ML21076A464

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Cimarron Environmental Response Trust Facility Decommissioning Plan, Revision 2, Appendix L, 2020 Groundwater Flow Model Part 5
ML21076A464
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Site: 07000925
Issue date: 02/26/2021
From:
Environmental Properties Management, Enercon Services, Burns & McDonnell Engineering Co, Veolia Nuclear Solutions Federal Services
To:
Office of Nuclear Material Safety and Safeguards, Cimarron Environmental Response Trust, NRC Region 4
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TABLES CIMARRON ENVIRONMENTAL RESPONSE TRUST TABLE 3-1 GROUNDWATER MODEL INPUTS Burial Area #1 Western Alluvial Area Subsurface Units: Value Units Source Subsurface Units: Value Units Source KH 3.30E+00 ft/day Average of Silt, Sand & Clay KH 2.35E+02 ft/day Pumping Test (ENSR , 2006a) 3.30E-01 10% of KH Kv 2.35E+01 ft/day 10% of KH Kv ft/day ~

Horizontal Anisotropy 1 ----- No horizontal anisotropy Q} Horizontal Anisotropy 1 ----- No horizontal anisotropy Fill >,

m Vertical Anisotropy 1 ----- No vertical anisotropy  ::::, Vertical Anisotropy (KH/Kv) 1 ----- No vertical anisotropy (Kh/Kv) "O Porosity 30  % Freeze & Cherry, 1979 Table 2.4 C:

m Specific Storage 0.01 ----- Default, not used in steady state model Cl)

KH 2.83E-01 ft/day ENSR CSM Sec 3 .2.1 Specific Yield 0 .01 ----- Default, not used in steady state model Kv 2.83E-02 ft/day 10% of KH Porosity 30  % Freeze & Cherry, 1979 Table 2.4 Horizontal Anisotropy 1 ----- No horizontal anisotropy KH 3.00E+00 ft/day Slug Test, Calibration (ENSR, 2006a)

Silt Vertical Anisotropy N' 1.S0E-01 ft/day 5% of KH 1 ----- No vertical anisotropy Q} Kv (Kh/Kv) >,

m ----- No horizontal anisotropy Porosity 20  % Freeze & Cherry, 1979 Table 2.4  ::::, Horizontal Anisotropy 1 u Vertical Anisotropy (KH/Kv) 1 ----- No vertical anisotropy KH 2 .35E+02 ft/day Average of Pumping Test (ENSR , 2006a) d.,

C:

Kv 2 .53E+01 ft/day 10% of KH 0 Specific Storage 0 .01 ----- Default, not used in steady state model iii Horizontal Anisotropy 1 ----- No horizontal anisotropy "O

C: Specific Yield 0.01 ----- Default, not used in steady state model Sand m Cl)

Vertical Anisotropy 5  % Freeze & Cherry, 1979 Table 2.4 (KH/Kv) 1 ----- No vertical anisotropy Porosity Porosity 30  % Freeze & Cherry, 1979 Table 2.4 ENSR, 2006a (Artificially high to improve Cimarron River: Value Units Source KH 5.00E-01 ft/day model stability)

Kv 5 00E-02 ft/day 10% of KH Upstream Elevation 929.1 feet Based on Dover and Guthrie gage/Calibration Clay Horizontal Anisotropy 1 ----- No horizontal anisotropy Downstream Elevation 928 .5 feet Based on Dover and Guthrie gage/Calibration Vertical Anisotropy Riverbed Conductance 20,000 (ft2/day)/ft ENSR, 2006a 1 ----- No vertical anisotropy (KH/Kv)

Porosity 20  % Freeze & Cherry, 1979 Table 2.4 KH 8 .43E+00 ft/day Calibration (ENSR, 2006a) Areal Boundaries: Value Units Source Kv 4 .22E-01 ft/day 5% of~ Recharge 5.40E-04 ft/day ENSR CSM Sec-3.1 .1 & 3 .1.4 Siltstone Horizontal Anisotropy 1 ----- No horizontal anisotropy Vertical Anisotropy (KH/Kv) 1 ----- No vertical anisotropy Notes:

Porosity 1  % Freeze & Cherry, 1979 Table 2.4 1. All inputs are identical to those in the presented in the ENSR (2006} model report, except the Cimarron River Calibrated to high end of range in ENSR CSM KH 4.00E+01 ft/day Elevation. However, the actual model files the porosity was 1%.

Sec-3.2.1 (ENSR, 2006a)

Kv 2.00E+00 ft/day 5% of KH 2. Clay: The ENSR report shows input parameters for clay materials in the WAA model. Although there is a Sandstone-A Horizontal Anisotropy 1 ----- No horizontal anisotropy variable-thickness clay layer overlying the sand in the WAA, this is not represented in the model as a layer. Since Vertical Anisotropy its effect on recharge should be reflected in the recharge input, any references to clay in the table are omitted, (KH/Kv) 1 ----- No vertical anisotropy including Longitudinal Dispersivity, which is not needed for purposes of this model as chemical transport Porosity 5  % Freeze & Cherry, 1979 Table 2.4 modeling will not be performed.

KH 5 .00E+00 ft/day Slug Test, Calibration (ENSR , 2006a)

Kv 2.50E-01 ft/day 5% of KH Sandstone-B Horizontal Anisotropy 1 ----- No horizontal anisotropy Vertical Anisotropy 1 ----- No vertical anisotropy (KH/Kv)

Porosity 5  % Freeze & Cherry , 1979 Table 2.4 KH 3.00E+00 ft/day Slug Test, Calibration (ENSR, 2006a)

Kv 1.50E-01 ft/day 5% of KH Sandstone-C Horizontal Anisotropy 1 ----- No horizontal anisotropy Vertical Anisotropy 1 ----- No vertical anisotropy (KH/Kv)

Porosity 5  % Freeze & Cherry, 1979 Table 2.4 i

Cimarron River: Value Units Source Elevation 927.4 feet Based on Dover and Guthrie gage/Calibration Notes:

1. All inputs are identical to those in the presented in the ENSR (2006) model report, except the Cimarron River Elevation . However, the actual model files the porosity was 1%.

CIMARRON ENVIRONMENTAL RESPONSE TRUST TABLE 3-2 WESTERN ALLUVIAL AREA WATER LEVEL MEASUREMENTS NOVEMBER 2013 Water Elevation (11/15/2013)

Well Easting Northing (feet amsl)

T-51 2,091,962.33 322,775.31 929.71 T-52 2,092,329.67 322,774.93 929.59 T-53 2,092,658.88 322,773.47 929.46 T-54 2,092,870.50 321,927.51 930.36 T-55 2,093,119.60 322,069.59 930.09 T-56 2,093,377.95 322,211.22 929.89 T-57 2,092,460.78 321,788.03 930.51 T-58 2,092,165.08 321,742.40 930.55 T-59 2,092,954.88 322,773.96 929.43 T-60 2,093,281.82 322,773.99 929.48 T-61 2,093,609.54 322,774.36 929.24 T-62 2,091,852.83 321,470.61 930.76 T-63 2,091,976.65 321,623.17 930.63 T-65 2,091,814.49 321,568.90 930.69 T-66 2,091,841.97 321,712.16 930.6 T-67 2,091,742.89 321,657.32 930.65 T-68 2,091,713.09 322,052.25 930.34 T-69 2,091,871.69 321,961.92 930.4 T-70R 2,091,625.71 321,577.88 930.74 T-72 2,091,716.89 321,899.31 930.47 T-73 2,091,492.01 321,770.59 930.61 T-74 2,091,531.32 321,541.25 930.79 T-75 2,091,598.42 321,910.86 930.46 T-76 2,091,730.57 321,776.39 930.56 T-77 2,091,578.18 322,010.24 930.38 T-78 2,091,493.75 321,897.01 930.44 T-79 2,091,581.67 322,212.51 930.21 T-81 2,091,475.97 321,993.82 930.38 T-82 2,091,568.93 322,413.79 930.09 T-83 2,091,500.85 322,296.59 930.18 T-84 2,091,869.00 322,295.49 930.13 T-85 2,092,242.87 322,346.29 930.02 T-86 2,092,646.71 322,374.17 929.94 T-87 2,092,979.21 322,421.78 929.8 T-88 2,093,383.60 322,464.01 929.53 T-89 2,093,072.37 323,042.18 929.07 T-90 2,092,830.41 323,042.30 929.19 T-91 2,092,965.54 323,228.28 928.97 T-92 2,093,124.95 323,142.63 928.94 T-93 2,093,413.80 323,104.00 928.93 T-94 2,093,266.80 323,409.22 928.7 T-95 2,092,457 .65 323,019.00 929.36 T-96 2,091,984.82 322,557.26 929.83 Page 1 of 1

CIMARRON ENVIRONMENTAL RESPONSE TRUST TABLE 3-3 BURIAL AREA #1 WATER LEVEL MEASUREMENTS NOVEMBER 15, 2013 Well New Easting New Northing Water Elevation (11/15/2013) Top of Screened Interval (MSL) Bottom of Screened Interval (MSL) 02W01 2095439.69 322842.79 933.37 936 926 02W02 2095451.04 322881.61 930.97 934 924 02W03 2095372.73 322882.37 928.93 935 926 02W04 2095333.62 322903.05 928.01 933 924 02W05 2095319 .21 322952.00 928.00 932 923 02W06 2095307.98 323007.93 927.99 932 917 02W07 2095343.77 323005.17 927.97 932 917 02W08 2095390.56 323011.59 927.97 931 916 02W09 2095598.18 322763.68 935.67 941 926 02W10 2095579.82 322829.34 934.73 939 924 02Wll 2095440.73 323055.82 927 .91 934 915 02W12 2095453 .66 323035.56 927 .84 935 915 02Wl3 2095478.76 322982.90 928 .14 930 916 02W14 2095394.40 323056.26 927 .88 934 914 02W15 2095284.14 322896.65 928.03 931 926 02W16 2095269.31 322944.49 928.03 931 921 02W17 2095259.08 323006.59 927.99 931 916 02W18 2095344.50 323094.37 927 .89 933 914 02W19 2095328 .70 323053.20 927.96 931 917 02W20 2095670.14 322655.42 937 .78 942 928 02W21 2095196.20 323055.69 927 .97 929 914 02W22 2095217.52 322937.41 928 .02 932 922 02W23 2095207.01 323008.48 928.01 930 916 02W24 2095260.88 323055.20 927 .93 934 915 02W25 2095463.70 322653.27 947.82 946 926 02W26 2095629.00 322716.17 936.45 942 928 02W27 2095396.97 322825.07 932 .37 935 925 02W28 2095535.69 322830.33 934.48 935 923 02W29 2095551.60 322758.33 935 .37 939 929 02W30 2095470.17 322767.25 935.15 936 924 02W31 2095501.15 322860.00 933 .99 938 923 02W32 2095430.36 322964.35 928.00 933 919 02W33 2095250.57 322916.93 928.06 933 923 02W34 2095184.86 323104.27 927 .96 933 914 02W35 2095253.16 323155.84 927.87 932 913 02W36 2095250.07 323107.00 927.92 933 914 02W37 2095324.68 323156.60 927.82 934 914 02W38 2095392.31 323099.02 927.86 934 914 02W39 2095575.12 322735.34 935.76 943 928 02W40 2095529.95 322660.67 939.61 939 925 02W41 2095578.86 322682.92 937 .99 940 926 02W42 2095470.24 322724.55 938.96 944 924 02W43 2095321.85 323206.65 927 .79 931 912 02W44 2095373.85 323155.44 927.79 932 913 02W45 2095285 .68 323197.77 927.81 931 912 02W46 2095469.90 322907.34 929 .56 931 922 02W47 2095524.52 322626.66 940.58 947 927 02W48 2095423.83 323407.99 927 .49 904 884 02W50 2095525.35 322566.64 941.10 948 928 02W51 2095475.07 322582.30 952 .43 953 928 02W52 2095558 .69 322568.16 940.34 947 927 02W53 2095381.90 322827.48 932.42 939 924 02W62 2095207.49 323140.54 928.14 933 914 1344 2095776.39 323500.38 927.21 930 915 1314 2095467.35 322412.22 944.61 942 927 TMW-01 2095505.83 322696.66 941.11 942 927 TMW-02 2095508.07 322598.27 941.02 945 930 TMW-05 2095554.17 322882.67 933.27 935 921 TMW-06 2095637.00 322794.74 935.43 942 932 TMW-08 2095537.44 322724.36 935.71 941 926 TMW-09 2095489.80 322825.00 934.11 938 924 TMW-13 2095377 .00 322952.48 928.03 931 921 TMW-17 2095498.17 322764.05 932.51 913 903 TMW-18 2095338.37 322866.63 928.69 930 923 TMW-19 2095338.16 322865.04 929.00 936 931 TMW-20 2095612.55 322616.13 939.13 948 934 TMW-21 2095437.57 322700.53 937.88 942 932 TMW-23 2095473.70 323056.46 928.69 910 900 TMW-24 2095432.72 323408.70 927 .58 924 914 TMW-25 2095624.78 322654.44 937.87 945 931 1314 2095467.35 322412.22 944.61 942 927 1315R 2095504.06 322756.51 934.94 939 924 1316R 2095438.45 322776.98 933.45 936 922 1361 2095439.83 323265.37 927.69 931 911 Page 1 of 1

CIMARRON ENVIRONMENTAL RESPONSE TRUST TABLE 3-4 WATER BUDGET Western Alluvial Area Mass Balance Burial Area #1 Mass Balance 3 3 3 Inflow (ft /day) Outflow (tt3 /day) Inflow (ft /day) Outflow (ft /day)

General Head Boundary 49,182.93 33,896.13 General Head Boundary 36,086.41 31,638.40 River Boundary 1,257.59 20,675.69 River Boundary - 5,665.77 Recharge 4,154.75 - Recharge 1,227.78 -

Total 54,595.27 54,571.82 Total 37,314.19 37,304.17

% Error 0.043  % Error 0.023

CIMARRON ENVIRONMENTAL RESPONSE TRUST TABLE 3-5 TARGET RESIDUALS WESTERN ALLUVIAL AREA Name X y Layer Observed Computed Residual T-51 2091962.326 322775.3141 1 929.71 929.631123 0.078877 T-52 2092329.671 322774.9303 1 929.59 929 .571402 0.018598 T-53 2092658.885 322773.4698 1 929.46 929.51156 -0.05156 T-54 2092870.502 321927.5096 1 930.36 930.262255 0.097745 T-55 2093119.602 322069.585 1 930.09 930.10832 -0.01832 T-56 2093377.952 322211.2172 1 929.89 929.843322 0.046678 T-57 2092460. 776 321788.0337 1 930.51 930.327332 0.182668 T-58 2092165.082 321742.3981 1 930.55 930.404948 0.145052 T-59 2092954.879 322773.9552 1 929.43 929.457315 -0.027315 T-60 2093281.825 322773.9893 1 929.48 929.409401 0.070599 T-61 2093609.543 322774.3576 1 929.24 929.372255 -0.132255 T-62 2091852.828 321470.6101 1 930.76 930.674002 0.085998 T-63 2091976.647 321623.1691 1 930.63 930.514589 0.115411 T-65 2091814.49 321568.8952 1 930.69 930.581133 0.108867 T-66 2091841.967 321712.1628 1 930.6 930.468861 0.131139 T-67 2091742.89 321657.3189 1 930.65 930.524398 0.125602 T-68 2091713.087 322052.2532 1 930.34 930.225643 0.114357 T-69 2091871.687 321961.92 1 930.4 930.276362 0.123638 T-70R 2091625.712 321577 .8812 1 930.74 930.607608 0.132392 T-72 2091716.886 321899.3089 1 930.47 930.345744 0.124256 T-73 2091492.007 321770.5934 1 930.61 930.469952 0.140048 T-74 2091531.319 321541.2476 1 930.79 930.650591 0.139409 T-75 2091598.422 321910.8582 1 930.46 930.348807 0.111193 T-76 2091730.573 321776.3871 1 930.56 930.43871 0.12129 T-77 2091578.181 322010.2388 1 930.38 930.271741 0.108259 T-78 2091493.754 321897 .0149 1 930.44 930.368192 0.071808 T-79 2091581.67 322212.5107 1 930.21 930.113355 0.096645 T-81 2091475.972 321993.8212 1 930.38 930.291712 0.088288 T-82 2091568.929 322413.7919 1 930.09 929.956848 0.133152 T-83 2091500.85 322296.589 1 930.18 930.052948 0.127052 T-84 2091868.999 322295.4869 1 930.13 930.014964 0.115036 T-85 2092242.869 322346.2922 1 930.02 929.909285 0.110715 T-86 2092646.711 322374.1651 1 929.94 929.807601 0.132399 T-87 2092979.209 322421.7774 1 929.8 929.702394 0.097606 T-88 2093383.604 322464.0053 1 929.53 929.587511 -0.057511 T-89 2093072.365 323042.1839 1 929.07 929.25402 -0.18402 T-90 2092830.414 323042.2988 1 929.19 929.286906 -0.096906 T-91 2092965.544 323228.2819 1 928.97 929.127403 -0.157403 T-92 2093124.953 323142.6274 1 928.94 929.176394 -0.236394 T-93 2093413.804 323104.0008 1 928.93 929.185053 -0.255053 T-94 2093266. 798 323409.2186 1 928.7 928.962405 -0.262405 T-95 2092457.652 323019.0016 1 929.36 929.368038 -0.008038 T-96 2091984.823 322557.2578 1 929.83 929.794245 0.035755 Page 1 of 2

CIMARRON ENVIRONMENTAL RESPONSE TRUST TABLE 3-5 TARGET RESIDUALS WESTERN ALLUVIAL AREA Residual Mean 0.043 Absoluate Residual Mean 0.112 Residual Std. Deviation 0.118 Sum of Squares 0.675 RMS Error 0.125 Min. Residual -0.262 Max. Residual 0.183 Number of Observations 43 Range in Observations 2.09 Scaled Residual Std. Deviation 0.056 Scaled Absolute Residual Mean 0.054 Scaled RMS Error 0.060 Scaled Residual Mean 0.021 Page 2 of 2

CIMARRON ENVIRONMENTAL RESPONSE TRUST TABLE 3-6 TARGET RESIDUALS BURIAL AREA #1 Name X y Layer Observed Computed Residual 02W02 2095451 322881.6 6 930.97 928.91 2.06 02W03 2095373 322882.4 5 928.93 928.84 0.09 02W04 2095334 322903.1 6 928.01 928.75 -0.74 02W05 2095319 322952 5 928.00 928.58 -0.58 02W06 2095308 323007.9 7 927.99 928.40 -0.41 02W07 2095344 323005.2 7 927.97 928.40 -0.43 02W08 2095391 323011.6 7 927.97 928.37 -0.40 02W09 2095598 322763.7 6 935.67 935.52 0.15 02W10 2095580 322829.3 6 934.73 933.07 1.66 02W11 2095441 323055.8 8 927.91 928.21 -0.30 02W12 2095454 323035.6 8 927.84 928.25 -0.41 02W13 2095479 322982.9 8 928.14 928.41 -0.27 02W14 2095394 323056.3 8 927.88 928.24 -0.36 02W15 2095284 322896.7 5 928.03 928.76 -0.73 02W16 2095269 322944.5 6 928.03 928.60 -0.57 02W17 2095259 323006.6 7 927.99 928.41 -0.42 02W18 2095345 323094.4 8 927.89 928.16 -0.27 02W19 2095329 323053.2 7 927.96 928.27 -0.31 02W20 2095670 322655.4 5 937.78 938.26 -0.48 02W21 2095196 323055.7 8 927.97 928.28 -0.31 02W22 2095218 322937.4 6 928.02 928.62 -0.60 02W23 2095207 323008.5 8 928.01 928.40 -0.39 02W24 2095261 323055.2 8 927.93 928.28 -0.35 02W26 2095629 322716.2 5 936.45 936.95 -0.50 02W27 2095397 322825.1 6 932.37 930.62 1.75 02W28 2095536 322830.3 6 934.48 932.09 2.39 02W29 2095552 322758.3 5 935.37 935.54 -0.17 02W30 2095470 322767.3 7 935.15 934.72 0.43 02W31 2095501 322860 6 933.99 929.70 4.29 02W32 2095430 322964.4 7 928 928.53 -0.53 02W33 2095251 322916.9 6 928.06 928.69 -0.63 02W34 2095185 323104.3 8 927.96 928.17 -0.21 02W35 2095253 323155.8 8 927.87 928.05 -0.18 02W36 2095250 323107 8 927.92 928.15 -0.23 02W37 2095325 323156.6 7 927.82 928.04 -0.22 02W38 2095392 323099 8 927.86 928.13 -0.27 02W39 2095575 322735.3 5 935.76 936.40 -0.64 02W40 2095530 322660.7 7 939.61 939.39 0.22 02W41 2095579 322682.9 6 937.99 938.02 -0.03 02W42 2095470 322724.6 7 938.96 937.06 1.90 02W43 2095322 323206.7 8 927.79 927.95 -0.16 02W44 2095374 323155.4 8 927.79 928.02 -0.23 02W45 2095286 323197.8 8 927.81 927 .97 -0.16 02W46 2095470 322907.3 6 929.56 928.81 0.75 Page 1 of 2

CIMARRON ENVIRONMENTAL RESPONSE TRUST TABLE 3-6 TARGET RESIDUALS BURIAL AREA #1 Name X y Layer Observed Computed Residual 02W47 2095525 322626.7 7 940.58 940.68 -0.10 02W50 2095525 322566.6 7 941.10 942.53 -1 .43 02W52 2095559 322568.2 7 940.34 941.81 -1.47 02W53 2095382 322827.5 6 932.42 930.50 1.92 02W62 2095207 323140.5 8 928.14 928.09 0.05 1314 2095467 322412.2 8 944.61 947.73 -3.12 1344 2095776 323500.4 7 927.21 927.51 -0.30 1361 2095440 323265.4 8 927.69 927.82 -0.13 1361 2095440 3232,65.4 8 927.69 927.82 -0.13 1362 2095451 323187 10 927.77 927.61 0.16 1315R 2095504 322756.5 7 934.94 935.43 -0.49 1316R 2095438 322777 7 933.45 933.95 -0.50 TMW-01 2095506 322696.7 7 941.11 938.20 2.91 TMW-02 2095508 322598.3 7 941.02 941.91 -0.89 JMW-05 2095554 322882.7 7 933.27 930.62 2.65 TMW-06 2095637 322794.7 4 935.43 935.15 0.28 TMW-08 2095537 322724.4 6 935.71 936.80 -1.09 TMW-09 2095490 322825 6 934.11 931.23 2.88 TMW-13 2095377 322952.5 6 928.03 928.58 -0.55 TMW-17 2095498 322764.1 12 932.51 934.54 -2.03 TMW-18 2095338 322866.6 6 928.69 928.87 -0.18 TMW-19 2095338 322865 4 929 929.19 -0.19 TMW-20 2095613 322616.1 5 939.13 939.57 -0.44 TMW-21 2095438 322700.5 6 937.88 938.27 -0.39 TMW-24 2095433 323408.7 7 927.58 927.66 -0.08 TMW-25 2095625 322654.4 5 937.87 938.46 -0.59 Residual Mean -0.00123 Absoluate Residual Mean 0.759309 Residual Std. Deviation 1.156653 Sum of Squares 93.64937 RMS Error 1.156654 Min. Residual -3.12031 Max. Residual 4.286187 Number of Observations 70 Range in Observations 17.4 Scaled Residual Std. Deviation 0.066474 Scaled Absolute Residual Mean 0.043638 Scaled RMS Error 0.066474 Scaled Residual Mean -7.lE-05 Page 2 of 2

CIMARRON ENVIRONMENTAL RESPONSE TRUST TABLE 3-7 SENSITIVITY ANALYSIS Western Alluvial Area Southern General Head River Elevation change Boundary Calibrated Result +1 ft -1 ft +1 ft -1 ft*

Residual Mean 0.04 -0.19 0.30 -0.68 0.81 Absolute Residual Mean 0.11 0.21 0.30 0.68 0.81 Residual Std. Deviation 0.12 0.20 0.07 0.07 0.19 Sum of Squares 0.67 3.23 4.16 20.15 29.92 RMS Error 0.13 0.27 0.31 0.68 0.83 Scaled Residual Std. Deviation 0.06 0.11 0.04 0.04 0.11 Scaled Absolute Residual Mean 0.05 0.11 0.17 0.37 0.45 Scaled RMS Error 0.06 0.15 0.17 0.38 0.46 Scaled Residual Mean 0.02 -0.10 0.17 -0.37 0.45 Burial Area #1 Southern General Head River Elevation change Boundary Calibrated Result +1 ft -1 ft +1 ft -1 ft Residual Mean 0.00 -0.20 0.31 0.05 0.06 Absolute Residual Mean 0.76 0.91 0.84 0.76 0.76 Residual Std. Deviation 1.16 1.20 1.19 1.16 1.16 Sum of Squares 93.65 103.53 106.16 98.58 98.26 RMS Error 1.16 1.22 1.23 1.19 1.18 Scaled Residual Std. Deviation 0.07 0.08 0.08 0.08 0.08 Scaled Absolute Residual Mean 0.04 0.06 0.06 0.06 0.05 Scaled RMS Error 0.07 0.08 0.08 0.08 0.08 Scaled Residual Mean 0.00 -0.01 0.02 0.00 0.00 Page 1 of 1

FIGURES Legend

--- I 1oso Topographic Contour and Elevation j 1,000 500 0 1 ,000 Feet ~

COORD .

(NAO 63) STAT E PLANE OKLAHO MA NOR TH F EET 2082400 2082800 2083200 2063600 2064000 2084400 2064600 2085200 2085600 2086000 2086400 2086600 2087200 2067600 2058000 2088400 2088600 2089200 2089600 2090000 2090400 2090800 2091200 2091600 2092000 2092400 2092 800 2093200 2093600 2094000 2094400 2094800 2095200 2095600 2096000 2096400 2096800 2097200 2097600 2098000 2098400 2098800 2099200 2099600 2100000 2100400 2100600 2101200 2101600 2102000 2102400 2102800 2103200

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APPENDIX A - GROUNDWATER FLOW MODEL REPORT (ENSR, 2006)

Prepared for:

Cimarron Corporation (Tronox)

Oklahoma City, Oklahoma Groundwater Flow Modeling Report ENSR Corporation October 2006 Document No.: 04020-044 ENSR AECOM

Prepared for:

Cimarron Corporation (Tronox)

Oklahoma Groundwater Flow Modeling Report Maya Desai and Ken Heim 1Y Pre L,

, d By

~~ iL../d=--

Michael Meenan and James Cao Reviewed By ENSR Corporation October 2006 Document No.: 04020-044-327 E SR AECOM

ENSR Contents

1.0 INTRODUCTION

........................................................................................................................................ 1-1 1.1 Overview ........................................ .. .... .................... .... ... ....... ............ .. ...... ... .. .... .. .. .. ....................... 1-1 1.2 Background and Objectives ...... .... ..... ... .. .. .............. ..... ...... .... .......... .... .. ......... ..... .. ... ...................... 1-1 2.0 HYDROGEOLOGIC FRAMEWORK ......................................................................................................... 2-1

2. 1 Site Setting ...................................................................................................................................... 2-1 2.2 Precipitation .... .. ...... ... .... ...... ... ....... .. .... ... .... .. ............................ .............. ..... ................................. ... 2-1 2.3 General Geology .... .............. ....... .... .. .... .... ..... .. ............ ................................ .... .. ............................. 2-1 2.4 Site-Specific Geology .. .... ... ...... ........ .. ..... ... ..... ... ....................................... ...................................... 2-2 2.4.1 BA #1 Area ...................... ............................................................................................... .... 2-2 2.4.2 Western Alluvial Area ....... .... .. ..... .. ........... ................ .. ........ ... ........... ..... ... ... ....... ........ ....... 2-2 2.5 Hydrogeology ............................. ... .. ........................................ .. .............................. ....... ... ........... ... 2-3 2.6 Hydrologic Implications ....................... ................. .............. ......... .......... ....... ................... ... ........ ..... 2-3
2. 7 Conceptual Model of Site Groundwater Flow ................................................................................. 2-4
2. 7.1 The Cimarron River ...... .... .... .. ..................... ...... ........... ....... ... .... .. ...... ....... ... .... .. ..... ..... ..... 2-4
2. 7.2 BA #1 Area .. .. .... ........ ... ... .. .. ... ........... ... .... .. .. ... ... ...... ..... ... ...... ..... .... .... ... .... .. ....... ....... .. ...... 2-4
2. 7.3 Western Alluvial Area ........................................................................................................ 2-5 3.0 MODELING APPROACH .......................................................................................................................... 3-1 3.1 Groundwater Model Domain ........................................................ .. .. ... ..... ........... .... ... ... .... ... ..... ..... . 3-1 3.1.1 BA #1 Area .... ....... .. ...... ... ... .. ... ... ........................................................................................ 3-2 3.1.2 WA Area ....... ... ........ .. ........ .... .. ........ ............................ ........... ...... ................. .................. ... 3-2 3.2 Hydrogeologic Physical Properties ........................ ........... .. .......... ..... .................... ... ... .... ... ............ 3-3 3.3 Boundary Conditions ...... ... ... ............... .................... ... ... .............. .. ..... ....... .. .... ........ .... ..... ... ............ 3-4 3.3.1 Recharge ................................................. ..... ........ .. ............................. ......................... .. ... . 3-4 3.3.2 Surface Water/Groundwater Interactions .. ............. ....... ... .. ..... ... .............. ... ... .................. 3-4 3.3.3 Upgradient General Head Boundary ................................................................................ 3-5 3.3.4 Underlying General Head Boundary ..... ................. ....... .......... .... ....... ......... ...... ... ..... ... .. ... 3-5 3.4 Summary of Modeling Approach .. ......................................... ... ...................................................... 3-5 4.0 MODEL CALIBRATION ............................................................................................................................ 4-1 4.1 Calibration Approach .. ............................................... .... ..................... ....... ... ..... .... ........ ... ............... 4-1 4.1.1 Measured and Predicted Water Levels ............. .. ....... .. ..... .......... ... ...... .... ......... ...... .. .... .... 4-1 4.1.2 Volumetric Flow-Through Rate .................................................. ....... ................... .. ........... 4-1 4.1.3 Plume Migration ... .. .... ... .............................. ................... .............................................. ...... 4-2 4.2 Calibration Parameters .......................... ... ............................ ..... .......... ................... .. ................. ... .. 4-2 Report No. 04020-044 October 2006 Groundwater Modeling Report

ENSR Contents, continued 4.3 Calibration Results .............................. ... .... ..... ... ...... ... ....... .. ... .......... .. ....... .. ... ...... ........... ... .. ......... . 4-3 4.3.1 BA #1 ... ... .. ....... ... ..... ........... .... ... ....... .. ....... .. ... ..... .. ... ... .. .... ........ .............................. ...... ..... 4-3 4.3.2 WA area ............................................ ................................................................................. 4-4 4.3.3 Discussion ... ............ ... ....... .. ........ .... ... .. .............................................................................. 4-5 4.3.4 Summary of Calibration Results ........................................................................................ 4-5 4.4 Sensitivity Analysis .......................................................................................................................... 4-6 4.5 Uncertainties and Assumptions ..... .. ........ .......... .......... .......... .............. .... ... .. .... ..... .. ........ ...... ......... 4-7 5.0

SUMMARY

AND CONCLUSIONS ........................................................................................................... 5-1

6.0 REFERENCES

........................................................................................................................................... 6-1 Report No. 04020-044 ii October 2006 Groundwater Modeling Report

ENSR List of Tables Table 1 - Summary of Slug and Aquifer Test Results Table 2 - Summary of Groundwater Elevation Data used for Calibration Table 3 - BA #1 Summary of Model Inputs Table 4 - WA Area Summary of Model Inputs List of Figures Figure 1 - Site Location Map Figure 2 - Geology Along the Cimarron River From Freedom to Guthrie, Oklahoma Figure 3 - BA #1 - Geological Cross-Section Figure 4-Western Upland and Alluvial Areas - Geological Cross-Section Figure 5 - BA#1 Model Domain Figure 6 - WA Area Model Domain Figure 7 - BA #1 Boreholes and Cross-sections Figure 8 - BA #1 Solids Developed from Borehole data Figure 9 - BA #1 3D grid incorporating geologic information Figure 10 - WA Area Boreholes and Cross-sections Figure 11 - WA Area Solids Developed from Borehole data Figure 12 - WA Area 3D grid incorporating geologic information Figure 13 - BA #1 Calibration Results Figure 14 -WA Calibration Results Report No. 04020-044 iii October 2006 Groundwater Modeling Report

ENSR

1.0 INTRODUCTION

1.1 Overview In order to depict and predict groundwater flow and to evaluate groundwater remediation alternatives, two groundwater flow models were developed for the Cimarron Site. These two models address two of the three areas on site that require remediation of Uranium (U) in the groundwater. The two models included Burial Area #1 (BA #1) and the Western Alluvial (WA) area.

Calibration was evaluated by comparing measured groundwater elevations, flow path data, and water budgets, with simulated elevations, paths, and budgets. Both flow models achieved adequate calibration to the observed groundwater elevation data, to observed flow path trajectories, and to the estimated water budgets.

Discrepancies between observations and predictions are considered reasonable. The overall water table configuration for each model was consistent with expectations based on observations of U concentrations.

Overall hydrogeological concepts as presented in the Conceptual Site Model (CSM), Rev 01 (ENSR, 2006) were captured by the numerical models.

The resulting models are useful tools to evaluate groundwater flow characteristics (velocities, flux rates, etc.)

and to evaluate different remediation scenarios including, but not limited to, understanding the permanence of the proposed remedial technique and to design the injection of reagents.

1.2 Background and Objectives Cimarron Corporation's site near Crescent, Oklahoma is a former nuclear fuel manufacturing facility. Since stopping operations, the site has been undergoing decommissioning under the oversight of the Nuclear Regulatory Commission (NRC) and the Oklahoma Department of Environmental Quality (ODEQ). As a result of the facility processes there are several areas at the Cimarron Site that have residual concentrations of Uranium (U) in the groundwater. Cimarron Corporation is currently considering remedial actions in Burial Area

  1. 1, the Western Alluvial Area, and the Western Uplands area. To support the design of these remedial systems, numerical groundwater flow models were developed for two of these areas. These models, based largely on data and concepts presented in the Conceptual Site Model (Rev 01, ENSR, 2006), serve as tools to evaluate remediation strategies.

The overall objective of this modeling effort was to provide tools by which remediation alternatives could be evaluated. This objective was achieved by setting up the numerical models to include geologic and hydrologic conditions as observed and documented in the CSM-Rev 01 (ENSR, 2006). The models were then calibrated to specific targets. This calibration process yielded two models that compared well to observations and therefore could provide a frame of reference with which to evaluate impacts from remediation alternatives.

These models were initially developed to support ENSR's remediation via pump and treat. While Cimarron was considering remediation via pump and treat, they were also considering bioremediation . In this latter process, via additives, the geochemical conditions in the aquifer would be converted to a reducing environment which would immobilize the U. This process has been conceptualized and proposed by Arcadis.

Data from these calibrated models and simulations using these numerical models can help to design either these or other remediation alternatives.

Note that even though there are detectable concentrations of U in the Western Upland area of the site, a numerical model was not constructed for that area. The conceptual site model for the WU area is presented in the CSM Rev 01 (ENSR, 2006). This conceptual site model forms the basis for ARCADIS' evaluation and selection of remedial design for this area. Given the extent of the U concentrations, complex numerical modeling for this area may not be necessary based on the remedial approach.

Report No. 04020-044 1-1 October 2006 Groundwater Modeling Report

ENSR 2.0 HYDROGEOLOGIC FRAMEWORK Much of the following has been extracted and paraphrased from the CSM-Rev 01 Report (ENSR, 2006) . This section largely focuses on the parts of the CSM that were directly used in the modeling effort.

2.1 Site Setting The Cimarron Site lies within the Osage Plains of the Central Lowlands section of the Great Plains physiographic province, just south of the Cimarron River (Figure 1). The topography in the Cimarron area consists of low, rolling hills with incised drainages and floodplains along major rivers. Most of the drainages are ephemeral and receive water from storms or locally from groundwater base flow. The major drainage included in the models was the Cimarron River, which borders the site on the north. This river drains 4,186 square miles of Central Oklahoma from Freedom to Guthrie, Oklahoma (Adams and Bergman, 1995). The Cimarron River is a mature river with a well-defined channel and floodplain . The stream bed is generally flat and sandy and the river is bordered by terrace deposits and floodplain gravels and sands (Adams and Bergman, 1995). In the area of the Cimarron Site, the ancestral Cimarron River has carved an escarpment into the Garber-Wellington Formation. Floodplain alluvial sediments currently separate most of the river channel from the escarpment. Surface elevations in the Cimarron area range from 930 feet above mean sea level (amsl) along the Cimarron River to 1,010 feet amsl at the former plant site. Between the river and the escarpment, the ground surface is flat relative to the variable topography of the escarpment and leading up to the uplands. Vegetation in the area consists of native grasses and various stands of trees along and near drainages. Soil thickness in the project area ranges from about one to eight feet.

2.2 Precipitation Adams and Bergman (1995) summarized the precipitation for the Cimarron River Basin from Freedom to Guthrie, Oklahoma. Their study showed that precipitation ranges from an average of 24 in/yr near Freedom, Oklahoma, in the northwest part of the Cimarron River floodplain in Oklahoma, to 32-42 in/yr at Guthrie, Oklahoma. Wet weather years occurred between 1950and 1991, 1973-1975, 1985-1987, and 1990-1991.

The wettest months of the year are May through September, while the winter months are generally the dry months. The period from 1973 through 1975 had a total measured rainfall that was 23 inches above normal (Carr and Marcher, 1977). Precipitation data collected by the National Oceanic and Atmospheric Administration (NOAA) for Guthrie County, Oklahoma, from 1971 to 2000 indicates that the annual average precipitation is 36.05 inches.

2.3 General Geology The regional geology of the Cimarron area and the site-wide stratigraphic correlations for the project area can be combined into a general geological model for the Cimarron Site (Figure 2). The site consists of Permian-age sandstones and mudstones of the Garber-Wellington Formation of central Oklahoma overlain by soil in the upland areas and Quaternary alluvial sediments in the floodplains and valleys of incised streams. The Garber sandstones dip gently to the west and are overlain to the west of the Cimarron Site by the Hennessey Group. The Wellington Formation shales are found beneath the Garber sandstones at a depth of approximately 200 feet below ground surface in the project area. The Garber Formation at the project site is a fluvial deltaic sedimentary sequence consisting of channel sandstones and overbank mudstones. The channel sandstones are generally fine-grained, exhibit cross-stratification, and locally have conglomeratic zones of up to a few feet thick. The sandstones are weakly cemented with calcite, iron oxides, and hydroxides. The silt content of the sandstones is variable and clays within the fine fraction are generally kaolinite or montmorillonite. The mudstones are clay-rich and exhibit desiccation cracks and oxidation typical of overbank deposits. Some of the mudstones are continuous enough at the Cimarron Site to allow for separation of the sandstones into three main units, designated (from top to bottom) as Sandstones A, B, and C. Correlation of these three sandstone units is based primarily on elevation and the presence of a thick mudstone unit at the Report No. 04020-044 2-1 October 2006 Groundwater Modeling Report

ENSR base of Sandstones A and B that can be correlated between borings. Within each sandstone unit, there are frequent mudstone layers that are discontinuous and not correlative across the project area.

The Cimarron Site is located on part of an upland or topographic high between Cottonwood Creek and the Cimarron River. The project site is dissected by shallow, incised drainages that drain northward toward the Cimarron River. Groundwater base flow and surface water runoff during storms have been ponded in two reservoirs (Reservoirs #2 and #3) on the project site. The Cimarron River is a mature river that has incised the Garber Formation, forming escarpments that expose the upper part of the Garber sandstones. Within the Cimarron Site, the Cimarron River has developed a floodplain of unconsolidated sands, silts, and clays that separate the Garber sandstones exposed in an escarpment from the main river channel. Surface drainages within the project site flow toward the Cimarron River. Geological features of each modeled area of the Cimarron Site are as follows:

  • BA #1 Area - The upland is underlain by a sequence of sandstone and mudstone units, namely, from top to bottom, Mudstone A, Sandstone B, Mudstone B, and Sandstone C. The alluvium can be divided into a transitional zone located within the erosional drainage area and an alluvial zone located north of the escarpment line. The transitional zone consists predominantly of clay and silt and overlies Sandstone B or Mudstone B. A paleochannel appears to exist in the transitional zone, which may control the flow of groundwater in the vicinity of the upland in this area. The alluvium consists of mainly sand and overlies Sandstone C and Mudstone B. Additional descriptions of the geology of this area are included in the CSM-Rev 01 Report (ENSR, 2006).
  • Western Alluvial Area - Alluvial sediments in this area consist of predominantly sand with minor amounts of clay and silt. Sandstone B and Mudstone B exist beneath the alluvial sediments near the escarpment and Sandstone C underlies the alluvial sediments farther out in the floodplain. Additional descriptions of the geology of this area are included in the CSM-Rev 01 (ENSR, 2006).

2.4 Site-Specific Geology 2.4.1 BA #1 Area Geologic logs from seventy-five boreholes were used to describe the subsurface geology in the immediate vicinity of the Uranium (U) plume at the BA #1 area. The lithologic logs collected from borehole cuttings described the subsurface geology as a sequence of interbedded layers of near surface unconsolidated alluvial material and deeper consolidated sandstones and mudstones. The logs identified twenty-seven unique material types, which included unconsolidated materials of varying degrees of sand, silt, and clay, anthropogenically disturbed surficial deposits, and sedimentary rock. In an effort to simplify the conceptualization of the subsurface geology these twenty-seven different material types were collapsed into nine distinct material types representing strata with significantly different hydrogeologic characteristics. The four unconsolidated materials include, fill, sand, silt, and clay, and the underlying consolidated units include Sandstone A, Sandstone B, and Sandstone C, interbedded with two distinct mudstone layers (Figure 3). The simplified lithologic units describe, from the surface downward, fill material in the uplands and widely scattered silt in the upland and alluvial areas. In the alluvial areas this is underlain by a thick sandstone unit with a relatively thick bed of clay within the unit. The upland areas and beneath the alluvium consist of interbedded sandstone and mudstone. Because of varied topography and elevation the exposure of materials at the site varies widely. In the upland areas most of the exposed material is either sandstone or mudstone while in the alluvium most of the exposed material is either sand or to a lesser extent silt and clay. All data in the lithologic logs was used in the development of the model 2.4.2 Western Alluvial Area The subsurface geology at the WA area was depicted by geologic logs from twenty boreholes near the escarpment. In contrast to the geology of the BA#1 area, the subsurface of the WA area is a relatively flat, "pancake" geology where Sandstone C, the lowest sandstone indicated in the BA #1 area, is overlain by a continuous unit of unconsolidated alluvial sand, which is overlain by a intermittent unit of unconsolidated clay Report No. 04020-044 2-2 October 2006 Groundwater Modeling Report

ENSR (Figure 4). A simplification of the information from the lithologic logs was not necessary for the WA and the inconsistent distribution of clay around the site was largely due to topography and the erosion of the clay in the low lying areas. All data in the lithologic logs was used in the development of the model 2.5 Hydrogeology Groundwater flow through above-described regional geologic units is governed by recharge areas and discharge areas.

Regionally, recharge is precipitation (rain, snow, etc) that infiltrates past the root zone to the water table. As discussed above, the average annual precipitation rate is approximately 30 in/yr. Recharge to the alluvium and terrace deposits along the Cimarron River was estimated to be 8 percent of precipitation based on baseflow calculations and the assumptions of steady-state equilibrium in the alluvium and terrace sands (Adams and Bergman, 1995). Rainfall recharge to groundwater is therefore estimated to be approximately 2.4 4

in/yr (5.5 x 10- ft/day).

Discharge of groundwater occurs at low points in the watershed and generally coincides with streams and lakes. At this site the Cimarron River is a local and regional discharge boundary. Average annual baseflow in the Cimarron River should equal average annual recharge indicating that the recharge and discharge rates are balanced.

Recharge to the groundwater system typically occurs at topographic highs. The application of this water to the groundwater system results in downward gradients in the recharge areas; that is, there is a component of flow downward in addition to horizontal. Conversely, discharge from the groundwater system occurs at the topographic low points in any given watershed, for instance at a stream, river, or lake. Because of this, groundwater gradients tend to be upward in these areas; that is, there is component of flow upward in addition to horizontal. The flow path of any given unit of groundwater depends on where in the watershed it originates as recharge and how far it has to flow to discharge.

2.6 Hydrologic Implications The site-specific geology suggests several hydrologic implications including:

  • The alluvial material was largely deposited by the historical meandering of the Cimarron River and the deposition of overbank deposits that result from intermittent floods on the river. This inconsistent and repeating depositional cycle resulted in a series of inter-bedded unconsolidated material types that are collectively referred to as alluvium, which on a small scale can exhibit variable hydrogeologic characteristics but on a larger scale can be considered collectively.
  • Groundwater discharged from the Garber-Wellington formation largely discharges through the alluvial deposits on its way to its final destination, the Cimarron River.
  • Since both the WA and the BA #1 areas are within the Cimarron River alluvial valley, both areas receive groundwater from both upgradient discharge of groundwater to the alluvial deposits and from subsurface discharge of water from the deeper aquifer to the alluvium and river system. In general, flow from the southern upgradient sandstones to the alluvium is characterized as horizontal flow and flow from the sandstone underlying the alluvium is characterized as having a component of vertical (upward) flow.
  • The sandstone and siltstone/mudstones of the Garber-Wellington formation are relatively impermeable when compared to the unconsolidated alluvial sands adjacent to the river. This suggests that the water table gradient in the sandstone would be relatively steep when compared to the alluvial sand. This would further suggest that water could be more easily withdrawn from the alluvial sand than from the consolidated sediments occurring both beneath, and upgradient of the alluvial material.

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ENSR

  • In addition, within the bedrock, the sandstone units have higher permeability relative to the mudstones. Therefore, more groundwater flow is expected to take place horizontally within these water bearing units, with less flow between the units.

The hydrogeologic characteristics of the Cimarron River alluvial system are typical of a relatively permeable aquifer system receiving groundwater from an adjacent, less permeable bedrock aquifer and transferring the groundwater to the discharge zone, in this case the Cimarron River.

2.7 Conceptual Model of Site Groundwater Flow The Conceptual Site Model (CSM) of the Cimarron River flow system was developed prior to the development of groundwater models for the WA area and the BA #1 area. The CSM was incorporated into the groundwater models to ensure that the models used existing information and an accepted interpretation of the site-wide geology. The conceptual models for the WA area and the BA #1 area were developed separately and as such are discussed separately. However, it is recognized that the conceptual models for the two areas must be consistent.

2.7.1 The Cimarron River The Cimarron River is a significant hydrogeologic boundary for the entire Cimarron Site. The headwaters of this river are in New Mexico and from there it flows through Colorado, Kansas, and Oklahoma. In the vicinity of the Site (Freedom to Guthrie, OK) the Cimarron River is a gaining river. That is, it is a discharge zone for groundwater. Groundwater flow into the river is controlled by the difference in elevation of groundwater and in the river and by the conductivity of the river bottom sediments. The elevation of the river changes seasonally, but this can be represented as an average annual elevation for this steady-state modeling effort. Changes in the elevation of the river may result in short-term changes in the groundwater flow directions and gradients in the nearby alluvial materials. However, over the long-term, an average elevation is appropriate to reflect the average groundwater flow system. Cimarron River streamflows and associated water level elevations in the immediate vicinity of the Western Alluvial area and BA#1 model domains has not been historically measured.

The variability in river water levels at the site were estimated using long term flow records (1973 through 2003) from the USGS stream gages at Dover (30.0 miles upstream to the west) and Guthrie (10.3 miles downstream to the east). Daily averaged water level elevations at each of the two sites were averaged and the average water level elevation for the area of the model domains was determined through linear interpolation to be 925. 0 feet. A further statistical evaluation indicated that the 5th percentile of water level elevations at the site th was 924.1 feet and the 95 percentile of water level elevations was 927. 7 feet; therefore, 90% of the time the Cimarron River water level at the site varies within a range of 3.60 feet.

2.7.2 BA #1 Area Groundwater in the vicinity of the BA #1 Area originates as precipitation that infiltrates into the shallow groundwater in recharge zones, both near the BA #1 area and in areas upgradient of the BA #1 area. The amount of water flowing from the sandstones into the modeled area and into the alluvial material is controlled by the changes in groundwater elevation and hydraulic conductivities between the two units.

Local to the BA #1 area, infiltrated rainwater recharges the shallow groundwater in the area of the former disposal trenches and then flows into Sandstone B. The reservoir also contributes water to the groundwater system. This groundwater then flows across an escarpment that is an interface for the Sandstone B water-bearing unit and the Cimarron River floodplain alluvium, and finally into and through the floodplain alluvium to the Cimarron River. Flow in Sandstone B is mostly northward west of the transitional zone and northeastward along the interface with the transitional zone. Flow is driven by a relatively steep hydraulic gradient (0.10 foot/foot) at the interface between Sandstone B and the floodplain alluvium. Once groundwater enters the transition zone of the floodplain alluvium, the hydraulic gradient decreases to around 0.023 foot/foot and flow is refracted to a more northwesterly direction. The decrease in hydraulic gradient is due in part to the much higher overall hydraulic conductivity in the floodplain alluvium compared to Sandstone B (10-3 to 10-2 cm/sin Report No. 04020-044 2-4 October 2006 Groundwater Modeling Report

ENSR alluvium versus 10-5 to 10-4 cm/s in Sandstone B). The refraction to the northwest is primarily due to a paleochannel in the floodplain alluvial sediments. The direction of this paleochannel is to the northwest near the buried escarpment and then is redirected to the north as it extends farther out into the floodplain. Once groundwater passes through the transitional zone, it enters an area where the hydraulic gradient is relatively flat. Data indicates that the gradient in the sandy alluvium is approximately 0.0007 ft/ft. Figure 3-4 in the CSM-Rev 01 Report (ENSR, 2006) presents a potentiometric surface map of Sandstone Band the alluvium for the BA #1 area based on groundwater level measurements during August/September 2004. Seasonal data between 2003 and 2005 indicate that although groundwater levels may change seasonally, the hydraulic gradients and groundwater flow directions do not change significantly over time (ENSR, 2006).

2.7.3 Western Alluvial Area Groundwater in the vicinity of the WA area originates as precipitation that infiltrates into the shallow groundwater in recharge zones both near the WA area and in areas upgradient of the WA area. Most of the groundwater in the WA area comes from the discharge of groundwater from Sandstones B and C to the alluvial materials. The amount of water flowing from the sandstones to the alluvial material is controlled by the difference in groundwater elevation and hydraulic conductivities between the two geologic units. Groundwater flow in the WA area is generally northward toward the Cimarron River; flow is driven by a relatively flat hydraulic gradient of 0.002 foot/foot. Figure 3-6 in CSM-Rev 01 Report (ENSR, 2006) presents a potentiometric surface map of the alluvium for the WA area based on groundwater level measurements during August/September 2004. As with the BA#1 Area, although groundwater levels may change seasonally, there is little change over time in hydraulic gradient and groundwater flow directions.

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ENSR 3.0 MODELING APPROACH Groundwater flow at the two Cimarron sites (BA #1 and WA areas) was simulated using the three-dimensional MODFLOW model (McDonald and Harbaugh, 1988). The MODFLOW model uses a block-centered finite-difference method to simulate groundwater flow in three dimensions. The MODFLOW model was selected because of its wide acceptance by the technical community, because of its robustness, and because several Windows based applications support the model, including the GMS 6.0 modeling package, which was used for this project. The GMS 6.0 software package is a visualization package that facilitates easy manipulation of the MODFLOW input and output files. In addition to using the MODFLOW groundwater model, the MODPATH particle tracking program was used to simulate the transport of groundwater particles within the model domain as a direct result of a flow field predicted by MODFLOW.

3.1 Groundwater Model Domain The domains of the BA #1 area and WA groundwater models were set up to include the specific areas of interest and all important boundary conditions.

For the BA #1 area, the specific area of interest was located northwest of the Reservoir #2 from the source area in the uplands, downgradient through the transition zone, and into the alluvial sands (Figure 5). The downgradient boundary was the Cimarron River and the upgradient boundary was along an east-west line coincident with the Reservoir #2 dam. Groundwater flow is primarily northward, so boundaries parallel to groundwater flow were set up at locations upstream and downstream along the Cimarron River far enough away from the high U concentrations and parallel to flow lines to not influence the interior of the model domain during pumping simulations. The lower boundary (i.e., bottom) of the BA #1 model domain was fixed at elevation 900 feet, well below the lower extent of the alluvial aquifer.

In the case of the WA area, the specific area of interest was located just downgradient of the escarpment along a north-trending line of high U concentrations (Figure 6). The downgradient boundary was the Cimarron River and the upgradient boundary was set at the escarpment. Groundwater flow is primarily northward so boundaries parallel to groundwater flow were set up at locations upstream and downstream along the Cimarron River far enough away from the high U concentrations to not influence the interior of the model domain during pumping simulations. The lower boundary (i.e., bottom) of the WA area model domain was fixed at 870 feet, well below the lower extent of the alluvial aquifer.

The model domain for the BA #1 area was set up to include the area from the upgradient reservoir to the south, to the Cimarron River to the north, and to distances east and west adequate enough to have a negligible effect on the interior of the model domain. The model was developed with grid cells that are 10 feet square in the X-Y plane and with 12 layers extending from the land surface down to a depth of elevation 900 feet, resulting in approximately 270,000 grid cells within the model domain.

The model domain for the WA area was set up to include the area from the escarpment to the south to the Cimarron River to the north and east and west to distances adequate enough to have a negligible effect on the interior of the model domain. The model was developed with grid cells that are 10 feet square in the X-Y plane and with 2 layers extending from the land surface down to a depth of elevation 870 feet, resulting in 97,830 grid cells within the model domain. The high density of grid cells within each model domain was selected for two reasons including: 1) to provide for a finely discretized model within the area of the U plume for testing the effects of groundwater pumping, and 2) to provide for adequate representation of the subsurface geology into discrete geologic material types, particularly for the BA#1 area.

Report No. 04020-044 3-1 October 2006 Groundwater Modeling Report

ENSR 3.1.1 BA #1 Area The model layers for the BA #1 area were developed directly from the lithologic information from the seventy-two boreholes that were available for the site. A simplification of the original borehole data, which had originally described 27 unique lithologic types, was imported directly into the GMS 6.0 modeling platform, as the basis for the groundwater model. The simplified geology included the following geologic units/materials:

1) fill, 2) silt, 3) an upper sand unit, 4) clay, 5) a lower sand unit, 6) an upper sandstone unit (Sandstone A), 7) an upper mudstone (A), 8) a middle sandstone unit (Sandstone B), 9) a lower mudstone (8), and 10) a lower sandstone unit (Sandstone C). Each of the boreholes was reviewed in light of the surrounding boreholes to ensure that the inter-relationships between boreholes were realistic and representative of the CSM-Rev 01 (ENSR, 2006) developed for the site. Following the importation and adjustment of the borehole information, each layer in each of the seventy-two boreholes was assigned a Horizon ID to indicate the layer's position in the depositional sequence at the Site. The GMS 6.0 modeling platform was then used to "connect" the boreholes to form cross-sections based on the Horizon IDs assigned to each of the boreholes. Since a cross-section was developed for every adjacent borehole, this resulted in a total of one hundred sixty-five cross-sections; each of which was reviewed to ensure the sensibility of the interpretations. In cases where the cross-section did not make geologic sense, the cross-section was manually modified (Figure 7).

Once the cross-sections were developed and checked for accuracy, the GMS 6.0 program was used to develop three-dimensional solids of each material type within the intended model X-Y model domain. Each of the 3-D solids was represented by upper and lower TIN (triangularly integrated network) surfaces and was created using the previously developed cross-sectional data. Each of the solids types corresponded to the nine geologic units indicated by the lithologic information for the boreholes (Figure 8).

The model boundaries were identified and incorporated into the GMS 6.0 platform, including the location of the river boundary, the general head boundary, and the recharge boundary (discussed in the next section).

One of the last steps in the development of the BA #1 area groundwater model was to develop a generic, twelve layer 3D grid that encompassed the model domain on a 10 ft by 1Oft horizontal spacing. The next step in the development of the model was to assign hydrogeologic properties to each of the material types and boundaries and then transition all of the 3-D solids information to the 3-D grid that is used by the MODFLOW and MODPATH models (Figure 9). The final step was to make modifications to the distribution of material types (i.e., hydraulic conductivities) to adjust for the discrepancies between the mathematically interpreted version of the distribution of soil types and the interpretation of soil types based on the CSM (ENSR, 2006).

3.1.2 WA Area The model layers for the WA area were developed directly from the lithologic information from the twenty boreholes that were available for the site. The borehole data was imported directly into the GMS 6.0 modeling platform as the basis for the groundwater model. Each of the boreholes was reviewed in light of the surrounding boreholes to ensure that the inter-relationships between boreholes were realistic and representative of the CSM, Rev.1 (ENSR, 2006) developed for the site. Following the importation and adjustment of the borehole information, each layer in each of the twenty boreholes was assigned a Horizon ID to indicate the layer's position in the depositional sequence at the site. The GMS 6.0 modeling platform was then used to "connect" the boreholes to form cross-sections based on the Horizon IDs assigned to each of the boreholes. Since a cross-section was developed for every adjacent borehole, this resulted in a total of forty-one cross-sections; each of which was reviewed to ensure the sensibility of the interpretations. In cases where the cross-section did not make geologic sense, the cross-section was manually modified (Figure 10).

Once the cross-sections were developed and checked for accuracy, the GMS 6.0 program was used to develop three-dimensional solids of each material type within the intended model X-Y model domain. Each of the 3-D solids was represented by upper and lower TIN (triangularly integrated network) surfaces and was created using the previously developed cross-sectional data. Each of the solids types corresponded to the three geologic units indicated by the lithologic information for the boreholes (Figure 11). It should be noted that the geologic materials in the WA area consisted only of sandy alluvium and the underlying bedrock (Sandstone C), so this process was much simpler than for the BA#1 area.

Report No. 04020-044 3-2 October 2006 Groundwater Modeling Report

ENSR The model boundaries were identified and incorporated into the GMS 6.0 platform including the location of the river boundary, the general head boundary, and the recharge boundary (discussed in the next section).

One of the last steps in the development of the WA area groundwater model was to develop a generic, two layer 3D grid that encompassed the model domain on a 10 ft by 10 ft horizontal spacing. The final step in the development of the model was to assign hydrogeologic properties to each of the material types and boundaries and then transition all of the 3-D solids information to the 3-D grid that is used by the MODFLOW and MODPATH models (Figure 12).

3.2 Hydrogeologic Physical Properties The physical property most commonly used to characterize subsurface permeability is the hydraulic conductivity. This parameter is applied to Darcy's Law as a proportionality constant relating groundwater flow rate to groundwater gradient and cross-sectional area, and is a measure of the ability of a soil matrix to transport groundwater through the subsurface. Hydraulic conductivity values are required to describe the permeability of each cell in the MODFLOW groundwater model because Darcy's equation is used by the model to solve for groundwater head in each model cell. If hydraulic conductivity values in the model area were spatially the same, the multiple model layers could act as a single layer. However, this degree of uniformity is not evident at the Cimarron site, so each model layer was assigned a unique horizontal and vertical hydraulic conductivity value consistent with the geology assigned to that layer.

In the case of the BA #1 area model, the MODFLOW model represents the complicated ten layer geologic system of largely continuous material types with twelve model layers. From the surface downward these include, 1) fill, 2) silt, 3) an upper sand unit, 4) clay, 5) a lower sand unit, 6) an upper sandstone unit (Sandstone A), 7) an upper mudstone (A), 8) a middle sandstone unit (Sandstone B), 9) a lower mudstone (B),

and 10) a lower sandstone unit (Sandstone C). A single, constant hydraulic conductivity value was assigned to each of these 10 material types.

In the case of the WA area model, the MODFLOW groundwater model represents the (simple relative to the BA #1 model) subsurface by assigning the two dominant material types (sand and sandstone) to two different model layers. (Note: even though clay was present in the boring logs, it was not saturated, therefore was not modeled). These are 1) a sandy alluvium layer beneath the clay layer and exposed at several locations throughout the site and 2) an underlying sandstone layer beneath the sandy alluvial aquifer (Sandstone C). A single, constant hydraulic conductivity value was assigned to each of the two layers.

Hydraulic conductivity values for both the alluvium and the sandstone were derived from slug and pumping tests conducted during the field investigations, as described in the Burial Area #1 Groundwater Assessment Report (Cimarron Corporation, 2003). Table 1 summarizes the findings from these tests. Results for the alluvium ranged from 0.04 to 312 ft/day with a median value of 38 ft/day. Results for the sandstones ranged from 0.07 to 2.83 with a median value of 0.35 ft/ day. The conductivity values are consistent with literature (Freeze & Cherry, 1979).

In general, the vertical hydraulic conductivity is assumed to be less than the horizontal because of the inter-bedding that occurs during sedimentary deposition. While relatively small layers and lenses of fine material do not significantly effect the lateral movement of groundwater they can effect the vertical movement by creating more tortuous pathway for groundwater flow, and resistance to vertical flow. In general, the vertical hydraulic conductivity in sedimentary or alluvial deposits can be 1 to 30% of the horizontal hydraulic conductivity.

The alluvial materials (sand, clay, silt) were assumed to have vertical components of flow consistent with a sedimentary environment. Therefore, the vertical hydraulic conductivity of the alluvial materials was set to 10% of horizontal hydraulic conductivity. For the sandstones and mudstones, the vertical hydraulic conductivity was set to 5% of horizontal hydraulic conductivity. The groundwater flow in sandstone and mudstone may be controlled not only by primary (matrix) pathways, but also secondary (remnant fracture) pathways. However, there is no data (i.e., groundwater elevation data) to suggest that fractures flow is significant at this site, especially on the scale of the entire model domain. Note that the conceptual Report No. 04020-044 3-3 October 2006 Groundwater Modeling Report

ENSR understanding of fractures at this site is that most of fractures occur on bedding planes (i.e., in the horizontal direction); thus, flow in the stone fractures would be controlled by horizontal hydraulic conductivity, not the vertical .

Anisotropy values are used if there is some reason to believe that the aquifer has a substantially different permeability along one horizontal axis than another. This is not believed to be the case in either the WA area or the BA #1 model domain and therefore the horizontal anisotropy was assumed to be unity.

3.3 Boundary Conditions The boundary conditions at the perimeter of the model domain play an important role in the outcome of a groundwater simulation because of the dependence of hydraulic behavior within the interior of the model on the water levels and fluxes fixed at the model boundaries. Ideal model boundaries are natural hydrogeologic features (i.e., groundwater divides, rivers). Recharge to groundwater is also a boundary condition. Model predictions can be inaccurate when the areas of interest in the model domain are too close to a poorly selected boundary condition. In the absence of natural hydrogeologic boundaries, boundaries are chosen at distances great enough such that they do not affect the outcome of simulations in the area of interest. In the groundwater models of the Cimarron Site, the downgradient boundary was selected to coincide with the Cimarron River, a natural hydrogeologic boundary. Since there are no nearby natural features for the other boundaries, the domain was extended to distances sufficient such that simulations would not be significantly affected by the model boundaries.

3.3.1 Recharge Recharge to groundwater is simulated using the MODFLOW Recharge Package. This package can be used to apply a spatially and temporally distributed recharge rate to any layer within a model domain. In general, the recharge package is used to represent the fraction of precipitation that enters the subsurface as rainfall recharge directly to the groundwater water table. In model domains representing relatively small geographic regions, and without significant variability in site wide precipitation, the recharge package is applied uniformly throughout the model domain. The recharge package can be temporally varied in unsteady simulations to predict system response to unique or seasonal events but can be applied at a constant rate for steady state simulations. For the steady-state simulation of groundwater flow at the two Cimarron sites the recharge package was applied uniformly over the entire model domains at a constant rate. Since the model was steady-state and no losses of groundwater were assumed, the recharge rate, determined through model calibration, was expected to be similar to the rate indicated in the CSM-Rev 01 (ENSR, 2006) of 8% of precipitation or 2.4 in/yr.

3.3.2 Surface Water/Groundwater Interactions The Cimarron River is included in each of the models, as it is the regional groundwater discharge point. The Cimarron River is represented in the model domain using the MODFLOW River Package. The channel bed elevations at these sites were linearly interpolated from the gage datum of 999.2 feet at the USGS stream gage at Dover, OK (#07159100) located about 30 miles upstream, and the gage datum of 896.5 feet at the USGS stream gage at Guthrie, OK (#07160000) located about 10 miles downstream. The resulting value of 922.8 feet was assigned as the river bed elevation for both the BA #1 and WA areas. The surface water elevations were assumed to be 2 feet higher than the bed elevations at both locations resulting in a constant water surface elevation of 924.8 feet.

Depending on the difference between the measured river surface elevation and the predicted groundwater elevation in the cells adjacent to the river cells, the river will either be simulated to lose water to the aquifer or gain water from the aquifer. Based on the topography and hydrogeology of the site, the streams and rivers are generally expected to gain groundwater. The rate of water gain or loss from the Cimarron River is represented in MODFLOW using three parameters that include (1) the river bed area, (2) the channel bottom thickness, and (3) the hydraulic conductivity of the river bed sediments. While the product of the hydraulic conductivity Report No. 04020-044 3-4 October 2006 Groundwater Modeling Report

ENSR and the riverbed area divided by the bed thickness results in a conductance term (C), this value was established through model calibration rather than being calculated, due to a lack of site-specific information.

Model cells that were assigned river properties are shown with blue dots on Figures 9 and 12 for the BA #1 and WA models, respectively.

The reservoir south of the BA#1 area was incorporated into the General Head Boundary condition as described below. None of the other intermittent surface waters, such as the drainageways, were included in the model, as their influence on the groundwater system is local and sporadic.

3.3.3 Upgradient General Head Boundary The upgradient boundaries for both the BA #1 and the WA area were represented as a General Head Boundary (GHB) in MODFLOW. Unlike a constant head boundary, which holds the water level constant and offers no control over the amount of water passing through the boundary, the GHB offers a way to limit the supply of upgradient water entering the model domain. This limitation provides a better representation of the system that is limited by the transfer of groundwater from the upgradient aquifer to the upgradient model boundary. The general head boundary requires the designation of a head, or groundwater elevation along the boundary, and conductivity. The head assigned to the GHB defines the groundwater level at the boundary and largely dictates the downgradient water levels and the gradients. The conductivity of the GHB defines the permeability of the boundary and controls the amount of water that can pass through the boundary. Water can pass into or out of the model domain through the general head boundary, depending on the relative hydraulic heads.

3.3.4 Underlying General Head Boundary In addition to representing the upgradient boundary using a GHB, the upward hydraulic gradient from the underlying bedrock described in the site CSM-Rev 01 (ENSR, 2006) can also be represented this way.

Because the Cimarron River is a major discharge area, the discharge of deep groundwater through the alluvium and into the river is an expected phenomenon. To simulate this upward flow of groundwater a GHB was used in both model domains to varying degrees to represent a higher water level at depth than in the alluvial aquifer. The volumetric flow rate of water into the alluvial aquifer was limited by adjusting to a relatively low conductance during the calibration process.

Some of the model cells that were assigned general head boundary properties are shown with brown dots on Figures 9 and 12 for the BA #1 and WA models, respectively. Other cells were also assigned this boundary type, but are not visible in this view of the model domain. Basically, all cells at the base of the models and at the southern limit were assigned GHB boundaries.

3.4 Summary of Modeling Approach Model parameters used to setup the groundwater models for the BA #1 and WA areas were developed from measured information and from interpretations made based on material characteristics. These parameters largely control the predictions made by the groundwater and pathline models.

Report No. 04020-044 3-5 October 2006 Groundwater Modeling Report

ENSR 4.0 MODEL CALIBRATION 4.1 Calibration Approach Once the model domain was established, the model grid developed, and the model inputs entered, the calibration process began. The calibration process is a quality control step used to provide a frame of reference for evaluating simulation results. The calibration of groundwater models proceeds by making adjustments to the boundary conditions and the hydraulic conductivities until the simulated groundwater elevations adequately match the observed groundwater elevations. In addition to comparing model predicted elevations to observed elevations, a good calibration was also dependent on capturing gradients and flow directions such that simulated flow paths were congruent with inferred flow paths from U concentration data.

The overall regional water balance was also considered. The following sections (4.1.1, 4.1.2, and 4.1.3) discuss the three ways the model calibration was evaluated.

4.1.1 Measured and Predicted Water Levels Comparing model predicted groundwater levels with measured levels is a rigorous, obvious, and straightforward way to evaluate the ability of a groundwater model to meet the project objectives. In steady-state models the groundwater predictions are generally compared with representative average groundwater water levels at several locations around the site. Since a single round of groundwater elevation measurements may not be representative of the average water table due to seasonal variations, it is preferable to use the results of several temporally distributed water level surveys to provide a better representation of the average water table.

The water level data used to evaluate the BA #1 and WA groundwater model calibrations was from each of the wells/boreholes used to develop the models. Water levels from each of four surveys including September 2003, December 2003, during August and September of 2004, and in May of 2005 were averaged to arrive at a set of average water levels for comparison to model predictions. Table 2 summarizes the average groundwater elevations from four sampling rounds. This data set served as the calibration data set.

During the calibration, the model calibration parameters were adjusted in order to reach a quantitative target:

the mean absolute difference between the predicted and measured water levels within 10% of the measured site-wide groundwater relief.

For the BA #1 area, the maximum groundwater elevation was 950.96 feet at Well 02W51 and the minimum elevation was 925.37 feet at Well 02W17; therefore, the calibration target is 10% of that difference or approximately 2.6 feet.

For the WA area, the maximum groundwater elevation in the model domain is 931.75 feet (at T-63) and the minimum elevation is 930.35 feet (at T-82), then the calibration target of 10% of the difference is approximately 0.14 feet.

In addition, it is recognized that the two models, although developed separately, must be consistent with each other. That is, values for inputs between the two models cannot be significantly different from each other.

4.1.2 Volumetric Flow-Through Rate Both of these models are dominated by the boundary conditions, that is, the boundary conditions have a strong influence on the model results. Therefore, in addition to simply matching steady-state water levels in the model domain by successive adjustment of aquifer properties and boundary conditions, comparing estimated steady-state flow-through rates was also considered as a means for evaluating calibration. There are a variety of ways to estimate a flow-through rate based on drainage area, baseflow, recharge, etc. This Report No. 04020-044 4-1 October 2006 Groundwater Modeling Report

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