ML20213C652

Ensr Corp., Groundwater Flow Modeling Report

ML20213C652
Person / Time
Site:	07000925
Issue date:	10/30/2006
From:	Desai M, Heim K ENSR Corp
To:	Cimarron Corp, Document Control Desk, Office of Nuclear Material Safety and Safeguards
References
04020-044
Download: ML20213C652 (51)

Text

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 U,..f"'-';1(4 c.-= Q..-,~

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Michael Meenan and James Cao 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 1O - 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.

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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

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 th 925. 0 feet. A further statistical evaluation indicated that the 5 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 B and the alluvium for the BA #1 area based on groundwater level measurements during AugusUSeptember 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 fooUfoot. 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 AugusUSeptember 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 (B), 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 1O 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 1O ft by 1O 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 1O 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

ENSR section discusses one of the methods using one set of input values. Though not a rigorous calibration target, it is important to be mindful of the water budget, or flow-through volumes for the models. Therefore, the estimate of flow-through rate presented here is intended to provide a general , agai n not rigorous, frame of reference by which to evaluate the calibration.

One estimate of the steady-state flow rate through each model domain was made by multiplying an estimate of rainfall recharge by the total drainage area to arrive at an annual recharge rate. This recharge volume represents the water that enters the groundwater system over the entire watershed - not just the model domain and/or immediate site vicinity. However, this entire volume will pass through the model domain on its way to the regional discharge boundary - The Cimarron River. During the calibration process, the model boundary conditions were adjusted in consideration of this calculated annual flow-through rate. Note that in making this estimate, it is assumed that the surface water divides as represented from the topographic contours coincide with groundwater divides.

For the BA #1 area, the total drainage area upgradient and including the model domain is approximately 2.1 square miles. Based on an annual recharge rate of 2.4 in/yr over the BA #1 watershed , the total flow through 3

rate for the BA #1 model domain was estimated to be approximately 32,000 ft /day. For the WA area, the total 2

upgradient drainage area and model domain is 0.32 mi resulting in an estimated total flow through rate of the 3

WA model domain of approximately 5,000 ft /day.

During the calibration process, adjustments of hydrogeologic characteristics and boundary conditions were made in light of these estimates of flow. Comparing these estimates with the calibrated results provides one way to evaluate calibration.

4.1.3 Plume Migration In addition to accurately reproducing water levels and volumetric flow rate through the groundwater system, a pathline analysis was conducted to demonstrate an accurate representation of groundwater movement in the system. This was especially important for BA #1 area where there is ample water quality data by which to infer flow paths. In the case of the BA #1 site, the current distribution of the U plume was compared to predicted particle pathlines developed from particles initiated in the original U source area. By demonstrating that particles seeded in the source area would effectively follow the path of a measured plume, the pathline simulation can illustrate the accuracy of the model in representing flow directions and groundwater gradients.

For the BA #1 area, the MODPATH model was used to predict the fate of particles seeded at the approximate location of the initial U source. The results of the steady-state MODFLOW model were used as the groundwater flow driver for the MODPATH simulation and the predicted paths of the particles were compared with the plume map for U at the BA #1 area. For the simpler WA model, a pathline comparison was not required.

4.2 Calibration Parameters For both of these models there are strong boundary conditions . These are the general head boundary at the upgradient (south) edge of each of the models to simulate water entering the model domain from the sandstones, the general head boundary along the bottom of the models to simulate flow up from the sandstone into overlying soils, and the river where groundwater discharges. Flow and elevations in the model are dominated by the flow entering the model through the general head boundaries and flow leaving the model through the river. When models are so strongly influenced by these boundary conditions, calibrated solutions can result from a variety of non-unique combinations of boundaries and hydraulic conductivities.

Early in the calibration process, adjustments to hydraulic conductivity, recharge rate, and river conductance were made to simulate groundwater elevations similar to measured groundwater elevations. Once these initial adjustments were made, calibration focused on adjusting the head and conductance of the general head boundaries.

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ENSR The general head boundary uses two variables to control the transfer of water across a model boundary including a water level (head) and a conductance term. The assigned groundwater elevation indicates the pressure head along the boundary. This is essentially the starting point for predicted heads along the boundary and adjacent water levels in the model are either higher or lower depending on boundary conditions and the additions or losses of water elsewhere within the model domain. The rate at which water enters the model through the general head boundary is controlled by the conductance term. A high conductance indicates a relatively limitless supply of water to the aquifer when the water table downgradient of the boundary is stressed and a low conductance indicates a limited supply of water to the aquifer. Limiting the conductance is of particular importance if only a portion of the total aquifer is included within the model domain and it is unrealistic to assume that the upgradient supply of water is limitless.

Each groundwater model was re-run several times with successive adjustment to the calibration parameters (general head boundaries) until the models were satisfactorily calibrated.

4.3 Calibration Results In the following sections the results of each model's calibration is discussed with respect to the calibration targets discussed in Section 4.1 .

4.3.1 BA #1 In the calibration process, hydraulic conductivity, recharge, and river elevation and conductance were adjusted; the final calibration values are summarized in Table 3. The other adjusted parameters were the elevation and the conductance of the general head boundaries both at the back edge and on the bottom of the model. Table 3 also includes the calibrated values for these inputs.

Through successive adjustment of the general head boundary parameters, the mean absolute error (MAE) between the measured and predicted water levels was calculated to be 1.2 feet. This value is much less than the 2.6 feet which is 10% of the total water table relief at the site; this indicates an acceptable model calibration. Additional adjustments to the shape and orientation of the underlying general head boundary were made to simulate flow paths (using MODPATH) consistent with that which is inferred from the concentrations downgradient of the burial area. Finally, adjustments to the general head boundary were also made to simulate an approximate flow-through volume consistent with what is expected based on the drainage area size and recharge rate. The following are calibration results that indicate transfer rates of groundwater through the BA #1 model domain.

• Calibrated transfer rate of water from the model domain to the Cimarron River is 19,100 ft3/day.

• Calibrated inflow rate from upgradient sandstone/mudstone units to the model domain is 16,900 ft3/day.

3

• Recharge rate to the aquifer is 1,200 ft /day.

3 3 The difference between the total inflow (18,100 ft /day) and the total outflow (19,100 ft /day) equals ~1,000 3

ft /day, which represents less than a 5% error in the water balance and is considered acceptable. Figure 13 summarizes the calibration results showing the measured versus predictefd groundwater elevations, the static simulated groundwater contours and a comparison of the particle pathlines originating from the burial area with the plume map as drawn from concentrations measured in August 2004. In the calibration process, targets with the best data (i.e., water level, flow path) are given preference over targets with less data (i.e., flow through rates). Thus, a good match of water levels, flow paths, and gradients is achieved, but justifiably at the expense, somewhat, of the flow-through match . The total calibrated flow through value above is less than the calculated flow-through rate based on drainage area and recharge presented in Section 4.1.2.

One of Arcadis' bioremediation design objectives is to estimate flux (dissolved oxygen) through the plume.

Based on the calibrated flow-through rates, ZoneBudget (Harbaugh, 1990) was used in conjunction with the Report No. 04020-044 4-3 October 2006 Groundwater Modeling Report

ENSR MODFLOW output to calculate the flux through the plume areas only. The 2004 plume area for the BA #1 area is depicted on Figure 4-11 (CSM, Rev.1, ENSR, 2006); the plume was assumed to extend to the bottom of model Layer 7, which coincides with the lowest elevation where concentrations over 180 pCi/L were detected in August 2004. The flux was estimated at 19 gpm.

4.3.2 WA area In the calibration process, hydraulic conductivity, recharge, and river elevation and conductance were adjusted and the final calibration values are summarized in Table 4. The other adjusted parameter was the elevation and the conductance of the general head boundaries both at the back edge and on the bottom of the model.

Table 4 also includes the calibrated values for these inputs.

Conceptually the interaction of the sandstones with the alluvial materials should be very similar regardless of model area. That is, the conductance of Sandstone B and Sandstone C should be the same for the BA #1 model and for the WA model. Because the BA #1 model is so much more complicated, it was calibrated first and then the calibrated conductance values were applied to the WA model. In effect, calibration of the WA model relied almost exclusively on changing the elevations assigned to the general head boundaries.

Through successive adjustment of the general head boundary elevation the average absolute error between the measured and predicted water levels was determined to be 0.31 feet. This value is more than the target of 0.14 feet, which is 10% of the total water table relief at the site. When the gradient is very flat as it is in this case measured groundwater elevation differences over short distances can be very difficult to simulate, especially when spatial variations in hydraulic conductivity are not considered. Furthermore, because the calibration data set is averaged over several rounds of data, seasonal differences may be more apparent.

The flow paths generated based on the MODFLOW head field and the MODPATH model indicates that groundwater flow paths are generally from the south to the north, consistent with the conceptual model and with the inferred flow paths based on U concentrations from August 2004.

The following are calibration results that indicate transfer rates of groundwater through the WA area model domain.

• Calibrated transfer rate of water from the aquifer to the Cimarron River is 57,000 ft3/day.

• Calibrated inflow rate from upgradient sandstone/mudstone units to the model domain is 54,300 3

ft /day.

3

• Recharge rate to the aquifer is 2,600 ft /day .

3 3 The difference between the total inflow (56,900 ft /day) and the total outflow (57,000 ft /day) equals ~100 3

ft /day, which represents less than a 1% error and is considered acceptable. Figure 14 summarizes the calibration results showing the measured versus predicted groundwater elevations and the static simulated groundwater contours. In the calibration process, targets with the best data (i.e., water level, flow path) are given preference over targets with less data (i.e., flow through rates). Thus, a good match of water levels, flow paths, and gradients is achieved, but justifiably at the expense, somewhat, of the flow through match. The total flow through value presented above is more than the flow-through rate calculated based on drainage area and recharge presented in Section 4.1.3.

One of Arcadis's bioremediation design objectives is to estimate flux (dissolved oxygen) through the plume.

Based on the calibrated flow-through rates, ZoneBudget (Harbaugh, 1990) was used in conjunction with the MODFLOW output to calculate the flux through the plume areas only. For the WA model the total U distribution was assumed to be an area that extends from near the base of the escarpment northward toward the Cjmarron River, apparently originating where the western pipeline entered the alluvium north of the former Sanitary Lagoons. Uranium concentrations that exceeded 180 pCi/L in August 2004 are presented in Figure 4-15, CSM-Rev 01, ENSR, 2006). This impacted area extended only to the bottom of model Layer 1 since Report No. 04020-044 4-4 October 2006 Groundwater Modeling Report

ENSR there were no concentrations of U detected in the sandstone (i.e., Layer 2). The flux for this plume area was 31 gpm.

4.3.3 Discussion In addition to evaluating the calibration of the model from the standpoint of quantitative targets, another way to evaluate the model is how well it aligns with the conceptual model. Because there is often aquifer test data (i.e., slug tests, pumping tests), comparison of calibrated and measured hydraulic conductivities is a good way to evaluate how well the model corresponds with the conceptual model. Table 1 summarizes the measured hydraulic conductivities and Tables 3 and 4 summarize the calibrated hydraulic conductivities. Tables 3 and 4 also summarize the calibrated inputs for the river, recharge, and general head boundaries.

There are no measured hydraulic conductivity data for Fill, Silt, Clay, and Sandstone A. For Alluvium, the measured hydraulic conductivity values range from about 20 to more than 275 ft/day. Pumping tests generally provide a better estimate of aquifer hydraulic conductivity than slug tests. Focusing on just pumping test results, the hydraulic conductivity ranges from about 120 to about 275 ft/day. The calibrated value, 235 ft/day, is consistent with this range.

Slug test data was also available from four wells screened in Sandstone B. The hydraulic conductivity results ranged from approximately 0.1 to 2 ft/day. The calibrated value for Sandstone B was 5 ft/day. One slug test was completed in Sandstone C and the result was 0.2 ft/day, less than the calibrated value of 3 ft/day. In both instances, the calibrated values are higher than the measured. Values derived from pump tests and values from calibrated models are often higher than slug test data. The locations of slug tests represent only a tiny fraction of each Sandstone Band C. During model calibration, the values are adjusted upward and may ultimately be more representative of site conditions than just a few data points may indicate.

In some instances, the hydraulic conductivities were adjusted upward to provide numerical stability to the model. The model can become numerically unstable when there are large changes (in hydraulic conductivity, groundwater elevation, etc) over short distances. In the BA#1 model this happens, for instance where clay (hydraulic conductivity less than 1 ft/day) comes into contact with sand (over 200 ft/day). This instability can be mitigated by smoothing those contrasts. Sometimes this is done at the expense of making a perfect match with measured data. As long as the adjustments are consistent with the conceptual model, the conceptual understanding of how different soils transmit water, and are mindful of the project objectives, smoothing typically does not impact simulations. The model will simulate this general behavior whether the contrast is 100 or 1000 times different. This change was evaluated in the sensitivity analyses, discussed below.

In the absence of data for fill, silt, clay and Sandstone A, estimates were made based on literature values and on qualitative site observations. Adjustments to these values were made during the calibration to encourage a good match of simulated and measured groundwater elevation and to encourage numerical stability.

Figures 13 and 14 summarize the calibration results. The graph shows the measured versus predicted groundwater elevations. Each point represents the groundwater elevation at a particular well. The closer the point is to the line, the less difference there is between the simulated and observed groundwater elevation.

These figures also show the simulated groundwater contour map. Overall these match well for both models.

For the BA#1 model, Figure 13 also shows a comparison of a particle pathline originating from the Burial Area with the plume map as drawn from U concentrations measured on August 2004. As discussed above, these pathlines are a good match for the groundwater flow paths suggested by the distribution of U in groundwater.

4.3.4 Summary of Calibration Results Three calibration targets were set as objectives prior to model calibration: achieve a good match between simulated and measured groundwater elevations and gradients, achieve a good match with the site conceptual model, and yield relatively consistent correlation of water budget estimates. For the most part, the first two objectives were achieved without difficulty. The measured and simulated groundwater elevations are in Report No. 04020-044 4-5 October 2006 Groundwater Modeling Report

ENSR concert and especially for the BA#1 model, the simulated flow directions agree with flow directions indicated by U concentrations. Discrepancies between measured and simulated groundwater elevations, flow paths, and water budgets are explainable and can be accounted for when interpreting simulation results. Ultimately, the discrepancies in estimated flow-through volumes and simulated flow-through volumes are explained by ranges in recharge to and discharge from the site as well as uncertainties inherent in the modeling.

4.4 Sensitivity Analysis In order to characterize the effects of uncertainty in the modeling parameters (recharge, hydraulic conductivity, and general head boundaries) on model predictions, sensitivity runs were conducted. In these runs, each parameter was varied from the base run (calibrated model). Differences were noted and these differences help in understanding the range of possible predictions, and how uncertainties in these parameters may affect model predictions.

Rainfall recharge, hydraulic conductivity and the general head boundary were the three primary variables tested in the sensitivity evaluation. Rainfall recharge has a direct impact on the amount of water moving through the aquifer and an impact on the amount of water that can be withdrawn from an aquifer. The conductivity is the fundamental parameter describing how effectively groundwater is transmitted in an aquifer.

The sensitivity evaluation was focused on the hydraulic conductivity of the sand. The upgradient head boundary and the aquifer bottom boundary in the model of the BA #1 area were both represented using the general head boundary (GHB) in MODFLOW. This boundary fixes a water level at a specific group of cells in a model domain and uses a conductance term to facilitate the calculation of the volume of water that can be moved across the general head boundary. Like recharge, the general head boundary has a significant effect on the hydrologic budget and can largely control the amount of water entering or leaving the model domain.

Therefore the models' sensitivity to this parameter was evaluated also.

One parameter was adjusted to complete the sensitivity analysis of the BA #1 area to enable this already complex and numerically sensitive model to iterate to a solution under the range of conditions imposed by the sensitivity analysis. During the sensitivity analysis, the horizontal hydraulic conductivity of the clay was increased from the 0.5 ft/day that was used during the model calibration, to 10 ft/day. By increasing the hydraulic conductivity of the clay, the gradients were decreased resulting in a smoother transition across adjacent model cells and therefore, a more stable model.

With the parameters selected for the sensitivity analysis a sequence of model scenarios were developed and run to evaluate the effect of varying the magnitudes of the selected parameters on the calibration. The results are as follows.

For the BA#' 1 area, with the increased hydraulic conductivity of the clay, calibration results were marginally different results then when the original calibrated clay conductivity value was used .

Modification of the recharge rate by a factor of 50% and 200% resulted in only minor changes to the steady-state head calibration. This is largely because of the relatively small component of the hydrologic budget that surface recharge represents in the calibrated model, which is less than 10% of the overall budget.

Changing the hydrologic conductivity in the sand aquifer by a factor of 50% and 200% resulted in a relatively minor change to the steady state calibration. Small differences in the Mean Absolute Error (MAE) between the calibration run and the sensitivity runs are primarily because the Mean Absolute Error value is calculated using several wells outside of the sand aquifer that were relatively unaffected by the change and because the flow regime is so strongly controlled by the recharge and discharge boundary conditions.

Changes made independently to the head and the conductance of the subsurface general head boundary by factors of 50% and 200% resulted in fairly substantial changes to the steady state calibration. This is because water flowing into the model through the subsurface general head boundary represents a significant portion of Report No. 04020-044 4-6 October 2006 Groundwater Modeling Report

ENSR the total water budget in the model. Both the elevation and the conductance are strong controllers of how much water is permitted to enter the model, thus have obvious impacts to model predictions.

4.5 Uncertainties and Assumptions In order to fully understand the predictions and simulations, it is important to understand the factors that contribute to model uncertainty. Addressing these uncertainties allows users to understand and interpret the results of the simulations.

Flow-Through Volumes As discussed above, estimates of flow-through volume were made based on drainage area and recharge rates. Comparing these estimates to simulated flow-through volumes was one way calibration was evaluated.

Other methods can also be used to estimate flow-through volumes. For instance, one method varies recharge rates based on the ranges of annual precipitation rates of 24 inches, 30 inches, 32 inches, and 42 inches (CSM-Rev 01, ENSR, 2006). Another method uses streamflow measurements collected by the USGS on the Cimarron River at Dover (upstream) and Guthrie (downstream) and basin scaling to estimate the rate of groundwater discharge from the Western Alluvial area and the Burial Area #1. These approaches indicated that flow-through volume estimates may range over more than an order of magnitude depending on the methodology for making the estimate. In turn, depending on the technique to calculate flow-through volumes, different groundwater fluxes through the plume areas may be calculated.

Equivalent Porous Media Assumption The MODFLOW model assumes that flow is through a porous media. That is, MODFLOW is designed to model groundwater flow through unconsolidated materials. MODFLOW is often used to model consolidated soils and bedrock, but flow through these materials may be governed by fractured flow, not porous media flow.

The presence of fractures may greatly affect the direction and rate of groundwater flow especially on a local scale. For example, if the local groundwater flow system is dominated by a single fracture, the orientation of the fracture will control the direction of travel. Depending on the fracture's size, groundwater velocity through the fracture may be higher than would occur in more diffuse flow through a porous media even if the flux is the same. There is no evidence that groundwater flow and contaminant transport at the Cimarron Site are necessarily controlled by fracture flow. However, there may be local effects associated with fracturing the bedrock units. It is beyond the capabilities of the current model to accurately predict the time of travel through fractures in the consolidated soils or bedrock. Travel times through the consolidated units (sandstones and mudstones) can be calculated by MODPATH based on the assumption that the consolidated units are an equivalent porous media. The use of equivalent porous media assumptions are best suited for predictions over the scale of the model and may not provide accurate predictions local to a fracture or fracture system.

Despite this uncertainty, groundwater flow is still likely to coincide generally with the surface water catchments and groundwater will discharge to the surface waters located within and adjacent to the site.

Steady-State Assumption If the model should be used to simulate either groundwater extraction or injection, it should be noted that the groundwater model assumes that steady-state is reached instantaneously. In fact, there will be some time that will elapse before steady-state will be reached. Simulated pumping or injection also assumes that groundwater will be extracted from or injected into the entire cell saturated thickness. In fact, depending on where the well screen is placed and where the pump is set, this may not hold true. Simulated pumping or injection also occurs throughout the entire 10 foot by 10 foot cell. For these reasons, pumping and injection scenarios implemented in the field may result in drawdown and flow rates different from what has been predicted. Because the model accurately represents the conceptual model and overall observed flow rates, directions, and gradients, overall capture zones should be relatively accurate. As field data become available, they may be used to update and refine the model.

Report No. 04020-044 4-7 October 2006 Groundwater Modeling Report

ENSR Fate and Transport Issues It should be noted that this application is a flow model and, as such, only considers the movement of water in the subsurface. Constituents dissolved in groundwater may be subject to processes that result in migration that cannot be explained exclusively by groundwater velocity (i.e., advection).

Groundwater velocities generated by the model and presented in the CSM, Rev.1 (ENSR, 2006) require input of a value for porosity for each of the geologic materials. There are no site-specific data on porosities, and they are likely to be very variable. Literature values were used. It should be recognized that the calculated velocities are directly dependent on these input values of porosity. Changes to the porosity values could potentially change estimate velocities by more than an order of magnitude.

Report No. 04020-044 4-8 October 2006 Groundwater Modeling Report

ENSR 5.0

SUMMARY

AND CONCLUSIONS Numerical groundwater models for the BA #1 and the WA areas have been conceptualized, developed, and calibrated to provide tools by which groundwater flow can be evaluated and changes to groundwater flow can be assessed as different remedial alternatives are simulated. In particular, in consideration of a bioremediation approach, the model may be used design scenarios for injection of reagents that will enhance stabilization of U and to demonstrate the permanence of uranium stabilization in groundwater.

The objective was achieved by developing and calibrating the numerical models to include key data that characterize groundwater flow at the site consistent with the CSM-Rev 01 (ENSR, 2006). Specifically, the BA

1. 1 model domain included portions of the uplands at the site, which are underlain by a series of sandstone and mudstone layers, the transition zone, which is characterized by silts and clays underlain by sandstone and mudstone, and the alluvial valley where the geology is predominantly sand with smaller fractions of silt and clay. The BA #1 model was bounded on the south, in part, by the reservoir and on the north by the Cimarron River. The WA model included only the alluvial materials (sands, silts, clay) from the escarpment that forms the northern edge of the uplands to the Cimarron River. In the WA area, the alluvial materials are underlain by sandstone. Upgradient sandstones in both models are assumed to contribute groundwater to the alluvial soils and overlying sandstone and mudstone units. The Cimarron River is a discharge boundary to which all modeled groundwater flows.

Calibration targets included measured groundwater elevations, flow budgets, and flow path data. The flow models achieved good calibration to the observed groundwater elevation data, to the estimated water budgets, and to observed flow path trajectories. Discrepancies between observed and predicted elevations were reasonable. The simulated water table configuration for each model was consistent with flow paths suggested by observations of U concentrations. Overall hydrogeological concepts as presented in the Conceptual Site Model, Rev 01 (ENSR, 2006) were captured by the numerical models. A sensitivity evaluation established that the model simulations will be most sensitive to boundary conditions, especially the recharge from upgradient sandstone units. Uncertainties, especially associated with boundary conditions, are important when interpreting and using model predictions in remedial designs.

Ultimately, the resulting numerical models have captured key hydrologic and geologic features that shape the groundwater flow directions, patterns, and rates, thus satisfying the objective to provide useful tools to consider remediation design options. For instance, groundwater extraction can be simulated to create capture zones that include areas of high U concentration . Injection scenarios can also be simulated to ensure adequate distribution of reagents. Even the calibrated model itself can yield valuable information about groundwater flow directions and rates. For instance, the design of the bioremediation system requires estimates of groundwater flux to the plume area, which can be extracted from the model. The calibrated BA #1 model indicates that there are 19 gpm to the plume area. The calibrated WA area model indicates that there are 31 gpm to the impacted area. ARCADIS will use the model further to help design the bioremediation effort; their uses of the model will be documented in their work plan.

Report No. 04020-044 5-1 October 2006 Groundwater Modeling Report

ENSR

6.0 REFERENCES

Adams, G.P. and D.L. Bergman. 1995. Geohydrology of Alluvium and Terrace Deposits, Cimarron River from Freedom to Guthrie, Oklahoma. USGS WRI 95-4066.

Cimarron Corporation, 2003. Burial Area #1 Groundwater Assessment Report for Cimarron Corporation's Former Nuclear Fuel Fabrication Facility, January.

Freeze, R.A. and J. A. Cherry. 1979. Groundwater. Englewood Cliffs, NJ: Prentice-Hall.

Harbaugh, Arlen W., 1990. A computer program for calculating subregional water budgets using results from the U.S. Geological Survey modular three-dimensional ground-water flow model: U.S. Geological Survey Open-File Report 90-392, 46 p.

MacDonald, Michael G. and Arlen, W. Harbaugh. 1988. A Modular Three-Dimensional Finite-Difference Ground-Water Flow Model. U.S. Geological Survey Open File Report 83-875.

Pollock, David W. 1994. User's Guide for MODPATH/MODPATH-PLOT, Version 3:A particle tracking post-processing package for MODFLOW, the U. S. Geological Survey finite-difference ground-water flow model. U.

S. Geological Survey Open-File Report 94-464.

Weaver, J.C., 1998. Low-Flow Characteristics and Discharge Profiles for Selected Streams in the Cimarron River Basin, Oklahoma. U.S. Geological Survey Water-Resources Investigations Report 98-4135.

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

ENSR Tables Report No. 04020-044 October 2006 Groundwater Modeling Report

Table 1 Summary of Slug and Aquifer Test Results Cimarron Corporation Crescent, Oklahoma Hydraulic Conductivity (emfs)

Analysis Methodology t-'umpmg Test- Pumping Slug Test Jacob Test- Cooper-Bouwer & Slug Test Sieve Straight Pumping distance- Butler and Bredehoeft- Geometric Geometric Geology Well Rice Hvorslev Analysis Line Test - tit' drawdown Garnett Papadopulos Mean (emfs) Mean (ft/day)

Alluvium TMW-09*** 6.01 E-03 1.20E-03 2.69E-03 7.61 TMW-13 6.99E-02 6.20E-02 6.58E-02 186.61 02W2* 1.92E-05 1.92E-05 0.05 02W10* 3.36E-04 2.80E-04 3.07E-04 0.87 02W11*** 3.24E-03 4.00E-03 1.70E-03 2.80E-03 7.95 02W15 1.09E-02 1.80E-02 1.00E-02 1.25E-02 35.49 02W16 3.66E-02 3.90E-02 1.1 0E-02 2.50E-02 70.98 02W17 3.25E-02 6.00E-02 6.00E-03 2.27E-02 64.35 02W22 8.90E-02 8.90E-02 252.28 02W33 1.30E-02 1.90E-02 1.70E-03 7.49E-03 21 .23 02W46* 3.56E-05 1.37E-05 2.21 E-05 0.06 02W56** 4.20E-02 7.10E-02 1.70E-02 8.30E-02 8.30E-02 8.60E-02 5.58E-02 158.04 02W58 9.60E-02 8.60E-02 9.09E-02 257.56 02W59 1.40E-02 3.30E-02 9.60E-02 8.00E-02 4.34E-02 123.03 02W60 1.10E-01 8.60E-02 9.73E-02 275.70 02W61 2.20E-02 2.30E-02 1.10E-01 8.90E-02 4.72E-02 133.73 02W62 2.80E-02 2.80E-02 79.37 TMW-24 4.13E-02 4.13E-02 117.07 Sandstone B TMW-01 6.35E-05 2.70E-05 4.14E-05 0.12 TMW-20 9.97E-04 4.10E-04 6.39E-04 1.81 02W40 5.50E-04 5.50E-04 1.56 02W51 7.10E-05 2.39E-05 4.12E-05 0.12 Sandstone C 02W48 7.85E-05 7.85E-05 0.22 Notes:

All data presented is summarized from the Burial Area #1 Groundwater Assessment Report (Cimarron Corporation, 2003).

• Clay present at or near this well; data excluded from calculating ranges, mean .

• • Pumping Well

• • • Some clays/silts present in well screen; data excluded from calculating ranges, means.

October 22, 2006 Page 1 of 1

Table 2 Summary of Groundwater Elevation Data used for Calibration Cimarron Corporation Crescent, Oklahoma 9/16/03 12/16/03 Aug/Sep 04 5/24/05 AvgWL Summary Water Level Water Level Water Level Water Level Elevation ID (feet) (feet) (feet) (feet) (feet)

• • 1206 n/a-SEEP -----

• • 1206 n/a-SEEP -----

• • 1208 n/a-SEEP -----

• • 1208 n/a-SEEP -----

1311 965.48 964.83 966.02 962.70 964.76 1312 962.66 963.64 964.48 964.66 963.86 1312 964 .66 964.66 1313 963.60 963.19 964.04 963.97 963.70 1314 944.02 943.67 944.14 944.57 944.10 1315R 932.31 934.73 935.46 936.45 934.74 1315R 936.45 936.45 1316R 931 .57 932.89 936.84 936.12 934.35 1319 A-1 969.86 969.63 970.37 969.88 969 .93 1319 A-2 969 .74 969.49 - 969.79 969 .68 1319 A-3 968.46 968 .56 968.45 968.35 968.45 1319 B-1 946.73 947.13 948.35 pumping 947.40 1319 B-1 pumping -----

1319 B-2 947.73 948.25 949.44 950.06 948.87 1319 B-3 946.67 947.12 948.37 949.02 947.79 1319 B-4 946.18 946.52 947.84 948.54 947.27 1319 B-5 945.61 944.87 946.24 947 .37 946.02 1319 C-1 942.27 943.81 946.01 pumping 944.03 1319 C-1 pumping -----

1319 C-2 939.80 940.69 941.94 941.50 940.98 1319 C-3 939.06 939.78 941.07 940.85 940.19 1320 967.04 966.58 968.34 968.20 967.54 1321 935.97 936.45 937.74 938.07 937.06 1322 967.97 966.43 967.95 968.48 967.71 1323 941.84 942.49 943.29 944.19 942.95 1324 968.10 967.45 969.20 969.28 968.51 1325 971.25 970.62 972.44 972.31 971.66 1326 970.85 970.49 971.45 971.54 971.08 1327 966.02 965.95 966.62 966.19 1327B 966.05 965.55 966 .01 966.63 966.06 1328 948.85 950.79 950.71  ? 950.12 1329 968.26 967.97 968.00 968.62 968.21 1330 967.97 967.72 969.37 970 .07 968.78 1331 965.80 965.30 967.02 966.63 966.19 1332 940.00 940.47 941.75 942.43 941.16 1333 967.92 967.16 968.48 969.03 968.15 1334 966.51 966.58 968.20 967.72 967.25 1335A 969.81 969.07 970.78 970.45 970.03 1336A 959.65 959.57 960.53 960.08 959.96 1337 965.90 965.48 966.95 966.11 October 22, 2006 Page 1 of 5

Table 2 Summary of Groundwater Elevation Data used for Calibration Cimarron Corporation Crescent, Oklahoma 9/16/03 12/16/03 Aug/Sep 04 5/24/05 AvgWL Summary Water Level Water Level Water Level Water Level Elevation ID (feet) (feet) (feet) (feet) (feet) 1338 943.71 943.62 945.25 939.32 942.98 1339 951.68 952.74 938.46 955.13 949.50 1340 961.49 961.42 962.42 961.78 1341 936.75 936.75 939.39 937.63 1342 929.95 930.13 930.40 930.16 1343 928.37 928.57 929.40 928.78 1344 925.84 926.22 928.62 926.89 1345 933.74 933.63 935.32 936.30 934.74 1346 937.60 937.31 938.81 939.22 938.23 1347 965.13 964.47 965.96 965.18 1348 975.27 975.26 977.96 977.50 976.49 1348 977.96 977.50 977 .73 1349 971 .74 971.23 973.71 973.83 972.63 1349 973.71 973.71 1350 974.98 974.69 977.08 980 .01 976.69 1350 977.08 977.08 1351 969.93 969.78 971.33 970.80 970.46 1351 971.33 971.33 1352 966.49 966.06 967.89 967.50 966.99 1352 967.89 967.50 967.70 1352 967.89 967.89 1353 985.70 988.00 988.31 988.04 987.52 1353 988.31 988.31 1354 965.51 965.24 967.00 966.46 966.05 1354 967 .00 967.00 1355 967.64 967.01 968 .71 968.85 968.05 1355 968.71 968.71 1356 968.83 968.24 969.38 969.57 969.00 1356 969.38 969.57 969.47 1357 969.51 968.88 970.72 970.47 969.89 1357 970.72 970.72 1358 971.26 970.53 972.67 972.49 971.74 1358 972.67 972 .74 972.71 1359 972.79 972.79 1359 972.79 974.82 973.80 1360 974.88 974.88 1360 974.88 974.88 02W01 930.56 932.92 934.49 934.51 933.12 02W02 928.87 930.72 932.30 932.25 931 .03 02W03 926.43 927.99 930.33 930.40 928.79 02W04 927.64 928.09 929.64 929.81 928.79 02W04 929.81 929.81 02W05 927.43 927.86 929.56 929.77 928.65 02W06 927.37 927.77 929.56 929.78 928.62 October 22, 2006 Page 2 of 5

Table 2 Summary of Groundwater Elevation Data used for Calibration Cimarron Corporation Crescent, Oklahoma 9/16/03 12/16/03 Aug/Sep 04 5/24/05 AvgWL Summary Water Level Water Level Water Level Water Level Elevation ID (feet) (feet) (feet) (feet) (feet) 02W07 927.53 927.98 929.53 929.76 928.70 02W07 929.76 929.76 02W08 927.57 928.02 929.57 929.80 928.74 02W08 929.80 929.80 02W09 933.09 935.51 936.32 936.57 935.37 02W10 931.73 934.39 935.54 935.62 934.32 02W11 927.27 927.85 929.57 929.73 928.61 02W12 927.29 927.83 929.69 929.71 928.63 02W13 927.41 927.91 929.71 929.89 928.73 02W14 927.27 927.77 929.50 929.70 928.56 02W15 927.34 927.81 929.60 929.80 928.64 02W16 927.37 927.81 929.50 929.77 928.61 02W17 914.25 927.87 929.55 929.80 925.37 02W18 927.30 927.75 929.47 929.69 928.55 02W19 927.56 927.95 929.47 929.41 928.59 02W19 929.41 929.41 02W20 936.42 937.88 938.04 937.99 937.58 02W21 927.43 927.84 929.46 929.74 928.62 02W22 927.42 927.85 929.50 929.72 928.62 02W23 927.42 927.74 929.56 929.79 928.63 02W23 929.79 929.79 02W24 927.32 927.75 929.53 929.75 928.59 02W25 940.60 941.84 947.51 946.01 943.99 02W26 934.13 936.34 937.00 937.14 936.15 02W27 930.37 931.97 934.48 933.97 932.70 02W28 931.52 934.17 935.30 935.41 934.10 02W29 932.59 935.12 936.19 936.65 935.14 02W30 932.19 934.13 937.03 937.17 935.13 02W31 931.19 933.83 934.97 935.02 933.75 02W32 927.31 927.84 929.61 931.65 929.10 02W33 927.44 927.85 929.52 929.77 928.65 02W33 929.77 929.77 02W34 927.44 927.71 929.39 929.66 928.55 02W35 938.70 927.92 929.36 929.60 931.39 02W36 927.42 927.83 929.46 929.71 928.60 02W37 934.00 934.40 935.82 936.03 935.06 02W38 926.67 927.10 929.47 929.64 928.22 02W39 933.00 935.46 936.43 936.90 935.45 02W40 938.36 939.05 940.18 940.18 939.44 02W41 936.42 937.80 938.62 938.66 937.88 02W42 934.42 936.09 941.05 940.34 937.98 02W43 927.35 927.91 929.29 929.53 928.52 02W43 929.53 929.53 02W44 929.23 927.77 929.35 929.55 928.97 October 22, 2006 Page 3 of 5

Table 2 Summary of Groundwater Elevation Data used for Calibration Cimarron Corporation Crescent, Oklahoma 9/16/03 12/16/03 Aug/Sep 04 5/24/05 AvgWL Summary Water Level Water Level Water Level Water Level Elevation ID (feet) (feet) (feet) (feet) (feet) 02W45 927.55 927.86 929.32 929.56 928.58 02W46 927.97 929.10 930.88 930.73 929.67 02W47 937.87 939.46 941.28  ??? 939.54 02W48 925.58 926.13 929.09 926.93 02W50 939.89 940.20 941.60 941 .70 940.85 02W51 949.20 949.84 952.77 952.03 950.96 02W52 938 .96 939.45 940.74 940.97 940.03 02W53 930.40 932 .03 934.70 934.13 932 .81 02W62 927.68 928.02 929.44 929.69 928.71 02W62 929.69 929.69 T-51 929.26 929.25 930.45 929.66 T-52 929.07 929.14 930.42 929.55 T-53 929.09 929.16 930.57 929.61 T-54 929.65 929.88 930.94 931.61 930.52 T-55 929.30 929.58 931.25 930.04 T-56 929 .21 929.54 931.27 930.01 T-57 929.83 929.90 930.94 931.85 930.63 T-58 929.87 929.83 930.77 931.87 930.58 T-59 928.94 929.04 930.60 929.53 T-60 928.89 969.49 930.89 943.09 T-61 928.65 928.65 930.79 929.36 T-62 930.14 930.14 930.82 932.15 930.81 T-63 931.48 932.01 931.75 T-63 930.02 930.02 931.48 932.01 930.88 T-63 931.48 931.48 T-64 930.31 930.31 931.57 932.43 931.15 T-65 930.06 929.93 930.90 932.05 930.74 T-65 932.05 932.05 T-66 931.71 931.71 T-67 931.17 931.17 T-67 931 .17 931.17 T-67 931.17 931.17 T-67 931.17 931.17 T-68 930.81 930.81 T-69 930.93 930.93 T-70 -----

T-70R 931.24 931.24 T-71 -----

T-72 930.96 930.96 T-73 931.02 931.02 T-74 931.20 931.20 T-75 930 .88 930.88 T-76 931 .04 931.04 T-77 930.82 930.82 October 22, 2006 Page 4 of 5

Table 2 Summary of Groundwater Elevation Data used for Calibration Cimarron Corporation Crescent, Oklahoma 9/16/03 12/16/03 Aug/Sep 04 5/24/05 AvgWL Summary Water Level Water Level Water Level Water Level Elevation ID (feet) (feet) (feet) (feet) (feet)

T-77 930.82 930.82 T-77 930.82 930.82 T-78 930.87 930.87 T-79 930.53 930.53 T-81 930.80 930.80 T-82 930.35 930.35 TMW-01 939.36 940.23 942 .38 943.82 941.45 TMW-02 940.65 940.99 941.29 941.62 941.14 TMW-05 930.74 933.29 934.56 934.02 933.15 TMW-06 932.81 935.77 936.02 936.05 935 .16 TMW-07 930 .17 932.54 933.41 933.05 932.29 TMW-08 933.75 935.89 936.50 936.99 935.78 TMW-09 931.68 934.32 935.02 935.28 934.08 TMW-09 935 .28 935.28 TMW-13 927.66 928.18 929.36 929.77 928.74 TMW-13 929 .77 929.77 TMW-17 932.23 933 .08 933.97 934.11 933.35 TMW-17 933.97 933.97 TMW-18 927.30 927.76 930.18 930.05 928.82 TMW-19 dry dry n/a -----

TMW-20 938.43 939.35 939.91 939.23 TMW-21 936.45 937.09 944.33 942.49 940.09 TMW-23 928.33 928.87 929.94 930.37 929.38 TMW-24 927.71 928.05 928.73 929.19 928.42 TMW-25 936.83 938.41 938.42 938.32 937.99 October 22, 2006 Page 5 of 5

Table 3 BA #1 Summary of Model Inputs Cimarron Corporation Crescent, Oklahoma Burial Area (BA#1)

Subsurface Units: , Value Units \, Reference 3.30E+00 ft/day Average of Silt, Sand, & Clay Kv 3.30E-01 ft/day 10% of KH Horozontal Anisotropy 1.0 No horizontal anisotropy Vertical Anisotropy (Kh/Kv) 1.0 No vertical anisotropy u::

Specific Storage NA Not required for steady-state simulation Specific Yield NA Not required for steady-state simulation Lonq. Disp. NA ----- Not required for flow model Porosity 30  % Freeze & Cherry, 1979 Table 2.4 KH 2 .83E-01 ft/day ENSR CSM Sec-3.2.1 Kv 2 .83E-02 ft/day 10% of KH Horozontal Anisotropy 1.0 ----- No horizontal anisotropy u5

~

_Vertical

_ _ _Anisotropy_ ___._.......,_(Kh/Kv)

_ _..___ _ _ 1.0 No vertical anisotropy Specific Storage NA ----- Not required for steady-state simulation Specific Yield NA ----- Not required for steady-state simulation Lonq. Disp. NA ----- Not required for flow model Porosity 20  % Freeze & Cherry, 1979 Table 2.4 KH 2.53E+02 ft/day Average of pumping tests in alluvial wells Kv 2 .53E+01 ft/day 10% of KH Horozontal Anisotropy 1.0 ----- No horizontal anisotropy

~ Vertical Anisotropy (KH/Kv) 1.0 ----- No vertical anisotropy cu Cf) Specific Storage NA ----- Not required for steady-state simulation Specific Yield NA ----- Not required for steady-state simulation Long . Disp. NA ----- Not required for flow model Porosity 30  % Freeze & Cherry, 1979 Table 2.4 KH 5.00E-01 ft/day Artificially high to improve model stability Kv 5.00E-02 ft/day 10% of KH Horozontal Anisotropy 1.0 ----- No horizontal anisotropy

>- Vertical Anisotropy (KH/Kv) 1.0 ----- No vertical anisotropy roi-------------+---------1----------------------

U Specific Storage NA ----- Not required for steady-state simulation Specific Yield NA ----- Not required for steady-state simulation Lonq. Disp. NA ----- Not required for flow model Porosity 20  % Freeze & Cherry, 1979 Table 2.4 KH 4.00E+01 ft/day Calibrated to high end of range in ENSR CSM Sec-3.2.1 Kv 2 .00E+00 ft/day 5% of KH

<f'.

(I.) _ _ _ _ _ _ _____,........__ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _____,........__ _ _ _ _ _ _ _ _ _ __

Horozontal Anisotropy 1.0 ----- No horizontal anisotropy

§ Vertical Anisotropy (KH/Kv) 1.0 ----- No vertical anisotropy 1n-----------------1----------------------------1

-o Specific Storage NA ----- Not required for steady-state simulation

§---------------------------'---------------------

Cf) 1--S__.p,_e_c_if_ic_Y_ie_ld_ _ _ _ ____,1---N_A _ _i--_--_--_--+-N_o_t_re_iq_._u_ir_e_d_f_or_s_t_e_ad_.Iv....-_st_a_te_s_i_m_u_la_ti_o_n_ _ _ _ _ _ ----1 Lonq. Disp. NA ----- Not required for flow model Porosity 5  % Freeze & Cherry, 1979 Table 2.4 October 22, 2006 Page 1 of 2

Table 3 BA #1 Summary of Model Inputs Cimarron Corporation Crescent, Oklahoma Burial Area (BA#1)

Sub~'Grface KH uri,'t;:J, ' ,;

ii i/ } ,value ,

8.43E+00

+ Units 1*,'.'.]*** j!

ft/day 1>******* . Reference .+( *i 'i ;;;iliil:!l!ill( %. t Kv 4.22E-01 ft/day 5% of KH

())

Horozontal Anisotropy 1.0 ----- No horizontal anisotropy C

0 Vertical Anisotropy (KH/Kv) 1.0 ----- No vertical anisotropy

~ Specific Storage NA ----- Not required for steady-state simulation u5 Specific Yield NA ----- Not required for steady-state simulation Long. Disp. NA ----- Not required for flow model Porosity 1  % Freeze & Cherry, 1979 Table 2.4 KH 5 .00E+00 ft/day Calibrated to high end of range in ENSR CSM Sec-3.2.1 Kv 2.50E-01 ft/day 5% of KH ca (1) Horozontal Anisotropy 1.0 ----- No horizontal anisotropy C

0 Vertical Anisotropy (KH/Kv) 1.0 ----- No vertical anisotropy 1n "O

C Specific Storage NA ----- Not required for steady-state simulation ro Cf) Specific Yield NA ----- Not required for steady-state simulation Long . Disp. NA ----- Not required for flow model Porosity 5  % Freeze & Cherry, 1979 Table 2.4 KH 3.00E+00 ft/day Slug test results at well 02W48 Kv 1.50E-01 ft/day 5% of KH u Horozontal Anisotropy 1.0 ----- No horizontal anisotropy (1)

C 0 Vertical Anisotropy (KH/Kv) 1.0 ----- No vertical anisotropy 1n "O

C Specific Storage NA ----- Not required for steady-state simulation ro Cf) Specific Yield NA ----- Not required for steady-state simulation Long. Disp. NA ----- Not required for flow model Porosity 5  % Freeze & Cherry, 1979 Table 2.4 Upstream Elevation 924.8 feet Downstream Elevation 924.8 feet 2

Conductance 10,000 (ft /da )/ft October 22, 2006 Page 2 of 2

Table 4 WA Summary of Model Inputs Cimarron Corporation Crescent, Oklahoma Western Alluvial Area (WA]

Su6;urface Units: *****{.****il. .!Value 'itUnits .

• 11;:< **1I ; *rn:::i Reference \>.*>:*:*p--****

• • • • • • • • • • • • • A;i KH 5.00E-01 ft/day ENSR CSM Sec-3.2.1 Kv 5.00E-02 ft/day 10% of KH Horozontal Anisotropy 1.0 ----- No horizontal anisotropy ro Vertical Anisotropy (KH/Kv) 1.0 ----- No vertical anisotropy 0 Specific Storage 0.001 ----- Default Specific Yield 0.001 ----- Default Long. Disp. 10 ----- Default Porosity 20  % Freeze & Cherry, 1979 Table 2.4 KH 2.35E+02 ft/day Average of pumping tests in alluvial wells Kv 2.35E+01 ft/day 10% of KH Horozontal Anisotropy 1.0 ----- No horizontal anisotropy "O

C Vertical Anisotropy (KH/Kv) 1.0 ----- No vertical anisotropy ro (f)

Specific Storage 0.001 ----- Default Specific Yield 0.001 ----- Default Long. Disp. 10 ----- Default Porosity 30  % Freeze & Cherry, 1979 Table 2.4 KH 3.00E+00 ft/day Slug test results at well 02W48 Kv 1.50E-01 ft/day 5% of KH u Horozontal Anisotropy 1.0 ----- No horizontal anisotropy Cl)

C 0 Vertical Anisotropy (KH/Kv) 1.0 ----- No vertical anisotropy in "O

C Specific Storaqe 0.001 ----- Default ro (f) Specific Yield 0.001 ----- Default Long. Disp. 10 ----- Default Porosity 5  % Freeze & Cherry, 1979 Table 2.4 Value Upstream Elevation 924.8 feet Downstream Elevation 924.8 feet 2

Conductance 20,000 (ft /da )/ft October 22, 2006 Page 1 of 1

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I BA #1 Model Domain N Cimarron Corporation ENSR AECOM c:J BA #1 Boundary A Crescent, Oklahoma Figure NOTTO SCALE DATE PROJECT 5 October 2006 04020-044-300

\Water\PROJEC-2\P40\4020\044-CH \modeling \MODEL_-1 \GIS\fi 9 ure5.m xd

WAArea Model Domain ENSR AECOM N

D WAArea Boundary Cimarron Corporation A Crescent, Oklahoma Figure NOTTO SCALE DATE PROJECT 6 October 2006 04020-044-300 J\Water\PROJEC-2\P40\4020\044-CH lmodeling\MODEL_-1 IGISIFI0BD2-1.MXD

BA #1 Boreholes and Cross-sections Cimarron Corporation ENSR AECOM Crescent, Oklahoma Figure DATE PROJECT 7 October 2006 04020-044-300 J:\Water\PROJE C~2 \P40\4020\044-C 1~1 \modeling \MODEL_~1 \GIS\figure7 .mxd

BA #1 Solids Developed from Borehole Data ENSR AECOM Cimarron Corporation Crescent, Oklahoma Figure DATE PROJECT 8 October 2006 04020-044-300 J: \Water\PROJEC-2 \P40\4020\044-CH\model ing \MODEL_- 1\GIS\figure8 .mxd

BA #1 30 Grid Incorporating Geologic Information ENSR AECOM Cimarron Corporation Crescent, Oklahoma Figure DATE PROJECT 9 October 2006 0402 0-044-300 J:\Water\PROJEC~2\P40\4020\044-C l~1 \modeling\MODEL_~1\GIS\figure9.mxd

Note:

Shows extent of borings and cross-sections .

Figure 11 shows extrapolation of geology to model domain.

WAArea Boreholes and Cross-sections ENSR AECOM Cimarron Corporation Crescent, Oklahoma Figure DATE PROJECT 10 October 2006 0402 0-044-300 J:\Water\PROJEC-2\P40\4020\044-C 1-1 \modeling\MODEL_-1\GIS\figure10 .mxd

WAArea Solids Developed from Borehole Data ENSR AECOM Cimarron Corporation Crescent, Oklahoma Figure DATE PROJECT 11 October 2006 0402 0-044-300 J:\Water\PROJEC~2\P40\4020\044-CH \modeling\MODEL_~1 \GIS\figure11 .mxd

WAArea 3D Grid Incorporating Geologic Information ENSR AECOM Cimarron Corporation Crescent, Oklahoma Figure DATE PROJECT 12 October 2006 0402 0-044-300 J:\Water\PROJEC~2\P40\4020\044-Cl~1 \modeling\MODEL_~1IGIS\figure12 .mxd

Predicted Groundwater Contours and Particle Pathlines MODFLOW Computed vs Observed Groundwater Levels 955 950 ,

945 940 935 930

• 925 '

920 920 925 930 935 940 945 950 955 Observed (feet)

Results of Burial Area #1 Model Calibration:

N Predicted Groundwater Contours with Pathline ENSR AECOM A and Measured vs Predicted Water Levels Figure NOTTO SCALE October 2006 13 J:\Water\PROJEC~2\P40\4020\044-CH \modeling\MODEL_ ~1\GIS\FIFF2A~1 .MXD

Predicted Groundwater Contours MODFLOW Computed vs Observed Groundwater Levels 932.00 g~ 931.50 -

-0 Q)

lo_

g 931.00 -

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• 930.00 _,.....

, ----~------------~---~

930.0 930.5 931.0 931.5 932.0 932 .5 Observed (feet)

Results of Western Alluvial Area Model Calibration:

N Predicted Groundwater Contours and ENSR AECOM A Measured vs Predicted Water Levels Figure NOTTO SCALE October 2006 14 J :\Water\P ROJ EC-2\P40\4020\044-Cl-1 \model ing\M ODEL_ -1 \GIS\figure14.mxd