Settlement monuments currently exist in Cell 2 and the eastern portion of Cell 3 where interim cover has been placed, and the monuments have been measured since 1989 and 1999, respectively. The standard operating procedure (SOP) for settlement monitoring was revised in October 2011 to incorporate comments provided by the Division in their letter dated July 2, 2012 (DRC, 2012). The updated SOP has been Interrogatory 03/1: R313-24-4; 10CFR40.Appendix A, Criteria 1 and 4: Construction Quality Assurance/Quality Control Plan, Cover Constructability, and Filter and Rock Riprap Layer Criteria and Placement Page 8 of 96 used since October 2011 for settlement monitoring. For the remainder of Cell 3, and for Cells 4A and 4B, settlement monuments will be installed after placement of interim cover using the procedures provided in the updated SOP. Monuments will be monitored on a regular basis in order to verify that 90 percent of the settlement due to tailings dewatering and interim cover placement has occurred prior to construction of the final cover. Additional interim cover, if necessary, will be placed in any low areas in order to maintain positive drainage of the cover surface. Settlement analyses for the proposed cover design were provided Appendix F of the Updated Tailings Cover Design Report (Appendix D of the Reclamation Plan, Rev. 5.0). Settlement of the thickest profile of tailings in Cells 2, 3, and 4A and 4B was estimated to range from 2 to 10 inches after placement of interim cover and dewatering. This settlement analysis will be updated to include recent data and further review of historical data, as discussed in the responses to Interrogatory 07/01. Additional settlement due to the construction of the final cover is estimated to be on the order of 5 to 6 inches. The estimated amount of additional settlement is sufficiently low such that ponding is not expected with cover slopes of 0.5 to 1 percent. The recommended tolerances provided Section 5.6.5 of the CQA/CQC Plan are sufficient to meet the specified grading for the final cover surface. 3. In Section 5.7.1.2, described material sampling frequency and filter gradation and filter permeability calculations (with associated acceptance criteria) that will be performed for the granular materials used in constructing the granular filter layer beneath the riprap layer on the sideslopes, to ensure that all applicable filter acceptance criteria will be achieved between the granular filter layer and each topslope cover layer component. Response 3: Section 5.7.1.2 will be revised to include a testing requirement for particle size distribution testing prior to placement, using ASTM D-422. The recommended testing frequency is at least one test per 10,000 cubic yards of filter material placed, or when filter material characteristics show significant variation. The filter material gradation requirements will be updated based on the results of laboratory tests currently being conducted on additional samples of cover borrow material. The procedure from NRCS (1994) will be used to determine the filter gradation limits, in addition to other procedures as deemed appropriate. Reference for Response 3: Natural Resource Conservation Service (NRCS), 1994. Gradation Design of Sand and Gravel Filters, U.S. Department of Agriculture, National Engineering Handbook, Part 633, Chapter 26, October. 4. In Section 5.7.1, specify the minimum required thickness of the rock riprap layer on the sideslopes – equal to 1.5 times the D50 of the rock rip diameter of 7.4 inches, or the D100 of the rock rip rap materials, whichever is greater, as per NUREG-1623 (NRC 2002) –for clarity and transparency in the CQA/CQC process. Interrogatory 03/1: R313-24-4; 10CFR40.Appendix A, Criteria 1 and 4: Construction Quality Assurance/Quality Control Plan, Cover Constructability, and Filter and Rock Riprap Layer Criteria and Placement Page 9 of 96 Response 4: Section 5.7.1 of the CQA/CQC Plan will be revised to include the minimum required thickness of the side slope riprap of 1.5 times the D50 or the D100 of the riprap, whichever is greater. To be consistent with the CQA/CQC Plan, Section 8.2.4 of the Technical Specifications will be will be revised to include the minimum required thickness of the side slope riprap of 1.5 times the D50 or the D100 of the riprap, whichever is greater. 5. In Sections 5.7.2, 5.7.4, and 5.7.5 provide additional details regarding the minimum thickness for placed riprap layer material and requirements for using specialized equipment or rearranging of rocks by hand, as needed, in accordance with the specified minimum required final thickness of the rock rip rap layer. Also provide additional details and requirements regarding procedures to be used to verify proper in-place rock riprap layer thickness and procedures for gradation testing in a completed initial riprap layer section, and for visual observations of the test section by field personnel. Provide criteria and procedures for testing additional test sections where observations suggest rock placement appears to be inadequate or where difficulties are experienced during rock place activities. Response 5: Sections 5.7.2 and 5.7.4 of the CQA/CQC Plan will be revised to include reference to Section 5.7.1 for the minimum required thickness for the riprap layers (see Response 4 above). Section 5.7.2 of the CQA/CQC Plan will be revised to include the following text at the end of the section “Hand placing will be required only to the extent necessary to secure the results specified above.” Section 5.7.4 of the CQA/CQC Plan will be revised to include the following text at the end of the section “Riprap layer thickness will be directly measured as outlined in Section 5.7.2. A measurement device (i.e. tape measure) may be used to determine the distance from the top of the bedding or filter layer to the top of the riprap layer.” Section 5.7.2 of the CQA/CQC Plan will be revised to include the following text “An initial section of each type of riprap constructed shall be visually examined and used to evaluate future riprap placement. The initial section will be constructed with material meeting gradation and riprap thickness requirements.” Section 5.7.1.1 of the CQA/CQC Plan will be revised to include the following text at the end of the section “Gradations will also be performed at the direction of the QC Technician for any locations considered inadequate based on visual inspection by the QC Technician, or if difficulties are experienced by the Contractor during rock placement.” BASIS FOR INTERROGATORY: In Section 5.4.4 of the CQA.CQC it states that backfill materials placed around placed demolition debris might include stockpiled soils, contaminated soils, tailings and or other approved materials [as approved by the Construction Manager and CQA officer]; however, in other sections of the CQA/CQAC Plan and in the Reclamation Plan it is indicated that no tailings placement would occur in the Cell 1 area. Interrogatory 03/1: R313-24-4; 10CFR40.Appendix A, Criteria 1 and 4: Construction Quality Assurance/Quality Control Plan, Cover Constructability, and Filter and Rock Riprap Layer Criteria and Placement Page 10 of 96 The ability to accurately construct the extremely flat topslope areas with a uniform slope to the proposed specified grades and within the associated allowable tolerances, and the ability to accurately verify that these flat slopes have been constructed uniformly and without the occurrence of areas of flow concentrations or areas where ponding of water could occur has not been adequately demonstrated. It has not been adequately demonstrated that all applicable filter layer criteria have been met for all interfaces that would occur between the sideslope filter layer and topslope cover components. NUREG-1623 (NRC 2002), Section 2.1.2 recommends that the minimum required thickness of a rock riprap layer be no less than 1.5 times the D50 of the rock riprap materials, or the D100 of the rock rip rap materials, whichever is greater. NUREG-1623 (NRC 2002), Appendix F provides specific recommendations regarding rock rip placement procedures and procedures for conducting testing and visual observations during rock rip rap placement that should be adhered to during construction and that should be addressed in the CQA/CQC Plan. REFERENCES: NRC 2002. U.S. Nuclear Regulatory Commission, “Design of Erosion Protection for Long-Term Stability”, NUREG-1623, September 2002. Interrogatory 04/1: R313-24-4; 10CFR40.Appendix A, Criterion 4: Void Space Criteria and Debris, Rubble Placement and Soil/Backfill Requirements Page 11 of 96 INTERROGATORY WHITEMESA RECPLAN REV5.0; R313-24-4; 10CFR40, APPENDIX A, CRITERION 4; INT 04/1: VOID SPACE CRITERIA AND DEBRIS, RUBBLE PLACEMENT AND SOIL/BACKFILL REQUIREMENTS REGULATORY BASIS: UAC R313-24-4 invokes the following requirement from 10CFR40, Appendix A, Criterion 4: “The following site and design criteria must be adhered to whether tailings or wastes are disposed of above or below grade: …(c) Embankment and cover slopes must be relatively flat after final stabilization to minimize erosion potential and to provide conservative factors of safety assuring long-term stability. The broad objective should be to contour final slopes to grades which are as close as possible to those which would be provided if tailings were disposed of below grade; this could, for example, lead to slopes of about 10 horizontal to 1 vertical (10h:1v) or less steep. In general, slopes should not be steeper than about 5h:1v. Where steeper slopes are proposed, reasons why a slope less steep than 5h:1v would be impracticable should be provided, and compensating factors and conditions which make such slopes acceptable should be identified. (d) A full self-sustaining vegetative cover must be established or rock cover employed to reduce wind and water erosion to negligible levels. Where a full vegetative cover is not likely to be self-sustaining due to climatic or other conditions, such as in semi-arid and arid regions, rock cover must be employed on slopes of the impoundment system. The Executive Secretary will consider relaxing this requirement for extremely gentle slopes such as those which may exist on the top of the pile. …Rock covering of slopes may be unnecessary where top covers are very thick (or less); bulk cover materials have inherently favorable erosion resistance characteristics; and, there is negligible drainage catchment area upstream of the pile and good wind protection as described in points (a) and (b) of this criterion. Furthermore, all impoundment surfaces must be contoured to avoid areas of concentrated surface runoff or abrupt or sharp changes in slope gradient. In addition to rock cover on slopes, areas toward which surface runoff might be directed must be well protected with substantial rock cover (rip rap). In addition to providing for stability of the impoundment system itself, overall stability, erosion potential, and geomorphology of surrounding terrain must be evaluated to assure that there are not ongoing or potential processes, such as gully erosion, which would lead to impoundment instability. INTERROGATORY STATEMENT: 1. Refer to Section 6.0 of Appendix G and Section 7.0 of Attachment A (Technical Specifications) of the Reclamation Plan, Rev. 5.0: a. Please define and justify a maximum void space percentage that will be allowed when disposing of demolition and decommissioning debris fragments and rubble in Cell 1. Response 1(1a): The procedures for sizing and placement of debris were developed from mill demolition and debris placement at other uranium mill sites in the western US. The procedures reflected in the Technical Specifications were based on whether the demolition materials were compressible. These procedures are incorporated in the Technical Specifications, as summarized below. Interrogatory 04/1: R313-24-4; 10CFR40.Appendix A, Criterion 4: Void Space Criteria and Debris, Rubble Placement and Soil/Backfill Requirements Page 12 of 96 Compressible materials are to be crushed and covered with soils, and incompressible materials are to be placed in the cell, with the void spaces outside of the materials filled with soils. Internal void spaces of incompressible materials are to be filled with soil where possible, or grout if needed. Materials such as pipe and tubing have a varying degree of compressibility, depending on the diameter and wall thickness of the pipe. Pipe with a 12-inch diameter or larger is to be filled with grout or soil for burial, and pipe with smaller diameter was crushed before burial. A requirement for the maximum void space percentage is not included because there is no practical method for measuring this percentage in the placed debris or the compacted soil during or after placement. Therefore a method specification reflecting best management practice from other projects was incorporated in the Technical Specifications. b. Describe, in detail, construction practices that will enable satisfying this specified limit. Response 1(1b): The debris is to be spread in a layer such that structural shapes or other large pieces do not lie on across or on top of each other, to prevent nesting. The soil to be used for filling voids around the debris is to be spread in loose layers over the debris, and worked into and around the debris materials until the void spaces are minimized. Enough soil should be placed so that the surface is accessible with tracked equipment. The debris is then walked with heavy tracked equipment to compress the debris as much as possible into the underlying soil. After additional soil fill placement, the soil and debris lift can be compacted with compaction equipment. From the proposed specifications: “The debris, contaminated soils and other materials for the first lift will be placed to a depth of up to four feet thick, in a bridging lift, to allow access for placing and compacting equipment. The first lift will be compacted by the tracking of heavy equipment, such as a Caterpillar D6 Dozer (or equivalent), using at least 4 passes, prior to the placement of the next lift. Subsequent lifts will not exceed 12 inches and will be compacted using a minimum of 4 passes with the tracked equipment or a vibratory compactor. The CQA technicians will monitor and approve of the final debris placement. In areas where voids are observed during placement, the contractor shall re- excavate the area, fill any voids encountered with soil and recompact the materials, or grout the voids.” Vessels and tanks will either be crushed (if thin-walled and compressible) or cut open (if thick-walled and incompressible). Vessels that are to be cut open and filled, will be placed in the cell such that fill can also be placed around them and compacted. For thick-walled tanks or vessels that cannot be cut open due to cutting difficulties or worker health concerns with cutting these items open, these tanks or vessels will be placed in the designated area of disposal, with interior voids spaces grouted full. c. Please provide detailed procedures that will be used to control residual voids to meet the specified maximum allowable void space percentage(s) and a description of the specific Interrogatory 04/1: R313-24-4; 10CFR40.Appendix A, Criterion 4: Void Space Criteria and Debris, Rubble Placement and Soil/Backfill Requirements Page 13 of 96 construction quality assurance / quality control and verification procedures to be used to demonstrate that the void space criteria will be achieved. Response 1(1c): Quality assurance observation during fill and debris placement must be used to monitor the occurrence of voids that will require additional material to fill, or additional compaction of the debris layer. The contractor must ensure that debris is size-reduced to meet the specifications, so that it can be placed in the cell efficiently and without nesting or the occurrence of large voids. The Contractor will be required to repetitively attempt to make passes over the debris and fill voids with soil until the QA staff has determined that the voids are adequately filled, or an alternate method such as grouting will be required. The QA staff will make a recommendation to the Contractor for the implementation of a grouting program in instances when voids, either within a debris mass, or within a vessel, cannot be properly filled with soil using conventional equipment. d. Demonstrate how the percentage of allowable void space relates to the settlement analyses performed to evaluate the effectiveness of the procedures for placing debris fragments and rubble, placement of backfill in/around/under debris items, and compaction of the debris/backfill materials, for precluding the potential for slope reversal in the Cell1 cover system. Please also refer to “INTERROGATORY WHITEMESA RECPLAN REV. 5.0; R313- 24-4; 10CFR40 APPENDIX A; INT 07/1: TECHNICAL ANALYSIS - SETTLEMENT AND POTENTIAL FOR COVER SLOPE REVERSAL AND/OR COVER LAYER CRACKING”. Response 1(1d): Limiting the percentage of allowable void space within the debris fill will minimize the resulting settlement caused by the consolidation of the debris mass and the potential for slope reversal. However, the in-situ void characteristics of debris mass consisting of concrete and steel of various shapes and sizes, can be difficult to quantify for settlement analyses. The settlement analyses and any correlation to the percentage of voids within the debris will be discussed further in responses to that interrogatory. It should be noted that the cover on top of the disposal cell will not be placed until settlement monitoring of the subsurface shows that anticipated settlement has taken place. e. Please further define the characteristics of, and estimate the percentage of organic materials (including, for example, wood, branches, roots, paper, and plastic), expected to be disposed of. Provide specifications and procedures for disposing of organic materials such that long- term biodegradation of the disposed organic materials will not compromise the integrity and stability of the cover system. Response 1(1e): The percentage of organic materials to be disposed of is anticipated to be a small percentage of the total material being disposed. Because the quantity of organics for disposal is minimal and because these materials are likely be mixed with incompressible debris and soil, the biodegradation of these materials is not anticipated to compromise the integrity of the cover system. Additionally, the organic materials will be spread Interrogatory 04/1: R313-24-4; 10CFR40.Appendix A, Criterion 4: Void Space Criteria and Debris, Rubble Placement and Soil/Backfill Requirements Page 14 of 96 throughout the disposal area which will minimize concentrated areas of compressible organic materials. Organic debris should be size-reduced by crushing, chipping, or shredding prior to placement. As described in the Technical Specifications, organic material should only be placed in lifts less than 12 inches thick and should be mixed with the soil and other incompressible debris during placement to prevent pockets of organic material from being created. Organics mixed with soil for spreading should be limited to 30% by volume of the mixture. This limit will be added to the Technical Specifications. f. Please provide detailed specifications for segmenting and placing metallic waste materials in layers so that structural shapes or other large pieces will not lie across or on top of each other. Please indicate that placement of metallic materials will allow large voids to be minimized and filled with soil. Please address special handling and disposal procedures for oversized and/or odd-shaped steel materials, including cutting or trimming dimensions before positioning for burial, and placement procedures to ensure that no large “slip planes” will occur within the disposal mass. Specify maximum allowable lift thickness for such material placement. Please also describe shredding, cutting or trimming procedures required to ensure that such materials following shredding, cutting or trimming can be placed within the specified allowable layer thickness. Response 1(1f): The Contractor will select and place metallic debris by sizes so that larger pieces are not stacked on top of each other at angles. Large structural shapes will either be laid edge to edge so that they can be covered by soil that will fill in open spaces or they must be spaced far enough apart that equipment can operate between them to compact fill. As stated in the Technical Specifications, long structural (incompressible) members will be oriented horizontally. Metallic materials will be size reduced before placement and burial to a maximum dimension of 20 feet and a maximum volume of 30 cubic feet. Any metallic materials exceeding the specified dimensions will be cut or trimmed until they meet this specification. g. Provide additional details of type of materials and placement practices, including specific dimensions of all demolition debris expected to be disposed of in Cell 1. Please justify that items needing to be size-reduced prior to disposal will in fact be size reduced. Provide additional information to justify that a maximum allowable size of dismantled or cut materials of 20 feet in the longest dimension (as proposed) and a maximum volume of 30 cubic feet are acceptable criteria for placement of such objects in a disposal cell. Response 1(1g): At this time the specific dimensions of all demolition debris expected to be disposed of is not available. These maximum allowable sizes of cut or dismantled materials have been specified for demolition of multiple uranium mill sites in the western US. While the specified maximum dimensions of 30 cubic feet, 20 feet for debris, and 10 feet for pipe, may be larger than the references cited (DOE, 1995, 2000), typically demolition is sized for the haulage equipment and often the individual pieces of debris will be less than these maximum dimensions in order to fit in trucks. Debris objects approaching 20 feet in length or 30 cubic feet are most likely to be long slender shapes which will have to be laid flat for disposal, or they are large blocky, or open vessel objects, which will be filled Interrogatory 04/1: R313-24-4; 10CFR40.Appendix A, Criterion 4: Void Space Criteria and Debris, Rubble Placement and Soil/Backfill Requirements Page 15 of 96 for placement. In either case, it is the method of placement in the cell and controlling the lift thickness, rather than the dimension of the debris that will determine the potential for excessive void spaces. The references cited by the reviewer describe limiting the maximum volume to 27 cubic feet however only one of the references cited (DOE, 1995) includes a maximum dimension of 10 feet. The second reference, specifications for Weldon Springs Disposal Facility (DOE, 2000) does not include a maximum dimension for metal waste or large metal pieces, it states only that pipe stockpiled “…has been cut to 10 feet or less…” Based on our experience at other sites, and the review of the cited specifications, the proposed maximum length of 20 feet falls within the range of maximum lengths specified by the cited specifications. The proposed specifications include a maximum dimension of 20 feet for all debris and a 10-foot maximum dimension for pipes. h. Please provide a contingency plan to address the situation in which an insufficient quantity of demolition debris and rubble and contaminated soil would be available to fill the Cell 1 footprint area to a sufficiently high final waste grading configuration to provide a smooth, continuous transition between the completed Cell 1 cover system and the Cell 2 cover system, with no sudden, abrupt changes in slope between the two cover systems. Discuss means and methods that will be used, regardless of achieved final debris/rubble/contaminated soil placement grades, for ensuring that a smooth cover slope transition will occur between these two cell area cover systems. Response 1(1h): If sufficient debris, rubble and contaminated soil is not available to fill Cell 1 as designed, the footprint of Cell 1 can be reduced in size so that the horizontal dimension extending out from the Cell 2 is reduced and the lateral extent of the disposed materials is reduced to be closer the base of the Cell 2 impoundment. This would allow the height of the cell to be maintained and the volume reduced, so that the cover slopes, as designed, will create a smooth, positive sloping transition from the Cell 2 to Cell 1. While it is unlikely that the volume of contaminated soil will be insufficient, if additional fill is needed to raise the elevation above the disposed material, clean fill could be used to establish proper positive drainage on the cover. i. Clearly and consistently define procedures/specifications for backfilling of interior void spaces inside debris objects (e.g., backfill of insides of smaller segmented pipe sections). Rectify apparent current inconsistencies between descriptions of backfill materials proposed for such use as described in Attachment A (e.g., controlled low-strength materials [CLSM] or flowable fill) and backfill materials for this use as described in Appendix (random fill materials). Provide rationale for selecting preferred backfill materials (e.g., CLSM) for different types and/or sizes of internal void space, as appropriate. For CLSM/ flowable fill, etc… used, provide information on the minimum required compressible strength of the material. Response 1(1i): The proposed procedure for filling void spaces, either within vessels, pipes that cannot be crushed (with a diameter of larger than 12 inches), or other miscellaneous voids, is to first attempt to fill the voids with soil. This would be done in the case of vessels by either placing soil through an existing opening, or cutting them open so that soil can be placed Interrogatory 04/1: R313-24-4; 10CFR40.Appendix A, Criterion 4: Void Space Criteria and Debris, Rubble Placement and Soil/Backfill Requirements Page 16 of 96 using the bucket of an excavator. Pipe sections, that cannot be crushed flat, can be cut short enough to stand on their ends, and then filled with soil from the bucket of an excavator. To rectify the discrepancy between Attachment A and Appendix G, the language in the specification Section 7.3.6 of the Technical Specifications will be modified as follows: “The voids on the inside of the item shall be filled with contaminated soil, clean fill soil, or grout (controlled low-strength material, flowable fill, etc.). Contaminated soil (Section 7.3.3) or clean fill will be placed outside of the items and compacted with standard compaction equipment (where possible) or hand-operated equipment to the compaction requirements in Specification Section 7.4.” For debris where internal voids cannot practically be filled with soil, a grouting program would be initiated to pump controlled low strength material (CLSM, flowable fill) into the voids. Debris would be grouped together and characterized as materials that would require grouting, so that a significant volume of debris can be grouted in a single action, rather than grouting individual lengths of pipe. Pipe sections could be stacked horizontally, or cut short enough to stand vertically in a safe manner. Grout would then likely be batched offsite and delivered to the site and a pump truck would likely be required to place the material within the debris, within the cell. A soil berm would be used to contain the grout laterally around the perimeter of the selected debris. The debris voids would be grouted, and grout would also be placed around the debris to develop a monolithic grouted mass. The specified unconfined compressive strength of the CLSM would be between 30 psi (minimum) and 150 psi (maximum). Unit weights on the order of 100 to 120 pcf will be specified. These requirements will be added to the specifications. j. Describe how the compressive strength requirement for CLSM or other grout backfill, in conjunction with the void space backfilling requirements and ultimate allowable void space and organic waste percentages relate to the design objectives for minimizing settlement of the backfilled Cell 1 area debris/rubble/backfill mass to preclude the possibility for long-term cover slope reversals. Response 1(1j): If CLSM is required for the grouting of voids that cannot be filled mechanically with soil, the mix design for the grout should mimic, as closely as possible, the strength and hydraulic properties of the contaminated soil that will also be used for filling voids within the debris. This will minimize any effects of differential settlement that would result from the grout having a higher strength and being less compressible than the surrounding soil. BASIS FOR INTERROGATORY: The placement of debris materials in the reclaimed tailings embankment has the potential to create voids or areas of insufficient compaction. The presence of excessive voids in the final reclaimed waste disposal embankment following waste placement and construction of the final closure cover could lead to unacceptable amounts of long-term total or differential settlement in the reclaimed embankment. Excessive amounts of such settlement could impact the integrity of the final closure cover system, and, if sufficient in extent, result in localized slope change(s) and/or slope reversal(s) in the final slopes of the Interrogatory 04/1: R313-24-4; 10CFR40.Appendix A, Criterion 4: Void Space Criteria and Debris, Rubble Placement and Soil/Backfill Requirements Page 17 of 96 reclaimed embankment. A slope reversal would create an opportunity for localized ponding of moisture or water which could result in increased infiltration rates through the embankment. To address/mitigate potential concerns relating to settlement following waste placement, procedures for placing and compacting soil and debris wastes should incorporate several requirements, including specifying a method or methods for filling of larger-sized void spaces (e.g., with CLSM/flowable fill or other grout, etc…) that cannot be readily accessed by standard construction equipment for backfilling with soil or tailings. Appendix G to the Reclamation Plan Rev. 5.0 states “Contaminated soils will be disposed of in last active tailings cell or Cell 1. Contaminated soils will be placed in the last active cell or Cell 1 as random fill material (material used to fill voids within mill material, achieve desired cover system slopes, and provide a firm base for construction of the cover system)”. In contrast, Attachment A to the Reclamation Plan Rev. 5.0 states “…The voids on the inside of the item shall be filled with sand or grout (controlled low-strength material, flowable fill, etc.)”. Clarification needs to be made on which method/methods will be used for filling larger-sized void spaces. It is recommended that if the void space resulting from placement of such large concrete monoliths is greater than approximately 5%, then an acceptable cement grout or flowable fill such as controlled low- strength material be placed between the monoliths, or alternativelythat monoliths be placed far enough apart to allow proper equipment access to compact as necessary. Attachment A to the Reclamation Plan Rev. 5 states that “the maximum size of dismantled or cut materials shall not exceed 20 feet in the longest dimension and a maximum volume of 30 cubic feet for placement in the cells”. Additional justification needs to be provided to demonstrate that these dimensions will be adequate for disposal with respect to minimizing potential for differential settlement occurring within the disposal cell. For other similar projects (e.g., DOE 1995; DOE 2000), based on experience gained at several uranium mill demolition debris and rubble disposal projects, specified the following procedures for placing and compacting soil and debris and rubble wastes into tailings repositories to address/mitigate potential concerns relating to settlement: • Limiting the maximum dimension of larger-sized debris items to a maximum allowable length (e.g., 10 ft) in longest dimension; • Limiting at least one dimension of larger-sized debris items to no more than a maximum allowable width (e.g., 10 to 12 inches for pipes); and • Specifying a method or methods for filling of larger-sized void spaces (e.g., with flowable fill or grout) that cannot be readily accessed by standard construction equipment for backfilling with soil or tailings. To accomplish the above objectives, it was specified that larger sized items be placed as flatly as possible rather than in a tangled mass that could result in “nesting”, i.e., result in a compressible mass that would be subject to excessive compression as additional fill is placed and compacted. For these projects, individual loads of larger sized items were also specified to be spread out as necessary to ensure proper filling of any open voids with contaminated soil or tailings and so that contaminated soil or tailings backfill materials and the debris items could be adequately compacted. Additionally, these projects included specifications that window frames, siding, and roofing material be placed and compacted, at a minimum, as pieces or stacks of such materials (e.g., bundles of siding) in an 18-inch lift, occasionally increased to 24 inches for taller bundles of wood pieces; that placement be accomplished in a compact, dense layer with bundles placed next to each other to the extent possible, that voids between bundles be reduced to the minimum achievable, and that bundles that are broken be separated into stacks 12 inches or less in height; and that contaminated soil or tailings then be spread and compacted over the layer not exceeding 12-inches in loose lift thickness. Interrogatory 04/1: R313-24-4; 10CFR40.Appendix A, Criterion 4: Void Space Criteria and Debris, Rubble Placement and Soil/Backfill Requirements Page 18 of 96 Similar sets of detailed specifications were developed and used on the above-described projects for size- reduction and controlled placement of pipe sections, concrete rubble, monoliths, and large rock fragments, and associated backfill placement, and compaction of debris/rubble and soil mixtures. The applicability and benefit of employing these specifications or similarly detailed specifications, should be evaluated, and implemented for this project as warranted. REFERENCES: Denison Mines (USA) Corporation. 2011. Reclamation Plan, Revision5.0, White Mesa Mill, Blanding, Utah: September 2011 Denison Mines (USA) Corporation. 2009a. Reclamation Plan, Revision 4.0, White Mesa Mill, Blanding, Utah, Exhibit C: November 2009 Exhibit C: Probable Maximum Precipitation (PMP) Event Computation, White Mesa Mill - Cell 4B, Blanding , Utah”. September 10, 2009. Letter to Dane Finerfrock, dated September 11, 2009. DOE (U.S. Department of Energy). 1989. Technical Approach Document, Revision II. UMTRA-DOE/AL 050425.0002. DOE 1995. Uranium Mill Tailings Remedial Action Project, Slick Rock, Colorado Subcontract Documents. U.S. Department of Energy, Albuquerque, New Mexico. October 1, 1995. DOE/AL/62350— 21F-Rev. 1-Attachment. DOE 2000. WSSRAP Disposal Facility Technical Specifications, Section 2300: Waste Removal, Handling, and Placement. WP-437, Disposal Cell Construction. May 15, 2000. EPA (U.S. Environmental Protection Agency). 1989a. Final Covers on Hazardous Waste Landfills and Surface Impoundments, Technical Guidance Document, EPA/530-SW-89-047, Office of Solid Waste and Emergency Response, Washington, D.C. URL: http://webcache.googleusercontent.com/search?q=cache:VEVCaJfyPDQJ:nepis.epa.gov/Exe/ZyPURL.cg i%3FDockey%3D100019HC.txt+site:epa.gov+EPA+Final+Covers+Guidance&cd=4&hl=en&ct=clnk &gl=us. EPA 1991. Seminar Publication, Design and Construction of RCRA/CERCLA Final Covers. EPA/625/4- 91/025.May 1991, 208 pp. EPA 2004. (Draft) Technical Guidance for RCRA/CERCLA Final Covers. U.S EPA 540-R-04-007, OSWER 9283.1-26. April 2004, 421 pp. URL: nepis.epa.gov/Exe/ZyPURL.cgi?Dockey=P10074PP.txt. Gilbert, P.A., and Murphy, W.M. 1987. Prediction/Mitigation of Subsidence Damage to Hazardous Waste Landfill Covers.EPA/600/2-87/025, March 1987, 81 pp. NTIS PB-175386. Nelson, J.D., Abt, S.R., Volpe, R.L, van Zyl, D., Hinkle, N.E., and Staub, W.P. 1986. Methodologies for Evaluating Long-Term Stabilization Designs of Uranium Mill Tailings Impoundments. Prepared for Nuclear Regulatory Commission, Washington, DC.NUREG/CR-4620, ORNL/TM-10067.June 1986, 151 pp. NRC 2002. U.S. Nuclear Regulatory Commission, “Design of Erosion Protection for Long-Term Stability”, NUREG-1623, September 2002. Interrogatory 04/1: R313-24-4; 10CFR40.Appendix A, Criterion 4: Void Space Criteria and Debris, Rubble Placement and Soil/Backfill Requirements Page 19 of 96 NRC 2003. Standard Review Plan for the Review of a Reclamation Plan for Mill Tailings Sites under Title II of the Uranium Mill Tailings Radiation Control Act of 1978. Washington DC, June 2003. Interrogatory 05/1: R313-24-4; 10CFR40.Appendix A: Seismic Hazard Evaluation Page 20 of 96 INTERROGATORY WHITEMESA RECPLAN REV. 5.0 R313-24-4, 10 CFR 40 APPENDIX A; INT 05/1: SEISMIC HAZARD EVALUATION REGULATORY BASIS: UAC R313-24-4 invokes the following requirement from 10CFR40, Appendix A, Criterion 1: “ The general goal or broad objective in siting and design decisions is permanent isolation of tailings and associated contaminants by minimizing disturbance and dispersion by natural forces, and to do so without ongoing maintenance. For practical reasons, specific siting decisions and design standards must involve finite times (e.g., the longevity design standard in Criterion 6). Refer to R313-24-4, 10 CFR 40 Appendix A, Criterion 4 (e): The impoundment may not be located near a capable fault that could cause a maximum credible earthquake larger than that which the impoundment could reasonably be expected to withstand. As used in this criterion, the term “capable fault” has the same meaning as defined in section III(g) of Appendix A of 10 CFR Part 100. The term “maximum credible earthquake” means that earthquake which would cause the maximum vibratory ground motion based upon an evaluation of earthquake potential considering the regional and local geology and seismology and specific characteristics of local subsurface material. UAC R313-24-4 invokes the following requirement from 10CFR40, Appendix A, Criterion 6(1): “In disposing of waste byproduct material, licensees shall place an earthen cover (or approved alternative) over tailings or wastes at the end of milling operations and shall close the waste disposal area in accordance with a design which provides reasonable assurance of control of radiological hazards to (i) be effective for 1,000 years, to the extent reasonably achievable, and, in any case, for at least 200 years, and (ii) limit releases of radon-222 from uranium byproduct materials, and radon-220 from thorium byproduct materials, to the atmosphere so as not to exceed an average release rate of 20 picocuries per square meter per second (pCi/m2s) to the extent practicable throughout the effective design life determined pursuant to (1)(i) of this criterion. In computing required tailings cover thicknesses, moisture in soils in excess of amounts found normally in similar soils in similar circumstances may not be considered. Direct gamma exposure from the tailings or wastes should be reduced to background levels. The effects of any thin synthetic layer may not be taken into account in determining the calculated radon exhalation level. If non-soil materials are proposed as cover materials, it must be demonstrated that these materials will not crack or degrade by differential settlement, weathering, or other mechanism, over long- term intervals.” NUREG-1620 specifies that “Reasonable assurance [shall be] provided that the requirements of 10 CFR Part 40, Appendix A, Criterion 6(1), which requires that the design of the disposal facility provide reasonable assurance of control of radiological hazards to be effective for 1,000 years, to the extent reasonably achievable, and, in any case, for at least 200 years, have been met.” INTERROGATORY STATEMENT: Refer to Appendix E and Attachment E.1 to Appendix E to Appendix D, Updated Tailings Cover Design Report of the Reclamation Plan, Rev. 5: Please provide the following: 1. Please further clarify the rationale for selecting the annual probability of exceedance of hazard for the facility. Response 1: Previous seismic hazard analyses for the site evaluated peak ground acceleration (PGA) at the site for the operational life (MFG, 2006) and long-term reclaimed conditions (Tetra Tech, Inc. (Tetra Tech), 2010). The seismic hazard analysis by MFG (2006) compared the results of a deterministic seismic hazard analysis (DSHA) to USGS National Seismic Hazard Maps showing the peak ground acceleration (PGA) Interrogatory 05/1: R313-24-4; 10CFR40.Appendix A: Seismic Hazard Evaluation Page 21 of 96 associated with a 2 percent probability of exceedance in 50 years, or a return period of 2,475 years. The projected operational lifetime of the most recently constructed tailings cell at the site is estimated to be approximately 50 years, from the time of construction through the time when the cell will have been dewatered and reclaimed. Therefore, use off a 2,475-year return period in formulating the probabilistic operational design criteria is considered conservative as this event has a 2-percent probability of exceedance over the anticipated 50-year operational design life. The seismic hazard analysis by Tetra Tech (2010) evaluated the PGA for long-term site conditions. Tetra Tech conducted a deterministic seismic hazard analysis and compared the results with the PGA associated with a 2 percent probability of exceedance during a 200-year design life, based on the USGS 2008 National Seismic Hazard Mapping Program (NSHMP) PSHA Interactive Deaggregation data. Two percent probability of exceedance during a 200-year period is equivalent to a return period of 9,900 years. The U.S. Environmental Protection Agency (EPA) Standards for the Control of Residual Radioactive Materials from Inactive Uranium Processing Sites (40 CFR 192) and the NRC Criteria Relating to the Operation of Uranium Mills and the Disposition of Tailings or Wastes Produced by the Extraction or Concentration of Source Material From Ores Processed Primarily for Their Source Material Content (NRC 10 CFR Appendix A to Part 100 A) both specify that control of residual radioactive material must be effective for up to 1,000 years to the extent reasonably achievable, and for at least 200 years. Use of a 9,900-year return period in formulating the probabilistic design criteria for reclaimed conditions is considered conservative as this event has a 2 percent probability of exceedance during a 200-year period and a less than 10 percent probability of exceedance in a 1,000-year period. A site-specific probabilistic seismic hazard analysis (PSHA) for both operational conditions and long-term reclaimed conditions has been performed for the site. The results of the analysis are discussed in Response 5. References for Response 1: MFG, Inc. (MFG), 2006. White Mesa Uranium Facility, Cell 4 Seismic Study, Blanding, Utah. November 27. Tetra Tech, Inc (Tetra Tech), 2010. Technical Memorandum: White Mesa Uranium Facility, Seismic Study Update for a Proposed Cell, Blanding Utah. February 3. 2. Adjust the cited USGS National Hazard Map PGA (peak ground acceleration) value of 0.15 g for the site Vs30 as appropriate. Response 2: The site Vs30 was calculated by Tetra Tech (2010) for the uppermost 100 feet of soil and bedrock underlying the site. The site-specific Vs30 was determined to be 586 m/s. This seismic velocity correlates to materials characterized as Site Class E – Soft Soil, by both the International Building Code (IBC) and the National Earthquake Hazard Reduction Program (NEHRP). Denison’s consultant MWH Americas, Inc. (MWH) checked Tetra Tech’s calculation of Vs for the uppermost 100 feet of soils and bedrock underlying the site. The drilling logs by Tetra Tech (2010) and Dames and Moore (1978) were used to obtain information about the subsurface conditions at the site (Standard Penetration Test (SPT) blow counts, bedrock descriptions, and depths of Interrogatory 05/1: R313-24-4; 10CFR40.Appendix A: Seismic Hazard Evaluation Page 22 of 96 auger drilling versus coring) and to calculate values of Vs for the soils and estimate values of Vs30 for the underlying bedrock materials. The average value of SPT blow counts for the silty sand and soil material encountered in the top 30 feet of the Tetra Tech boring is 58.6 (Tetra Tech, 2010). Using information in Sykora (1987) (eqs.20, 21 and Table 4 eq. 8) values of Vs30 were calculated to range from approximately 660 feet/second (ft/s) to 990 ft/s (approximately 200 to 300 meters/second (m/s)). This is also consistent with information presented in Fig. 5, Fig. 6, Fig. 10, and Table 8 of Sykora (1987). Based on the bedrock descriptions presented in the drilling logs by Dames and Moore (1978) to a maximum depth of 140 feet, the estimated seismic velocity for the remaining 70 feet of generally well-cemented sandstone with minor interbedded claystone, siltstone and conglomerate, is estimated to range from 800 to 1,000 m/s. A weighted average of seismic velocity for the upper 100 feet below the site was calculated to range from approximately 620 m/s to 700 m/s. This seismic velocity correlates with materials characterized as Site Class D – Stiff Soil by both the IBC and NEHRP. The NSHMP 2008 PSHA Interactive Deaggregation web site used by Tetra Tech to calculate the PGA for the site limits input values of Vs30 to either 760 m/s or 2,000 m/s. These seismic velocities correspond to Site Class BC (intermediate between dense soil and rock) and Site Class A (hard rock), respectively. Although the text that accompanies the PSHA program states that site-specific values of Vs30 can be input for sites in the Western US, the White Mesa site is considered to be located within the Central/Eastern, United States for the program (Martinez, 2012), and input values for Vs30 are limited to 760 m/s or 2,000 m/s. The available input value of Vs30 of 760 m/s is appropriate for the site-specific analysis based on the range of seismic velocity estimated for the site. References for Response 2: Dames and Moore, 1978. Site Selection and Design Study - Tailing Retention and Mill Facilities, White Mesa Uranium Project. January 17. Martinez, E., 2012. Electronic communication from E. Martinez, U.S. Geological Survey, to E. Dornfest, MWH Americas, Inc., regarding 2008 deaggregations web site bug, May 16. Sykora, D.W., 1987. Examination of Existing Shear Wave Velocity and Shear Modulus Correlations in Soils. U.S. Army Corps of Engineers Miscellaneous Paper GL- 87-22. September. Tetra Tech, Inc (Tetra Tech), 2010. Technical Memorandum: White Mesa Uranium Facility, Seismic Study Update for a Proposed Cell, Blanding Utah. February 3. 3. Explain why the calculated hazard for the background earthquake PGA of 0.24 g was estimated but ignored in the recommendations provided in Appendix E. Response 3: Evaluation of the PGA due to a background earthquake unassociated with a known structure is typically included as a portion of a deterministic seismic hazard analysis. The analysis includes evaluating the potential for low to moderate earthquakes Interrogatory 05/1: R313-24-4; 10CFR40.Appendix A: Seismic Hazard Evaluation Page 23 of 96 unassociated with tectonic structures to contribute to the seismic hazard of the site. The seismic hazard analysis performed by Tetra Tech included an evaluation of a background earthquake because it was a deterministic analysis. However, in order to evaluate the contribution from a background event in a deterministic analysis, one must estimate a likely magnitude and distance from the site. Tetra Tech (2010) estimated a magnitude 6.3 event consistent with that used in previous seismic evaluations performed for sites in the Colorado plateau, and cited in their report. The 15km distance to a background earthquake was chosen as a distance which would provide a conservative PGA at the site. The total seismic hazard at a site is better quantified by performing a probabilistic seismic hazard analysis to determine the likelihood of a specific ground acceleration occurring at the site within a given time frame (operational or reclaimed design life). A site-specific PSHA has been performed for the site. The results of the analysis are discussed in Response 5. References for Response 3: Dames and Moore, 1978. Site Selection and Design Study - Tailing Retention and Mill Facilities, White Mesa Uranium Project. January 17. Tetra Tech, Inc (Tetra Tech), 2010. Technical Memorandum: White Mesa Uranium Facility, Seismic Study Update for a Proposed Cell, Blanding Utah. February 3. 4. Provide information to justify the use of 15 km distance for a background earthquake Mw 6.3 event. Response 4: See Response 3. 5. Perform and report results of a site-specific probabilistic seismic analysis in lieu of using the USGS National Hazard Maps for developing site-specific seismic design parameters. Response 5: Denison’s consultant MWH performed a site-specific PSHA for the Site. The PGA associated with a 2 percent probability of exceedance in 50 years, calculated for the operational lifetime of the facility, is 0.07g. The PGA associated with a 2 percent probability of exceedance in 200 years, calculated for the long-term reclaimed site conditions, is 0.15g. The details of the analysis are presented in Attachment A. BASIS FOR INTERROGATORY: The rationale for selecting the annual probability of exceedance of hazard for the facility needs to be clarified. Appendix E to the Appendix D of the Reclamation Plan Rev. 5 states that the “10,000 year return period (1 in 10,000 annual probability) is adopted for evaluating the long-term stability of the facility”. However, in the following sentences, the report states that a return period of 2,500 years (1 in 2500 annual probability) is appropriate for the operational conditions of the facility. It needs to be clarified if or how the facility is being evaluated for the two annual probabilities. Is so, further details would need to be provided. Interrogatory 05/1: R313-24-4; 10CFR40.Appendix A: Seismic Hazard Evaluation Page 24 of 96 It is unclear how the 0.15 g PGA is “reasonable for the White Mesa site”. Appendix E cites the USGS National Hazard Maps and a PGA of 0.15 g for a 10,000 year return period. This value is for a Vs30 of 760 m/sec. The report continues by stating that the Vs30 for the site is 586 m/sec. The 0.15 g value cited in this regard needs to be adjusted for the site Vs30. Appendix E describes background earthquakes and adopts an Mw 6.3 event at a distance of 15 km. Additional justification needs to be provided for the use of the 15 km distance. A single ground motion prediction model should not be used in hazard analysis because the epistemic uncertainty in ground motion prediction is being ignored. Currently, there are five Next Generation Attenuation (NGA) ground motion models, including an update of Campbell and Bozorgnia (2007), which should be used in the deterministic calculation for the PGAs in Table 1, Peak Ground Accelerations for White Mesa, in Attachment E.1 of Appendix E. The USGS National Hazard Maps should not be used for developing site-specific seismic design parameters (Personal Communication between Dr. Mark Petersen, Chief, National Seismic Hazard Mapping Project, and Ivan Wong of URS Corporation 2010) for critical and important facilities. For such types of facilities, a site-specific probabilistic seismic hazard analysis is recommended. REFERENCES: Campbell, K.W. and Bozorgnia, Y., 2007, Campbell-Bozorgnia NGA Ground motion relations for the geometric mean horizontal component of PGA, PGV, PGD and 5% Damped Linear Elastic Response Spectra for Periods Ranging from 0.01 to 10 s: Earthquake Spectra 24, pp. 139-171. 2008 Denison Mines (USA) Corp., 2011. Reclamation Plan, White Mesa Mill, Blanding, Utah, Radioactive Materials License No. UT1900479, Revision 5.0, Appendix E, September 2011. Interrogatory 06/1: R313-24-4; 10CFR40.Appendix A, Criterion 1: Slope Stability Page 25 of 96 INTERROGATORY WHITEMESA RECPLAN REV5.0; R313-24-4; 10CFR40 APPENDIX A, CRITERION 1; INT 06/1: SLOPE STABILITY REGULATORY BASIS: UAC R313-24-4 invokes the following requirement from 10CFR40 Appendix A, Criterion 1: The general goal or broad objective in siting and design decisions is permanent isolation of tailings and associated contaminants by minimizing disturbance and dispersion by natural forces, and to do so without ongoing maintenance. For practical reasons, specific siting decisions and design standards must involve finite times (e.g., the longevity design standard in Criterion 6). . . . Refer also to INTERROGATORY WHITEMESA RECPLAN Rev. 5.0 R313-24-4, 10 CFR 40 APPENDIX A; INT 05/1: SEISMIC HAZARD EVALUATION above. Slope Stability NUREG-1620, Section 2.2.3: The analysis of slope stability will be acceptable if it meets the following criteria: (1) Slope characteristics are properly evaluated. (a) Cross sections and profiles of natural and cut slopes whose instability would directly or indirectly affect the control of radioactive materials are presented in sufficient number and detail to enable the reviewer to select the cross sections for detailed stability evaluation. (b) Slope steepness is a minimum of five horizontal units (5h) to one vertical unit (1v) or less. The use of slopes steeper than 5h:1v is considered an alternative to the requirements in 10 CFR Part 40, Appendix A, Criterion 4(c). When slopes steeper than 5h:1v are proposed, a technical justification should be offered as to why a 5h:1v or flatter slope would be impractical and compensating factors and conditions are incorporated in the slope design for assuring long-term stability. (c) Locations selected for slope stability analysis are determined considering the location of maximum slope angle, slope height, weak foundation, piezometric level(s), the extent of rock mass fracturing (for an excavated slope in rock), and the potential for local erosion. (2) An appropriate design static analysis is presented. (a) The analysis includes calculations with appropriate assumptions and methods of analysis (NRC, 1977). The effect of the assumptions and limitations of the methods used is discussed and accounted for in the analysis. Acceptable methods for slope stability analysis include various limit equilibrium analysis or numerical modeling methods. (b) The uncertainties and variability in the shape of the slope, the boundaries and parameters of the several types of soils and rocks within and beneath the slope, the material properties of soil and rock within and beneath the slope, the forces acting on the slope, and the pore pressures acting within and beneath the slope are considered. (c) Appropriate failure modes during and after construction and the failure surface corresponding to the lowest factor of safety are determined. The analysis takes into account the failure surfaces within the slopes, including through the foundation, if any. (d) Adverse conditions such as high water levels from severe rain and the probable maximum flood are evaluated. (e) The effects of toe erosion, incision at the base of the slope, and other deleterious effects of surface runoff are assessed. Interrogatory 06/1: R313-24-4; 10CFR40.Appendix A, Criterion 1: Slope Stability Page 26 of 96 (f) The resulting safety factors for slopes analyzed are comparable to the minimum acceptable values of safety factors for slope stability analysis given in NRC Regulatory Guide 3.11 . . . . (3) Appropriate analyses considering the effect of seismic ground motions on slope stability are presented. (a) Evaluation of overall seismic stability, using pseudostatic analysis or dynamic analysis, as appropriate (U.S. Army Corps of Engineers, 1977; NRC, 1977). Alternatively, a dynamic analysis following Newmark (1965) can be carried out to establish that the permanent deformation of the disposal cell from the design seismic event will not be detrimental to the disposal cell. The reviewer should verify that the yield acceleration or pseudostatic horizontal yield coefficient necessary to reduce the factor of safety against slippage of a potential sliding mass to 1.0 in a “Newmark-type” analysis has been adequately estimated (Seed and Bonaparte, 1992). (b) An appropriate analytical method has been used. A number of different methods of analysis are available (e.g., slip circle method, method of slices, and wedge analysis) with several variants of each (Lambe and Whitman, 1979; U.S. Army Corps of Engineers, 1970b; NRC, 1977; Bromhead, 1992). Limit-equilibrium analysis methods do not provide information regarding the variation of strain within the slope and along the slip surface. Consequently, there is no assurance that the peak strength values used in the analysis can be mobilized simultaneously along the entire slip surface unless the material shows ductile behavior (Duncan, 1992). Residual strength values should be evaluated if mobilized shear strength at some points is less than the peak strength. The reviewer should ensure that appropriate conservatism has been incorporated in the analysis using the limit equilibrium methods. The limit equilibrium analysis methodologies may be replaced by other techniques, such as finite element or finite difference methods. If any important interaction effects cannot be included in an analysis, the reviewer must determine that such effects have been treated in an approximate but conservative fashion. The engineering judgment of the reviewer should be used in assessing the adequacy of the resulting safety factors (NRC, 1983a,b). (c) For dynamic loads, the dynamic analysis includes calculations with appropriate assumptions and methods (NRC, 1977; Seed, 1967; Lowe, 1967; Department of the Navy, 1982a,b,c; U.S. Army Corps of Engineers, 1970a,b, 1971, 1972; Bureau of Reclamation, 1968). The effect of the assumptions and limitations of the methods used is discussed and accounted for in the analysis. (d) For dynamic loads, a pseudostatic analysis is acceptable in lieu of dynamic analysis if the strength parameters used in the analysis are conservative, the materials are not subject to significant loss of strength and development of high pore pressures under dynamic loads, the design seismic coefficient is 0.20 or less, and the resulting minimum factor of safety suggests an adequate margin, as provided in NRC Regulatory Guide 3.11 (NRC, 1977). (e) For pseudostatic analysis of slopes subjected to earthquake loads, an assumption is made that the earthquake imparts additional horizontal force acting in the direction of the potential failure (U.S. Army Corps of Engineers, 1970b, 1977; Goodman, 1989). The critical failure surface obtained in the static analysis is used in this analysis with the added driving force. Minimum acceptable values for safety factors of slope stability analysis are given in Regulatory Guide 3.11 (NRC, 1977). (f) The assessment of the dynamic stability considers an appropriate design level seismic event and/or strong ground motion acceleration, consistent with that identified in Chapter 1 of this review plan. Influence of local site conditions on the ground motions associated with the design level event is evaluated. The design seismic coefficient to be used in the pseudostatic analysis is either 67 percent of the peak ground acceleration at the foundation level of the tailings piles for the site or 0.1g, whichever is greater. Interrogatory 06/1: R313-24-4; 10CFR40.Appendix A, Criterion 1: Slope Stability Page 27 of 96 (g) If the design seismic coefficient is greater than 0.20g, then the dynamic stability investigation (Newmark, 1965) should be augmented by other appropriate methods (i.e., finite element method), depending on specific site conditions. (h) In assessing the effects of seismic loads on slope stability, the effect of dynamic stresses of the design earthquake on soil strength parameters is accounted for. As in a static analysis, the parameters such as geometry, soil strength, and hydrodynamic and pore pressure forces are varied in the analysis to show that there is an adequate margin of safety. (i) Seismically induced displacement is calculated and documented. There is no universally accepted magnitude of seismically induced displacement for determining acceptable performance of the disposal cell (Seed and Bonaparte, 1992; Goodman and Seed, 1966). Surveys of five major geotechnical consulting firms by Seed and Bonaparte (1992) indicate that the acceptable displacement is from 15 to 30 cm [6 to 12 in.] for tailings piles. The reviewer should ensure that this criterion is also augmented by provisions for periodic maintenance of the slope(s). (j) Where there is potential for liquefaction, changes in pore pressure from cyclic loading are considered in the analysis to assess the effect of pore pressure increase on the stress-strain characteristics of the soil and the post-earthquake stability of the slopes. Liquefaction potential is reviewed using Section 2.4 of this review plan. Evaluations of dynamic properties and shear strengths for the tailings, underlying foundation material, radon barrier cover, and base liner system are based on representative materials properties obtained through appropriate field and laboratory tests (NRC, 1978, 1979). (k) The applicant has demonstrated that impoundments will not be located near a capable fault on which a maximum credible earthquake larger than that which the impoundment could reasonably be expected to withstand might occur. (4) Provision is made to establish a vegetative cover, or other erosion prevention, to include the following considerations: (a) The vegetative cover and its primary functions are described in detail. This determination should be made with respect to any effect the vegetative cover may have on reducing slope erosion and should be coordinated with the reviewer of standard review plan Chapter 3. If strength enhancement from the vegetative cover is taken into account, the methodology should be appropriate (Wu, 1984). (b) In arid and semi-arid regions, where a vegetative cover is deemed not self-sustaining, a rock cover is employed on slopes of the mill tailings. If credit is taken for strength enhancement from rock cover, the reviewer should confirm that appropriate methodology has been presented. The design of a rock cover, where a self-sustaining vegetative cover is not practical, is based on standard engineering practice. Standard review plan Chapter 3 discusses this item in detail. (5) Any dams meet the requirements of the dam safety program if the application demonstrates the following: (a) The dam is correctly categorized as a low hazard potential or a high hazard potential structure using the definition of the U.S. Federal Emergency Management Agency;(b) If the dam is ranked as a high hazard potential, an acceptable emergency action plan consistent with the Federal Emergency Management Agency guide (U.S. Federal Emergency Management Agency, 1998) has been developed. (6) The use of steeper slopes as an alternative to the requirements in 10 CFR, Part 40, Appendix A, will be found acceptable if the following are met: (a) An equivalent level of stabilization and containment and protection of public health, safety, and the environment is achieved. Interrogatory 06/1: R313-24-4; 10CFR40.Appendix A, Criterion 1: Slope Stability Page 28 of 96 (b) A site-specific need for the alternate slopes is demonstrated. INTERROGATORY STATEMENT: 1. Demonstrate slope stability for the tailings impoundment and new cover system using shear strength parameters and other soil properties assigned to the various components (cover, embankment/dike, tailings, and foundation) consistent with soil type, degree of compaction, and anticipated degree of variability. Justify selection of values for soil parameters. Response 1: A site investigation to further evaluate cover borrow materials was conducted on April 19, 2012. Laboratory testing is currently in progress and will be used to develop updated cover material parameters for slope stability analyses. The strength properties of the other materials will be revised or additional justification provided for selection of the parameters. The results of the updated analyses will be provided as part of a second response submittal to the Division on August 15, 2012. 2. In evaluating slope stability, address and report the effects of shallow and non-circular failure surfaces, in addition to circular and/or deeper ones. Response 2: See Response 1. The stability analyses will also be revised to include evaluation of shallow and non-circular failures. 3. Demonstrate that assumed drainage conditions are appropriate, are at least consistent with, or are conservative compared with drainage/seepage results, projected immediately at closure and at the end of the impoundment design life (i.e., 1,000 years, to the extent reasonably achievable, and, in any case, for at least 200 years). Response 3: See Response 1. The phreatic conditions used for the revised stability analyses will be consistent with or conservative with regards to the tailings dewatering analyses. 4. Assess the slope stability of Cell 1 adjacent to Cell 2 where mill debris and contaminated soils are to be placed and covered. Response 4: See Response 1. The stability analyses will also be revised to include evaluation of the stability of the Cell 1 Disposal Area embankment. 5. Explain and justify the selection of the pseudo-static coefficient used in the assessment of seismic stability. If the selected value of the pseudo-static coefficient cannot be justified, revise the value of the coefficient used in stability analyses and revise and report the results of stability analyses. Interrogatory 06/1: R313-24-4; 10CFR40.Appendix A, Criterion 1: Slope Stability Page 29 of 96 Response 5: An update to the previous seismic study for the site has been conducted and is included as Attachment A. The pseudo-static coefficient is estimated as 0.10 corresponding to 2/3 of the Peak Ground Acceleration (PGA) presented in the Attachment A. This pseudo-static coefficient will be used for the updated slope stability analyses to be provided in the second response document to the Division on August 15, 2012. BASIS FOR INTERROGATORY: The slope stability analyses presented by the Licensee uses the same shear strength parameters (phi=26 degrees, c=900 psf) for the reclamation cover, impoundment dikes, and the foundation soils above the bedrock. These properties were derived from limited triaxial testing of very stiff / very dense material recovered from apparently in-situ soil. Given that the different soil zones in the cover system are to be placed with varying degrees of compaction (some being quite loose) and that the density of the dikes may vary from that of the foundation, the use of singular soil properties throughout the analyses is inappropriate. Shear strength parameters and other soil properties such as unit weight should be assigned to the various earthen components consistent with soil type, degree of compaction, and anticipated degree of variability. The selection of strength parameters should also be explained and justified. Because of the relatively loose state proposed for some of the cover soils, the Licensee’s stated approach (i.e., “circular failure surface analyses were conducted by targeting deeper, full-slope failures as opposed to shallower, superficial failures.”) may miss truly critical failure surfaces. Shallow surfaces as well as non-circular ones should be considered. The slope stability analyses performed by the Licensee assume that the tailings impoundment cells behave fully drained, thus phreatic surfaces were not included in the analyses. The Licensee should demonstrate that such assumptions are appropriate (i.e., are at least consistent with, if not conservatively interpreted) based on the results of drainage/seepage analyses representing conditions immediately at closure as well as at the end of the design storage life of the facility. Such analyses should reflect the variations in the tailings properties and drainage systems (slimes dewatering systems) particular to each tailings management cell (e.g., approximately 600-ft by 400-ft area containing slimes “burrito drain” array in each of Cell 2 and Cell 3 vs. area blanket sand layer and slimes drain piping system in Cells 4A and 4B; ). Tailings properties will vary in response to variations in historic (and future) milling processes as well as deposition history (and future) and discharge –related distribution within each cell. The soil shear strength parameters (particularly those of the tailings) used in the slope stability analyses should be consistent with the drainage conditions thus demonstrated. As described in the Basis for Interrogatory section of “INTERROGATORY WHITEMESA RECPLAN REV. 5.0 R313-24-4; 10CFR40 APPENDIX A, CRITERION 4; INT 07/1: TECHNICAL ANALYSIS - SETTLEMENT AND POTENTIAL FOR COVER SLOPE REVERSAL AND/OR COVER LAYER CRACKING”, the tailings dewatering analyses presented in Appendix H to the Updated Tailings Cover Design Report, do not adequately represent (i.e., account for) potential variations in the tailings properties, nor their potential distribution within the various tailings management cells. As requested in the interrogatory cross-referenced above, the tailings dewatering analyses should be revisited or at least clarified and better substantiated, and the Licensee should test actual tailings specimens from the site. The number of specimens involved should be commensurate with anticipated variability of the tailings conditions in the containment cells. The slope stability analyses presented by the Licensee are based on a selected cross-section in Cell 4A apparently intended to represent the greatest height of an otherwise uniformly designed embankment. However, different conditions exist in Cell 1 adjacent to Cell 2 where mill debris and contaminated soils are to be placed and covered. The slope stability of this section should be analyzed. Interrogatory 06/1: R313-24-4; 10CFR40.Appendix A, Criterion 1: Slope Stability Page 30 of 96 To aid future review, the shading applied to the slices of the failure mass should be removed (thus enabling the profile lines of the underlying soil type to be seen). It is also suggested that contours for the factor of safety be added to the search grid as well as definitions of the search radii. The explanation and justification for the factor applied to the PGA to establish the pseudo-static coefficient provided by the Licensee appears to be flawed. The Licensee’s report reads thusly: “The seismic coefficient represents an inertial force due to strong ground motions during the design earthquake, and is represented as a fraction of the PGA at the site (typically at the base of the structure). Tetra Tech (2010) recommended using a value of 0.1 g for the seismic coefficient in accordance with IBC (2006) recommendations to multiply the PGA by 0.667 to determine a design acceleration value. The strategy of representing the seismic coefficient as a fraction of the PGA has been adopted in review of uranium tailings facility design and documented in DOE (1989). A value of 0.667 typically represents post-reclamation conditions. Based on this guidance and the recommendations in Tetra Tech (2010), the seismic coefficient used for the pseudo-static stability analysis was 0.1 g.” The 2006 International Building Code (IBC) does not contain such a recommendation (it does not discuss pseudo-static slope analysis). The code does use a factor of 2/3 to convert MCE ground accelerations to design accelerations for structural components, but this is an issue separate from and not related to the seismic coefficient used for slope stability. Explain why reference is made to the IBC since that document is for the design of buildings and not earthen tailings impoundments, or revise the discussion accordingly to more clearly state the justification for use of the selected seismic coefficient. Assessment of slope stability under seismic conditions is dependent upon the Licensee’s seismic hazard analysis. Any revisions to the seismic hazard analysis may necessitate revisions to this assessment. NUREG-1620 (NRC 2003), Section 2.2.3 specifies that: “The analysis of slope stability will be acceptable if it meets the following criteria: (1) Slope characteristics are properly evaluated. (a) Cross sections and profiles of natural and cut slopes whose instability would directly or indirectly affect the control of radioactive materials are presented in sufficient number and detail to enable the reviewer to select the cross sections for detailed stability evaluation. (b) Slope steepness is a minimum of five horizontal units (5h) to one vertical unit (1v) or less. The use of slopes steeper than 5h:1v is considered an alternative to the requirements in 10 CFR Part 40, Appendix A, Criterion 4(c). When slopes steeper than 5h:1v are proposed, a technical justification should be offered as to why a 5h:1v or flatter slope would be impractical and compensating factors and conditions are incorporated in the slope design for assuring long-term stability. (c) Locations selected for slope stability analysis are determined considering the location of maximum slope angle, slope height, weak foundation, piezometric level(s), the extent of rock mass fracturing (for an excavated slope in rock), and the potential for local erosion. (2) An appropriate design static analysis is presented. (a) The analysis includes calculations with appropriate assumptions and methods of analysis (NRC, 1977). The effect of the assumptions and limitations of the methods used is discussed and accounted for in the analysis. Acceptable methods for slope stability analysis include various limit equilibrium analysis or numerical modeling methods. Interrogatory 06/1: R313-24-4; 10CFR40.Appendix A, Criterion 1: Slope Stability Page 31 of 96 (b) The uncertainties and variability in the shape of the slope, the boundaries and parameters of the several types of soils and rocks within and beneath the slope, the material properties of soil and rock within and beneath the slope, the forces acting on the slope, and the pore pressures acting within and beneath the slope are considered. (c) Appropriate failure modes during and after construction and the failure surface corresponding to the lowest factor of safety are determined. The analysis takes into account the failure surfaces within the slopes, including through the foundation, if any. (d) Adverse conditions such as high water levels from severe rain and the probable maximum flood are evaluated. (e) The effects of toe erosion, incision at the base of the slope, and other deleterious effects of surface runoff are assessed. (f) The resulting safety factors for slopes analyzed are comparable to the minimum acceptable values of safety factors for slope stability analysis given in NRC Regulatory Guide 3.11 . . . . (3) Appropriate analyses considering the effect of seismic ground motions on slope stability are presented. (a) Evaluation of overall seismic stability, using pseudostatic analysis or dynamic analysis, as appropriate (U.S. Army Corps of Engineers, 1977; NRC, 1977). Alternatively, a dynamic analysis following Newmark (1965) can be carried out to establish that the permanent deformation of the disposal cell from the design seismic event will not be detrimental to the disposal cell. The reviewer should verify that the yield acceleration or pseudostatic horizontal yield coefficient necessary to reduce the factor of safety against slippage of a potential sliding mass to 1.0 in a “Newmark-type” analysis has been adequately estimated (Seed and Bonaparte, 1992). b) An appropriate analytical method has been used. A number of different methods of analysis are available (e.g., slip circle method, method of slices, and wedge analysis) with several variants of each (Lambe and Whitman, 1979; U.S. Army Corps of Engineers, 1970b; NRC, 1977; Bromhead, 1992). Limit-equilibrium analysis methods do not provide information regarding the variation of strain within the slope and along the slip surface. Consequently, there is no assurance that the peak strength values used in the analysis can be mobilized simultaneously along the entire slip surface unless the material shows ductile behavior (Duncan, 1992). Residual strength values should be evaluated if mobilized shear strength at some points is less than the peak strength. The reviewer should ensure that appropriate conservatism has been incorporated in the analysis using the limit equilibrium methods. The limit equilibrium analysis methodologies may be replaced by other techniques, such as finite element or finite difference methods. If any important interaction effects cannot be included in an analysis, the reviewer must determine that such effects have been treated in an approximate but conservative fashion. The engineering judgment of the reviewer should be used in assessing the adequacy of the resulting safety factors (NRC, 1983a,b). (c) For dynamic loads, the dynamic analysis includes calculations with appropriate assumptions and methods (NRC, 1977; Seed, 1967; Lowe, 1967; Department of the Navy, 1982a,b,c; U.S. Army Corps of Engineers, 1970a,b, 1971, 1972; Bureau of Reclamation, 1968). The effect of the assumptions and limitations of the methods used is discussed and accounted for in the analysis. (d) For dynamic loads, a pseudostatic analysis is acceptable in lieu of dynamic analysis if the strength parameters used in the analysis are conservative, the materials are not subject to significant loss of strength and development of high pore pressures under dynamic loads, the design seismic coefficient is 0.20 or less, Interrogatory 06/1: R313-24-4; 10CFR40.Appendix A, Criterion 1: Slope Stability Page 32 of 96 and the resulting minimum factor of safety suggests an adequate margin, as provided in NRC Regulatory Guide 3.11 (NRC, 1977). (e) For pseudostatic analysis of slopes subjected to earthquake loads, an assumption is made that the earthquake imparts additional horizontal force acting in the direction of the potential failure (U.S. Army Corps of Engineers, 1970b, 1977; Goodman, 1989). The critical failure surface obtained in the static analysis is used in this analysis with the added driving force. Minimum acceptable values for safety factors of slope stability analysis are given in Regulatory Guide 3.11 (NRC, 1977). (f) The assessment of the dynamic stability considers an appropriate design level seismic event and/or strong ground motion acceleration, consistent with that identified in Chapter 1 of this review plan. Influence of local site conditions on the ground motions associated with the design level event is evaluated. The design seismic coefficient to be used in the pseudostatic analysis is either 67 percent of the peak ground acceleration at the foundation level of the tailings piles for the site or 0.1g, whichever is greater. (g) If the design seismic coefficient is greater than 0.20g, then the dynamic stability investigation (Newmark, 1965) should be augmented by other appropriate methods (i.e., finite element method), depending on specific site conditions. h) In assessing the effects of seismic loads on slope stability, the effect of dynamic stresses of the design earthquake on soil strength parameters is accounted for. As in a static analysis, the parameters such as geometry, soil strength, and hydrodynamic and pore pressure forces are varied in the analysis to show that there is an adequate margin of safety. (i) Seismically induced displacement is calculated and documented. There is no universally accepted magnitude of seismically induced displacement for determining acceptable performance of the disposal cell (Seed and Bonaparte, 1992; Goodman and Seed, 1966). Surveys of five major geotechnical consulting firms by Seed and Bonaparte (1992) indicate that the acceptable displacement is from 15 to 30 cm [6 to 12 in.] for tailings piles. The reviewer should ensure that this criterion is also augmented by provisions for periodic maintenance of the slope(s). REFERENCES International Building Code 2006. International Code Council, Inc. MWH Americas 2011. Appendix E – Slope Stability Analysis, contained in Appendix D, Updated Tailings Cover Design Report, White Mesa Mill, September 2011 to the Reclamation Plan, White Mesa Mill, Rev. 5.0, September 2011. Tetra Tech, Inc. (Tetra Tech) 2010. “White Mesa Uranium Facility Seismic Study Update for a Proposed Cell,” Technical Memorandum to Denison Mines, February 3. U.S. Department of Energy (DOE) 1989. Technical Approach Document, Revision II, UMTRADOE/AL 050425.0002, Uranium Mill Tailings Remedial Action Project, Albuquerque, New Mexico. NRC 1982. U.S. Nuclear Regulatory Commission, “Regulatory Guide 3.8; Preparation of Environmental Reports for Uranium Mills”, Washington DC, Rev. 2, October 1982. NRC 2003. Standard Review Plan (NUREG–1620) for Staff Reviews of Reclamation Plans for Mill Tailings Sites Under Title II of The Uranium Mill Tailings Radiation Control Act”, NUREG-1620, June 2003. Interrogatory 06/1: R313-24-4; 10CFR40.Appendix A, Criterion 1: Slope Stability Page 33 of 96 NRC 2008. DG-3024, “Standard Format and Content of License Applications for Conventional Uranium Mills,” Draft Regulatory Guide DG-3024, May, 2008. Interrogatory 07/1: R313-24-4; 10CFR40.Appendix A, Criterion 4: Technical Analysis – Settlement and Potential for Cover Slope Reversal and/or Cover Layer Cracking Page 34 of 96 INTERROGATORY WHITEMESA RECPLAN REV. 5.0; R313-24-4; 10 CFR 40 APPENDIX A, CRITERION 4; INT 07/1: TECHNICAL ANALYSIS - SETTLEMENT AND POTENTIAL FOR COVER SLOPE REVERSAL AND/OR COVER LAYER CRACKING REGULATORY BASIS Refer to UAC R313-24-4 which invokes the following requirement from 10CFR40, Appendix A, Criterion 4: “The following site and design criteria must be adhered to whether tailings or wastes are disposed of above or below grade: …(c) Embankment and cover slopes must be relatively flat after final stabilization to minimize erosion potential and to provide conservative factors of safety assuring long-term stability. The broad objective should be to contour final slopes to grades which are as close as possible to those which would be provided if tailings were disposed of below grade; this could, for example, lead to slopes of about 10 horizontal to 1 vertical (10h:1v) or less steep. In general, slopes should not be steeper than about 5h:1v. Where steeper slopes are proposed, reasons why a slope less steep than 5h:1v would be impracticable should be provided, and compensating factors and conditions which make such slopes acceptable should be identified. (d) A full self-sustaining vegetative cover must be established or rock cover employed to reduce wind and water erosion to negligible levels. Where a full vegetative cover is not likely to be self-sustaining due to climatic or other conditions, such as in semi-arid and arid regions, rock cover must be employed on slopes of the impoundment system. The Executive Secretary will consider relaxing this requirement for extremely gentle slopes such as those which may exist on the top of the pile. …Rock covering of slopes may be unnecessary where top covers are very thick (or less); bulk cover materials have inherently favorable erosion resistance characteristics; and, there is negligible drainage catchment area upstream of the pile and good wind protection as described in points (a) and (b) of this criterion. Furthermore, all impoundment surfaces must be contoured to avoid areas of concentrated surface runoff or abrupt or sharp changes in slope gradient. INTERROGATORY STATEMENT Refer to Appendix D, Updated Tailings Cover Design Report of the Reclamation Plan, Rev. 5, and Drawings TRC-1 through TRC-8 in the Reclamation Plan, Rev. 5.0 : 1. Please revise (i.e., steepen) the slopes of the top slope portions of the final cover system to provide an adequate factor of safety to ensure long-term stability of the covered embankment area considering: a. The potential for future slope reversal(s) and/or cracking to occur in the cover system due to long-term total and differential settlement or subsidence which could lead to conditions where ponding of precipitation could occur on the cover system in the future, after the end of the active institutional control period; and b. The significant disparity between the presently proposed topslope inclination ranges and published recommended ranges of slopes for final cover systems for uranium mill tailings repositories, surface impoundments, and landfills – namely ranging between 2% to 5% (e.g., see DOE 1989; EPA 1989; EPA 1991, and ITRC 2003 and EPA 2004). Interrogatory 07/1: R313-24-4; 10CFR40.Appendix A, Criterion 4: Technical Analysis – Settlement and Potential for Cover Slope Reversal and/or Cover Layer Cracking Page 35 of 96 OR, alternatively, provide additional evaluations that clearly and unequivocally demonstrate (1) the ability to construct such gently sloped cover systems as proposed, designed, and specified and (2) the ability of the proposed embankment closure cover design to accommodate settlement- induced slope changes (including slope reversal) without increasing infiltration into the stabilized tailings impoundment. Response 1: In the Basis for Interrogatory, it is stated that the top cover slopes range from 0.1 to 1 %. This is not correct. The top cover slopes range from 0.5 to 1%. While the EPA references listed above specify cover slopes of 2 to 5 %, they are for landfill covers, which cover significantly different materials and have different erosional stability performance criteria than uranium mill tailings. Denison does not currently plan to steepen the top cover slopes. As noted in Response 2 to Interrogatory 03/1, cover with similar slopes have been permitted and constructed for Uranium Mill Tailings Radiation Control Act (UMTRCA) Title I and II sites including: • Falls City Title I site in Texas (less than 1% cover slopes) • Bluewater Title II site in New Mexico (0.5 – 4% cover slopes) • Conquista Title II site in Texas (0.5 – 1% cover slopes) • Highland Title II site in Wyoming (0.5 – 2% cover slopes) • Panna Maria Title II site in Texas (0.5% cover slopes) • Ray Point Title II site in Texas (0.5 – 1% cover slopes) • Sherwood Title II site in Washington (0.25% cover slopes) • L-Bar Title II site in New Mexico (0.1% cover slopes) Denison will provide cover cracking analyses for the 2.5-ft highly compacted cover layer and evaluate differential settlement as discussed in Response 2. The final response to this interrogatory, as well as revised and new analyses, will be provided as part of a second response document to be submitted to the Division on August 15, 2012. 2. Provide technical justification for 1) quantitative acceptance criteria to be used as the basis for evaluating the potential for slope reversal within the cover system in terms of potential long-term total and differential settlement, 2) quantitative assessments of maximum tensile strain capacity and other engineering properties such as Atterberg limits of the materials to be used in design of the cover system, and 3) quantitative acceptance criteria, including maximum allowable linear and angular distortion values, including effects of bending within any select layer or layers of the cover, and (4) the minimum acceptable factor of safety for concluding that cover layer cracking will not occur. Response 2: Denison will conduct one-dimensional consolidation analyses at select locations along sections through the cells to evaluate differential settlement. Analyses will be conducted to evaluate the effects of distortion and bending within the 2.5-ft highly compacted cover layer. The range of Atterberg limits for the cover material will be based on previous laboratory testing of cover borrow soils, in addition to laboratory testing currently being conducted on samples collected in April 2012 from the cover borrow stockpiles. The results of these analyses will be included as part of a second response document to be submitted to the Division on August 15, 2012. Interrogatory 07/1: R313-24-4; 10CFR40.Appendix A, Criterion 4: Technical Analysis – Settlement and Potential for Cover Slope Reversal and/or Cover Layer Cracking Page 36 of 96 3. Provide engineering analyses (including calculations and numerical modeling simulations as applicable) documenting the range of anticipated total and differential settlements within each of the containment cells. In doing so, use consolidation parameters obtained from site-specific testing of the tailings materials, reflecting both spatial and temporal variations in the tailings. Data from other sources may supplement (but not replace) site-specific test data in the analyses. Response 3: See Response 2. Denison will not be conducting site-specific testing of tailings. Denison will update estimations for consolidation parameters based on further evaluation of historical settlement monitoring data and incorporation of more recent settlement monitoring data. The analyses will be revised as necessary to incorporate conservative tailings dewatering assumptions. Consolidation analyses will include sensitivity analyses to evaluate a range of coefficients of consolidation and compression indices. 4. Demonstrate that tailings have been deposited in such a way that variations in tailings properties by location do not compromise the stability of the tailings as a foundation for cover system construction. Consider effects of sand-rich tailings zones lying adjacent to our near slime-rich tailings zones, due to deposition during slurry flow. Describe and account for effects of any different tailings placement methods (e.g., wet slurry vs. thickened slurry deposition) used throughout the mill’s operating life. Identify and quantify the effects on stability of variations in such tailings physical characteristics as moisture content, consolidation coefficients, specific gravity, hydraulic conductivity (as listed in Appendix D Updated Tailings Cover Design Report, September 2011). Perform and provide results of numerical analyses using this information to project differential settlement across the tailings impoundments using software such as the Fast Lagrangian Analysis of Continuum (FLAC®) code (Itasca 2009) or other similar software, as appropriate. Alternatively, provide information to justify why such analyses are not warranted. Response 4: See Response 2. Observation of the response of tailings to interim cover placement is the most reliable method of identifying the potential for, and location of slimes or other soft zones. Interim cover has been placed over the tailings in Cell 2 and the portions of Cell 3. Cover stability issues have not occurred since placement of the interim cover in either cell. Typically the worst-case foundation conditions for cover stability occur as the interim cover is first placed and the saturated tailings thicknesses are at a maximum. As the tailings dewater and the saturated thickness decreases, settlement within the tailings is observed as the unsaturated tailings provide additional loading on the underlying saturated tailings. As tailings consolidation and settlement occur, the stability of the tailings as a foundation for the cover system improves. Observation and monitoring of the tailing behavior will continue be conducted as the interim cover is being placed. 5. Include secondary settlement (i.e., creep) and any seismically induced settlement of the tailings in settlement analyses and consider their effects when assessing the anticipated performance of the cover system. Interrogatory 07/1: R313-24-4; 10CFR40.Appendix A, Criterion 4: Technical Analysis – Settlement and Potential for Cover Slope Reversal and/or Cover Layer Cracking Page 37 of 96 Response 5: The revised settlement analyses will include secondary settlement. The potential for seismically induced settlement will be evaluated as part of the updated liquefaction analyses. 6. Demonstrate that the results of settlement analyses are consistent with results of drainage/dewatering analyses. Ensure that drainage/dewatering analyses reflect the tailings and drainage conditions (including slime drain system) existing in each cell. Response 6: The revised settlement analyses will be consistent with or conservative with regards to the dewatering analyses. 7. Perform and report results of sensitivity and uncertainty analyses to demonstrate that the cover system will remain stable despite the effects of differential settlement. Report the time required to reach 90% consolidation. Response 7: Sensitivity analyses will be performed for the differential settlement analyses. The settlement analyses will include the estimates for the time required to reach 90 percent consolidation. 8. As part of the analyses identified above, please also perform a seepage analyses to evaluate the shape of the phreatic surface within the tailings prism for each representative area within Cells 2 and/or 3, 4A, and 4B to be analyzed for consolidation timeframes and in differential settlement analyses. Ensure that effects of planned dewatering procedures and the dewatering system design configuration in each specific cell analyzed are reflected in seepage analyses. Response 8: Supplemental seepage analyses will be performed if there is not sufficient detail in dewatering analyses to provide estimates of phreatic conditions (or pore pressure distributions) over time. The potential effects of variations in phreatic conditions during dewatering on differential settlement will be evaluated. 9. Provide sensitivity analyses to assess the effect a of changes in tailings coefficients of consolidation parameters, void ratios, and tailings hydraulic conductivity values (note: it is acknowledged that values of all of these parameters are subject to uncertainty) on the amount of time required to reach approximately 90% consolidation of the tailings at each locations assessed within each cell and/or across individual tailings cells. Response 9: Sensitivity analyses will be performed for the rate parameters for the 90 percent consolidation calculations. Interrogatory 07/1: R313-24-4; 10CFR40.Appendix A, Criterion 4: Technical Analysis – Settlement and Potential for Cover Slope Reversal and/or Cover Layer Cracking Page 38 of 96 10. Using the information obtained from the analyses identified above, for each critical section defined, complete differential settlement analyses and compare the analyses results to the specified design criteria and evaluate the potential for slope reversal(s) to occur in the cover system over the tailings cells over the worst-case sections analyzed. Response 10: See Response 2. 11. Provide information on the expected range of plasticity characteristics of the soil materials proposed for use for constructing the highly compacted upper portion of the radon attenuation and radon attenuation and grading layer of the proposed cover system, and specify design criteria (including maximum allowable values of both linear and angular distortion) to be used for evaluating the potential for cracking of this layer to occur as a result of any differential settlement that may occur. Response 11: See Response 2. BASIS FOR INTERROGATORY The proposed cover slope (minimum of 0.1% to a maximum of 1.0 %) is very flat and, based on the information provided, has to be considered to likely be problematic from the standpoint of potential long- term subsidence/differential settlement. 10CFR 40, Appendix A, Technical Criterion 4(c) specifies that embankment and cover slopes must be relatively flat after final stabilization to minimize erosion and provide conservative factors of safety assuring long-term stability (emphasis added). Technical guidance developed for and typically utilized by the U.S. Department of Energy on the UMTRA Project for design and construction of uranium mill tailings repositories included typical repository topslope inclinations of 2 to 3 percent (U.S. DOE 1989, Section 3, Figure 3-3). Further, minimum technology guidance for final cover systems for surface impoundments recommended by the USEPA (EPA 1989; EPA 1991) consists of the following: “…a top layer…, the surface of which slopes uniformly at least 3 percent but not more than 5 percent, to facilitate runoff while minimizing erosion, …” Additionally, an EPA document published in 2004 (EPA) further discusses this guideline in the following context: “…[In the Draft Technical Guidance for RCRA/CERCLA Final Covers, EPA states that] most landfill cover system top decks are designed to have a minimum inclination of 2% to 5%, after accounting for settlement, to promote runoff of surface water. …However, [EPA states that] in some cases involving the closure or remediation of existing landfills, waste piles, or source areas, flatter slopes may already exist and that the cost to increase the slope inclination by fill placement or waste excavation may be significant. In these cases, slightly flatter inclinations can be considered if the future settlement potential can be demonstrated to be small, if concerns about localized subsidence can be adequately addressed, and if monitoring and maintenance provisions exist to repair areas of grade reversal or subsidence…” The proposed cover topslope inclinations (minimum of 0.1%) are much flatter than the above recommended ranges. The cover design should include a topslope slope inclination that ensures that an Interrogatory 07/1: R313-24-4; 10CFR40.Appendix A, Criterion 4: Technical Analysis – Settlement and Potential for Cover Slope Reversal and/or Cover Layer Cracking Page 39 of 96 adequate factor of safety is provided to maintain long-term stability of the completed embankment(s), considering the potential for future slope reversal(s) due to long-term differential settlement or subsidence, given a reasonable estimate of the range of different tailings characteristics and tailings consolidation conditions that may exist within the different tailings placement cells. The final topslope inclinations must ensure that the topslope portion of the embankment will maintain a positive slope across the entire embankment after settlement/subsidence, thus providing lateral runoff of precipitation without ponding throughout the performance period of the covered and closed embankment. Drawings TRC-3 through TRC-8 of the Reclamation Plan Rev. 5.0 depict several areas where slopes are nearly flat and have low-lying areas already (e.g. over portions of Cell 2) where differential settlement, if it were to occur, could further aggravate these areas from the standpoint of further flattening or creating of larger areas of flat ground surface for future ponding of incident precipitation. Available published information and/or testing should be used to estimate the maximum amount of strain/maximum distortion value that can be tolerated within the compacted layer over the design life of the embankment and not crack the radon barrier. Such a limit should be based on properties (e.g., range of plasticity indices) of the soils proposed for constructing the compacted portion of the radon barrier layer. Engineering analyses should be provided for various representative disposal configurations involving disposed tailings to demonstrate that predicted settlement/subsidence magnitudes and locations will not exceed specified acceptance criteria for strain or distortion value. To quantify the amount of settlement in the tailings due to the placement of the interim and final soil covers, the Licensee has attempted to quantify the coefficients of consolidation (cv) and compression indices (Cc) for the tailings based on back-analysis of existing settlement monitoring data from Cells 2 and 3. While this approach is a conceptually sound approach for obtaining site-specific parameters, successful implementation often proves to be problematic. For instance, high quality monitoring data is needed. Unfortunately, the monitoring data exhibits an appreciable amount of “noise” and numerous erratic shifts, making it uncertain as to which data points are the "real data" to which the modeled settlement response should be matched. This approach also typically requires that the initial portion of the load-settlement curve be well defined. Without this initial data, the total amount of settlement ultimately expected to occur can be difficult to accurately quantify, particularly if the rate of consolidation is rapid relative to the rate of loading (i.e., cover placement). Any settlement occurring during construction of the cover and before monitoring begins is lost, leading to questions as to how tightly the “bend” in the time rate of consolidation curve should be matched in the absence of a well- defined starting point for the settlement model. It should also be noted that assessing the goodness of the fit itself can also be problematic. For example, while the report states that the model values of Cc and cv were varied “until the observed settlement curve correlated well with the calculated settlement”, it is the reviewer’s opinion that the degree of correlation achieved was not always “well”, particularly for the first and most meaningful part of the consolidation time history curve shown in Fig F-1, and for the entire plots shown for cells 2W1, 2W3, 3-1C, 3-1S. It may be simply fortuitous that the back-calculated values appear to be within the ranges suggested Keshian and Rager (cited by the Licensee), particularly recognizing that the ranges cover one or more orders of magnitude. It should also be noted that no assessment has been made as to whether or not the tailings’ behavior in Cells 2 and 3 are applicable to the other cells. It is noted that the calculated/estimated amounts of settlement presented in the report appear to be based on assumed dry and saturated unit weights of 86.3 and 117.1 pcf, respectively. However, elsewhere in the report, (Section C.2.4 of sub-Appendix C in Appendix D), the tailings are described as having a dry unit weight of 74.3 pcf. Consistent characterization of the tailings throughout the report seems to be needed, or at least this variation should be accounted for when reporting values of settlement. It is also noted that all the back analyses involved the same initial void ratio for the tailings which is a very unlikely scenario given that the other consolidation parameters (which are not entirely independent of void ratio) were varied. Interrogatory 07/1: R313-24-4; 10CFR40.Appendix A, Criterion 4: Technical Analysis – Settlement and Potential for Cover Slope Reversal and/or Cover Layer Cracking Page 40 of 96 A key deficiency of the settlement assessment presented by the Licensee lies in the following conclusion: “Additional settlement due to the construction of the final cover is estimated to be on the order of 5 to 6 inches. The estimated amount of additional settlement is sufficiently low such that ponding is not expected with a cover slope of 0.5 percent.” The calculated settlements are magnitudes of settlement without specified locations, whereas an assessment of ponding potential (i.e., localized grade reversal of the cover) requires that the spatial variation of settlement be known or calculated. The reported magnitudes of vertical settlement need to be translated into reliable estimates of differential settlement in order to properly assess the adequacy of the cover slope. In doing this, the Licensee should evaluate the various areas within individual tailings placement cells and/or or spanning more than one of the tailings Cells 2, 3, and 4A/B where tailings slurry deposition modes may vary, leading to different tailings conditions within and/or between cells (e.g., tailings areas comprised of sand/slime mixture located laterally adjacent to tailings areas containing mostly slimes, including, for example, areas near side slope portions of tailings placement cells where more sand-rich tailings may be laterally juxtaposed against slime-rich tailings areas). The analysis should particularly account for varying thicknesses of compressible tailings along the side slopes of the cells as well as the potential for differences in stress conditions along such slopes. The locations and characteristics for the different tailings materials (such as moisture content, horizontal and vertical coefficients of consolidation, specific gravity, void ratios, unit weights, hydraulic conductivity, etc.) should be clearly shown for one or more analyzed critical cross- sections. While the above discussion focuses on the settlement of tailings, different conditions exist in Cell 1 adjacent to Cell 2 where mill debris and contaminated soils instead of tailings are to be placed and covered. Total and differential settlement based on the particular conditions of this cell together with their effects on both the liner and cover systems should be assessed. To more reliably quantify total and differential settlements as well as settlement rates for the tailings impoundments, the Licensee should test tailings specimens to determine their consolidation properties. The number of specimens involved should be commensurate with anticipated variability of the tailings conditions in the containment cells. The Licensee should then consider performing coupled stress and seepage analyses of critical cross-section of Cells 2 and 3, and/or 4A/B. As a minimum, the settlement analyses should be compared with the drainage/seepage/dewatering analyses to demonstrate that they are consistent. It appears that such a check was not performed since the discussion of the results of the time-rate of consolidation/settlement does not make any reference to the dewatering analyses in sub- Appendix H, despite the fact that the back-calculated coefficients of consolidation of the former should be proportional to the hydraulic conductivity values of the latter (the coefficient of consolidation is a composite variable which includes hydraulic conductivity). Unfortunately, the tailings dewatering analyses presented in sub-Appendix H do not adequately represent (i.e., account for) potential variations in the tailings properties, nor their potential distribution within the containment cells. In the models presented for Cells 2 and 3, isotropic conditions are assumed (which is very unlikely) and a single hydraulic conductivity value is assigned to all of the tailings (which might be acceptable if the effect/sensitivity of the parameter had been assessed parametrically – but it wasn’t). The hydraulic conductivity value itself appears to be flawed, apparently being based on the geometric mean of four discrete hydraulic conductivity values taken from technical literature (representing four generic soil types ranging from medium sand to silty clayey) which span 5 orders of magnitude. It is inappropriate to use a type of average, single value to represent such a vast range of hydraulic conductivity. (Although there is seemingly contradictory information as to what was really used as the basis for the hydraulic conductivity in the analysis. On page J[sic]-4 of sub-Appendix H, the text states that hydraulic conductivity values are based on testing from the Canon City Mill tailings whereas attachment H-2 indicates that the hydraulic value is based on the aforementioned averaging of typical values. Clarification is needed). The tailings dewatering analyses should be revisited or at least clarified Interrogatory 07/1: R313-24-4; 10CFR40.Appendix A, Criterion 4: Technical Analysis – Settlement and Potential for Cover Slope Reversal and/or Cover Layer Cracking Page 41 of 96 and better substantiated. To reliably quantify total and differential both drainage and settlement characteristics of the tailings, the Licensee should test actual tailings specimens from the site. Drainage/seepage/dewatering analyses performed should reflect the tailings and drainage conditions (including drainage system) associated with each particular cell. One or more cross-sections may need to be considered. Due to uncertainty and/or inherent variability of the tailings materials, multiple analyses bracketing the ranges of anticipated engineering properties should be performed. Contingencies for less-than-most-likely performance should be incorporated into the design of the cover system. Particular consideration should be given to variations in the magnitude of differential settlement as well as the time required to reach 90% consolidation. In light of the particularly large range in the coefficients of consolidation already presented by the Licensee, it can be misleading to cite or use “average” values when discussing or planning other activities (for example, see the monitoring section of the report (sub-Appendix I of Appendix D) which states, “a monitoring period of four years prior to final cover system construction is anticipated, based on the estimated time required to reach 90 percent consolidation.” All references to settlement magnitude, rate, and duration should be provided as ranges. Given the erratic nature exhibited in the existing settlement monitoring data, it is recommended that the monitoring process be reviewed and revised to assure greater accuracy. As a minimum, the data should be reviewed as soon as it is gathered and its quality be checked by plotting it with previous data and making certain that the data makes sense (i.e., is consistent with expected trends; not showing significant amounts of upward displacement, for example). Questionable data should be confirmed or replaced with new measurements. Without such quality control measures, it may become difficult or impossible to demonstrate that 90% consolidation has been reached and that cover materials can be placed. It is suggested that statements such as the following from page I-2 of sub-Appendix I of Appendix D: “typically less than 0.1 feet (30 mm) of cumulative settlement over a 12 month period is acceptable” be avoided because such statements might be mistakenly substituted for the real requirement of 90% consolidation. The Licensee’s assessment of settlement only addresses primary settlement and does not consider secondary settlement effects (i.e., creep) or seismically-induced settlement of the tailings. Secondary settlement and seismically induced settlement of the tailings (if any) and their subsequent effects on the cover system should be assessed. Assessment of settlement under seismic conditions is dependent upon the Licensee’s seismic hazard analysis. Any revisions to the seismic hazard analysis may necessitate revisions to such an assessment. NUREG-1620 (NRC 2003), Section 2.3.3, specifies that: “The analysis of tailings settlement will be acceptable if it meets the following criteria: (1) Computation of immediate settlement follows the procedure recommended in NAVFAC DM–7.1 (Department of the Navy, 1982). If a different procedure is used, the basis for the procedure is adequately explained. The procedure recommended in NAVFAC DM–7.1 (Department of the Navy, 1982) for calculation of immediate settlement is adequate if applied incrementally to account for different stages of tailings emplacement. If this method is used, the reviewer should verify that the computation of incremental tailings loading and the width of the loaded area, as well as the determination of the undrained modulus and Poisson’s ratio, have been computed and documented. Settlement of tailings arises from compression of soil layers within the disposal cell and in the underlying materials. Because compression of sands occurs rapidly, compression of sand layers in the disposal cell and foundations must be considered in the assessment of immediate settlement. However, the contribution of immediate settlement to consolidation settlement cannot be ignored. Clay layers and slime undergo instantaneous elastic compression controlled by their undrained stiffness as well as long-term inelastic compression controlled by the processes of consolidation and creep (NRC, 1983a). Interrogatory 07/1: R313-24-4; 10CFR40.Appendix A, Criterion 4: Technical Analysis – Settlement and Potential for Cover Slope Reversal and/or Cover Layer Cracking Page 42 of 96 (2) Each of the following is appropriately considered in calculating stress increments for assessment of consolidation settlement: (a) Decrease in overburden pressure from excavation (b) Increase in overburden pressure from tailings emplacement\ (c) Excess pore-pressure generated within the disposal cell (d) Changes in ground-water levels from dewatering of the tailings (e) Any change in ground-water levels from the reclamation action (3) Material properties and thicknesses of compressible soil layers used in stress change and volume change calculations for assessment of consolidation settlement are representative of in situ conditions at the site. (4) Material properties and thicknesses of embankment zones used in stress change and volume change calculations are consistent with as-built conditions of the disposal cell. (5) Values of pore pressure within and beneath the disposal cell used in settlement analyses are consistent with initial and post-construction hydrologic conditions at the site. (6) Methods used for settlement analyses are appropriate for the disposal cell and soil conditions at the site. Contributions to settlement by drainage of mill tailings and by consolidation/compression of slimes and sands are considered. Both instantaneous and time-dependent components of total and differential settlements are appropriately considered in the analyses (NRC, 1983a,b,c). The procedure recommended in NAVFAC DM–7.1 (Department of the Navy, 1982) for calculation of secondary compression is adequate. (7) The disposal cell is divided into appropriate zones, depending on the field conditions, for assessment of differential settlement, and appropriate settlement magnitudes are calculated and assigned to each zone. (8) Results of settlement analyses are properly documented and are related to assessment of overall behavior of the reclaimed pile. (9) An adequate analysis of the potential for development of cracks in the radon/infiltration barrier as a result of differential settlements is provided (Lee and Shen, 1969).” REFERENCES DOE (U.S. Department of Energy). 1989. Technical Approach Document, Revision II. UMTRA-DOE/AL 050425.0002. EPA (U.S. Environmental Protection Agency). 1989. Final Covers on Hazardous Waste Landfills and Surface Impoundments, Technical Guidance Document, EPA/530-SW-89-047, Office of Solid Waste and Emergency Response, Washington, D.C. URL: http://webcache.googleusercontent.com/search?q=cache:VEVCaJfyPDQJ:nepis.epa.gov/Exe/ZyPURL.cg i%3FDockey%3D100019HC.txt+site:epa.gov+EPA+Final+Covers+Guidance&cd=4&hl=en&ct=clnk &gl=us. Interrogatory 07/1: R313-24-4; 10CFR40.Appendix A, Criterion 4: Technical Analysis – Settlement and Potential for Cover Slope Reversal and/or Cover Layer Cracking Page 43 of 96 EPA 1991. Seminar Publication, Design and Construction of RCRA/CERCLA Final Covers. EPA/625/4- 91/025.May 1991, 208 pp. EPA 2004. (Draft) Technical Guidance for RCRA/CERCLA Final Covers. U.S EPA 540-R-04-007, OSWER 9283.1-26. April 2004, 421 pp. URL: nepis.epa.gov/Exe/ZyPURL.cgi?Dockey=P10074PP.txt. U.S. Nuclear Regulatory Commission 2003. “Standard Review Plan (NUREG–1620) for Staff Reviews of Reclamation Plans for Mill Tailings Sites Under Title II of The Uranium Mill Tailings Radiation Control Act”, NUREG-1620, June, 2003. Interrogatory 08/1: R313-24-4; 10CFR40.Appendix A, Criterion 4: Technical Analysis – Erosion Stability Evaluation Page 44 of 96 INTERROGATORY WHITEMESA RECPLAN REV5.0 R313-24-4; 10CFR40 APPENDIX A CRITERION 4; INT 08/1: TECHNICAL ANALYSIS –EROSION STABILITY EVALUATION REGULATORY BASIS: UAC R313-24-4 invokes the following requirement from 10CFR40, Appendix A, Criterion 4: “The following site and design criteria must be adhered to whether tailings or wastes are disposed of above or below grade: … (c) Embankment and cover slopes must be relatively flat after final stabilization to minimize erosion potential and to provide conservative factors of safety assuring long-term stability. The broad objective should be to contour final slopes to grades which are as close as possible to those which would be provided if tailings were disposed of below grade; this could, for example, lead to slopes of about 10 horizontal to 1 vertical (10h:1v) or less steep. In general, slopes should not be steeper than about 5h:1v. Where steeper slopes are proposed, reasons why a slope less steep than 5h:1v would be impracticable should be provided, and compensating factors and conditions which make such slopes acceptable should be identified. (d) A full self-sustaining vegetative cover must be established or rock cover employed to reduce wind and water erosion to negligible levels. Where a full vegetative cover is not likely to be self-sustaining due to climatic or other conditions, such as in semi-arid and arid regions, rock cover must be employed on slopes of the impoundment system. The Executive Secretary will consider relaxing this requirement for extremely gentle slopes such as those which may exist on the top of the pile. The following factors must be considered in establishing the final rock cover design to avoid displacement of rock particles by human and animal traffic or by natural process, and to preclude undercutting and piping: • Shape, size, composition, and gradation of rock particles (excepting bedding material average particles size must be at least cobble size or greater); • Rock cover thickness and zoning of particles by size; and • Steepness of underlying slopes. Individual rock fragments must be dense, sound, and resistant to abrasion, and must be free from cracks, seams, and other defects that would tend to unduly increase their destruction by water and frost actions. Weak, friable, or laminated aggregate may not be used. Rock covering of slopes may be unnecessary where top covers are very thick (or less); bulk cover materials have inherently favorable erosion resistance characteristics; and, there is negligible drainage catchment area upstream of the pile and good wind protection as described in points (a) and (b) of this criterion. Furthermore, all impoundment surfaces must be contoured to avoid areas of concentrated surface runoff or abrupt or sharp changes in slope gradient. In addition to rock cover on slopes, areas toward which surface runoff might be directed must be well protected with substantial rock cover (rip rap). In addition to providing for stability of the impoundment system itself, overall stability, erosion potential, and Interrogatory 08/1: R313-24-4; 10CFR40.Appendix A, Criterion 4: Technical Analysis – Erosion Stability Evaluation Page 45 of 96 geomorphology of surrounding terrain must be evaluated to assure that there are not ongoing or potential processes, such as gully erosion, which would lead to impoundment instability. INTERROGATORY STATEMENT: Refer to Section 3.3.5 of the Reclamation Plan, Rev. 5.0 and Section 4.9 and Appendix G to Appendix D (Updated Tailings Cover Design Report), and Drawings TRC-1 through TRC-8 to the Reclamation Plan, Rev. 5.0: Please provide the following: 1. To further confirm the appropriateness and currency of the calculated Probable Maximum Precipitation (PMP) value and as used, for example, in the ET cover design erosion protection rock rip rap sizing calculations, please provide a revised PMP calculation updating the PMP distribution that incorporates information from the following documents, in addition to HMR 49 (Hansen et al.1984): • “2002 Update for Probable Maximum Precipitation, Utah 72 Hour Estimates to 5,000 sq. mi”. – March 2003 Jensen 2003); and • “Probable Maximum Precipitation Estimates for Short Duration, Small Area Storms in Utah” – October 1995 (Jensen 1995) Response 1: The local-storm Probable Maximum Precipitation (PMP) events used to calculate the peak discharges for evaluation of erosional stability were the six-hour duration PMP (with a precipitation total of 10.0 inches) and the one-hour duration PMP (with a precipitation total of 8.3 inches). These events were determined for the site area using HMR No. 49 (Hansen et al. 1984). These PMP values were evaluated for appropriateness using the two references listed above by Jensen (1995 and 2003) and the updated calculations are provided as Attachment B. The updated PMP values are 8.3 and 9.6 for the one-hour and six-hour duration PMP, respectively. 2. Using the revised PMP information obtained from Item 1 above, provide revised calculations of required rock rip rap sizes for the cover sideslope areas using the updated method developed for round-shaped rip rap as described in Abt et al. 2008. Update and revise other erosion protection calculation presented in Appendix G, as required and appropriate, to reflect the revised PMP determination. Response 2: There are no modifications required to the erosion protection calculations as a result of updating the PMP calculations. The procedure provided in Abt et al. (2008) has not been approved or adopted by the NRC for sizing round-shaped riprap (personal communication with Dr. Steven Abt on May 12, 2012). The latest NRC guidance for sizing round-shaped riprap is the method presented in Abt and Johnson (1991) and referenced in NUREG-1623 (NRC, 2002). References for Response 2: Abt, S., 2012. Personal communication from Steven Abt, Colorado State University, to Melanie Davis, MWH Americas, Inc., May 12. Abt, S., and Johnson, T. 1991. Riprap Design for Overtopping Flow, Journal of Hydraulic Engineering, Vol. 117, No. 8, August. Interrogatory 08/1: R313-24-4; 10CFR40.Appendix A, Criterion 4: Technical Analysis – Erosion Stability Evaluation Page 46 of 96 U.S. Nuclear Regulatory Commission (NRC), 2002 “Design of Erosion Protection for Long-Term Stability”, NUREG-1623, September. 3. Please provide additional calculations to estimate the magnitude and location of a potential gully intrusion into each soil-covered portion of the proposed cover system (e.g., using the procedure described in Thornton and Abt 2008). Demonstrate that excluding rock (gravel) particles from the currently proposed flattest (0.1 % and 0.5%) top slope areas would adequately protect against sheet flow under potential precipitation conditions and would adequately control longer- term rill and/or gully initiation and development. Provide information on required “overdesign” of the cover thickness needed to accommodate maximum predicted gully depths and locations. Response 3: The gully intrusion analysis procedure described in Thornton and Abt (2008), as well as the precursor gully analysis procedure developed by Abt and documented in Appendix B of NUREG-1623 (NRC, 2002) are intended for soil-covered embankment slopes. The procedure is not applicable to the flatter top slope only (personal communication with Dr. Steven Abt on May 12, 2012). The top slopes have been designed to meet erosional stability using the Temple method as presented in Appendix A of NUREG-1623 (NRC, 2002). Gully intrusion analysis was not conducted for the side slopes which have been designed with rock protection. References for Response 3: Abt, S., 2012. Personal communication from Steven Abt, Colorado State University, to Melanie Davis, MWH Americas, Inc., May 12. Thornton, C., and Abt, S., 2008. “Gully Intrusion into Reclaimed Slope: Long-Term Time-Average Calculation Procedure”, Journal of Energy Engineering, Vol. 134, No. 1, March 2008, pp. 15-23. U.S. Nuclear Regulatory Commission (NRC), 2002 “Design of Erosion Protection for Long-Term Stability”, NUREG-1623, September. 4. Provide additional detailed cross sections showing every interface that will occur between sidelope cover layers and topslope cover layers. Demonstrate that all applicable filter criteria will be met for each interface between each topslope cover layer component and the proposed granular filter layer on the sideslope, including standard filter gradation criteria as well as applicable permeability filter criteria (e.g., for filter layer underlying riprap on sideslope areas). Consider filter criteria for preventing migration of granular materials into an adjacent coarser grained granular layer (e.g., Nelson et al. 1986, Equation 4.35); for preventing piping of finer grained cohesionless soil particles into an adjacent coarser-grained material layer (e.g., Cedegren 1989, Equation 5.3); and for preventing erosion of a finer-grained material layer from occurring over the long term as a result of flows in an adjacent coarser (filter zone) layer (e.g., Nelson et al. 1986, Equation 4.36). Include consideration of different specific filter stability criteria (e.g., NRCS 1994, Tables 26-1 and 26-2) for determining the maximum allowable D15 of a granular filter layer material for preventing erosion of any adjacent layer (e.g., sacrificial soil layer) consisting of fine-grained/finer-grained particles, as a function of soil type. Address applicable filter permeability criteria for the filter layer in the sideslope cover system, including Table 26-3 of NRCS 1994. Interrogatory 08/1: R313-24-4; 10CFR40.Appendix A, Criterion 4: Technical Analysis – Erosion Stability Evaluation Page 47 of 96 Response 4: The Drawings will be revised to show include the filter and riprap layers. The filter gradation requirements were determined using NRCS (1994) as documented in Appendix G of Appendix D of the Reclamation Plan. The filter material gradation requirements will be updated based on the results of laboratory tests currently being conducted on additional samples of cover borrow material. The procedure from NRCS (1994) will be used to determine the filter gradation limits, in addition to other procedures and NRC guidance as deemed appropriate. Reference for Response 4: Natural Resource Conservation Service (NRCS), 1994. Gradation Design of Sand and Gravel Filters, U.S. Department of Agriculture, National Engineering Handbook, Part 633, Chapter 26, October. 5. Provide revised cover system cross sections to include a thicker riprap layer on the cover sideslope areas (i.e., minimum thickness of 1.5 times the D50 of the rock rip size of 7.4 inches, or the D100 of the rock rip rap materials, whichever is greater) to bring the cover design into compliance with recommendations contained in Section 2.1.2 of NUREG-1623 (NRC 2002). Response 5: The Drawings will be updated to show a minimum thickness of 2.0 times the D50 of the rock riprap size. As noted in the response to Interrogatory 02/1, updates to the Drawings will be provided as part of a second response document submitted to the Division on August 15, 2012. 6. Provide revised construction drawings for the final cover that preclude the presence of low areas that have the potential for experiencing future concentrated flows (e.g., portion of cover overlying Cell 2 as depicted on Section B-3 on Drawing TRC-7) and that avoid areas having abrupt changes in slope gradient across the cells, (e.g., areas of cover having proposed 5h:1v slopes shown on Sections B-3 and C-3 on Drawings TRC-6 and TRC-7 and Detail 7/8 on Drawing TRC- 8, etc..) to be consistent with UAC R313-24-4 10CFR40, Appendix A, Criterion 4. Response 6: Section B-3 on Drawing TRC-7 will be revised to show the correct direction of the 0.5 percent slope to be toward the south to match the plan view shown on Drawing TRC-3. The 5H:1V slopes shown on the cover top slope will be revised to be 10H:1V. As noted in the response to Interrogatory 02/1, updates to the Drawings will be provided as part of a second response document submitted to the Division on August 15, 2012. BASIS FOR INTERROGATORY: When determining the PMP for facilities such as High Hazard and Moderate Hazard dams, the State of Utah currently requires the use of HMR 49, which DUSA has used in Attachment G to the Reclamation Plan 4.0 (Denison 2009) and referenced in Appendix D to the Reclamation Plan 5.0 (Denison 2011), but also in conjunction with the use of two other reports: (1) the “2002 Update for Probable Maximum Precipitation, Utah 72 Hour Estimates to 5,000 sq. mi. – March 2003” and (2) “Probable Maximum Precipitation Estimates for Short Duration, Small Area Storms in Utah – October 1995.” Although these Interrogatory 08/1: R313-24-4; 10CFR40.Appendix A, Criterion 4: Technical Analysis – Erosion Stability Evaluation Page 48 of 96 two methods were developed (by the Utah Climate Center) for estimating PMF conditions for design of dams, these methods are considered to be more representative of actual meteorological conditions in Utah than those considered in HMR 49. The erosion protection calculations presented in Appendix G (Erosion Stability Evaluation) should to be revised as needed to reflect the revised PMP determination findings, as appropriate, to demonstrate that applicable erosion protection requirements will be met. The Modified Universal Soil Loss Equation (MUSLE) was used (Appendix G to Appendix D to the Reclamation Plan) to evaluate erosion losses from the topslope areas of the cover due to sheet flow but does not consider the potential for gully development or intrusion due to the topographic features of the tailings area which are assumed to remain constant with time (Nelson 1986). Although the Temple method (Appendix D) was appropriately used to evaluate the erosional stability of portions of the cover comprised of “topsoil and vegetation” and “topsoil mixed with gravel” –covered slopes, the method assumes only minor channeling, gullying, or rilling. Due to the relatively large and flat nature of the currently proposed topslope areas, these assumptions may or may not reflect actual conditions that are expected to occur. It is possible that less or more severe flow concentrations would occur and vegetation would or would not provide significant protection. Research has demonstrated that if localized erosion and gullying occurs, damage to unprotected soil covers may occur rapidly, probably in a time period shorter than 200 years (NUREG-1623 [NRC 2002]). It needs to be demonstrated that all slopes are designed to meet NUREG-1623 requirements, i.e., that “Soil slopes of a reclaimed tailings impoundment should be designed to be stable and thus inhibit the initiation, development, and growth of gullies.” A procedure developed by Thornton and Abt (2008), which builds upon a preliminary procedure developed by Abt et al. 1997 (as discussed in Appendix B of NUREG-1623), provides a means of estimating the magnitude and location of a potential gully intrusion into the flat topslope areas of the cover. Additional descriptive information and supporting calculations need to be provided to demonstrate that all applicable filter criteria are met for all topslope cover/ sideslope cover layer interfaces. Acceptable filter sizing criteria for preventing migration of the selected filter/bedding materials into the riprap and for minimizing or preventing erosion of the soil layer below the filter/bedding layer, and for meeting filter permeability criteria are described in NUREG/CR-4620 (Nelson et al. 1986), Cedegren 1989 and NCRS 1994. In addition, currently, it is unclear from Drawings TRC-1 through TRC-8 of the Reclamation Plan Rev. 5.0 as to whether filter blankets or bedding layers are or are not included in some areas, for example, areas along toes of slopes, transition areas, diversion ditches and channels, stilling areas, and flow impact areas, which are typically areas described in NUREG-1623 as areas where filters are generally recommended. A demonstration of long-term layer stability is needed to justify the omission of a filter/bedding blanket in the final cover system and in any such areas. Cross sections TRC-6 and TRC-7 provided in the Reclamation Plan Rev. 5.0 depict abrupt slope changes in the tailings cover when crossing Cell 2 to Cell 1 and Cell 2 to Cell 3. The cross sections should be revised to meet the above UAC R313-24-4, 10CFR40, Appendix A, Criterion 4 “….all impoundment surfaces must be contoured to avoid areas of concentrated surface runoff or abrupt or sharp changes in slope gradient.” NUREG-1623 (NRC 2002), Section 2.1.2 recommends that the minimum required thickness of a rock riprap layer be no less than 1.5 times the D50 of the rock riprap materials, or the D100 of the rock rip rap materials, whichever is greater. Interrogatory 08/1: R313-24-4; 10CFR40.Appendix A, Criterion 4: Technical Analysis – Erosion Stability Evaluation Page 49 of 96 REFERENCES: Abt, S.R., Thornton, C.I., Batka, J.H., and Johnson, T.L. 1997. “Investigation of Gully Stabilization Methods with Launching Stone: Pilot Laboratory Tests” Prepared for the U.S. Nuclear Regulatory Commission, Washington, D.C. February 1997. Abt, S.R., Thornton, C.I., Gallegos, H., and Ullmann, C. 2008. “Round-Shaped Riprap Stabilization in Overtopping Flow,” Journal of Hydraulic Engineering, Vol. 134, No. 8, August 2008, pp. 1035–1041. Bertram, G.E. 1940. An Experimental Investigation of Protective Filters. Graduate School of Engineering, Harvard University, Cambridge, Massachusetts. Soil Mechanics Series No. 7. pp. 1-21. Cedegren.H.R. 1989. Seepage, Drainage, and Flow Nets. 3rd Edition. John Wiley $ & Sons, Inc., New York, NY. Denison Mines (USA) Corporation. 2011. Reclamation Plan, Revision 5.0, White Mesa Mill, Blanding, Utah, September 2011. Hansen, E., Schwarz, F., and Riedel, J. 1984. Probable Maximum Precipitation Estimates, Colorado River and Great Basin Drainages. Hydrometeorological Report No. 49. U.S Department of Commerce, National Oceanic and Atmospheric Administration, Reprinted 1984. Jensen, D. 1995. 2002 Update for Probable Maximum Precipitation, Utah 72 Hour Estimates to 5,000 sq. mi. - March 2003. Utah Climate Center. Jensen, D. 2003. Probable Maximum Precipitation Estimates for Short Duration, Small Area Storms in Utah - October 1995. Utah Climate Center. Nelson, J.D., Abt, S.R., Volpe, R.L, van Zyl, D., Hinkle, N.E., and Staub, W.P. 1986. Methodologies for Evaluating Long-Term Stabilization Designs of Uranium Mill Tailings Impoundments. Prepared for Nuclear Regulatory Commission, Washington, DC. NUREG/CR-4620, ORNL/TM-10067. June 1986, 151 pp. NRC 2002. U.S. Nuclear Regulatory Commission, “Design of Erosion Protection for Long-Term Stability”, NUREG-1623, September 2002. NRCS (Natural Resources Conservation Service) 1994. U.S. Department of Agriculture, Part 633, National Engineering Handbook, Chapter 26: Gradation Design of Sand and Gravel Filters. October 1994. Thornton, C., and Abt, S. 2008. “Gully Intrusion into Reclaimed Slope: Long-Term Time-Average calculation Procedure”, Journal of Energy Engineering, Vol. 134, No. 1, March 2008, pp. 15-23. Interrogatory 09/1: R313-24-4; 10CFR40.Appendix A, Criterion 1: Liquefaction Page 50 of 96 INTERROGATORY WHITEMESA RECPLAN REV. 5.0; R313-24-4; 10CFR40 APPENDIX A CRITERION 1; INT 09/1: LIQUEFACTION REGULATORY BASIS UAC R313-24-4 invokes the following requirement from 10CFR40 Appendix A, Criterion 1: The general goal or broad objective in siting and design decisions is permanent isolation of tailings and associated contaminants by minimizing disturbance and dispersion by natural forces, and to do so without ongoing maintenance. For practical reasons, specific siting decisions and design standards must involve finite times (e.g., the longevity design standard in Criterion 6). The following site features which will contribute to such a goal or objective must be considered in selecting among alternative tailings disposal sites or judging the adequacy of existing tailings sites: • Remoteness from populated areas; • Hydrologic and other natural conditions as they contribute to continued immobilization and isolation of contaminants from ground-water sources; and • Potential for minimizing erosion, disturbance, and dispersion by natural forces over the long term. …While isolation of tailings will be a function of both site and engineering design, overriding consideration must be given to siting features given the long-term nature of the tailings hazards. Tailings should be disposed of in a manner that no active maintenance is required to preserve conditions of the site. INTERROGATORY STATEMENT: Refer to Section 4.8 and Appendices C and F to the Appendix D, Updated Tailings Cover Design Report of the Reclamation Plan, Rev. 5: 1. Provide revised liquefaction analyses that rely upon actual site-specific data for the tailings materials, rather than assumed parameters. In doing so, revise the Reclamation Plan to correctly and defensibly characterize tailings properties consistent with these revisions throughout the document. Response 1: The liquefaction analyses will be revised to be applicable for long-term steady-state pore pressure conditions within the tailings, and will be consistent with or conservative with regards to the tailings dewatering analyses. The revised analyses will also incorporate the update to the previous seismic study (see Attachment A). The weight of the cover system will be included in the analyses. An uncorrected (SPT) blow count of 2 in 12 inches will be assumed for the tailings zones that will remain saturated under long-term steady state conditions. The unsaturated tailings zones will not be susceptible to liquefaction and will not be included in the analyses. The long-term dry density of the tailings will be revised to be 100 pcf to be consistent with the value to be used for the updated radon emanation analyses which is the default long-term tailings density as recommended by the Nuclear Regulatory Commission in Regulatory Guide 3.64 (NRC, 1989). The revised liquefaction analyses will be provided as part of the second response document to be submitted to the Division on August 15, 2012. Interrogatory 09/1: R313-24-4; 10CFR40.Appendix A, Criterion 1: Liquefaction Page 51 of 96 2. Correct apparent errors and conduct revised analyses using parameter values that are based on site-specific data. Correct discrepancies between calculated results and summarized, reported results. Response 2: See Response 1. 3. Demonstrate that conditions assumed for liquefaction analyses are consistent with or conservative compared to results of tailings dewatering analyses. If this is not true, revise liquefaction analyses to be consistent with or conservative compared to results of tailings dewatering analyses, report results, and demonstrate that impoundments will remain stable with regard to liquefaction. Response 3: See Response 1. We agree that the liquefaction analyses should be consistent with or conservative with regards to the tailings dewatering analyses. BASIS FOR INTERROGATORY NUREG-1620 (NRC 2003), Section 2.2.3, specifies the following with respect to slope stability analyses and assessment of liquefaction potential: “…The analysis of slope stability will be acceptable if it meets the following criteria: …(3) Appropriate analyses considering the effect of seismic ground motions on slope stability are presented. …(j) Where there is potential for liquefaction, changes in pore pressure from cyclic loading are considered in the analysis to assess the effect of pore pressure increase on the stress-strain characteristics of the soil and the post-earthquake stability of the slopes. Liquefaction potential is reviewed using Section 2.4 of this review plan. Evaluations of dynamic properties and shear strengths for the tailings, underlying foundation material, radon barrier cover, and base liner system are based on representative materials properties obtained through appropriate field and laboratory tests (NRC 1978, 1979)…. NUREG-1620 (NRC 2003), Section 2.4.3, specifies that: “The analysis of the liquefaction potential will be acceptable if the following criteria are met: (1) Applicable laboratory and/or field tests are properly conducted (NRC, 1978, 1979; U.S. Army Corps of Engineers, 1970, 1972). (2) Data for all relevant parameters for assessing liquefaction potential are adequately collected and the variability has been quantified. (3) Methods used for interpretation of test data and assessment of liquefaction potential are consistent with current practice in the geotechnical engineering profession (Seed and Idriss, 1971, 1982; National Center for Earthquake Engineering Research, 1997). An assessment of the potential adverse effects that complete or partial liquefaction could have on the stability of the embankment may be based on cyclic triaxial test data obtained from undisturbed soil samples taken from the critical zones in the site area (Seed and Harder, 1990; Shannon & Wilson, Inc. and Agbabian-Jacobsen Associates, 1972). Interrogatory 09/1: R313-24-4; 10CFR40.Appendix A, Criterion 1: Liquefaction Page 52 of 96 (4) If procedures based on laboratory tests combined with ground response analyses are used, laboratory test results are corrected to account for the difference between laboratory and field conditions (NRC, 1978; Naval Facility Engineering Command, 1983). (5) The time history of earthquake ground motions used in the analysis is consistent with the design seismic event. (6) If the potential for complete or partial liquefaction exists, the effects such liquefaction could have on the stability of slopes and settlement of tailings are adequately quantified. (7) If a potential for global liquefaction is identified, mitigation measures consistent with current engineering practice or redesign of tailings ponds/embankments are proposed and the proposed measures provide reasonable assurance that the liquefaction potential has been eliminated or mitigated. (8) If minor liquefaction potential is identified and is evaluated to have only a localized effect that may not directly alter the stability of embankments, the effect of liquefaction is adequately accounted for in analyses of both differential and total settlement and is shown not to compromise the intended performance of the radon barrier. Additionally, the disposal cell is shown to be capable of withstanding the liquefaction potential associated with the expected maximum ground acceleration from earthquakes. The licensee may use post-earthquake stability methods (e.g., Ishihara and Yoshimine, 1990) based on residual strengths and deformation analysis to examine the effects of liquefaction potential. Furthermore, the effect of potential localized lateral displacement from liquefaction, if any, is adequately analyzed with respect to slope stability and disposal cell integrity. The liquefaction analysis presented by the Licensee is based on the procedures presented in Youd et al. (2001). While newer methods have been introduced and are being used, this method is still an acceptable, state-of-practice method provided that borderline finer-grained soils are appropriately assessed (see Boulanger and Idriss, 2006; Bray and Sancio, 2006; Boulanger and Idriss, 2011). Aside from the earthquake magnitude and ground acceleration, the most important parameter in the analysis is the in-situ penetration resistance parameter (which in this case is an SPT blowcount) which provides a measure of the soil’s resistance to liquefaction. In the Licensee’s analysis, this SPT blowcount has been assumed to be 4 without any substantial justification – the justification provided in the report is that the analyst considered the tailings to be “loose” and that such a term is often correlated with a blowcount in the range of 4 to 10. However, it seems that analyst could have alternatively assumed that the tailings were “very loose,” leading to a blowcount in the range of 0 to 4, thus significantly affecting the outcome of the analysis. Also, elsewhere in the report (when approximating the shear strength of the drained tailings), the Licensee assumes that the tailings have a relative density of near zero, and a relative density of zero and a blow count of 4 are typically inconsistent. A similar issue with consistency appears to exist in the characterization of the tailings’ unit weight where dry and saturated unit weights of 86.3 and 117.1 pcf, respectively, are presented in Section F.2.2 of sub- Appendix F in Appendix D of the Reclamation Plan, Rev. 5.0, whereas a dry unit weight of 74.3 pcf is presented in Section C.2.4 of sub-Appendix C of Appendix D). Consistent characterization of the tailings throughout the report seems to be needed, and more importantly, with respect to liquefaction, a more substantiated blowcount describing the tailings is needed. If data doesn’t exist, it must be collected, not manufactured. It is noted that the results presented in Table F.5 ‘Summary of Liquefaction Results’ do not agree with the calculated values shown in Attachment F.3. Further, it appears from the text that the Licensee intended to have the cover in place for the analysis (the Licensee should clearly explain the configuration of the Interrogatory 09/1: R313-24-4; 10CFR40.Appendix A, Criterion 1: Liquefaction Page 53 of 96 impoundment and tailings reflected in the calculations); however, the weight of the cover seems to have been omitted from the calculated total and effective vertical stresses. Also, if the depth parameter “z” in the calculations is intended to reference from the top of the tailings as the datum, and given the stated “depth from top of tailings to water surface”, it appears that effective stresses have been calculated incorrectly. Calculation of the overburden correction factor should also be checked. Assessment of liquefaction is dependent upon the Licensee’s seismic hazard analysis. Any revisions to the seismic hazard analysis may necessitate revisions to this assessment. Also, the applicability of the liquefaction hazard analysis is dependent upon the outcome of tailings dewatering analyses, and the Licensee should demonstrate that the results such analyses are appropriately interpreted (i.e., are at least consistent with, if not conservative) for the liquefaction hazard analysis. REFERENCES Boulanger, R.W. and Idriss, I.M. (2006). “Liquefaction susceptibility criteria for silts and clays.” J. of Geotechnical and Geoenvironmental Eng., ASCE, Vol. 132, No. 11, pp. 1413-1426. Bray, J.D. and Sancio, R.B. (2006). “Assessment of the liquefaction susceptibility of fine grained soils.” J. of Geotechnical and Geoenvironmental Eng., ASCE, Vol. 132, No. 9, pp. 1165-1177. Boulanger, R.W. and Idriss, I.M. (2011). “Cyclic failure and liquefaction: Current issues.” Proc. Fifth International Conf. of Earthquake Geotechnical Eng., Santiago, Chile. MWH Americas 2011. Appendix C - Radon Emanation Modeling, and Appendix F – Settlement and Liquefaction Analysis, contained in Appendix D, Updated Tailings Cover Design Report, White Mesa Mill, September 2011 to the Reclamation Plan, White Mesa Mill, Rev. 5.0, September 2011. NRC 1982. U.S. Nuclear Regulatory Commission, “Regulatory Guide 3.8; Preparation of Environmental Reports for Uranium Mills”, Washington DC, October 1982. NRC 2001. U.S. Nuclear Regulatory Commission, “Environmental Review Guidance for Licensing Actions Associated with NMSS Programs.” Washington, DC, 2001. NRC 2003. U.S. Nuclear Regulatory Commission, “Standard Review Plan for the Review of a Reclamation Plan for Mill Tailings Sites Under Title II of the Uranium Mill Tailings Radiation Control Act of 1978.” Washington DC, June 2003. Youd, T. L., Idriss, I. M., Andrus, R. D., Arango, I., Castro, G., Christian, J. T., Dobry, R., Finn, W. D. L., Harder, L. F., Jr., Hynes, M. E., Ishihara, K., Koester, J. P., Liao, S. S. C., Marcuson, W. F., III, Martin, G. R., Mitchell, J. K., Moriwaki, Y., Power, M. S., Robertson, P. K., Seed, R. B., and Stokoe, K. H., II. (2001). “Liquefaction resistance of soils: summary report from the 1996 NCEER and 1998 NCEER/NSF workshops on evaluation of liquefaction resistance of soils.” J. of Geotechnical and Geoenvironmental Eng., ASCE, Vol. 127, No. 10, pp. 817-833. 1. Interrogatory 010/1: R313-24-4; 10CFR40.Appendix A, Criterion 6: Technical Analyses – Frost Penetration Analysis Page 54 of 96 INTERROGATORY WHITEMESA RECPLAN 5.0 R313-24-4; 10CFR40 APPENDIX A, CRITERION 6; INT 10/1: TECHNICAL ANALYSES - FROST PENETRATION ANALYSIS REGULATORY BASIS: Refer to R313-25-8(4). Analyses of the long-term stability of the disposal site shall be based upon analyses of active natural processes including erosion, mass wasting, slope failure, settlement of wastes and backfill, infiltration through covers over disposal areas and adjacent soils, and surface drainage of the disposal site. The analyses shall provide reasonable assurance that there will not be a need for ongoing active maintenance of the disposal site following closure. UAC R313-24-4 invokes the following requirement from 10CFR40, Appendix A, Criterion 6(1): “In disposing of waste byproduct material, licensees shall place an earthen cover (or approved alternative) over tailings or wastes at the end of milling operations and shall close the waste disposal area in accordance with a design which provides reasonable assurance of control of radiological hazards to (i) be effective for 1,000 years, to the extent reasonably achievable, and, in any case, for at least 200 years, and (ii) limit releases of radon-222 from uranium byproduct materials, and radon-220 from thorium byproduct materials, to the atmosphere so as not to exceed an average release rate of 20 picocuries per square meter per second (pCi/m2s) to the extent practicable throughout the effective design life determined pursuant to (1)(i) of this criterion. In computing required tailings cover thicknesses, moisture in soils in excess of amounts found normally in similar soils in similar circumstances may not be considered. Direct gamma exposure from the tailings or wastes should be reduced to background levels. The effects of any thin synthetic layer may not be taken into account in determining the calculated radon exhalation level. If non-soil materials are proposed as cover materials, it must be demonstrated that these materials will not crack or degrade by differential settlement, weathering, or other mechanism, over long- term intervals.” NUREG-1620 specifies that “Reasonable assurance [shall be] provided that the requirements of 10 CFR Part 40, Appendix A, Criterion 6(1), which requires that the design of the disposal facility provide reasonable assurance of control of radiological hazards to be effective for 1,000 years, to the extent reasonably achievable, and, in any case, for at least 200 years, have been met.” INTERROGATORY STATEMENT: Refer to Section 4.3 of Appendix D (Updated Tailings Cover Design Report) and Appendix B (Freeze/Thaw Modeling) to Appendix D to the Reclamation Plan Rev. 5.0: 1. Please revise freeze/thaw analyses to incorporate the following: a. Extrapolation of frost depth to recurrence interval to a minimum period of up to 1,000 years, to the extent practicable, or, to not less than 200 years, using a Gumbel extreme statistics (probability functions) approach (e.g., Smith and Rager 2002; Smith 1999; Yevjevich 1982). b. Additional justification for selection of an N -factor (surface temperature correction factor) of 0.6, instead of an N –factor of 0.7, based on published recommendations (e.g., DOE 1989). c. Additional justification that using climate data for Grand Junction, Colorado in the Berggren Model Formula (BMF) is representative of site conditions at the White Mesa site Address the considerably lower elevation and average warmer temperatures of Grand Junction compared to the White Mesa site. Either (1) prepare and report results of the BMF calculations using a default location having an elevation and Design Freezing Index equal to or greater than 1. Interrogatory 010/1: R313-24-4; 10CFR40.Appendix A, Criterion 6: Technical Analyses – Frost Penetration Analysis Page 55 of 96 those of the White Mesa site AND mean average temperatures equal to or less than those of the White Mesa site OR (2) justify that the Grand Junction data is applicable and representative as input to the BMF calculations for the White Mesa site. Response 1: The freeze/thaw analyses have been revised to use Gumbel extreme statistics approach for a time period of 200 years. The revised analyses are provided as Attachment C to this document. An N-factor of 0.7 and climate data from the Blanding, Utah was used for the analyses. The resulting frost penetration depth was estimated as 32 inches. The analyses will be revised, as necessary, to incorporate laboratory testing results for samples collected from cover borrow stockpiles on April 19, 2012. 2. Based on the results of the revised frost penetration analysis, justify revised soil parameter values for soils within the cover system above the projected frost penetration depth considering the effects of repeated freezing and thawing over the recurrence interval considered (referred to in Item 1.a above). Use these parameter values in performance assessment modeling, including infiltration modeling and radon attenuation modeling, consistent with recommendation provided in Sections 2.5 and 5.1 of NUREG-1620 (NRC 2003). Response 2: The revised infiltration and radon emanation modeling will reflect potential modifications to the hydraulic and physical properties of the cover due to freeze/thaw processes based on recommendations provided in Benson et al. (2011). These results will be provided as part of a second response document to be submitted to the Division on August 15, 2012. Reference for Response 2: Benson, C.H., W.H. Albright, D.O. Fratta, J.M. Tinjum, E. Kucukkirca, S.H. Lee, J. Scalia, P.D. Schlicht, and X. Wang, 2011. Engineered Covers for Waste Containment: Changes in Engineering Properties and Implications for Long-Term Performance Assessment, Volume 1 and 2, NUREG/CR-7028, Report Prepared for the U.S. Nuclear Regulatory Commission, December. 3. If applicable after addressing the instructions stated above, revise Appendix B to Appendix D of the Reclamation Plan to ensure that all intended text is present in the document. Response 3: Appendix B to Appendix D of the Reclamation Plan will be updated to incorporate the revised freeze/thaw analyses for the next version of the Reclamation Plan. BASIS FOR INTERROGATORY: The Division acknowledges that the Modified Berggren Formula has been used to estimate the depth of frost penetration at the site, relying upon input from a built-in long-term weather database. However, the input parameters do not account for extreme climate conditions. In addition, in Appendix B, it is noted that the mean annual temperature for Blanding given by Dames and Moore (1978) is 49.8 degrees F and the mean annual temperature for Grand Junction, CO, is 53.1 degrees F. The Grand Junction mean annual temperature used in the White Mesa calculations is higher, i.e, less conservative, than Blanding’s 1. Interrogatory 010/1: R313-24-4; 10CFR40.Appendix A, Criterion 6: Technical Analyses – Frost Penetration Analysis Page 56 of 96 mean temperature. Grand Junction’s elevation is also considerably lower than that of either Blanding or the White Mesa site. The use of a Gumbel extreme value statistics approach provides an accepted means for extrapolating a worst case value from a limited set of data. This technical approach has been successfully applied at other similar facilities (e.g., Monticello, Utah tailings repository cover – 200 year recurrence interval; Crescent Junction, Utah tailings repository cover- 1,000 year recurrence interval [e.g., see NRC 2008]). Extending the recurrence interval for the frost depth penetration analysis further informs predictions of potential future maximum frost penetration depths and allows insights into the potential risk reduction afforded to performance assessment predictions made for evaluating the performance of the cover system over long term performance periods. U.S.D.O.E. (1989), based on recommendations by the U.S. Army Corps of Engineers Cold Regions Research and Engineering Laboratory (CRREL), and Smith (1999) recommend that an N-factor of 0.7 be used for landfill cover designs. Additional information should therefore be provided to support the selection and use of an N-factor value of 0.6, rather than 0.7, in the calculation, or alternatively, an N- factor value of 0.7 should be used in the calculation. Section numbers in Appendix B of Appendix D of the Reclamation Plan suggest that sections are missing or that the section numbering is incorrect. REFERENCES: Denison Mines (USA) Corporation. 2011. Reclamation Plan, Revision 5.0, White Mesa Mill, Blanding, Utah, Appendix D: September 2011. NRC 2003. NUREG-1620: Standard Review Plan for the Review of a Reclamation Plan for Mill Tailings Sites under Title II of the Uranium Mill Tailings Radiation Control Act of 1978. Washington DC, June 2003. NRC 2008. “Summary of Changes to Moab Disposal Cell Calculations”. NRC ADAMS Website: Document Accession Number ML081700262. Smith, G.M., and Rager, R.E. 2002. “Protective Layer Design in Landfill Covers Based on Frost Protection”. Journal of Geotechnical and Geoenvironmental Engineering, Vol. 128, No. 9, September 1, 2002, pp. 794-799. Smith, G.M., 1999. Soil Insulation for Barrier Layer Protection in Landfill Covers, in Proceedings from the Solid Waste Association of North America’s 4th Annual Landfill Symposium, Denver, Colorado, June 28-30, 1999. U.S.D.O.E. 1989. Technical Approach Document, Rev. II, UMTRA-DOE/AL 050425.0002, Albuquerque, New Mexico. Yevjevich, V. 1982. Probability and Statistics in Hydrology, 3rd Edition. Water Resources Publications, Littleton, Colorado. Interrogatory 011/1: R313-24-4; 10CFR40.Appendix A: Vegetation and Biointrusion Evaluation and Revegetation Plan Page 57 of 96 INTERROGATORY WHITE MESA RECPLAN REV 5.0 R313-24-4; 10CFR40 APPENDIX A; INT 11/1: VEGETATION AND BIOINTRUSION EVALUATION AND REVEGETATION PLAN REGULATORY BASIS: UAC R313-24-4 invokes the following requirement from 10CFR40, Appendix A, Criterion 1:-The general goal or broad objective in siting and design decisions is permanent isolation of tailings and associated contaminants by minimizing disturbance and dispersion by natural forces, and to do so without ongoing maintenance. For practical reasons, specific siting decisions and design standards must involve finite times (e.g., the longevity design standard in Criterion 6). The following site features which will contribute to such a goal or objective must be considered in selecting among alternative tailings disposal sites or judging the adequacy of existing tailings sites: • Remoteness from populated areas; • Hydrologic and other natural conditions as they contribute to continued immobilization and isolation of contaminants from ground-water sources; and • Potential for minimizing erosion, disturbance, and dispersion by natural forces over the long term. • The site selection process must be an optimization to the maximum extent reasonably achievable in terms of these features. In the selection of disposal sites, primary emphasis must be given to isolation of tailings or wastes, a matter having long-term impacts, as opposed to consideration only of short-term convenience or benefits, such as minimization of transportation or land acquisition costs. While isolation of tailings will be a function of both site and engineering design, overriding consideration must be given to siting features given the long-term nature of the tailings hazards. Tailings should be disposed of in a manner that no active maintenance is required to preserve conditions of the site. UAC R313-24-4 invokes the following requirement from 10CFR40, Appendix A, Criterion 4: The following site and design criteria must be adhered to whether tailings or wastes are disposed of above or below grade: (a) Upstream rainfall catchment areas must be minimized to decrease erosion potential and the size of the floods which could erode or wash out sections of the tailings disposal area. (b) Topographic features should provide good wind protection. (c) Embankment and cover slopes must be relatively flat after final stabilization to minimize erosion potential and to provide conservative factors of safety assuring long-term stabililty. The broad objective should be to contour final slopes to grades which are as close as possible to those which would be provided if tailings were disposed of below grade; this could, for example, lead to slopes of about 10 horizontal to 1 vertical (10h:1v) or less steep. In general, slopes should not be steeper than about 5h:1v. Where steeper slopes are proposed, reasons why a slope less steep than 5h:1v would be impracticable should be provided, and compensating factors and conditions which make such slopes acceptable should be identified. (d) A full self-sustaining vegetative cover must be established or rock cover employed to reduce wind and water erosion to negligible levels. Where a full vegetative cover is not likely to be self-sustaining due to climatic or other conditions, such as in semi-arid and arid regions, rock cover must be employed on slopes of the impoundment system. The Executive Secretary will consider relaxing this requirement for extremely gentle slopes such as those which may exist on the top of the pile…. Interrogatory 011/1: R313-24-4; 10CFR40.Appendix A: Vegetation and Biointrusion Evaluation and Revegetation Plan Page 58 of 96 UAC R313-24-4 invokes the following requirement from 10CFR40, Appendix A, Criterion 6(1): In disposing of waste byproduct material, licensees shall place an earthen cover (or approved alternative) over tailings or wastes at the end of milling operations and shall close the waste disposal area in accordance with a design which provides reasonable assurance of control of radiological hazards to (i) be effective for 1,000 years, to the extent reasonably achievable, and, in any case, for at least 200 years, and (ii) limit releases of radon-222 from uranium byproduct materials, and radon-220 from thorium byproduct materials, to the atmosphere so as not to exceed an average release rate of 20 picocuries per square meter per second (pCi/m2s) to the extent practicable throughout the effective design life determined pursuant to (1)(i) of this Criterion. In computing required tailings cover thicknesses, moisture in soils in excess of amounts found normally in similar soils in similar circumstances may not be considered. Direct gamma exposure from the tailings or wastes should be reduced to background levels. The effects of any thin synthetic layer may not be taken into account in determining the calculated radon exhalation level. If non-soil materials are proposed as cover materials, it must be demonstrated that these materials will not crack or degrade by differential settlement, weathering, or other mechanism, over long-term intervals. INTERROGATORY STATEMENT: Refer to Section 1.7.1, 3.3.1.0 and Appendices D and J of the Reclamation Plan Rev. 5.0: Please provide the following: 1. Provide additional information (e.g., in the form of a survey and additional documentation of existing animal and vegetation species that exist at the White Mesa site and nearby surrounding region at this time to update the older information provided earlier. Response 1: A plant and animal survey is planned for the White Mesa site in June 2012 to further document animal and vegetation species at the site and provide an update to information provided in the previous study by Dames and Moore (1978). A final response to address this comment will be provided as part of a second response document to be submitted to the Division on August 15, 2012. 2. Update the list of plant and animal species to include plant and animal species (e.g. burrowing animals) that could reasonably be expected to inhabit or colonize the White Mesa site within the required performance period of the embankment (1,000 years, and in no case less than 200 years). In revising these lists, account for the types of vegetation and soils present in the vicinity of the White Mesa site and proximity to the high quality northern pocket gopher and badger habitat indicated in Utah distribution maps (Utah Division of Wildlife Resources). Response 2: A plant and animal survey is planned for the White Mesa site in June 2012. The results from this survey, in addition to further literature review, will be used to update the list of plants and animals that could reasonably be expected to inhabit or colonize the White Mesa site within the required performance period. In addition, vegetation and soils in the vicinity of the White Mesa site will be assessed as they relate to habitat requirements of the northern pocket gopher and badger. A final response to address this comment will be provided as part of a second response document to be submitted to the Division on August 15, 2012. Interrogatory 011/1: R313-24-4; 10CFR40.Appendix A: Vegetation and Biointrusion Evaluation and Revegetation Plan Page 59 of 96 3. Please report the estimated range of burrowing depths and burrow densities for animal species found at the site and nearby surrounding region (once the updated study requested above is complete), and for burrowing species that may reasonably be expected to inhabit the site within the required performance period of the embankment (1,000 years, and in no case less than 200 years). Please comment on the root densities provided in Appendix D of the ICTM report. Indicate whether the correct root density units were used in Table D-3 and Figure D-1. Also verify that the correct values were used in the HYDRUS-2D infiltration model, since an erroneously high value of root density could overestimate plant transpiration and underestimate infiltration. Response 3: The estimated range of burrowing depths and burrow densities for animal species found at the site and nearby surrounding region will be reported following the site survey in June 2012. Information will be included for burrowing species that may reasonably be expected to inhabit the site within the required performance period. A final response to address this comment will be provided as part of a second response document to be submitted to the Division on August 15, 2012. The root densities provided in Appendix D of the Revised Infiltration and Contaminant Transport Modeling (ICTM) Report are incorrect because of a calculation error. Updated and recalculated root biomass values are shown in Table D-3 below. These corrected values will be used in the HYDRUS-1D infiltration model and results will be provided as part of a second response document to be submitted to the Division on August 15, 2012. Table D-3. Corrected root biomass (anticipated performance scenario and reduced performance scenario) for the White Mesa Mill Site. Depth (cm) Root Biomass (grams cm-3) Anticipated Performance Root Biomass (grams cm-3) Reduced Performance 0-15 0.11 0.04 15-30 0.17 0.12 30-45 0.035 0.02 45-60 0.023 0.015 60-75 0.021 0.014† 75-90 0.019 0.0 90-107 0.011 0.0 †Maximum rooting depth under the reduced performance scenario would be 68 cm. 4. Rectify the mischaracterization of two plant species as presented in the two referenced documents (Festuca ovina and common yarrow). Interrogatory 011/1: R313-24-4; 10CFR40.Appendix A: Vegetation and Biointrusion Evaluation and Revegetation Plan Page 60 of 96 Response 4: The seed mixture proposed for the ET cover at the White Mesa Mill site consists of native and introduced species. The majority of species are native to Utah and two species (Pubescent wheatgrass and sheep fescue) have been introduced to North America. Sheep fescue was introduced from Europe in the 19th century, is commonly found in Utah and highly used as a reclamation species. Pubescent wheatgrass was introduced from Eurasia in 1907 and is also distributed in Utah from reclamation seedings over the past 100 years. Common yarrow (Achillea millefolium, var. occidentalis) is native to North America and is found in Utah, according to the USDA Natural Resources Conservation Service’s Plant Database (http://plants.usda.gov/java/). However, seed that is most available for common yarrow (Achillea millefolium) is of an introduced origin and is commonly used in reclamation plantings in Utah and throughout the western U.S. Seed of the native variety, occidentalis, will be used in the seed mixture if seed is available. If the native variety is not available, then the more common introduced variety will be used. Table D-1. Species and seeding rates proposed for ET cover at the White Mesa Mill Site. Scientific Name Common Name Variety Native/ Introduced Seeding Rate (lbs PLS/acre)† Grasses Pascopyrum smithii Western wheatgrass Arriba Native 3.0 Pseudoroegneria spicata Bluebunch wheatgrass Goldar Native 3.0 Elymus trachycaulus Slender wheatgrass San Luis Native 2.0 Elymus lanceolatus Streambank wheatgrass Sodar Native 2.0 Elymus elymoides Squirreltail Toe Jam Native 2.0 Thinopyrum intermedium Pubescent wheatgrass Luna Introduced‡ 1.0 Achnatherum hymenoides Indian ricegrass Paloma Native 4.0 Poa secunda Sandberg bluegrass Canbar Native 0.5 Festuca ovina Sheep fescue Covar Introduced‡ 1.0 Bouteloua gracilis Blue grama Hachita Native 1.0 Forbs Achillea millefolium var. occidentalis Common yarrow No Variety Native 0.5 Artemisia ludoviciana White sage No Variety Native 0.5 Total 21.0 †Seeding rate is for broadcast seed and presented as pounds of pure live seed per acre (lbs PLS/acre). ‡Introduced refers to species that have been ‘introduced’ from another geographic region, typically outside of North America. Also referred to as ‘exotic’ species. Interrogatory 011/1: R313-24-4; 10CFR40.Appendix A: Vegetation and Biointrusion Evaluation and Revegetation Plan Page 61 of 96 5. Provide additional documentation to support conclusions made regarding the ability of the proposed vegetation to establish at the cover percentages predicted. Also, provide additional discussion regarding the potential sustainability of the cover design and characteristics as proposed relative to changes that could occur due to the effects of natural succession and climate change during the performance period (1,000 years, and in no case less than 200 years). Response 5: Additional documentation to support conclusions made regarding the ability of the proposed vegetation to achieve predicted cover percentages will be developed following the site vegetation survey planned for June 2012. Plant cover from surrounding plant communities will be used to refine predicted cover values. In addition, further discussion will be provided regarding potential sustainability of the cover design in relation to changes that could occur during natural succession and under possible climate change scenarios. A final response to address these comments will be provided as part of a second response document to be submitted to the Division on August 15, 2012. 6. Perform and report results of an additional infiltration sensitivity analysis to address the effects of deep-rooted plants projected by the updated analysis described above. In particular, account for any potentially deep-rooted species to assess the their effects of such deep-rooted species on the characteristics of soil layers in the embankment cover system. Please provide a forecasted percentage of potential species invasions in the ET cover system. Response 6: The effect of deep rooted species on the characteristics of soil layers in the cover system and forecasted percentages of potential species invasions in the ET cover system will be addressed following the vegetation survey planned for June 2012. The list of plant species that could reasonably be expected to colonize the White Mesa site needs to be updated before this interrogatory can be addressed. If the need arises, an additional infiltration sensitivity analysis would be completed to address the effects that may occur from the establishment of deep rooted plants. Such an analysis would require identification of the projected root biomass depth profiles. A final response to address this comment will be provided as part of a second response document to be submitted to the Division on August 15, 2012. BASIS FOR INTERROGATORY: Burrowing animals have the potential to penetrate the cover system and disturb the waste tailings of a cell. The burrowing animal could disturb the cover system resulting in “channels for movement of water, vapors, roots, and other animals” EPA, Draft Technical Guidance for RCRA/CERCLA Final Covers, April 2004 [EPA 2004]). The extent of damage caused by animal burrowing depends on the animals burrowing depth ability. Mammals such as the badger and deer mouse have been reported at the site and/or nearby the site and can burrow to depths of 150–230 cm [4.9 to 7.5 ft] (Anderson and Johns 1977, Gano and States 1982, Cline, et al. 1982 and Lindzey 1976) and 50 cm [1.6 ft], respectively (Reynolds and Laundre 1988 and Reynolds and Wakkinen 1987, and Smith, et al. 1997). Moisture content and physical features of the soil can affect burrowing potential (Reichman and Smith 1990). Maximum burrowing depths for animals at or near the site should be identified and appropriate measures taken to protect the cover system, especially the radon barrier layer, from potential long-term damage/disruption by burrowing animals. Interrogatory 011/1: R313-24-4; 10CFR40.Appendix A: Vegetation and Biointrusion Evaluation and Revegetation Plan Page 62 of 96 Although Dames and Moore (1978) did not report pocket gophers and reported badgers only had possibly a minor presence, the type of vegetation and soils present surrounding the facility is typical habitat and Utah distribution maps (Utah Division of Wildlife Resources) show that the facility is within or near the edge of high quality northern pocket gopher and badger habitat. Given the 34 years since the Dames and Moore study, these species could occur now and will likely occur at some point during the next 200 – 1000 years. Their potential presence needs to be acknowledged and considered in the design. Other burrowing species that are not addressed and should be assessed include coyote and red fox. The prairie dog species that could occur in this area is Gunnison’s prairie dog. The statement regarding maximum burrowing depths for Gunnison’s prairie dog does not appear to represent current data, for example Verdolin, Lewis, and Slobodchikoff (2008), which show studies with depths over one meter. The statement that prairie dogs are unlikely to colonize the tailing cells is generally true, but does not consider all potential events that could occur over an extended period of time, such as prolonged drought, fire, or natural succession, that could affect plant cover. The documents provide one reference (Waugh et al. 2008) for the ability to achieve 40% vegetation cover for a long-term average and 30% under drought conditions. More support is needed that this cover can be sustained long-term and under drought conditions. Regional data and/or data on the current plant cover of the grassland vegetation at the White Mesa Mill should be present to support these cover percentages. The ground cover measurements by Dames and Moore 1978 (provided on page 1-125 of Reclamation Plan) are substantially less than 40%, but were collected during a drought and were likely affected by past grazing. The vegetation map and cover data presented in the Reclamation Plan Rev. 5.0 for the vegetation present at the facility are 35 years old and do not represent current conditions. In addition, some of the cells are identified as being partially reclaimed and no information is provided on reclamation methods or success that would support the claim of being able to achieve 40% average cover. Current data should be provided to support the estimates of potential cover expected to be achieved on the tailing cells. More detailed information should be provided on deep-rooted species that currently occur in the study area and that could become established on the tailing cells. There is little information provided on the composition of local plant communities. The plan does not adequately address the potential for natural succession over the 200-1000 year time frame. The use of competitive grasses may exclude sagebrush for several decades, but may not work in perpetuity. Shrub succession in seeded grasslands is a common phenomenon, and appears to be occurring on portions of the seeded grasslands surrounding the White Mesa facility, based on current aerial photographs. There should be a discussion of natural successional processes that could occur. Big sagebrush is the regional climax dominant on deep soils such as the tailing cells will provide. The eventual occurrence of some amount of big sagebrush should be identified as a possibility and the analysis should include an evaluation of the compatibility of big sagebrush root systems with the cover design, including depth of the soil and compacted layers. The highly compacted zone is likely to exclude all or most roots, even for deep rooted species. References could be added to support this. There is a lower potential for establishment of piñon and juniper. According to Dames and Moore (1978), Table 2.8-2, community types identified within the site boundary include Pinion-juniper Woodland, Big Sagebrush, and Controlled Big Sagebrush. Different published references indicate that Big Sagebrush in the western U.S. can exhibit deeper rooting depths (e.g., see Waugh, et al. 1994; Foxx, et al.1984; Klepper, et al. 1985, Reynolds 1990b). The statement in D.4.3 to Appendix D to Appendix D of the Reclamation Plan Rev. 5.0, that “… species like sagebrush, piñon pine, and Utah juniper have become dominant components of the regional flora primarily because of decades of overgrazing that has removed more palatable grasses and forbs and allowed less palatable woody species to establish and expand their range…” is an oversimplification and does not recognize that these species are the climax species over a large portion of the Intermountain area. While overgrazing has Interrogatory 011/1: R313-24-4; 10CFR40.Appendix A: Vegetation and Biointrusion Evaluation and Revegetation Plan Page 63 of 96 certainly reduced the abundance of perennial grasses and has led to shrub/tree invasion in some areas, there is no evidence that these areas were primarily grassland prior to European settlement. Table D-3 lists root densities that were used in the infiltration modeling. The values range from zero to 6.2 grams per cubic centimeter. The same values are shown graphically in Figure D-1 and again in Appendix G, Figure G-1. It seems unreasonable to have such high root densities when the soil densities are no greater than about 2 grams per cubic centimeter. Clarify whether the units in Table D-3 (g cm-3) are correct. Alternative units might be milligrams (rather than grams) of roots per cubic centimeter or centimeters of root length per cubic centimeter of soil. It appears that all of the conclusions in the analysis of the effects of climate change are based on one 23- year old study. Additional support is needed. In particular, the effects of extended droughts should be addressed in more detail. The documents mischaracterize the native status of two species. Festuca ovina is considered to be introduced and not native throughout the entire lower 48 states (NRCS 2012). Common yarrow includes both introduced and native sub-species. The seed mix should specify the yarrow subspecies that is native to southern Utah. Several statements are made that the seed mix is comprised of natives, while it is actually a mix of native and introduced species. In the Reclamation Plan Rev. 5.0, no information is provided for the Tamarisk-Salix community identified in Section 1.7.1. Based on current photography, they appear to be wetlands. It is unclear how they will be affected by reclamation activities. REFERENCES: Anderson, D. C., and Johns, D.W. 1977. “Predation by Badger on Yellow-Bellied Marmot in Colorado,” Southwestern Naturalist, Vol. 22, pp. 283–284. Cline, J.F.. 1979. Biobarriers Used in Shallow-Burial Ground Stabilization. Technical Report.. Pacific Northwest Laboratory PNL-2918. March 1, 1979. Cline, J. F., K. A. Gano, and L. E. Rogers, 1980, “Loose Rock as Biobarriers in Shallow Land Burial,” Health Physics, Vol. 39, pp. 494–504. Cline, J. F., F.G. Burton, D. A. Cataldo, W. E. Skiens, and K. A. Gano. 1982. Long-Term Biobarriers to Plant and Animal Intrusion of Uranium Tailings, DOE/UMT-0209, Pacific Northwest Laboratory, Richland, Washington. Denison Mines (USA) Corp., 2011. Reclamation Plan, White Mesa Mill, Blanding, Utah, Radioactive Materials License No. UT1900479, Revision 5.0, September 2011. EPA (U.S. Environmental Protection Agency). 2004. (Draft) Technical Guidance for RCRA/CERCLA Final Covers. U.S EPA 540-R-04-007, OSWER 9283.1-26. April 2004, 421 pp. URL: nepis.epa.gov/Exe/ZyPURL.cgi?Dockey=P10074PP.txt. Foxx, T.S., G.D. Tierney, and J.M. Willimas, 1984. Rooting Depths of Plants Relative to Biological and Environmental Factors, Los Alamos Report LA-10254-MS, November 1984. Gano, K. A. and J. B. States, 1982, Habitat Requirements and Burrowing Depths of Rodents in Relation to Shallow Waste Burial Sites, PNL-4140, Pacific Northwest Laboratory, Hanford, Washington. Interrogatory 011/1: R313-24-4; 10CFR40.Appendix A: Vegetation and Biointrusion Evaluation and Revegetation Plan Page 64 of 96 Hakonson, T.E. 1986. Evaluation of Geologic Materials to Limit Biological Intrusion into Low-Level Radioactive Waste Disposal Sites. LA-10286-MS. Los Alamos National Laboratory, Los Alamos, New Mexico. Lindzey, F. G. 1976. “Characteristics of the Natal Den of the Badger,” Northwest Science, Vol. 50, No. 3, pp. 178–180. Natural Resource Conservation Service (NRCS). 2012. Plants Database. http://plants.usda.gov/java/ Reichman, O.J., and Smith, S. C. 1990. “Burrows and Burrowing Behavior by Mammals,” pp. 197-244 in H.H. Genoways, ed., Current Mammology. Plenum Press, New York and London. 1990. Reynolds, T. D. and J. W. Laundre, 1988. “Vertical Distribution of Soil Removed by Four Species of Burrowing Rodents in Disturbed and Undisturbed Soils,” Health Physics, Vol. 54, No. 4, pp. 445–450. Reynolds, T. D. and W. L. Wakkinen, 1987. “Burrow Characteristics of Four Species of Rodents in Undisturbed Soils in Southeastern Idaho,” American Midland Naturalist, Vol. 118, pp. 245–260. Smith, E.D., Luxmoore, R.J., and Suter, G.W. 1997. “Natural Physical and Chemical Processes Compromise the Long-Term Performance of Compacted Soil Caps,” in Barrier Technologies for Environmental Management – Summary of a Workshop. National Research Council, National Academy Press, Washington, DC., pp. D-61 to D-70. Verdolin, Jennifer, Kara Lewis, and Constantine N. Slobodchikoff. 2008. Morphology of Burrow Systems: A Comparison of Gunnison’s (Cynomy gunnisoni), White-tailed (C. leucurus), black-tailed (C. ludovicianus), and Utah (C. parvidens) Prairie Dogs. The Southwestern Naturalist 53(2): 201-207. Waugh, W. J., M. K. Kastens, L. R. L. Sheader, C. H. Benson, W. H. Albright, and P. S. Mushovic. 2008. Monitoring the performance of an alternative landfill cover at the Monticello, Utah, Uranium Mill Tailings Disposal Site. Proceedings of the Waste Management 2008 Symposium. Phoenix, AZ. Interrogatory 012/1: R313-24-4; 10CFR40.Appendix A, Criterion 6(4): Report Radon Barrier Effectiveness Page 65 of 96 INTERROGATORY WHITEMESA RECPLAN REV 5.0 R313-24-4; 10CFR40 APPENDIX A, CRITERION 6(4); INT 12/1: REPORT RADON BARRIER EFFECTIVENESS REGULATORY BASIS: UAC R313-24-4 invokes the following requirement from 10CFR40, Appendix A, Criterion 6(4): Within ninety days of the completion of all testing and analysis relevant to the required verification in paragraphs (2) and (3) of 10CFR40, Appendix A, Criterion 6, the uranium mill licensee shall report to the Executive Secretary the results detailing the actions taken to verify that levels of release of radon-222 do not exceed 20 pCi/m2s when averaged over the entire pile or impoundment. The licensee shall maintain records until termination of the license documenting the source of input parameters including the results of all measurements on which they are based, the calculations and/or analytical methods used to derive values for input parameters, and the procedure used to determine compliance. These records shall be kept in a form suitable for transfer to the custodial agency at the time of transfer of the site to DOE or a State for long-term care if requested. INTERROGATORY STATEMENT: Refer to Reclamation Plan Rev. 5.0, Section 3 (Tailings Reclamation Plan) and Appendix D (Updated Tailings Cover Design Report dated Sept 2011): Please revise radon flux calculations using actual site-specific material properties data. a. Clearly demonstrate that values of material parameters: 1) Are reasonably conservative 2) Are based on site material samples, measured values, assumptions, or other origins 3) Are based upon appropriate analytical methods and sufficient number of representative samples for cover soils and tailings 4) Consider the variability and uncertainties in actual site-specific data. 5) Are consistent with anticipated construction specifications 6) Are based upon representative long-term site conditions. Response a: A site investigation to further evaluate cover borrow materials was conducted on April 19, 2012. Laboratory testing is currently in progress and will be used to develop updated cover material parameters for radon emanation modeling. Other model parameters will be updated and justification provided as necessary to address comments in this interrogatory. The results of the updated analyses will be provided as part of a second response submittal to the Division on August 15, 2012. b. Justify values of material parameters used in the radon flux calculations Interrogatory 012/1: R313-24-4; 10CFR40.Appendix A, Criterion 6(4): Report Radon Barrier Effectiveness Page 66 of 96 Response b: See Response a. c. Demonstrate that test methods and their precision, accuracy, and applicability are supported by suitable standards and procedures. Response c: See Response a. d. Justify that values chosen for radon emanation and diffusion coefficients are consistent with long- term moisture contents projected to exist within tailings and cover materials in the impoundments. Response d: The radon emanation coefficient used in the model for tailings, 0.19, was based on measured laboratory data as documented in Appendix C of Appendix D to the Reclamation Plan Rev. 5.0. This parameter will be revised to be 0.20 based on recommendations in NUREG-1620 (NRC, 2003) that states a “value of 0.20 may be estimated for tailings based on the literature, if supported by limited site-specific measurements.” The radon emanation coefficient used in the model for cover layers, 0.19, was based on measured laboratory data as documented in Appendix C of Appendix D to the Reclamation Plan Rev. 5.0. The range of measured laboratory testing values is 0.11 to 0.22. The coefficient used in the model for the cover layers will be revised to be the upper bound of the measured values (0.22). The radon diffusion coefficients can be calculated within the RADON model or input directly using measured values (NRC, 2003). Although laboratory test data was available, the tests were performed at porosities and water contents different than those estimated to represent long-term conditions in the model. Therefore the values were calculated within the RADON model. The revised radon modeling will use radon diffusion coefficients that are calculated within the model. References for Response d: U.S. Nuclear Regulatory Commission (NRC), 2003. Standard Review Plan for the Review of a Reclamation Plan for Mill Tailings Sites under Title II of the Uranium Mill Tailings Radiation Control Act of 978. NUREG-1620, Revision 1, June. e. Demonstrate that the quality assurance program used in obtaining parameter data is adequate Response e: See Response a and Response d. Interrogatory 012/1: R313-24-4; 10CFR40.Appendix A, Criterion 6(4): Report Radon Barrier Effectiveness Page 67 of 96 f. Revise the design density and porosity values of cover soils to comply with the usual compaction of 95% of Standard Proctor (D 698). Alternatively, clearly justify the basis for the lower compactions utilized in the radon flux calculations and their expected long-term stability. Response f: The cover design consists of an evapotranspiration cover. The water storage layer will be compacted to 85 percent of standard Proctor density and the lower random fill layer is estimated to be compacted to 80 percent of standard Proctor density. Use of design density and porosity values corresponding to 95 percent of standard Proctor density would be inconsistent with the cover design. g. Please revise the tailings density, porosity, and moisture values to reflect expected long-term conditions in each of the disposal units. Alternatively, demonstrate the basis for the long-term stability of the values used in the radon flux calculations. Response g: See Response a. The long-term tailings density will be revised to be the recommended default vault values of 1.6 grams/cubic centimeter as recommended by the NRC in Regulatory Guide 3.64 (NRC, 1989). Reference for Response g: U.S. Nuclear Regulatory Commission (NRC), 1989. Calculation of Radon Flux Attenuation by Earthen Uranium Mill Tailings Covers, Regulatory Guide 3.64. June. h. Please utilize one of the two accepted methods for long-term moisture estimates (D 2325 or Rawls correlation) with representative samples. Alternatively, justify the use of an acceptable alternative method. Response h: See Response a. i. Please resolve or justify the discrepancy between the 91.4 pcf “best correlation” between the Rawls and in-situ moisture data (Appendix D page C-4) and the density range of 94 to 111 pcf used in the radon flux calculations. Revise and report results of radon flux calculations, as necessary to reflect the resulting changes. Response i: See Response a. j. Please utilize a source term based on representative sampling and analysis of the sand, slime, and mixed tailings to 12-ft depths in sufficient and representative locations of each tailings area (e.g., Cells 2, 3, 4A, and 4B.). Alternatively, justify and use the average ore grade method identified in Reg Guide 3.64 for the radon flux calculations. Interrogatory 012/1: R313-24-4; 10CFR40.Appendix A, Criterion 6(4): Report Radon Barrier Effectiveness Page 68 of 96 Response j: The revised analyses will incorporate use of the average ore grade method to estimate the radium activity concentration of the tailings. k. Please justify the assumed value of zero for Ra-226 concentrations in cover soils by sampling and measurement of background Ra-226 soil concentrations and comparison of their values with corresponding representative measurements in the proposed cover soils. Alternatively, use values of Ra-226 concentrations in radon flux calculations that are supported by cell-specific measurements. Response k: Denison has established background values for Ra-226 in surface soil in the White Mesa Mill area. These background values are very low, due to the absence of uranium mineralization in the mill area. The cover soils that have been stockpiled are derived from the same geologic formations as the soils measured for background values. Therefore a Ra-226 value for cover soils of zero is appropriate in the radon flux modeling, as outlined in NRC Regulatory Guide 3.64. Reference for Response k: U.S. Nuclear Regulatory Commission (NRC), 1989. Calculation of Radon Flux Attenuation by Earthen Uranium Mill Tailings Covers, Regulatory Guide 3.64. June. l. Please utilize measured radon emanation coefficients that are representative of the sand, slime, and mixed tailings in the various tailings cell areas; emanation coefficients averaged over measurements for each tailings cell. Alternatively, use default values conservatively estimated from site-specific measurements. Response l: See Response d. m. Please utilize measured or calculated radon diffusion coefficients in radon flux calculations that represent the long-term properties of the tailings and cover soil materials. Response m: See Response d. n. Please provide written procedures for identifying and placing contaminated soils into the disposal cell(s) and substantiating characterization data and site history. Response n: Procedures for identifying and placing contaminated soils is provided in Attachment A (Plans and Technical Specifications) of the Reclamation Plan. Additional information on Interrogatory 012/1: R313-24-4; 10CFR40.Appendix A, Criterion 6(4): Report Radon Barrier Effectiveness Page 69 of 96 procedures for identifying contaminated soils will provided in the responses to Interrogatory 20/1 as part of a second response submittal to the Division on August 15, 2012. o. Provide a revised radon emanation model that incorporates lower values of initial bulk density for the erosion protection layer in the model. The bulk density value selected needs to fall within the range of bulk densities that is recommended (approximately 1.2 to 1.8 g/cm3, or about 75 to 112 pcf) in the section entitled "Soil Requirements for Sustainable Plant Growth" and listed in Table D-5 in Appendix D to the Reclamation Plan as the recommended range required for promoting sustainable plant growth. Response o: See Response a. The density of the rock mulch erosion protection layer will be revised to be based on the additional laboratory testing of potential cover soils currently being tested. The previous density of the rock mulch provided in Appendix D of the Reclamation Plan should was incorrectly listed as 124.2 pcf. It should have been listed as 107 pcf based on the historical laboratory testing results. This value was used for the updated freeze/thaw analyses. BASIS FOR INTERROGATORY: a. The material parameters used in the radon flux calculations are not shown to be reasonably conservative, and in some cases appear to be non-conservative. For example, the tailings density (1.19 g/cc) appears to correspond to only 71% of standard proctor (based on Appendix D Table 3.4-1). If tailings settle to a greater density upon cover placement, the required cover thickness is likely to increase. b. The material parameters used in the radon flux calculations appear to ignore the variabilities and uncertainties in parameter values. For example, some random-fill moistures are estimated from 15-bar capillary suction values and others from the Rawls correlation, yet no account is given for their uncertainties, equivalence, or applicability in apparently combining them for the constant value of 7.8% moisture assumed for the range of cover layers (~78% to 92% of Proctor density based on Appendix D Table 3.4-1 values). c. Supporting information was not found for the test methods, their precisions, accuracies, and applicability for the radon flux calculations. d. Information was not found to identify the numerical origin of most parameter values used in the radon flux calculations, their basis in site samples, measurements, or assumptions. e. Information was not found to link the radon emanation and diffusion coefficients used in the radon flux calculations to estimated long-term moisture contents at the site. f. Information was not found to demonstrate that sufficient and representative samples were tested to adequately determine material property values. For example, the tailings radium and emanation values appear to be based on a single sample, whose identity, origin, or composition is not identified (sand, slime, mixture? [Attachment A.1.5]). Approximately half of all “random Interrogatory 012/1: R313-24-4; 10CFR40.Appendix A, Criterion 6(4): Report Radon Barrier Effectiveness Page 70 of 96 fill” to be used as cover soil appears to have never been sampled or characterized (Appendix D Table 2-1). g. Information was not found about quality assurance applicable to the parameter data used in the radon flux calculations. h. The consistency of material parameter values with anticipated construction specifications and representation of long-term site conditions is not demonstrated. For example, the material compactions of 71% for tailings, 82% for the first random fill layer, and 71% for the upper random fill layer may increase with time due to natural settlement under the cover weight and future land usage. i. The target compaction values for two of the cover soil layers are less than the guideline compaction values. j. The tailings density, porosity, and moisture value appear un-sustainable for long-term support of the overlying cover mass. k. The deep in-situ moisture data referred to by NUREG-1620 Sec 5.1.3.1 (6) are intended for comparison with D 2325 or Rawls values, not for averaging with them. The intent is to assure that the measured D 2325 or Rawls values do not exceed the present field values. (i.e., the smaller of the 15-bar or in-situ moistures should be used). l. The chosen long-term moisture values should have a clear and traceable origin in representative samples from the site. m. The present Ra-226 concentration and radon emanation coefficient utilized for tailings in the radon flux calculations is not justified by sampling and analysis data from representative sands, slimes, and mixed tailings over the requisite depth interval and spatial distribution in the different tailings areas nor by the ore-grade method described in Regulatory guide 3.64. n. The Reclamation Plan does not demonstrate that the proposed cover soil materials are not associated with ore formations or other radium-enriched materials or that their radioactivity is essentially the same as surrounding soils as demonstrated by an appropriate procedure. Procedures such as those in the MARSSIM manual are acceptable for this demonstration. o. The single measured radon emanation coefficient of 0.19 lacks representation of sand, slime, mixed, and cell-specific materials, and in particular, any potentially different values derived from processing of alternate feed materials at the mill. p. The radon diffusion coefficients used for tailings and cover soils in the radon flux calculations lack traceability to representative, valid estimates of long-term moisture contents, densities, and porosity values. q. A written procedure was not found in the Reclamation Plan for identifying and placing in the disposal cell all contaminated soils on and adjacent to the processing site , substantiated by radiological characterization data and site history. r. ….In the referenced section of Appendix D to the Reclamation Plan, it is stated that bulk densities of emplaced cover materials will be specified in the cover design and will be controlled during Interrogatory 012/1: R313-24-4; 10CFR40.Appendix A, Criterion 6(4): Report Radon Barrier Effectiveness Page 71 of 96 cover construction to be within the sustainability range shown in Table D-5. The radon emanation modeling should therefore assume bulk density values for all cover layers that are representative of the range of recommended bulk densities. NOTE: The same comments as above also apply to Appendix D (Vegetation Evaluation for the Evapotranspiration Cover) and Appendix H (Radon Emanation Modeling for the Evapotranspiration Cover) of the Infiltration and Contaminant Transport Modeling (ICTM) Report. REFERENCES: NRC 2000. NUREG-1575 Rev.1, Multi-Agency Radiation Survey and Site Investigation Manual (MARSSIM), August 2000. NRC 2003. Standard Review Plan for the Review of a Reclamation Plan for Mill Tailings Sites under Title II of the Uranium Mill Tailings Radiation Control Act of 1978. Washington DC, June 2003. Interrogatory 013/1: R313-24-4; 10CFR40.Appendix A, Criterion 6(6): Concentrations of Radionuclides Other Than Radium in Soil Page 72 of 96 INTERROGATORY WHITEMESA RECPLAN REV 5.0 R313-24-4; 10CFR40, APPENDIX A, CRITERION 6(6); INT 13/1: CONCENTRATIONS OF RADIONUCLIDES OTHER THAN RADIUM IN SOIL REGULATORY BASIS: UAC R313-24-4 invokes the following requirement from 10CFR40, Appendix A, Criterion 6(6): The design requirements in this criterion for longevity and control of radon releases apply to any portion of a licensed and/or disposal site unless such portion contains a concentration of radium in land, averaged over areas of 100 square meters, which, as a result of byproduct material, does not exceed the background level by more than: (i) 5 picocuries per gram (pCi/g) of radium-226, or, in the case of thorium byproduct material, radium-228, averaged over the first 15 centimeters (cm) below the surface, and (ii) 15 pCi/g of radium-226, or, in the case of thorium byproduct material, radium-228, averaged over 15-cm thick layers more than 15 cm below the surface. Byproduct material containing concentrations of radionuclides other than radium in soil, and surface activity on remaining structures, must not result in a total effective dose equivalent (TEDE) exceeding the dose from cleanup of radium contaminated soil to the above standard (benchmark dose), and must be at levels which are as low as is reasonably achievable. If more than one residual radionuclide is present in the same 100-square-meter area, the sum of the ratios for each radionuclide of concentration present to the concentration limit will not exceed "1" (unity). A calculation of the potential peak annual TEDE within 1000 years to the average member of the critical group that would result from applying the radium standard (not including radon) on the site must be submitted for approval. The use of decommissioning plans with benchmark doses which exceed 100 mrem/yr, before application of ALARA, requires the approval of the Executive Secretary after consideration of the recommendation of the staff of the Executive Secretary. This requirement for dose criteria does not apply to sites that have decommissioning plans for soil and structures approved before June 11, 1999. Relevant NRC Guidance Background Radiological Characteristics RG 3.8, Section 2.10: Regional radiological data should be reported, including both natural background radiation levels and results of measurements of concentrations of radioactive materials occurring in important biota, in soil and rocks, in air, and in regional surface and local ground waters. These data, whether determined during the applicant's preoperational surveillance program or obtained from other sources, should be referenced. INTERROGATORY STATEMENT: 1. Please propose appropriate soil background values (for different geological areas as needed) for Ra-226, U-nat, Th-230, and/or Th-232, as appropriate, with supporting data. Response 1: The responses to this interrogatory will be provided as part of a second response document to be submitted to the Division on August 15, 2012. 2. Please indicate whether elevated levels of uranium or thorium are expected to remain in the soil after the Ra-226 criteria have been met, and if so, describe your use of the radium benchmark dose approach (Appendix H of NUREG-1620) for developing decommissioning criteria for these radionuclides. Interrogatory 013/1: R313-24-4; 10CFR40.Appendix A, Criterion 6(6): Concentrations of Radionuclides Other Than Radium in Soil Page 73 of 96 Response 2: See Response 1. 3. Please provide a description of the instruments and procedures that will be used for soil background analyses, radium-gamma correlations, and verification data along with information about the sensitivity of the procedures. Response 3: See Response 1. 4. Please provide final verification (status survey) procedures to demonstrate compliance with the soil and structure cleanup standards. The procedures should specify instruments, calibrations, and testing, and the verification soil sampling density should take into consideration detection limits of samples analyses, the extent of expected contamination, and limits to the gamma survey. The gamma guideline value should be appropriately chosen, and the verification soil radium- gamma correlation should be provided along with the number of verification grids that had additional removal because of excessive Ra-226 values. The plan should provide for adequate data collection beyond the excavation boundary. Surface activity measurements should demonstrate acceptable compliance with surface dose standards for any structures to remain onsite. Response 4: See Response 1. BASIS FOR INTERROGATORY: 1. Soil background values with supporting data were not found in the Reclamation Plan for Ra-226, U-nat, Th-230, and/or Th-232. 2. No assessment of potentially elevated levels of uranium or thorium was found in the Reclamation Plan for the post-Ra-226-reclamation site condition. This assessment should be included with the requisite benchmark dose approach if elevated uranium or thorium may remain. 3. The Reclamation Plan does not describe the instruments and procedures that will be used for soil background analyses, radium-gamma correlations, and verification data, nor information about the sensitivity of the procedures. Helpful information may be found in the MARSSIM Manual. 4. The requisite procedures were not found for final verification surveys of the site to demonstrate compliance with the soil and structure cleanup standards. REFERENCES: NRC 1982. U.S. Nuclear Regulatory Commission, “Regulatory Guide 3.8; Preparation of Environmental Reports for Uranium Mills”, Washington DC, October 1982. Interrogatory 013/1: R313-24-4; 10CFR40.Appendix A, Criterion 6(6): Concentrations of Radionuclides Other Than Radium in Soil Page 74 of 96 NRC 2003. Standard Review Plan for the Review of a Reclamation Plan for Mill Tailings Sites under Title II of the Uranium Mill Tailings Radiation Control Act of 1978. Washington DC, June 2003. Interrogatory 014/1: R313-24-4; 10CFR40.Appendix A: Cover Test Section and Test Pad Monitoring Programs Page 75 of 96 INTERROGATORY WHITE MESA RECPLAN REV 5.0 R313-24-4; 10CFR40 APPENDIX A; INT 14/1: COVER TEST SECTION AND TEST PAD MONITORING PROGRAMS REGULATORY BASIS: UAC R313-24-4 invokes the following requirement from 10CFR40, Appendix A, Criterion 1:-The general goal or broad objective in siting and design decisions is permanent isolation of tailings and associated contaminants by minimizing disturbance and dispersion by natural forces, and to do so without ongoing maintenance. For practical reasons, specific siting decisions and design standards must involve finite times (e.g., the longevity design standard in Criterion 6). The following site features which will contribute to such a goal or objective must be considered in selecting among alternative tailings disposal sites or judging the adequacy of existing tailings sites: • Remoteness from populated areas; • Hydrologic and other natural conditions as they contribute to continued immobilization and isolation of contaminants from ground-water sources; and • Potential for minimizing erosion, disturbance, and dispersion by natural forces over the long term. • The site selection process must be an optimization to the maximum extent reasonably achievable in terms of these features. In the selection of disposal sites, primary emphasis must be given to isolation of tailings or wastes, a matter having long-term impacts, as opposed to consideration only of short-term convenience or benefits, such as minimization of transportation or land acquisition costs. While isolation of tailings will be a function of both site and engineering design, overriding consideration must be given to siting features given the long-term nature of the tailings hazards. Tailings should be disposed of in a manner that no active maintenance is required to preserve conditions of the site. UAC R313-24-4 invokes the following requirement from 10CFR40, Appendix A, Criterion 6(1): In disposing of waste byproduct material, licensees shall place an earthen cover (or approved alternative) over tailings or wastes at the end of milling operations and shall close the waste disposal area in accordance with a design which provides reasonable assurance of control of radiological hazards to (i) be effective for 1,000 years, to the extent reasonably achievable, and, in any case, for at least 200 years, and (ii) limit releases of radon-222 from uranium byproduct materials, and radon-220 from thorium byproduct materials, to the atmosphere so as not to exceed an average release rate of 20 picocuries per square meter per second (pCi/m2s) to the extent practicable throughout the effective design life determined pursuant to (1)(i) of this Criterion. In computing required tailings cover thicknesses, moisture in soils in excess of amounts found normally in similar soils in similar circumstances may not be considered. Direct gamma exposure from the tailings or wastes should be reduced to background levels. The effects of any thin synthetic layer may not be taken into account in determining the calculated radon exhalation level. If non-soil materials are proposed as cover materials, it must be demonstrated that these materials will not crack or degrade by differential settlement, weathering, or other mechanism, over long- term intervals. Interrogatory 014/1: R313-24-4; 10CFR40.Appendix A: Cover Test Section and Test Pad Monitoring Programs Page 76 of 96 INTERROGATORY STATEMENT: Refer to Section 8.0 of Attachment A (Technical Specifications and Attachment B (Construction Quality Assurance/Quality Control Plan) to the Reclamation Plan and Section 5.0 of Appendix D (Updated Tailings Cover Design Report) of the Reclamation Plan Rev. 5.0 (DUSA 2011a): 1. Please provide plans and specifications for constructing and performing monitoring and testing of a cover system section representative of the proposed ET cover system for verifying the hydraulic performance characteristics of the cover system. Demonstrate that the proposed test pad/plot will be sufficient in size to eliminate or minimize lateral boundary effects. Describe objectives and criteria for construction and testing of the test pad cover materials /layers. Include information in the CQAQC Plan regarding procedures for sampling and testing of the cover system section specifically pertinent to demonstrating the (short-term and long-term) performance of the ET cell cover design. Address, as part of the testing program, testing of parameters specifically recommended by Benson et al. 2011; Waugh et al. 2008; the National Research Council 2007; Albright et al. 2007; others) including, but not necessarily limited to: a. Monitoring of in-situ soil water tension and volumetric water content as a function of time (e.g., using heat dissipation probes and TDR [time domain reflectometry]); b. Monitoring of in-situ flux rates as a function of time (e.g., through use of one or more pan lysimeters as recommended by Benson et al. 2011 and Dwyer et al. 2007) on both north and south-facing slopes as required); c. Physical sampling and laboratory testing for index properties, including Plasticity Index and saturated hydraulic conductivity, and other pertinent parameters including compaction properties, organic matter and CaCO3 content, and measurement of soil edaphic properties (properties that influence vegetation establishment and growth – e.g., see Waugh et al. 2008); d. Other testing if needed for determining changes in water in storage and soil water characteristic curves (SWCCs, e.g., according to ASTM D6836 [ASTM 2008]) and monitoring for potential changes in SWCCs through time; e. Conducting soil vegetation surveys (as recommended by Benson et al. 2011); and f. Monitoring of relevant climatological parameters (precipitation and evaporation rates, temperature, barometric pressure, snow amounts, wind speed and wind direction, etc...), including continuous monitoring over several years necessary to understand how covers are influenced by fluctuations in climate and other environmental factors (Waugh et al. 2008) such as an extraordinarily wet year or consecutive wet years. Response 1: Denison proposes to install a performance monitoring section to evaluate the performance of the final tailings cover system. The performance monitoring section will be built into the final tailings cover system and will be monitored concurrently with the operation of the final cover system. The proposed conceptual design and quality assurance/quality control (QA/QC) of the performance monitoring section is briefly described below. Detailed plans, specifications, and a QA/QC plan for construction and sampling will be prepared and submitted following approval of the proposed performance monitoring by the Division. Interrogatory 014/1: R313-24-4; 10CFR40.Appendix A: Cover Test Section and Test Pad Monitoring Programs Page 77 of 96 Conceptual Design of the Performance Monitoring Section Design Basis The conceptual design of the performance monitoring section will be adopted from the installation instructions for the test sections used in the Alternative Cover Assessment Program (ACAP) (Benson et al., 1999) and incorporate the performance monitoring recommendations provided in NUREG/CR-7028 (Benson et al., 2011) and site-specific recommendations provided by Dr. Craig H. Benson (Craig H. Benson, personal communication, May 8, 2012). The performance monitoring area will be constructed as a large ACAP-style drainage lysimeter that provides direct measurement of all components of the water balance (esp. percolation), except evapotranspiration. In-situ soil water content and temperature measurements of the cover soils will be taken within the performance monitoring area and a weather station will be installed adjacent to the performance monitoring area. Specifications for the performance monitoring area will be patterned after the ACAP test section installation instructions (Benson et al., 1999) (see Attachment D) with the following exceptions: • Soil water tension sensors will not be installed. Experience in ACAP showed that data collected from the soil water tension sensors had little value for evaluating cover performance. Additionally, soil water tension sensors can be challenging to calibrate and operate. Soil water content sensors (water content reflectometers) and temperature sensors will be installed. Although soil water content and temperature are not direct measures of cover performance, data from these sensors are useful information for interpreting cover performance data, especially when performance metrics are not satisfied. • The water content reflectometers will be installed in two nests rather than the three nests used in ACAP. Experience at the ACAP test sites has shown little spatial variability within the test sections, such that data from the three sets of nested sensors was very similar (Craig H. Benson, personal communication, 8 May 2011). Two sensor nests will be used to provide a redundant set of water content measurements, as recommended in NUREG/CR-7028 (Benson et al., 2011). • A sediment basin will not be installed for the surface run-off drainage. Experience with the ACAP test sections showed that sediment control is not needed (Craig H. Benson, personal communication, May 8, 2012). Location The performance monitoring section is proposed to be located in the northeast corner of Cell 2 within the area that has a 0.5% slope. This location will have the flattest slope on the cover system with the lowest potential run-off and represent the lower bound for performance of the final cover system (Benson et al., 2011). Size The size of the performance monitoring section will be 10 meters (perpendicular to the slope gradient) by 20 meters (in the direction of the slope gradient), which is the same size as an ACAP-style lysimeter. This section size is greater than 3 times the typical Interrogatory 014/1: R313-24-4; 10CFR40.Appendix A: Cover Test Section and Test Pad Monitoring Programs Page 78 of 96 spatial correlation length of the cover soils, thus providing a spatially averaged percolation rate with little variability (Benson, 1991; Benson et al., 2011). A performance monitoring area of this size also minimizes lateral boundary effects. This is the same area that was used for the ACAP test cells and was found to be acceptable for all the ACAP sites evaluated (Craig H. Benson, personal communication, May 8, 2012). Components of Lysimeter The lysimeter will include the following components: • Geomembrane-lined (LLDPE) base and vertical side slopes. • Geocomposite drainage layer draining percolation to a collection sump above the LLDPE base. • Geosynthetic root barrier layer above the radon attenuation and grading layer (lower layer of cover system). • Earthen surface run-off collection berm that collects surface run-off, diverts surface run-on, and channels run-off to a single collection point. • Separate PVC drainage pipes for percolation and surface run-off that drain to separate measurement stations. Instrumentation Instrumentation will include water content reflectometers and temperature sensors to measure water content and temperature of the cover soils in the lysimeter, tipping buckets to measure percolation and surface runoff, and a weather station located immediately outside of the lysimeter area. Two nests of water content reflectometers and temperature sensors will be installed: one nest at the centerline of the upslope third of the lysimeter and one nest at the centerline of the downslope third of the lysimeter. Each nest will consist of six water content reflectometers and temperature sensors: two placed in the radon attenuation and grading layer, two placed in the radon attenuation layer, and two placed in the water storage layer. Continuous monitoring of climatic data to understand how the cover is influenced by fluctuations in climate and other environmental factors goes beyond performance monitoring of the cover system. Using a dedicated weather station will reduce the effort and inconsistencies that can be associated with integrating data from a site-wide weather station and data collected from the lysimeter. The lysimeter weather station will include a precipitation gauge, shielded temperature and humidity probe, pyranometer (solar radiation sensor), and wind sentry (wind speed and direction). All measurement devices will be wired to a single datalogger that can be accessed remotely (e.g., via cellular). This will facilitate accurate and convenient integration of the monitoring data and provide ready access for periodic quality control checks. Conceptual Quality Assurance and Quality Control Plan for Performance Monitoring Section The Construction Quality Assurance and Quality Control (CQA/CQC) plan for reclamation will be revised to include provisions to test the construction of the performance monitoring section and procedures for sampling and testing the cover soils Interrogatory 014/1: R313-24-4; 10CFR40.Appendix A: Cover Test Section and Test Pad Monitoring Programs Page 79 of 96 within the performance monitoring section. The QA/QC plan for the performance monitoring section will include the following components: • Preparing and compacting the foundation • Testing the geomembrane integrity, including testing of welds and boots • Leak testing the lysimeter, drainage pipes, and collection basins • Programming, calibrating and testing instrumentation • Testing of cover soil properties • Vegetation survey The QA/QC plan for testing of cover soil properties for the performance monitoring section will include measurement of index properties, organic matter, saturated hydraulic conductivity, and soil water content characteristic curves (SWCCs). These tests will be conducted during construction to verify that the cover soils in the performance monitoring section are representative of the as-built cover soils in other areas of the final cover system. Denison is not proposing to test the soils throughout the operational period to determine changes in properties with time. Monitoring the change in soil properties with time, such as that done for the NUREG/CR-7028 (Benson et al., 2011) is useful as a research endeavor to understand the evolution of the cover system, but is un-necessary as a direct performance-based metric for the cover system. Performance of the cover system will be evaluated by percolation from the cover to the percolation rate predicted for the ground water contaminant transport assessment. The QA/QC plan for vegetation surveys will be based on the recommendations in NUREG/CR-7028 (Benson et al., 2011). This includes annual inspections of the distribution of plant species, percent plant coverage, and leaf area index for the first five years of operation. The vegetation surveys will be conducted for the final cover over the tailings cells as well as for the performance monitoring section. Data from the performance monitoring section and the final cover will be compared to ensure that the vegetation on the monitoring section is representative of the vegetation on the final cover. References for Response 1: Benson, C.H., 1991. Predicting Excursions beyond Regulatory Thresholds of Hydraulic Conductivity Using Quality control Measurements, Proc. of the First Canadian Conference on Environmental Geotechnics, Montreal, May 14-17, 447-454. Benson, C.H., W.H. Albright, D.O. Fratta, J.M. Tinjum, E. Kucukkirca, S.H. Lee, J. Scalia, P.D. Schlicht, and X. Wang, 2011. Engineered Covers for Waste Containment: Changes in Engineering Properties and Implications for Long-Term Performance Assessment, Volume 1 and 2, NUREG/CR-7028, Report Prepared for the U.S. Nuclear Regulatory Commission, December. 2. Provide additional information and plans and specifications for constructing and testing a cover system “test pad/test plot” prior to construction of the proposed ET cover system over the consolidated, dewatered tailings. Demonstrate that the proposed test pad/plot will be sufficient in size to eliminate or minimize lateral boundary effects. Describe objectives and criteria for construction and testing of the test pad cover materials /layers including but not limited to: Interrogatory 014/1: R313-24-4; 10CFR40.Appendix A: Cover Test Section and Test Pad Monitoring Programs Page 80 of 96 a. Acquisition of data of the types described in Item 1. above; b. Determination of an acceptable zone (AZ) for soil textures in soils used for constructing the final cover system (e.g., Williams et al. 2010); c. Determination of most effective means of “bonding” individual soil cover soil layers (e.g., Dwyer et al. 2007); and d. Determination of appropriate lift thickness/placement and compaction equipment combinations (e.g., Dwyer et al. 2007). Response 2: Denison is not proposing to construct a cover system test pad prior to construction of the final cover system. Rather, Denison is planning to construct a performance monitoring section to evaluate the performance of the final tailings cover system. Denison’s recommendations for cover performance monitoring are outlined in Response 1. In addition, Denison has completed extensive modeling of the cover system to demonstrate that the cover will perform effectively for a variety of climatic and vegetative scenarios. As discussed in responses to the Revised Infiltration and Contaminant Transport Modeling Report (ICTM) Interrogatories – Round 1 (DRC, 2012) being submitted to the Division concurrently with this response document, Denison is in the process of refining the modeling to incorporate the results of supplementary laboratory testing being conducted on the borrow soils for the cover. The refined modeling and additional sensitivity analyses are being conducted to address the Revised ICTM Interrogatories. The results of the updated modeling will be provided as part of a second response document to the Revised ICTM Interrogatories. Denison also believes that a cover system test pad is unnecessary given the wealth of data collected at by ACAP at the Monticello Uranium Mill Tailings Disposal Facility near Monticello, Utah. The Monticello site is approximately 35 kilometers northeast from the White Mesa site. The earthen component of the Monticello cover, which is monitored by ACAP, is analogous to the cover to be employed at White Mesa. Thus, the data from Monticello provide an ideal analog for the performance expected at White Mesa. The Monticello cover has been monitored continuously for nearly 12 years. During the monitoring period from 12 August 2000 through 27 March 2012, the average annual percolation rate at Monticello was 0.7 mm/yr and the average annual precipitation was 368 mm. The peak annual percolation rate was 3.8 mm/yr, and was received during the second wettest year of the monitoring period (2005, 520 mm precipitation). During the wettest year of the monitoring period (2010, 559 mm precipitation), the annual percolation rate was 1.9 mm. This was the wettest year on record at Monticello (data from Craig H. Benson, personal communication, 24 May 2012). These percolation rates are within the range of rates and lower than maximum predicted rate for the infiltration modeling for White Mesa. The profile of the Monticello cover is shown in Figure 1. The profile of the White Mesa cover was provided on Drawing TRC-8 of the Reclamation Plan and in Figure 1-1 of Appendix D of the Reclamation Plan. A biointrusion layer embedded in the cover (cobbles embedded in the fine-textured cover soil) and a sand drainage layer (at the base of the cover) are the only additional features in the earthen component of the Monticello cover that are significantly different from the cover proposed for White Mesa. The biointrusion layer reduces water storage capacity, which potentially may increase Interrogatory 0 p co m b th m F B C ef tr b p u la B 14/1: R313-24-4; 10 ercolation a over at Mon may decreas iointrusion l hese differen marginal diffe igure 1. Mo Bonding Betw Concern abo ffectiveness ransmit less etween vert articularly im nsaturated c arger pores Benson, pers 0CFR40.Appendix A t Monticello nticello also se percolatio ayer and s nces betwee erences in hy onticello Ev ween Soil Lif out lift bon s of compact water latera tically orient mportant for conditions fo and spaces sonal commu A: Cover Test Section relative to W acts as a c on at Montic and drainag en the covers ydrologic pe vapotranspi fts nding is ba ted clay line ally between ted defects r saturated ound in a w s such as in unication, 24 n and Test Pad Mon White Mesa capillary bre cello relative ge layer at s at White M erformance. iration Cove ased on pr ers. Lifts tha n the lifts, a in adjacent conditions ( water balance nterlift zone 4 May 2012) nitoring Programs a. The sand eak, which e e to White Monticello Mesa and Mo er Profile (f ior studies at are caref and have low lifts (Benso (i.e., for a li e cover. Un s are not h ). d drainage la enhances w Mesa. Thu are offsettin onticello sho rom Waugh on factors fully bonded wer likelihoo on et al. 199 iner), but is nder unsatu hydraulically Page ayer beneat ater storage us, effects o ng. Accord ould result in h et. al, 2009 s controlling are assum od of connec 94). This ca not relevan urated condit active (Cra e 81 of 96 th the e and of the ingly, n only 9) g the med to ctivity an be nt for tions, aig H. Interrogatory 014/1: R313-24-4; 10CFR40.Appendix A: Cover Test Section and Test Pad Monitoring Programs Page 82 of 96 Field experience over the past two decades has also shown that complete bonding of lifts is nearly impossible (Craig H. Benson, personal communication, 24 May 2012). In nearly all cases, lift interfaces can be identified and lifts can be separated even if a high level of effort is applied to promote lift bonding. The pragmatic approach is to recognize that interlift zones exist and to use construction methods that render interlift zones as tortuous as practical. This is most effectively done by leaving a rough upper surface on the underlying lift prior to placement of the following lift (e.g., the impressions associated with a compactor foot or the tracks on a dozer are effective in creating this rough surface). Processes that promote a smooth surface, such as smooth drum compaction and smooth blading of the surface, result in a much more transmissive interlift zone and should be avoided (Craig H. Benson, personal communication, 24 May 2012). At White Mesa, a rough surface will be maintained on the surface of all but the uppermost lift to ensure that interlift zone is as non-transmissive as practical. Lift Thickness and Compactors Soil layers used for water storage in a water balance cover must have a pore space that retains water and provide a favorable environment for roots. These constraints require that the soil not be cover compacted, which is most effectively accomplished by using relatively thick lifts of soil and machinery with lower ground pressure (e.g., dozer tracks instead of a soil compactor). Lifts that are 18 inches thick and placed with a dozer can normally be deployed with a relative compaction between 80-90% of standard Proctor (i.e., a suitable density for root growth) (Albright et al. 2010). Prior to construction at White Mesa, test strips will be constructed where the lift thickness is varied and machinery is varied. Lift thicknesses and placement machinery that promote uniform compaction of the soil without over compaction will be identified. References for Response 2: Albright, W., Benson, C., and Waugh, W., 2010. Water Balance Covers for Waste Containment: Principles and Practice, ASCE Press, Reston, VA, 158 p. Benson, C. and Daniel, D., 1994. Minimum Thickness of Compacted Soil Liners: II- Analysis and Case Histories, J. Geotech. Eng., 120(1), 153-172. Utah Department of Environmental Quality, Division of Radiation Control (DRC), 2012. Denison Mines (USA) Corp’s White Mesa Reclamation Plan, Rev. 5.0; Interrogatories – Round 1. March. Waugh, W.J., C.H. Benson, W.H. Albright, 2009. Sustainable Covers for Uranium Mill Tailings, USA: Alternative Design, Performance, and Renovation, Proceedings of the 12th International Conference on Environmental Remediation and Radioactive Waste Management, ICEM2009-16369, October 11-15. BASIS FOR INTERROGATORY: The need for constructing and monitoring a cover test section representative of the proposed ET cover system, with supporting basis and rationale for building and monitoring such a test cover section, was Interrogatory 014/1: R313-24-4; 10CFR40.Appendix A: Cover Test Section and Test Pad Monitoring Programs Page 83 of 96 previously addressed in a Round 1A Interrogatory submitted to DUSA on Revision 4.0 of the Reclamation Plan in October 2010. DUSA’s response (DUSA 2011b) to that interrogatory indicated the following: “Denison is not proposing a test pad for demonstrating short- and long-term performance of the alternative tailings cell cover system. Rather, Denison has completed extensive modeling of the cover system for demonstrating that the cover will perform effectively for a variety of climatic and vegetative scenarios. It may be possible to extend a portion of the cover system beyond the edge of the first tailings cell such that the hydraulic conditions within the cover system could be evaluated through time (in a test pad like setting) without causing deleterious effects to the cover above the tailings. This "test pad" would be further evaluated after approval of the cover design”; and “Denison is proposing monitoring in situ performance of the alternative tailings cell cover system to include monitoring hydraulic conditions at nested intervals within the soil profile at three locations within the first tailings cell that is reclaimed. The depth intervals that are evaluated would depend on the final design specifications of the approved alternative cover system, but would likely represent data collected from three depths. The first depth interval would be located immediately below the soil-gravel admixture (0.6 feet), the second depth interval would be located near the midpoint of the maximum rooting depth (1.5 feet), and the third depth interval would be located at or slightly below the maximum rooting depth (3.8 feet) but above the proposed upper compacted layer; “The pertinent hydraulic properties to be monitored would include soil water tension and volumetric water content. Soil water tension would be measured with a heat dissipation probe, while volumetric water content would be measured with a time domain reflectometry (TDR) probe. The use of these monitoring methods is consistent with what was used to monitor conditions as part of the Alternative Cover Assessment Program (ACAP). Changes in water content through time can be used to assess changes in soil water storage through time. Measurements of volumetric water content and soil water tension can be related to the soil water retention and hydraulic conductivity curves to estimate a water flux rate and cover performance through time”…; and “Climatological parameters are currently being measured at the site and include precipitation, wind speed, and wind direction. In addition, air temperature and barometric pressures are measured monthly for environmental air station calibrations. Based on this information in addition to supplemental climate data from the nearest weather station (Blanding, Utah station 420738), the daily amount of evapotranspiration can be computed.” Although the response provided by DUSA to the Round 1A Interrogatory includes a proposal to monitor the performance of the cover, additional details, including plans and construction specifications for constructing a representative cover section, and detailed sampling and testing procedures and associated quality assurance and quality control methods need to be provided that demonstrate that the test section and monitoring/testing program: (1) is consistent with applicable current published guidance for such programs: (2) is fully integrated with, and compatible with, the essential elements of the currently proposed ET Cover design; (2) that data acquired from the monitoring/testing program will allow the short-term and longer-term performance predictions made with regard to the proposed cover system to be validated. Applicable recent published guidance documents include NUREG/CR-7028 (Benson et al. 2011), a peer- reviewed report published for the NRC in December 2011, which reports the findings from investigations of several earthen and soil/geosynthetic cover systems to assess changes in properties of cover materials in those cover systems 5 to 10 years following their construction. A key conclusion of the report is that findings from these investigations demonstrate that changes in the engineering properties of cover soils generally occur while in service (and that long-term engineering properties should be used as input to models employed for long-term performance assessments). The report indicates that changes in hydraulic properties occurred in all cover soils evaluated due to the formation of soil structure, regardless of Interrogatory 014/1: R313-24-4; 10CFR40.Appendix A: Cover Test Section and Test Pad Monitoring Programs Page 84 of 96 climate, cover design, or service life. The report includes the following conclusions and recommendations: • Because cover systems change over time, they should be monitored to ensure that they are functioning as intended. Monitoring using pan lysimeters combined with secondary measurements collected for interpretive purposes (water content, temperature, vegetation surveys, etc.) is recommended; and • At a minimum, at least one pan lysimeter having a minimum dimension of 10 m should be installed for performance monitoring. If only one lysimeter is installed, the location should be selected to represent the most unfavorable condition at the site. Additional relevant guidance documents include Waugh et al. 2008, Albright et al. 2007; Benson et al. 2007; and the National Research Council 2007, and Dwyer et al. 2007, which indicate that characteristics of the proposed alternative cover will inevitably change in the long term in response to climate, pedogenesis, and ecological succession. Monitoring the proposed alternative cover system or monitoring of a test cover section simulating the cover system components and geometry) to assess the long-term performance of the alternative cover is needed to verify the characteristics and infiltration performance of the constructed cover system as well as to gain confidence in understanding long-term changes that may occur in the physical/hydraulic properties of the alternative cover system over time following its construction. Additionally, a cover system test pad/test plot capable of assisting in confirming the performance of the proposed alternative cover system should be constructed and monitored. The proposed alternative cover design incorporates more loosely compacted soil layers. Dwyer et al. 2007, for example, describes results of recent research and field investigations of arid climate closure covers conducted by Los Alamos National Laboratory. As discussed in that report, lift thickness should be maximized for placement and compaction of a soil cover. During cover placement, it is crucial that each lift be bonded to the previous lift to cut down on the creation of interlift passageways (cracks) for the water to travel along as it passes from an overlying lift to a lower one. Test pads prior to cover material placement may prove beneficial in determining appropriate lift thickness/placement and compaction equipment combinations. A full-scale cover system test pad/test plot can provide information that can lead to additional performance criteria for the cover design process. Quantification of soil properties, soil placement conditions and agronomic characteristics used in the test pad could, for example, help refine selection criteria for selection of onsite soils for use in final cover construction, including, further definition of soils that would result in a texture within a defined Acceptable Zone (AZ). The determination of the AZ for soil texture may be based on the field test pad demonstration, hydraulic property testing, and percolation modeling of the successful test plot soils. REFERENCES: Albright, W.H., Waugh, W.J., and Benson, C.H. 2007. “Alternative Covers: Enhanced Soil Water Storage and Evapotranspiration in the Source Zone.” Enhancements to Natural Attenuation: Selected Case Studies, Early, T.O. (ed), pp 9-17. Prepared for U.S. Dept. of Energy by Washington Savannah River Company, WSRC-STI-2007-00250. URL: http://www.dri.edu/images/stories/research/programs/acap/acap-publications/10.pdf. Interrogatory 014/1: R313-24-4; 10CFR40.Appendix A: Cover Test Section and Test Pad Monitoring Programs Page 85 of 96 Benson, C.H., Sawangsuriya, A., Trzebiatowski, B., and Albright, W.H. 2007. “Postconstruction Changes in the Hydraulic Properties of Water Balance Cover Soils”, Journal of Geotechnical and Geoenvironmental Engineering, 133:4, pp. 349-359. Benson, C.H. W.H. Albright, W.H., Fratta, D.O.,Tinjum, J.M., Kucukkirca, E., Lee, S.H., J. Scalia, J., Schlicht, P.D., and Wang, X. 2011. Engineered Covers for Waste Containment: Changes in Engineering Properties and Implications for Long-Term Performance Assessment(in 4 volumes). NUREG/CR-7028, Prepared for the U.S. Nuclear Regulatory Commission, Washington, D.C., December 2011. Denison Mines (USA) Corp. 2011a. Reclamation Plan, White Mesa Mill, Blanding, Utah, Radioactive Materials License No. UT1900479, Revision 5.0, September 2011. Denison Mines (USA) Corp. 2011b. Responses to Supplemental Interrogatories – Round 1A for Reclamation Plan, Revision 4.0, November 2009. December 28, 2011. Dwyer, S.F., Rager, R.E., and Hopkins, J. 2007. Cover System Design Guidance and Requirements Document. LA-UR-06-4715. EP2006-0667. Los Alamos National Laboratory. April 2007. URL: http://www.lanl.gov/environment/cleanup/req_docs.shtml National Research Council 2007. Assessment of the Performance of Engineered Waste Containment Barriers. Board of Earth Sciences and Resources. The National Academies Press, Washington, D.C., 2007, 134 pp. Waugh, W. J., M. K. Kastens, L. R. L. Sheader, C. H. Benson, W. H. Albright, and P. S. Mushovic. 2008. Monitoring the performance of an alternative landfill cover at the Monticello, Utah, Uranium Mill Tailings Disposal Site. Proceedings of the Waste Management 2008 Symposium. Phoenix, AZ. Williams, L.O., Zornberg, J.G., Dwyer, S.F., Hoyt, D.L., and Hargreaves, G.A. 2010. “Design Rationale for Construction and Monitoring of Unsaturated Soil Covers at the Rocky Mountain Arsenal. 6th International Congress on Environmental Geotechnics, New Delhi, India. URL: http://www.ce.utexas.edu/prof/zornberg/pdfs/CP/Williams_Zornberg_Dwyer_Hoyt_Hargreaves_2010.pdf Interrogatory 015/1: R313-24-4; 10CFR40.Appendix A, Criterion 9: Financial Surety Arrangements Page 86 of 96 INTERROGATORY WHITEMESA RECPLAN REV 5.0 R313-24-4; 10CFR40, APPENDIX A, CRITERION 9; INT 15/1: FINANCIAL SURETY ARRANGEMENTS REGULATORY BASIS: UAC R313-24-4 invokes the following requirement from 10CFR40, Appendix A, Criterion 9: Financial surety arrangements must be established by each mill operator prior to the commencement of operations to assure that sufficient funds will be available to carry out the decontamination and decommissioning of the mill and site and for the reclamation of any tailings or waste disposal areas. The amount of funds to be ensured by such surety arrangements must be based on Executive Secretary-approved cost estimates in a Executive Secretary-approved plan for (1) decontamination and decommissioning of mill buildings and the milling site to levels which allow unrestricted use of these areas upon decommissioning, and (2) the reclamation of tailings and/or waste areas in accordance with technical criteria delineated in Section I of this Appendix. The licensee shall submit this plan in conjunction with an environmental report that addresses the expected environmental impacts of the milling operation, decommissioning and tailings reclamation, and evaluates alternatives for mitigating these impacts. The surety must also cover the payment of the charge for long-term surveillance and control required by Criterion 10. In establishing specific surety arrangements, the licensee's cost estimates must take into account total costs that would be incurred if an independent contractor were hired to perform the decommissioning and reclamation work. In order to avoid unnecessary duplication and expense, the Executive Secretary may accept financial sureties that have been consolidated with financial or surety arrangements established to meet requirements of other Federal or state agencies and/or local governing bodies for such decommissioning, decontamination, reclamation, and long-term site surveillance and control, provided such arrangements are considered adequate to satisfy these requirements and that the portion of the surety which covers the decommissioning and reclamation of the mill, mill tailings site and associated areas, and the long-term funding charge is clearly identified and committed for use in accomplishing these activities. The licensee's surety mechanism will be reviewed annually by the Executive Secretary to assure, that sufficient funds would be available for completion of the Reclamation Plan if the work had to be performed by an independent contractor. The amount of surety liability should be adjusted to recognize any increases or decreases resulting from inflation, changes in engineering plans, activities performed, and any other conditions affecting costs. Regardless of whether reclamation is phased through the life of the operation or takes place at the end of operations, an appropriate portion of surety liability must be retained until final compliance with the Reclamation Plan is determined. INTERROGATORY STATEMENT: 1. Justify the decrease in costs estimated for mill decommissioning and reclamation of Cells 1, 2, and 3 from those estimated in the White Mesa Reclamation Plan, Rev. 4.0 dated November 2009. Explain why several estimated levels of effort (e.g., total effort for Mill Yard Decontamination, Ore Storage Pad Decontamination, Equipment Storage Area Cleanup and Cell 1 Construct Channel) are smaller in 2011 than those estimated in 2009. Explain and rectify apparent discrepancies between labor rates used in cost estimates and those presented in the exhibit in Attachment C titled “Labor Costs”. Response 1: Comparison of the cost estimates for 2009 verses 2011 are meaningless at this time as the estimates are for different cover systems, and the costs have been updated annually to take into account variations in equipment rental rates, labor rates and changes in material costs. In addition, the 2011 estimate utilized labor rates specific to the type and size of equipment being operated, instead of an average labor rate for all machines. Haul routes were also revised and updated to reflect current site conditions. Mill Interrogatory 015/1: R313-24-4; 10CFR40.Appendix A, Criterion 9: Financial Surety Arrangements Page 87 of 96 decommissioning costs are also revised from year to year to take in to account the expected volume of ore material and alternate feed material that may have to be hauled to the tailings cells. These quantities can vary significantly from year to year. Once the final cover design is conceptually approved, the cost estimate will be updated utilizing revised material volumes, specific stockpile locations for each material type, and updated equipment rental rates, labor rates and changes in material costs. 2. Identify analytes for which soil samples identified in the cost estimate for “Cleanup of Windblown Contamination” will be analyzed. Justify (or revise with justification) the assumed sample analysis cost of $50. Response 2: Verification soil samples will be analyzed for uranium, radium and thorium. Updated analysis costs will be justified and utilized in the final cost estimate following conceptual approval of the revised cover design and revised reclamation plan. 3. Revise and report estimated reclamation costs, incorporating responses to instructions listed above. Response 3: See Response 1. 4. Estimate and report the costs for a third party to conduct decommissioning and impoundment reclamation in the coming year rather than at the end of planned life. Response 4: Estimated reclamation and decommissioning costs are current costs assuming the reclamation activity were to start immediately. The costs are for the facility as it exists at the time of the estimate and not at the end of the planned life. The estimated costs assume that the reclamation is conducted by an unaffiliated third party, overseen by the State of Utah, Division of Radiation Control. 5. Please provide and justify estimates of costs associated with complying with the current Air Quality Approval Order (DAQE-AN1205005-06, issue date July 20, 2006) and License Condition 11.4 and 11.5 during final reclamation, as stated in Section 1.5 of Reclamation Plan 5.0, Attachment A, Technical Plans and Specifications. Response 5: Compliance with the Air Quality Approval Order and current License conditions are incidental to the daily operation of the White Mesa Mill and will continue to be managed by the onsite staff during reclamation activities. The management expense for this activity is covered in the Miscellaneous section of the Reclamation Cost estimate. Interrogatory 015/1: R313-24-4; 10CFR40.Appendix A, Criterion 9: Financial Surety Arrangements Page 88 of 96 6. Please state and justify the times projected to be necessary to dewater Cell 2 and Cell 3. Provide and justify estimates of all costs associated with the apparently lengthy dewatering time for Cell 2 and Cell 3. Also see Interrogatory 7/01, item 8. Response 6: Cell 2 and Cell 3 dewatering costs are incidental to the daily operation of the White Mesa Mill and will continue to be managed by the onsite staff during reclamation activities. The management expense for this activity is covered in the Miscellaneous section of the Reclamation Cost estimate. In addition, the current estimate includes the construction and operation of a holding pond for solution from the dewatering of the tailings cells. O & M costs for the dewatering of Cell 2 and Cell 3 will be re-evaluated once the final cover design is conceptually approved. Consolidation of the tailings sands in Cell 2 and Cell 3 is being monitored and, based on an analysis of the data, placement of the final cover can take place prior to the termination of slimes drain dewatering. BASIS FOR INTERROGATORY: Comparing the cost estimate contained in Attachment C to Reclamation Plan Rev. 4.0 2009 with those contained in Attachment C to Reclamation Plan Rev. 5.0 2011 reveals differences that should be addressed. Contrary to expectations, the costs associated with mill decommissioning and reclamation of most of the cells and some durations and levels of effort are smaller in 2011 than they were in 2009. Some labor costs are not obviously supported by the data sources presented in the attachment. Once Items 1 and 2 above have been addressed, the reclamation cost estimate should be revised and resubmitted. Without justification for an assumption to the contrary, the Division interprets the cost estimate as applying to decommissioning and reclamation that occur at the projected end of facility life. If so, the Licensee should also estimate the cost to decommission the mill area and reclaim all ponds under conditions likely to exist within the next year. The financial assurance provided should ensure that funds sufficient to cover costs of decommissioning and reclaiming within the next year are available to the State. Costs associated with complying with the current Air Quality Approval Order and License Condition 11.4 and 11.5 during final reclamation need to be included in the surety. Section 1.5 of Reclamation Plan 5.0, Attachment A, Technical Plans and Specifications, states that reclamation will comply with State of Utah Air Quality Approval Order (DAQE-AN1205005-06, issue date July 20, 2006). The times required to dewater Cell 2 and 3 appear to will be lengthy, based on current dewatering rates. Costs associated with this lengthy dewatering time for Cell 2 and 3 need to be included in the surety. REFERENCES: Denison Mines (USA) Corp. 2009. Reclamation Plan, White Mesa Mill, Blanding, Utah, Radioactive Materials License No. UT1900479, Revision 4.0, November 2009. Denison Mines (USA) Corp., 2011. Reclamation Plan, White Mesa Mill, Blanding, Utah, Radioactive Materials License No. UT1900479, Revision 5.0, Appendix E, September 2011. Interrogatory 016/1: R313-15-501: Radiation Protection Manual Page 89 of 96 INTERROGATORY WHITE MESA REC PLAN REV 5.0 R313-15-501; INT 16/1; RADIATION PROTECTION MANUAL REGULATORY BASIS: UAC R313-15-501; Surveys and Monitoring General invokes the following requirement from 10CFR40, Appendix A, Criterion 1: “(1) Each licensee or registrant shall make, or cause to be made, surveys that:(a) Are necessary for the licensee or registrant to comply with Rule R313-15; and(b) Are necessary under the circumstances to evaluate:(i) The magnitude and the extent of radiation levels; and(ii) Concentrations or quantities of radioactive material; and(iii) The potential radiological hazards. INTERROGATORY STATEMENT: Refer to Appendix D, Radiation Protection Manual for Reclamation: Provide information on how these largely operational radiation protection practices will change to support the changed needs of decommissioning and reclamation. Describe how the Radiation Protection program will be evaluated and revised to address the range of activities required to support decommissioning and reclamation activities. The following are selected examples of topics (not exhaustive) that should be evaluated and possibly revised to support decommissioning and reclamation. • Section 1.3 Beta Gamma Surveys: Conduct beta gamma frisk surveys where appropriate during decommissioning and reclamation. • Section 1.4 Urinalysis Surveys: State the frequency of conducting urinalyses during decommissioning and reclamation. • Sections 2.1.2, 2.3.2, 2.4.2 Frequency/locations: State how the frequency and locations for all monitoring methods will be modified to accommodate decommissioning and reclamation activities. Response: The Radiation Protection Manual for Reclamation has been updated to include additional text regarding practices for decommissioning and reclamation and is included as Attachment E to this response document. BASIS FOR INTERROGATORY: The Radiation Protection program provides information on regarding current operations but does not any information on how these practices will change to support reclamation. While reclamation will occur at a future date and the specific details may not be available at this time, it is important that the Radiation Protection Program identify the approach that will be taken to address these needs. REFERENCES: Denison Mines (USA) Corp., 2011. Reclamation Plan, White Mesa Mill, Blanding, Utah, Radioactive Materials License No. UT1900479, Revision 5.0, Appendix E, September 2011 :Attachment D Radiation Protection Manual for Reclamation September 2011 Interrogatory 17/1: R313-15-1002: Release Surveys Page 90 of 96 INTERROGATORY WHITE MESA REC PLAN REV 5.0 R313-15-1002; INT 17/1; RELEASE SURVEYS REGULATORY BASIS: UAC R313-15-1002; Method for Obtaining Approval of Proposed Disposal Procedures. A licensee or registrant or applicant for a license or registration may apply to the Executive Secretary for approval of proposed procedures, not otherwise authorized in these rules, to dispose of licensed or registered material generated in the licensee's or registrant's operations. Each application shall include:(1) A description of the waste containing licensed or registered material to be disposed of, including the physical and chemical properties that have an impact on risk evaluation, and the proposed manner and conditions of waste disposal; and(2) An analysis and evaluation of pertinent information on the nature of the environment; and(3) The nature and location of other potentially affected facilities; and(4) Analyses and procedures to ensure that doses are maintained ALARA and within the dose limits in Rule R313-15. INTERROGATORY STATEMENT: Refer to Attachment D, Section 2.6, Release Surveys: Revise to address the decontamination, release, and disposal of equipment and buildings necessary to support decommissioning and reclamation. Develop and present detailed release survey procedures and identify appropriate radiation survey equipment that will be used. Develop and present additional decontamination procedures during decommissioning and reclamation and include section on disposal of equipment that cannot be decontaminated. Response: Section 2.6 of the Radiation Protection Manual for Reclamation (Attachment D of the Reclamation Plan, Revision 5.0) has been revised to include reference to a Release Form outlining the procedures for release. The Release Form is included in the updated Radiation Protection Manual for Reclamation (Attachment E to this response document). BASIS FOR INTERROGATORY: The decommissioning plan indicates equipment and structural material may be removed, decontaminated and surveyed for unrestricted release. But the radiation protection plan does not include procedures, or identify instruments that would be used on conduct these release surveys. NUREG-1575 Supplement 1 “Multi-agency Radiation Survey and Assessment of Materials and Equipment Manual (MARSAME)” may be helpful in developing these procedures. REFERENCES: Denison Mines (USA) Corp., 2011. Reclamation Plan, White Mesa Mill, Blanding, Utah, Radioactive Materials License No. UT1900479, Revision 5.0, Appendix E, September 2011 :Attachment D Radiation Protection Manual for Reclamation September 2011 Interrogatory 18/1: R313-15-12: Inspection and Quality Assurance Page 91 of 99 INTERROGATORY WHITE MESA REC PLAN REV 5.0 R313-12; INT 18/1: INSPECTION AND QUALITY ASSURANCE REGULATORY BASIS: UAC R313-12: an individual who has the knowledge and responsibility to apply appropriate radiation protection rules and has been assigned such responsibility by the licensee or registrant. INTERROGATORY STATEMENT: Refer to Attachment A, Plans and Technical Specifications, Section 1.6, Inspection and Quality Assurance: Revise the provided the “Radiation Protection Manual for Reclamation” cited in this section, to define the responsibilities and duties of the Radiation Safety Officer. Refer to Attachment A, Plans and Technical Specifications, Section 1.8b, Inspection and Quality Assurance: Revise the wording to indicate that the DRC must review and approve all design modifications to the Reclamation Plan. Response: Section 1 of the Radiation Protection Manual for Reclamation (Attachment D of the Reclamation Plan, Revision 5.0) has been revised to include the responsibilities of the Radiation Safety Officer during reclamation (see Attachment E to this response document). The wording in section 1.8b of the Technical Specifications will be revised to indicate the DRC must review and approve all design modifications to the Reclamation Plan. BASIS FOR INTERROGATORY: Although Attachment A points to “Radiation Protection Manual for Reclamation” in identifying responsibilities and duties of the Radiation Safety Officer, the provided manual does not identify these responsibilities. The Radiation Safety Officers responsibilities during reclamation need to be identified, as they will be different than what is required during operations. DRC must be designated to approve of any design modifications to the Reclamation Plan. Section 1.8b of Reclamation Plan 5.0, Attachment A, Technical Plans and Specifications, describes “Possible submittal to, and review by, DRC for approval” of design modifications. Attachment A needs to be revised to indicate that the DRC must review and approve all design modifications to the Reclamation Plan. REFERENCES: Denison Mines (USA) Corp., 2011. Reclamation Plan, White Mesa Mill, Blanding, Utah, Radioactive Materials License No. UT1900479, Revision 5.0, Appendix E, September 2011 :Attachment A, Plans and Technical Specifications Denison Mines (USA) Corp., 2011. Reclamation Plan, White Mesa Mill, Blanding, Utah, Radioactive Materials License No. UT1900479, Revision 5.0, Appendix E, September 2011 :Attachment D, Radiation Protection Manual for Reclamation September 2011 Interrogatory 19/1: R313-24; 10CFR40.42(J): Regulatory Guidance Page 92 of 99 INTERROGATORY WHITE MESA REC PLAN REV 5.0 R313-24; 10 CFR 40.42(J); INT 19/1: REGULATORY GUIDANCE REGULATORY BASIS: UAC R313-24 incorporates 10 CFR 40.42(j) by reference: As the final step in decommissioning, the licensee shall--(1) Certify the disposition of all licensed material, including accumulated wastes, by submitting a completed NRC Form 314 or equivalent information; and (2) Conduct a radiation survey of the premises where the licensed activities were carried out and submit a report of the results of this survey, unless the licensee demonstrates in some other manner that the premises are suitable for release in accordance with the criteria for decommissioning in 10 CFR part 20, subpart E or, for uranium milling (uranium and thorium recovery) facilities, Criterion 6(6) of Appendix A to this part. INTERROGATORY STATEMENT: Refer to Attachment A, Plans and Specifications, Sections 6.4 Guidance: Please revise the decommissioning plan to reference and incorporate current guidance, namely NUREG-1757 “Consolidated Decommissioning Guidance”; NUREG-1575 “Multi-Agency Radiation Survey and Site Investigation Manual (MARSSIM)”; and NUREG-1575 Supplement 1 “Multi-agency Radiation Survey and Assessment of Materials and Equipment Manual (MARSAME)” Response: The response to this interrogatory will be provided as part of a second response document to be submitted to the Division on August 15, 2012. BASIS FOR INTERROGATORY: This document references the use of NUREG-5849: “Manual for Conducting Radiological Surveys in Support of License Termination” as the applicable guidance document. The current NRC guidance documents for decommissioning are NUREG-1757 “Consolidated Decommissioning Guidance”; NUREG-1575 “Multi-Agency Radiation Survey and Site Investigation Manual (MARSSIM)”; and NUREG-1575 Supplement 1 “Multi-agency Radiation Survey and Assessment of Materials and Equipment Manual (MARSAME)”. REFERENCES: Denison Mines (USA) Corp., 2011. Reclamation Plan, White Mesa Mill, Blanding, Utah, Radioactive Materials License No. UT1900479, Revision 5.0, Appendix E, September 2011: Attachment A, Plans and Technical Specifications Interrogatory 20/1: R313-24; 10CFR40; Appendix A Criterion 6(6): Scoping, Characterization, and Final Surveys Page 93 of 96 INTERROGATORY WHITE MESA REC PLAN REV 5.0 R313-24,;10 CFR 40 APPENDIX A CRITERION 6(6); INT 20/1: SCOPING, CHARACTERIZATION, AND FINAL SURVEYS REGULATORY BASIS: UAC R313-24 incorporates by reference 10 CFR 40 Appendix A Criterion 6(6): The design requirements in this criterion for longevity and control of radon releases apply to any portion of a licensed and/or disposal site unless such portion contains a concentration of radium in land, averaged over areas of 100 square meters, which, as a result of byproduct material, does not exceed the background level by more than: (i) 5 picocuries per gram (pCi/g) of radium-226, or, in the case of thorium byproduct material, radium-228, averaged over the first 15 centimeters (cm) below the surface, and (ii) 15 pCi/g of radium- 226, or, in the case of thorium byproduct material, radium-228, averaged over 15-cm thick layers more than 15 cm below the surface. INTERROGATORY STATEMENT: 1. Refer to Attachment A, Plans and Specifications, Sections 6.6 Scoping Surveys & Figure A-1: Provide a figure identifying the areas and survey grid sizes. Clarify how use of the large grids and the spacing shown in Figure A-1 will ensure compliance with the 100 square meter criteria. Explain how samples will be collected from these larger grids. Response 1: The responses to this interrogatory will be provided as part of a second response document to be submitted to the Division on August 15, 2012. 2. Refer to Attachment A, Plans and Technical Specifications, Sections 6.6 Scoping Surveys: Provide details (including information on instrument sensitivity) on the beta gamma radiation instruments that will be used for the scoping surveys. Indicate the frequency of calibration checks, daily operational checks, and other QA/QC requirements for the instruments. Also indicate whether these same instruments (used during facility operations) will be used for subsequent characterization, remediation, and final survey work. Response 2: See Response 1. 3. Refer to Attachment A, Plans and Technical Specifications, Sections 6.6 Scoping Surveys: Explain how areas contaminated with radium, thorium, and uranium will be identified and surveyed to ensure they will not result in a dose that is greater than the radium standard alone. Response 3: See Response 1. 4. Refer to Attachment A, Plans and Technical Specifications, Sections 6.6 Scoping Surveys: Identify what types of samples (e.g., grab or composite samples) will be collected to support developing the gamma correlation. Explain how locations for taking these samples will be selected. State how many correlations will be developed and how they will differ from each other. Interrogatory 20/1: R313-24; 10CFR40; Appendix A Criterion 6(6): Scoping, Characterization, and Final Surveys Page 94 of 96 Response 4: See Response 1. 5. Refer to Attachment A, Plans and Technical Specifications, Sections 6.6 Scoping Surveys: Identify the analytes including radioisotopes for which samples will be analyzed by chemical analysis and identify the preferred analytical method. Response 5: See Response 1. 6. Refer to Attachment A, Plans and Technical Specifications, Sections 6.6 Scoping Surveys: Provide information on how other materials that may be left will be identified during scoping surveys. Identify additional survey procedures for alpha beta and gamma surface surveys as appropriate. Response 6: See Response 1. 7. Refer to Attachment A, Plans and Technical Specifications, Sections 6.7 Characterization and Remediation Control Surveys: Explain how many and how samples will be collected to ensure the correlation developed for the scoping is consistent with the characterization and reclamation surveys. Explain how the correlation will be modified to address gamma variations that may arise during decommissioning and reclamation? Response 7: See Response 1. 8. Refer to Attachment A, Plans and Technical Specifications, Sections 6.8 Final Survey, Figure A-2 and Attachment B Construction QA/QC Plan, Section 5.4.1: Please clarify the terminology used in the two documents. Ensure that the activities described are consistent. Provide details on how the 10% of locations are selected for sampling. Demonstrate that collection of four samples as shown on Figure A-2 is sufficiently representative of the entire 100-square-meter area. Explain whether samples taken from the four sample locations identified in Figure A-2 will be analyzed separately or will be composited. Response 8: See Response 1. 9. Refer to Attachment A, Plans and Technical Specifications, Sections 6.8 Final Survey, Figure A-2: Explain how the areas where final survey soil sample results exceed the criteria will be addressed. State the basis for determining whether additional removal will be required. A soil sample that exceeds the criteria may also indicate a problem with the gamma correlation. Since the majority of the area will be released based on the gamma correlation, explain how the gamma correlation will be reviewed to ensure the use of the correlation in place of sampling is still valid. Interrogatory 20/1: R313-24; 10CFR40; Appendix A Criterion 6(6): Scoping, Characterization, and Final Surveys Page 95 of 96 Response 9: See Response 1. BASIS FOR INTERROGATORY: 1. The discussion in Section 6.6 does not clearly identify the survey grid sizes that will be used in the described areas. Figure A-1 describes a serpentine gamma survey path, but this also indicates that a total of 3 transects across the 30 meter grid will be made. With each transect representing only a 1- meter-square area, a significant majority of the grid is not surveyed, and compliance with the 100- square-meter standard cannot be documented. It is unclear how the 30m x 30m grid relates to the 50m x50m grid. 2. Without more detailed information on the instrument that will be used it is impossible to determine if the sensitivity is appropriate to verify compliance with the standard. 3. While the radium standard is appropriate for much of the site, as mentioned in the technical specifications there are areas that are contaminated with a combination of nuclides, how will these be identified, and what other survey procedures will be used to ensure the uranium and thorium are addressed. 4. The general criteria for identifying appropriate sample locations should be developed to ensure the resulting correlation is appropriate. Typically correlations are generated based on grab samples but the discussion does not detail how the samples will be collected. Also it appears that multiple correlations may be developed so proper communication regarding which correlation is appropriate for each area is necessary to ensure compliance with the soil standard. 5. Specifics on the analyses to be performed are necessary to evaluate the proposed correlations. The analytical methods need to be identified to ensure the appropriate analytical costs are included in the cast estimate. 6. Additional definition and description is required to provide assurance that all contaminants will be identified and properly processed during decommissioning and reclamation. 7. The gamma correlation that is developed for the scoping surveys may be valid, how will variations in gamma rates associated with excavation depth and differences in material at depth be addresses. 8. The radiological survey descriptions in the documents are not consistent. The characterization survey described in Attachment B is different than the characterization remediation survey described in Attachment A. Without consistent terminology and survey descriptions it is impossible to evaluate the survey descriptions. To ensure that collecting samples at only 10% of the remediated grids is sufficient, the criteria used as the basis for the 10% must be provided. Typically, composite soil samples for a 100 square meter area include between 5 and 11 aliquots to ensure the data is representative of the entire area. 9. The plan should contain a commitment to perform a radium-gamma correlation on the verification data, to track soil samples that fail the Ra-226 criteria, and to perform additional cleanup after a verification soil sample exceeds the Ra-226 standard. Just cleaning the failed grid is not adequate because the failed sample could indicate that the gamma value may not be conservative and that some of the unsampled grids may also fail to meet the standard. For example, the plan could indicate that neighboring grids would also be analyzed for Ra-226 or, if the number of failed grids is excessive, the gamma guideline would be adjusted downward and areas further remediated, as necessary. Interrogatory 20/1: R313-24; 10CFR40; Appendix A Criterion 6(6): Scoping, Characterization, and Final Surveys Page 96 of 96 REFERENCES: Denison Mines (USA) Corp., 2011. Reclamation Plan, White Mesa Mill, Blanding, Utah, Radioactive Materials License No. UT1900479, Revision 5.0, Appendix E, September 2011; Attachment A, Plans and Technical Specifications Denison Mines (USA) Corp., 2011. Reclamation Plan, White Mesa Mill, Blanding, Utah, Radioactive Materials License No. UT1900479, Revision 5.0, Appendix E, September 2011: Attachment B, Construction Quality Assurance/Quality Control Plan U.S. Geological Survey. 2012. Personal Communication (email) with Mr. Eric Martinez, Application Developer. May 16.