ML20213C653

Burns & Mcdonnell Engineering Co, Inc., Groundwater Flow Model Update. Part 1 of 2

ML20213C653
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Site:	07000925
Issue date:	01/31/2014
From:	Burns & McDonnell Engineering Co
To:	Cimarron Environmental Response Trust, Document Control Desk, Office of Nuclear Material Safety and Safeguards
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Burns&

McDonnell SINCE 1898 GROUNDWATER FLOW MODEL UPDATE CIMARRON REMEDIATION SITE Prepared for CIMARRON ENVIRONMENTAL RESPONSE TRUST Prepared by Burns & McDonnell Engineering Company, Inc.

Kansas City, Missouri Project No. 72454 January 2014

GROUNDWATER FLOW MODEL UPDATE CIMARRON REMEDIATION SITE Prepared for CIMARRON ENVIRONMENTAL RESPONSE TRUST January 2014 Project No. 72454 Prepared by Burns & McDonnell Engineering Company, Inc.

Kansas City, Missouri COPYRIGHT© 2014 BURNS & McDONNELL ENGINEERING COMPANY, INC.

GROUNDWATER FLOW MODEL UPDATE Table of Contents TABLE OF CONTENTS Page No.

1.0 INTRODUCTION

................................................................................................................ 1-1 1.1 Background and Objectives ................................................................................... 1-1 2.0 GROUNDWATER MODEL DESCRIPTION AND UPDATES ......................................... 2-1 2.1 Conceptual Model .................................................................................................. 2-1 2.2 Groundwater Flow ................................................................................................. 2-1 3 .0 GROUNDWATER MODEL CONSTRUCTION ................................................................ 3-1 3.1 Model Construction ................................................................................................ 3-1 3 .2 Boundary Conditions ............................................................................................. 3-2 3 .2.1 No Flow Boundaries .............................................................................................. 3-2 3 .2.2 General Head Boundaries ....................................................................................... 3-2 3 .2.3 River Boundaries .................................................................................................... 3-2 3.3 Hydrogeologic Properties ....................................................................................... 3-3 3.4 Recharge ............................................................................................................... 3-3 3 .5 Model Calibration .................................................................................................. 3-3 3.5.1 Water Budget ......................................................................................................... 3-4 3.5.2 Comparison of Hydraulic Heads ............................................................................ 3-4 3.5.3 Sensitivity Analysis ................................................................................................ 3-5 3.6 Uncertainty ............................................................................................................. 3-5

4.0 REFERENCES

............................................................................................................... 4-l CIMARRON ENVIRONMENTAL RESPONSE TRUST TOC-1 Burns & McDonnell

GROUNDWATER FLOW MODEL UPDATE Table of Contents LIST OF TABLES Table No. Description 3-1 Model Inputs 3-2 Western Alluvial Area Water Level Measurements November 2013 3-3 Burial Area #1 Water Level Measurements November 2013 3-4 Model Water Budget 3-5 Target Residuals Western Alluvial Area 3-6 Target Residuals Burial Area# 1 3-7 Sensitivity Analysis LIST OF FIGURES Figure No. Description 1-1 Location of Cimarron Site 2-1 Western Alluvial Area November 2013 Potentiometric Surface Map 2-2 Burial Area #1 November 2013 Potentiometric Surface Map 3-1 Western Alluvial Area Model Domain 3-2 Burial Area# 1 Model Domain 3-3 Observed versus Simulated Water Levels Western Alluvial Area 3-4 Observed versus Simulated Water Levels Burial Area #1 3-5 Western Alluvial Area Simulated Water Levels and November 2013 Potentiometric Surface Map 3-6 Burial Area# l Simulated Water Levels and November 2013 Potentiometric Surface Map CIMARRON ENVIRONMENTAL RESPONSE TRUST 1-1 Burns & McDonnell

GROUNDWATER FLOW MODEL UPDATE Table of Contents LIST OF ACRONYMS AND ABBREVIATIONS amsl above mean sea level CSM Conceptual Site Model DCGL Derived Concentration Goal Level DEQ Oklahoma Department of Environmental Quality EPM Environmental Properties Management LLC ft foot/feet in/yr inches per year KMNC Kerr-McGee Nuclear Corporation gpm gallons per minute MCL maximum contaminant level NRC Nuclear Regulatory Commission pCi/L picoCuries per liter Site Cimarron Site Trust Cimarron Environmental Response Trust USGS United States Geological Survey

% percent

µg/L micrograms per liter CIMARRON ENVIRONMENTAL RESPONSE TRUST 1-2 Burns & McDonnell

GROUNDWATER FLOW MODEL UPDATE

1.0 INTRODUCTION

Environmental Properties Management LLC (EPM), Trustee for the Cimarron Environmental Response Trust (the Trust), submits this Groundwater Flow Model Update for the Cimarron site (the Site), located at 100 N. Highway 74, Guthrie, Oklahoma.

To evaluate groundwater remediation alternatives at two areas on the Cimarron Site, two existing groundwater flow models were updated. The areas include Burial Area #1 (BA #1) and the Western Alluvial (WA) area. These two models were originally developed as part of the Groundwater Flow Modeling Report (ENSR, 2006) included as Appendix A.

The models were updated with new geologic and hydrogeologic data, based on additional assessment performed in 2012 and 2013. The WA model area was expanded to include a larger area. The base of the alluvial aquifer was updated with new geologic information. The porosity was also updated in both models. Both models were recalibrated to a more comprehensive round of groundwater levels collected in November 2013. Calibration was evaluated by comparing measured groundwater elevations, groundwater flow direction, and water budgets, with simulated elevations, flow paths, and budgets.

Calibration goals included: 1) a mass balance error less than 1% of the water budget, 2) low residual mean, and 3) a qualitative match of model simulated potentiometric surface and observed potentiometric surface evaluated by comparing contours.

Upon Nuclear Regulatory Commission (NRC) and Oklahoma Department of Environmental Quality (DEQ) approval, the updated models will be used to evaluate alternative remediation scenarios using a particle tracking model (MOD PATH). Groundwater extraction with both groundwater recovery trenches and extraction wells will be added to the models, and these will be resubmitted with anticipated groundwater flow rates for both Phase I and Phase II remediation efforts. Upon approval of these revised flow models, a groundwater remediation design will be prepared; this will be included in a comprehensive license amendment request.

1.1 BACKGROUND

AND OBECTIVES The Cimarron facility was formerly operated by Kerr-McGee Nuclear Corporation (KMNC), a wholly owned subsidiary of Kerr-McGee Corporation. The Cimarron facility was utilized for the production of mixed oxide fuel and uranium fuel including enriched uranium reactor fuel pellets, and eventually fuel rods. Enriched uranium fuel was produced at the facility from 1966 through 1975. Process facilities CIMARRON ENVIRONMENTAL RESPONSE TRUST 1-1 Burns & McDonnell

GROUNDWATER FLOW MODEL UPDATE

1.0 INTRODUCTION

included a main production building; several ancillary buildings, five process related collection ponds, two original sanitary lagoons, one new sanitary lagoon, a waste incinerator, several uncovered storage areas, and three burial grounds.

Licensed material exceeds decommissioning criteria for unrestricted release only in groundwater. The concentration of uranium in groundwater must be reduced to achieve unrestricted release of the site and license termination. The Derived Concentration Goal Level (DCGL) for the site is 180 picoCuries per liter (pCi/L) total uranium, and the DEQ has approved a toxicological concentration release criterion of 110 micrograms per liter (µg/L) for uranium in groundwater. In addition to uranium, groundwater in portions of the Site contains two non-radiological chemicals of concern (COCs ): nitrate and fluoride.

DEQ has approved site-specific risk-based concentration limits of 52 milligrams per liter (mg/L) for nitrate and 4 mg/L for fluoride.

Uranium exceeds the license release criterion of 180 pCi/L in three areas: BA #1, the Western Upland (WU) Area and the WA Area (ENSR, 2006a and Cimarron, 2007). These areas are illustrated in Figure 1-1. Uranium exceeds the DEQ criterion of 110 µg/L in these same areas, and the extent within those areas roughly matches the extent of uranium exceeding the NRC criterion. The extent of uranium impact to groundwater has been adequately delineated for the development of a groundwater remedy. Years of environmental monitoring have already demonstrated that nitrate and/or fluoride exceed DEQ criteria in the following areas: the WU Area, the WA Area, the Uranium Pond #1 (UPl) Area, the Uranium Pond #2 (UP2) Area, and the uranium plant storage yard (Well 1319 Area). The flow model domain covers all of the areas that exceed the Maximum Contaminant Level (MCL) and that will eventually require remediation. Once the flow models are approved, two phases of groundwater extraction and injection will be evaluated: Phase I will address uranium exceeding NRC's release criteria, and Phase II will address COCs exceeding MCLs.

These groundwater flow models will be used as a tool to assist in the design of groundwater recovery and re injection systems to reduce the concentrations of COCs in groundwater to less than their release criteria.

CIMARRON ENVIRONMENTAL RESPONSE TRUST 1-2 Burns & McDonnell

GROUNDWATER FLOW MODEL UPDATE 2.0 FACILITY DESCRIPTION 2.0 GROUNDWATER MODEL DESCRIPTION AND UPDATES 2.1 CONCEPTUAL MODEL The Conceptual Site Model (CSM) of the Cimarron River flow system was developed and presented in the Conceptual Site Model-Rev-OJ Report (ENSR, 2006b) prior to the development of the original groundwater models for the WA area and the BA# 1 area. The CSM was then incorporated into the 2006 groundwater models to ensure that the models used existing information and an accepted interpretation of the site-wide geology. Appendix A (Groundwater Flow Modeling Report [ENSR, 2006a]) provides a summary of information on the CSM.

2.2 GROUNDWATER FLOW The Site consists of gently rolling hills, leading northward to the floodplain of the Cimarron River.

Ground elevation varies from approximately 925 ft above mean sea level (amsl) at the northeastern property line to approximately 1,045 ft amsl near the southern property line. Three surface water reservoirs are present on the Site. Unnamed ephemeral streams feed these reservoirs, which discharge to the floodplain of the Cimarron River.

Groundwater flow in the WA area is generally northeastward toward the Cimarron River; flow is driven by a relatively flat hydraulic gradient of 0.002 foot/foot. Figure 2-1 presents a potentiometric surface map of the alluvium for the WA area based on groundwater level measurements during November 2013.

Additional wells installed in the WA area have provided a more refined understanding of the groundwater flow and direction than was provided in the 2006 Groundwater Flow Modeling Report (ENSR, 2006a).

Groundwater in the vicinity of BA # 1 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. Figure 2-2 presents a potentiometric surface map of Sandstone B and the alluvium for the BA # 1 area based on groundwater level measurements collected during November 2013. Flow in Sandstone Bis 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 Band 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. Once groundwater passes through the transitional zone, it enters an area where the hydraulic gradient is relatively flat and CIMARRON ENVIRONMENTAL RESPONSE TRUST 2-1 Burns & McDonnell

GROUNDWATER FLOW MODEL UPDATE 2.0 FACILITY DESCRIPTION groundwater flow is toward the north. Data indicates that the gradient in the sandy alluvium is approximately 0.0007 ft/ft.

CIMARRON ENVIRONMENTAL RESPONSE TRUST 2-2 Burns & McDonnell

GROUNDWATER FLOW MODEL UPDATE 3.0 GROUNDWATER MODEL CONSTRUCTION 3.0 GROUNDWATER MODEL CONSTRUCTION A detailed description of the groundwater model construction is provided in Appendix A. The fo llowing sections describe the updates or new information in the model update.

3.1 MODEL CONSTRUCTION MODFLOW-2000 (Harbaugh et al, 2000), a three-dimensional, finite difference groundwater flow computer code, was selected to update the groundwater flow models. Pre- and post-processing was performed using Groundwater Vistas V (Rumbaugh, 2007). Both groundwater models were run using steady state assumptions.

The numerical model domain for the WA area is shown on Figure 3-1; the model was expanded eastward to address remedial alternatives in the entire area of the nitrate plume as defined by the 10-mg/L isoconcentration contour; it therefore covers a larger area than the 2006 groundwater model. The northern boundary of the model domain remains the Cimarron River and the southern boundary of the model is the extent of the transition zone. The grid size remains 10 feet by 10 feet and contains 159,343 active cells. The model origin (left-bottom comer) is located at X = 2090530 and Y = 320886 in Oklahoma State Plane Coordinates. The model grid is rotated (minus) 20 degrees. The WA model domain includes two layers: Layer 1 represents the alluvium and Layer 2 represents the underlying bedrock.

The numerical domain for BA # 1 is shown on Figure 3-2 and covers the same area as the 2006 groundwater model. The northern boundary of the model domain is the Cimarron River and the southern boundary of the model is the extent of the transition zone. The grid size is 10 feet by 10 feet and contains 267,440 active cells. The model origin (left-bottom comer) is located at X = 2094550 and Y = 322150 in Oklahoma State Plane Coordinates. There is no rotation of the model grid. There are twelve layers in the model. This complex model layering system setup was described in the 2006 Groundwater Flow Modeling Report (ENSR, 2006a) and was not modified during the model update.

No adjustments were made to the number of model layers for either model. For the WA area the base of Layer 1 was adjusted with new bedrock depth data. For BA # 1 new boring data collected in the alluvium suggested the model layer elevations for the sandstone needed to be adjusted, therefore slight adjustments were made to the bedrock elevation in the model. No additional changes were made to the top or base of layers.

CIMARRON ENVIRONMENTAL RESPONSE TRUST 3-1 Burns & McDonnell

GROUNDWATER FLOW MODEL UPDATE 3.0 GROUNDWATER MODEL CONSTRUCTION 3.2 BOUNDARY CONDITIONS The model boundary conditions represent the hydrologic interactions between the inside and outside of the model domain. The boundary conditions simulate flow into and out of the groundwater model.

3.2.1 No Flow Boundaries The active model domains are shown on Figures 3-1 and 3-2. Outside of the active domain are no flow cells that define the western and eastern boundary of both model domains. Within the active model domain all cells are active.

3.2.2 General Head Boundaries The upgradient boundaries for both the WA area and BA # 1 were represented as a General Head Boundary. The upward hydraulic gradient from the underlying bedrock described in the site Conceptual Site Model Revision 01 (ENSR, 2006b) was represented as a General Head Boundary. 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 upward flow of deep groundwater through the alluvium a General Head Boundary was used in the lowest layer in both model domains to represent a higher water level at depth than in the alluvial aquifer (ENSR, 2006a). The General Head Boundary along the southern edge of the model for the WA area was updated to account for the water level elevations observed in the wells during the November 2013 water level measurement event and to match the direction of groundwater flow observed with the recently installed wells in the WA area. No changes were made to the groundwater elevations in Sandstone B.

The general head boundaries for BA #1 were updated during model calibration to enable more accurate prediction of groundwater flow direction in the Sandstone and Alluvium. The general head boundary along the southern boundary of the model, which represents the upgradient boundary was adjusted (in some cases the head was higher, and in some cells the head was decreased). The general head boundary in layer 12 (representing an upward gradient from the lowest bedrock layer) was also adjusted slightly as part of model calibration to match the direction of groundwater flow. These adjustments were reasonable and were made to enable a better calibration to the larger data set available for this model update.

3.2.3 River Boundaries River boundary conditions were updated based on U.S. Geological Survey (USGS) monitoring station data, groundwater level measurements close to the river and as part of model calibration. Data from the CIMARRON ENVIRONMENTAL RESPONSE TRUST 3-2 Burns & McDonnell

GROUNDWATER FLOW MODEL UPDATE 3.0 GROUNDWATER MODEL CONSTRUCTION USGS monitoring stations at Dover (30.0 miles upstream to the west) and Guthrie (10.3 miles downstream to the east) were downloaded to determine river elevations at the time of the November water level measurement event. It was determined that the water levels in the area of the Site were on the order of 930 ft ams I to 933 ft ams I, from east to west. Small variations in river boundary heads were made during model calibration. No changes were made to the boundary conductance or the riverbed elevation.

3.3 HYDROGEOLOGIC PROPERTIES Pneumatic slug tests were performed on select wells in the Western Alluvium to collect data to supplement and verify hydraulic conductivities values used in the 2006 WA model. In addition, conventional slug testing was also performed on select Burial Area# 1 wells during the hydrogeologic investigation. After review of new and existing data, no changes were made to the hydraulic conductivity parameters from the 2006 models. The parameters used for each of the areas are provided in Table 3-1.

The porosity was updated and is also presented in Table 3-1. These values are based on either site-specific data or (where site data is not available) on values obtained from published literature, as listed in Table 3-1.

3.4 RECHARGE Based upon a review of precipitation data from 2013, this year appears to have been a higher than normal precipitation year and water levels at the site were higher than in the 2006 model in accordance with the higher recharge. The calendar year 2013 was the 9th wettest year on record for Central Oklahoma, with 41.1 inches of rainfall through October, compared to mean annual precipitation of 3 7 inches (Oklahoma Climatological Survey, 2013). No changes were made to the recharge values originally presented in the 2006 model because this year does not represent a typical year and the recharge values are meant to represent a long term average condition.

3.5 MODEL CALIBRATION Table 3-2 and Table 3-3 present the most recent water level measurements available from November 2013 for the WA area and BA# 1, respectively. All wells were used as calibration targets except BA# 1 wells 02W25 and 02W51, which are screened over multiple zones represented by multiple layers in the BA #1 model.

CIMARRON ENVIRONMENTAL RESPONSE TRUST 3-3 Burns & McDonnell

GROUNDWATER FLOW MODEL UPDATE 3.0 GROUNDWATER MODEL CONSTRUCTION Both models were recalibrated to water levels collected in November 2013. Calibration was evaluated by comparing measured groundwater elevations, groundwater flow direction, and water budgets, with simulated elevations, flow paths, and budgets. Calibration goals included: 1) a mass balance error less than 1% of the water budget, 2) absolute residual mean error of less than 5% of the range of water level measurements, and 3) a qualitative match of model simulated potentiometric surface and observed potentiometric surface evaluated by comparing contours. Discrepancies between observations and predictions are more pronounced in BA# 1 near the transition zone where the groundwater gradient is steep.

3.5.1 Water Budget The first model calibration goal is to evaluate the mass balance error. A model simulated water budget provides a picture of the flow volumes into and out of the model domain. Water budgets for BA #1 and the WA area for the calibration condition are provided in Table 3-4. General head boundaries account for the highest inflow and the head boundaries and river accounts for the largest outflow. The percent error in the water budget for both models is significantly less than l %, indicating a stable model.

3.5.2 Comparison of Hydraulic Heads Comparison of observed heads and simulated heads was conducted in two different ways including a statistical evaluation of the direct measurement of water level versus the simulated water level at the model targets and through a qualitative examination of simulated potentiometric surface and measured potentiometric surface.

For the WA area model, water level measurements were collected from 43 wells. Simulated and observed hydraulic heads for the steady-state model are compared in Table 3-5 and graphed on Figure 3-3. Both the river boundary elevation and the general head boundary condition were adjusted from the 2006 Model to account for the water elevations observed in November 2013. The simulated elevations near the river are influenced by the river and the exact stage of the river near the WA area is unknown, therefore there may be a slight bias to the water levels but the overall direction of groundwater flow matches the observed conditions. The residual mean is less than 0.1 feet.

For the BA #1 model water level measurements were collected from 70 wells. Simulated and observed hydraulic heads for the steady-state model are compared in Table 3-6 and graphed on Figure 3-4. The residual mean is less than 0.1 feet.

CIMARRON ENVIRONMENTAL RESPONSE TRUST 3-4 Burns & McDonnell

GROUNDWATER FLOW MODEL UPDATE 3.0 GROUNDWATER MODEL CONSTRUCTION The model simulated potentiometric surface and the observed potentiometric surface were compared visually (Figures 3-5 and 3-6). The overall simulated surface is similar to the observed, with some differences to data density especially near the transition zone of BA# l. Discrepancies between observations and predictions are more pronounced in BA# l near the transition zone where the groundwater gradient is steep.

3.5.3 Sensitivity Analysis In the 2006 Groundwater Model (Appendix A), a sensitivity analysis was conducted on the flow model.

The only parameters adjusted in this update in the WA area model were bedrock elevation (base of Layer l ), general head boundary, and river boundary stage. The only parameters adjusted in the BA# 1 model were general head and river boundary stage. Therefore, sensitivity analysis was not repeated for hydraulic conductivity which was addressed in the 2006 Groundwater Model. Modifying the river stage

+/- l foot changed the model calibration, indicating river stage (elevation) is a sensitive parameter (see Table 3-7). This parameter controls flows out of the groundwater models. In the WA area model modifications to the southern boundary general head changed the model calibration. In BA#l the southern boundary general head was a relatively insensitive parameter.

3.6 UNCERTAINTY Site conditions and hydrogeologic properties were estimated through extrapolation of measured or estimated properties or inferences from data measured or estimated based on existing site data and professional judgment. Groundwater models are by definition a simplified version of the aquifer system.

Therefore, these simplifications provide some model limitations.

CIMARRON ENVIRONMENTAL RESPONSE TRUST 3-5 Burns & McDonnell

GROUNDWATER FLOW MODEL UPDATE

4.0 REFERENCES

ENSR, 2006a. Groundwater Flow Modeling Report prepared for Cimarron Corporation (Tronox)

October.

ENSR, 2006b. Conceptual Site Model (CSM)-Rev-01 Report prepared for Cimarron Corporation (Tronox)

Harbough, Arlen, Banta, Edward R., Hill, Mary C., and McDonald, Michael, 2000. MODFLOW-2000, The US. Geological Survey Modular Ground-Water Model.

Oklahoma Climatological Survey, 2013. www.climate.ok.gov. Accessed October, 2013.

Pollock, D. W., 1989. Documentation of Computer Programs to Compute and Display Pathlines Using Results from the US. Geological Survey Modular Three-Dimensional, Finite-Difference, Groundwater Flow Model. USGS Open File Report no.89-391, 188 p.

Rumbaugh, J. 0. and D. B. Rumbaugh, 201 l. Groundwater Vistas, Version 6. Environmental Simulations, Inc., Reynolds, PA.

CIMARRON ENVIRONMENTAL RESPONSE TRUST 5-1 Burns & McDonnell

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)

Kv 3.30E-01 ft/day 10% of KH Kv 2 .35E+01 ft/day 10% of KH

~

Fi ll Horizontal Anisotropy 1 ----- No horizontal anisotropy ai Horizontal An isotropy 1 ----- No horizontal anisotropy Vertical Anisotropy (1l 1 ----- No vertical anisotropy d Vertical Anisotropy (KH/Kv) 1 ----- No vertical anisotropy (Kh/Kv)

-0 C

Porosity 30  % Freeze & Cherry, 1979 Table 2.4 (1l Specific Storage 0.0 1 ----- Default, not used in steady state model CJ)

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 Silt Horizontal Anisotropy 1 ----- No horizontal anisotropy KH 3 0OE+00 ft/day Slug Test, Calibration (ENSR, 2006a)

Vertical Anisotropy N° (Kh/Kv) 1 ----- No vertical anisotropy ai>, Kv 1.S0E-01 ft/day 5% of KH (1l Porosity 20  % Freeze & Cherry, 1979 Table 2.4 d Horizontal Anisotropy 1 ----- No horizontal anisotropy

(.)

KH 2 .35E+02 ft/day Average of Pumping Test (ENSR , 2006a) (I) Vertical Anisotropy (KH/Kv) 1 ----- No vertical anisotropy C

Kv 2 .53E+01 ft/day 10% of KH 0 Specific Storage 0.01 ----- Default, not used in steady state model en

-0 Sand Horizontal An isotropy 1 ----- No horizontal anisotropy C Specific Yield 0.01 ----- Default, not used in steady state model (1l Vertical Anisotropy CJ)

(KH/Kv) 1 ----- No vertical anisotropy Porosity 5  % Freeze & Cherry , 1979 Table 2.4 Porosity 30  % Freeze & Cherry, 1979 Table 2.4 ENSR, 2006a (Artificially high to improve KH 5 O0E-01 ft/day Cimarron River: Value Units Source model stability)

Kv 5 O0E-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 1 ----- No vertical anisotropy Riverbed Conductance 20 ,000 (ft2/day)/ft ENSR, 2006a (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 KH Recharge 5.40E-04 ft/day ENSR CSM Sec-3.1.1 & 3.1 .4 Siltstone Horizontal Anisotropy 1 ----- No horizontal anisotropy Vertical Anisotropy 1 ----- No vertical anisotropy Notes:

(KH/Kv)

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 i~ the WAA, this is not represented in the model as a layer. Since Vertical Anisotropy 1 ----- No vertical anisotropy its effect on recharge should be reflected in the recharge input, any references to clay in the table are omitted, (KH/Kv)

Porosity 5  % Freeze & Cherry, 1979 Table 2.4 including Longitudinal Dispersivity, which is not needed for purposes of this model as chemical transport KH 5.00E+O0 ft/day Slug Test, Calibration (ENSR, 2006a) modeling will not be performed.

Kv 2.SOE-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+O0 ft/day Slug Test, Ca libration (ENSR , 2006a)

Kv 1.S0E-01 ft/day 5% of KH Sandstone-C Horizontal Anisotropy 1 ----- No horizontal anisotropy Vertical Anisotropy (KH/Kv) 1 ----- No vertical anisotropy Porosity 5  % Freeze & Cherry, 1979 Table 2.4 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 (ft /day) Inflow (ft3 /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 323265.4 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 TMW-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

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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 I

ENSR I AECOM

Prepared for:

Cimarron Corporation (Tronox)

Oklahoma Groundwater Flow Modeling Report Maya Desai and Ken Heim

~d~})._:___ ,c_~_....,!.f_ --V~:::::::-

Michael Meenan and James Cao f' l~~ 1 t1-~o,.-,_._, (~ G,o Reviewed By ENSR Corporation October 2006 Document No.: 04020-044-327 ENSR I 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 1950 and 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