modeling analyses for fort lewis jblm drinking water system, aspect 2009

TECHNICAL MEMORANDUM Modeling Analyses for Fort Lewis Sequalitchew Springs and Lake Area Prepared for: CalPortland

Project No. 040001-012 June 10, 2009

401 Second Avenue S, Suite 201 Seattle, WA 98104 Tel: (206) 328-7443 Fax: (206) 838-5853 www.aspectconsulting.com

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Contents

Introduction.........................................................................................................1

Conceptual Model ...............................................................................................1 Outwash Gravel Aquifer .........................................................................................2 Surface Water Features and Groundwater Interaction ..........................................2

Summary of Current Modeling Effort ................................................................3 Updated Model .......................................................................................................4 Sequalitchew Lake Model ......................................................................................4 Sensitivity Analyses................................................................................................5

Model Boundary Conditions ..............................................................................6 Current Conditions Model Runs .............................................................................6 Future Conditions Model Runs...............................................................................7

Results of Additional Modeling Analyses.........................................................7 Original EIS Model .................................................................................................7 Updated Model .......................................................................................................8 Sequalitchew Lake Model ......................................................................................8 Sensitivity Analyses................................................................................................9

Conclusions ......................................................................................................10

References ........................................................................................................10

Limitations.........................................................................................................11

List of Tables 1 Wetland and Diversion Canal Monitoring Data

2 Recharge Estimates

3 Boundary Conditions and Hydraulic Conductivities, Original EIS Model

4 Boundary Conditions and Hydraulic Conductivities, Updated Model

5 Boundary Conditions and Hydraulic Conductivities, Sequalitchew Lake Model

6 Water Balance Summary, Updated Model

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7 Water Balance Summary, Sequalitchew Lake Model

8 Water Balance Summary, Dry Year Sensitivity Analysis

9 Water Balance Summary, Constant Flux Sensitivity Analysis

10 Calibration Results

List of Figures 1 Area Map

2 Hydrogeologic Cross Section, Showing Current and Predicted Water Levels

List of Appendices

A Model Configuration and Boundary Conditions

B Modeling Results

C Sensitivity Analyses

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Introduction This technical memorandum is prepared to provide additional information on groundwater modeling used to predict drawdown associated with the North Sequalitchew Creek project. Additional modeling analyses were performed for the Fort Lewis Department of the Army Public Works. The modeling analyses focused on the upper Sequalitchew Creek basin area around Sequalitchew Lake to address any potential for impact to the Fort Lewis Sequalitchew Springs water supply source.

In conducting this analysis, we updated a number of the original model inputs using the last 4 years of monitoring data. Monthly monitoring is being conducted throughout the Sequalitchew Creek basin and we used these data to adjust recharge assumptions for the drainage canal and water levels in the wetland areas. We also explicitly incorporate Sequalitchew Lake into the model as a major surface water feature in the area that is believed to be in hydraulic connection with groundwater. Finally, we conduct a sensitivity analysis looking at the worst-case dry year conditions, and the effect of changing boundary conditions in the area of the Sequalitchew Springs.

The revisions made to the model for this effort refine predicted surface water and groundwater interactions occurring upgradient of the mine because they incorporate the past four years of collected monitoring data, and Sequalitchew Lake, into the model. As with the previous modeling work (discussed in the EIS, the City’s Staff Report, and incorporate Glacier Northwest technical reports), the updated model results indicate drawdown at the Sequalitchew Springs area will be immeasurable.

The following sections of this report summarize the conceptual model of the project area, summarize the scope of the current modeling effort, provide information on model boundary conditions in each of the model layers, and present a summary of the findings from the modeling analyses.

This report should be reviewed in conjunction with other reports prepared for the project to get a full understanding of the area hydrogeology, interrelationships with the surface water system, and magnitude of the work completed for the North Sequalitchew Creek project. A list of the key reports is provided in the References section of this Technical Memorandum.

Conceptual Model The conceptual model describes the physical geologic and hydrologic conditions understood to exist in the area of the proposed mine expansion and forms the basis for the numerical model developed to predict groundwater drawdown as a result of the project. The conceptual model is based on numerous studies conducted in the basin over the past

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decade, including extensive field investigations and on-going long-term water level and streamflow monitoring.

The following sections describe the conceptual understanding of the surface and groundwater system in the project area as it relates to the groundwater model development and predictive analyses. Figures 1 and 2 provide a plan map and hydrogeologic cross-section of the basin area modeled for the project.

Outwash Gravel Aquifer The mine-expansion project lies within a thick glacial outwash sequence near Puget Sound just north of the Sequalitchew Creek canyon and east of the existing mine. The outwash includes the very coarse-grained, surficial, Steilacoom Gravel flood deposits, overlying older Vashon outwash. The water table is found at relatively shallow depths of 15 to 25 feet in the expansion area, east of the “Qob Truncation” (formerly called the Kitsap Cutoff). West of the Qob Truncation, the water table is found at a depth of roughly 190 feet in the existing mine. The Qob Truncation causes a unique hydrogeologic feature where groundwater in permeable outwash gravels drops roughly 160 feet in 800 feet (0.2 ft/ft) over the edge of the truncated Olympia Beds (Qob) aquitard. Figure 2 illustrates this steep hydraulic gradient within the current mine site.

Four aquifer pumping tests were conducted along the east side of the proposed expansion area to determine hydraulic properties of the outwash throughout its depth (CH2M Hill, 2000). These testing data, along with studies conducted for Fort Lewis Landfill 5 (WWC, 1991) and the DuPont Works site (Hart Crowser, 1994), provide the hydraulic parameters for the Vashon Aquifer layers in the model and were used to subdivide the Vashon Aquifer system into multiple layers to better represent the outwash aquifer stratification (CH2M Hill, 2003).

The surficial Steilacoom Gravels are highly permeable and are known to rapidly infiltrate precipitation and stormwater. The gravels form a relatively flat outwash plain in the area, in the center of which is a series of five large wetlands—referred to as Bell, McKay, Hamer, Sequalitchew Creek, and Edmond Marshes. The wetlands occur in areas where large ice blocks, stranded during the glacial flood outbursts, later melted forming kettle depressions lined with finer-grained lower permeability materials. These features store water for a much longer time. The wetland sediments were sampled and lab tested for permeability throughout the wetland complex. These permeability data were used to incorporate the wetland areas into the groundwater model (Aspect Consulting, 2004a).

Surface Water Features and Groundwater Interaction The principal drainage features in the Sequalitchew Creek watershed include Sequalitchew Creek, the Diversion Canal, and the series of interconnected wetlands through which these drainages flow (See Figure 1). The bulk of the surface water originates at Sequalitchew Lake and from several Fort Lewis stormwater facilities on the southeast project boundary. Both the Diversion canal and Sequalitchew Creek drain excess surface water from Sequalitchew Lake and the wetland complex to Puget Sound during high precipitation periods. A weir at the outlet of Sequalitchew Lake maintains the

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lake level at a target elevation of 211 feet to protect the Sequalitchew Springs water supply source at the east end of Sequalitchew Lake.

Sequalitchew Springs are a highly productive discharge of groundwater at the east end of Sequalitchew Lake. The springs supply the majority of Fort Lewis’s water supply needs, which can range up to 8,000 gpm during peak summer periods (James Gillie, personal communication, 2008). The Fort Lewis Springs are formed where the water table between American Lake (at an elevation of 329 to 233 feet) and Sequalitchew Lake (at 211 to 213 feet) intersects ground surface. Overflow at the Springs feeds Sequalitchew Lake. The lake is believed to be hydraulically connected to groundwater in the outwash, like other lake features that have been monitored in the area.

Figure 2 presents a Hydrogeologic Cross Section that illustrates the steep gradient between American Lake and Sequalitchew Lake where the Sequalitchew Springs occur and a much flatter gradient around Sequalitchew Lake and through the wetland complex. The flat gradient is due to the strong hydraulic connection between the groundwater and surface water in the area around and east of DuPont –Steilacoom Road. The gradient becomes very steep near the existing mine site approximately 3 miles west of the Springs, where the underlying Olympia Beds aquitard is not present and groundwater discharges to Puget Sound. The cross section shows both the existing water table (solid green line) and the predicted water table (dashed green line) with the North Sequalitchew Creek project.

The water sources to the groundwater system include a combination of direct precipitation, infiltrating surface water, and groundwater inflow. The wetlands and lake act as sources of recharge to groundwater when surface water elevations are higher than groundwater elevations, and groundwater discharges to the surface water features when groundwater elevations are higher than surface water. Groundwater also enters the project area as underflow from American Lake and regional groundwater inflow derived from upgradient recharge. Precipitation, flow between groundwater and surface water, and up-gradient inflow are all included in the model.

Summary of Current Modeling Effort A groundwater flow model was initially developed for the North Sequalitchew Creek Project to evaluate environmental impacts (see City of Dupont Environmental Impact Statement [EIS] for the project) from the mining project. The model area covers an approximately 10 mi2 area as shown in Figure 1. The original model developed by CH2M Hill (2003) was modified by Aspect Consulting to address a revised mining plan and findings from detailed field investigations conducted in the upstream wetlands and stream channels (Aspect Consulting, 2004a and b). The City of DuPont’s hydrogeologic consultant for the EIS, Pacific Groundwater Group, also participated in the model design and in review of the analytical results. The model used for predicting impacts as part of the EIS will be referred to as the Original EIS Model.

This report discusses modifications to the Original EIS Model and analyses conducted based on recent discussions and input from Fort Lewis consulting engineers (James

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Gillie, Senior Engineer, Versar and Mike Truex, Senior Program Manager, Pacific Northwest National Laboratory).

The model consists of two separate model runs, one reflecting current conditions and the other future conditions with the mine expansion and new tributary to Sequalitchew Creek. The potential effect of the project on wetlands and Fort Lewis Sequalitchew Springs was evaluated by estimating drawdown, or change in groundwater elevations, between the current conditions and future conditions model runs.

Updated Model For this additional modeling effort, two sets of revised conditions were developed. The first model, referred to as the Updated Model incorporated additional wetland water level and diversion canal flow data collected since the Original EIS Model was developed. Changes to develop this Updated Model included:

• Setting the heads in the wetlands (modeled as river cells) equal to the average wetland water levels measured between March 2004 and February 2009 (see Table 1). The original EIS model used wetland water level data from April 2004, which are slightly higher than the average values measured since that time. Depending on the wetland, the head applied in the Updated Model was reduced by 0.11 to 0.86 feet.

• Eliminating the additional recharge assigned to the diversion canal model cells. The Original EIS Model applied 2.7 cubic feet per second (cfs) of recharge to cells along the diversion canal to represent seepage losses. The estimated seepage loss was based on the difference in measured streamflows between canal gaging locations DC-1 and DC-3 in the spring of 2004. Review of the current database of monthly flow measurements indicates there is considerable variability in losses from the canal as shown in Table 1. The most significant change in seepage loss occurred following the beaver dam removals in December 2005 and January 2006. Since that time there has been less seepage loss. On an annual basis, flow changes in the canal range from a loss of 1.9 cfs to a gain of 0.6 cfs, with an overall average loss for the period of record of 0.5 cfs. Based on these data it was determined that losses from the canal may not be as significant a source of recharge as initially modeled, so these model cells were set equal to the areal precipitation recharge rate.

Sequalitchew Lake Model The Original EIS Model did not explicitly include Sequalitchew Lake as a model boundary, primarily because significant drawdown effects were not expected to propagate that far. The original focus was on the wetland complex located closer to the mine site because drawdown beneath the wetlands was of potential concern.

To better represent hydrogeologic conditions at Sequalitchew Lake and the Fort Lewis Springs a second set of model revisions were made. The resulting model, referred to as the Sequalitchew Lake Model (for the purposes of this memorandum), incorporates the changes made in the Updated Model, and explicitly models groundwater interaction with

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Sequalitchew Lake using river boundary conditions. The head applied to the river boundary condition for Sequalitchew Lake was set at 211 feet, the target lake elevation to prevent intrusion of lake water to the Fort Lewis Sequalitchew Springs (Shapiro and Associates 1997 and Northwest Hydraulic Consultants 2007). The vertical hydraulic conductivity used for the river bed was 0.23 feet per day (ft/day), equal to 1/100th of the low end of the range of estimated horizontal hydraulic conductivity values for the shallow outwash deposits (Woodward-Clyde, 1991).

Sensitivity Analyses A sensitivity analysis was performed on the Sequalitchew Lake Model to assess:

• The effects of an extreme dry year condition; and

• Evaluate effect of the constant head boundary condition between Sequalitchew Lake and American Lake on estimated drawdown by replacing the constant head boundary by a constant flux (wells) boundary.

The dry year conditions modeled were essentially a “drought” year. The dry year condition used the minimum water levels measured in the marshes (See Table 1) and assumed a water level of 208 feet in Sequalitchew Lake. In addition, the dry year sensitivity analysis was performed using reduced recharge rates and reduced groundwater inflow rates at the upgradient model boundary as discussed below.

Recharge rates were evaluated using Vacarro, et. al (1998) as shown in Table 2. Precipitation data used to estimate recharge are from the McMillan Reservoir station, with a period of record of 1942 through 2008. Recharge rates are estimated for a range in land use types. The modeled area is generally undeveloped, except for the residential areas of the City of DuPont and developed areas of Fort Lewis within the southern and northern model domain. The average recharge rate used in the Original EIS Model and the Updated Model is 19.8 inches/year, which we considered a reasonable representation of the average conditions for the area land use (less than undeveloped, but greater than for built up or residential).

For the dry year condition, we used the lowest recorded annual precipitation at McMillan Reservoir of 22.1 inches in 1952. This is 35% of the average precipitation, thus, using this relationship we reduced the recharge rate to 6.9 inches/yr from the average recharge rate.

In addition, groundwater inflow across the upgradient boundary was reduced to account for the dry year conditions. The average saturated thickness in the top model layer at the upgradient boundary is 15 feet. The monitoring data from SRC-MW-2, the well closest to the upgradient boundary, indicates the minimum water level to be 3 feet lower than the average water level. Based on these data, the saturated thickness (and by extension the transmissivity) in the top model layer along the upgradient boundary was reduced by about 20% to account for the dry conditions.

A second sensitivity analysis was conducted to assess the effect of the constant head boundary condition between Sequalitchew Lake and American Lake on estimated drawdown. This was assessed by replacing this boundary condition with a constant flux

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boundary condition. Additional details on the boundary conditions and model runs are provided in the following sections.

Model Boundary Conditions Appendix A presents figures showing model boundary conditions for each of the eight model layers for both the current conditions and future conditions model runs for the Sequalitchew Lake Model. The locations of the boundary conditions are identical for the Original EIS Model, the Updated Model, and the Sequalitchew Lake Model, with the exception that the river boundary conditions representing Sequalitchew Lake on Layer 1 of the Sequalitchew Lake Model are not included in the other two models.

Tables 3 through 5 summarize the values applied to the boundary conditions for each of the three models. Boundary conditions applied in the current condition and future condition model runs are described below.

Current Conditions Model Runs Boundary conditions for the current conditions model runs are shown in Appendix A and include:

• A constant head (shown in blue) boundary applied in the area between American Lake and Sequalitchew Lake. A constant head value of 211 feet was used in the Original EIS Model and the Updated Model. In the Sequalitchew Lake Model heads along this boundary were increased slightly to maintain inflow to the model across this boundary. Final constant head values applied in the Sequalitchew Lake Model ranged from 211.25 feet at the north end to 212.05 feet at the south end of the boundary. A constant head boundary with head values ranging from 184.1 to 190.2 feet was also applied at the downgradient model edge along the trace of North Sequalitchew Creek.

• A constant flux boundary (shown in red) applied along the upgradient boundary south of Sequalitchew Lake. This boundary was modeled using the MODFLOW well package. Flux values were developed based on a calibrated model run of the Original EIS Model using constant heads along this boundary. This boundary represents regional groundwater inflow that is expected to be controlled by upgradient recharge. A constant flux boundary was considered appropriate, as regionally derived inflow across this boundary is not expected to be influenced by changes in groundwater elevations due to the North Sequalitchew Creek project.

• Recharge from and discharge to the wetlands was modeled using the MODFLOW river boundaries (shown in green). The head applied to at each wetland in the Updated Model and the Sequalitchew Lake Model were the average of the water levels measured in the wetlands between March 2004 and February 2009. The vertical hydraulic conductivity of 0.08 ft/d was selected as the average laboratory-measured values from marsh sediment samples. In the Sequalitchew Lake Model the

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vertical hydraulic conductivity applied to boundary conditions representing Sequalitchew Lake was 0.23 ft/day, equal to 1/100th of the low end of the range of estimated horizontal hydraulic conductivity values for the shallow outwash deposits. In the Original EIS Model and the Updated Model, Sequalitchew Lake was not modeled with river cells.

• Discharge to Sequalitchew Creek downstream from the wetlands was modeled using drain boundary conditions (shown in yellow). Drain boundary conditions were also used to model discharge at the Olympia Beds (Qob) Truncation along the west side of the model.

• Areal recharge from precipitation was applied throughout the model, except in the wetlands and, for the Sequalitchew Lake Model, in Sequalitchew Lake. Recharge was set at 19.8 inches/yr for all models. The Original EIS model included higher recharge of 740 inches/yr along the diversion canal to represent seepage losses from the canal. This is equivalent to a seepage loss of 2.7 cfs along the canal.

Future Conditions Model Runs Boundary conditions for the Future Conditions model runs are also presented in Appendix A, following the Current Model Conditions. The downgradient constant head and drain boundary conditions were modified from the current conditions model runs to create the future conditions model runs. To do this the downgradient constant head boundary condition was removed and replaced by drain boundaries to represent groundwater discharge to the expanded mine and the constructed North Sequalitchew Creek. The upgradient constant head, recharge, constant flux, and river boundary conditions remain the same for the future conditions model runs.

Results of Additional Modeling Analyses The following sections summarize the changes in groundwater elevation, inflow and outflow, and resulting drawdown predicted based on:

• Updating the wetland surface water elevations and diversion canal recharge conditions in the Original EIS Model (Updated Model), and

• Incorporating Sequalitchew Lake into the model (Sequalitchew Lake Model).

Figures showing the results of the modeling analyses are presented in Appendix B. Tables 6 and 7 provide a water balance summary of the components of each model.

Original EIS Model Groundwater elevation contours and drawdown estimated with the Original EIS Model are presented in Appendix B. This model, which does not incorporate any connection to the surface water of Sequalitchew Lake, shows approximately 0.3 feet of drawdown at the west end of the lake and 0.2 feet of drawdown near the middle of the lake. Not

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allowing for the interaction of groundwater with Sequalitchew Lake is a conservative assumption with regard to estimated drawdown near the lake because the lake will act to recharge the groundwater system when groundwater elevations are below the lake elevation.

Updated Model The Updated Model indicates that removing the additional recharge from the diversion canal and reducing the modeled water levels in the wetlands results in a slight decrease in modeled groundwater elevations, primarily near Sequalitchew Lake and the diversion canal. However, the predicted drawdown is virtually identical to the drawdown predicted with the Original EIS Model. Based on these results it appears that the modeled drawdown is not very sensitive to recharge from the diversion canal or variations in head in the wetlands. Groundwater elevation contours and drawdown estimated with the Updated Model are presented in Appendix B following the figures for the Original EIS Model.

A summary of water balance terms for the current conditions and future conditions model runs are provided in Table 6. The water balance shows that about 90 percent of the inflows to the model are from areal recharge and recharge from the wetlands, with the remaining 10 percent coming from regional groundwater inflow and underflow from American Lake along the upgradient boundary. Virtually all of the upgradient inflow occurs in the upper two layers of the model, which represent the high hydraulic conductivity portions of the outwash aquifer.

Sequalitchew Lake Model Groundwater elevation contours and drawdown contours for the Sequalitchew Lake Model are presented in Appendix B following the Updated Model. The Sequalitchew Lake Model indicates a pronounced decrease in drawdown near the lake and springs relative to the Updated Model and Original EIS Model, with 0.2 feet of drawdown at the west end of the lake and 0.1 feet of drawdown near the middle of the lake. The shape of the drawdown contours near the lake in the Sequalitchew Lake Model are also different than predicted with the Updated Model due to attenuation of the drawdown by induced recharge from the lake.

A summary of water balance terms for the current conditions and future conditions model runs are provided in Table 7. Similar to the Updated Model, the water balance shows that about 90 percent of the inflows to the model are from areal recharge and recharge from the wetlands and lake, with the remaining 10 percent coming from regional groundwater inflow and underflow from American Lake along the upgradient boundary. For the current conditions model run the overall water balance and the inflows to the model from the wetlands and lake are essentially the same as the Updated Model, despite modeling Sequalitchew Lake with river boundaries. In this model, Sequalitchew Lake acts as a flow-through lake, with groundwater discharging to the lake from the northeast and south and lake water recharging groundwater to the west and north of the lake. This is consistent with monitoring data that show the diversion canal periodically gains water in the reach near the lake. Net modeled discharge from the lake to groundwater (i.e.,

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outflow from the lake to groundwater minus inflow to the lake from groundwater) is about 11,000 cubic feet per day, or 0.13 cfs.

The water balance for the future condition model run shows an increase in groundwater inflow across the constant head boundary between American Lake and Sequalitchew Lake of about 0.1 cfs and an increase in inflows from the wetlands of about 0.5 cfs relative to the current condition model run. The net modeled discharge from the lake to groundwater also increases by about 0.14 cfs. This increase in losses from the lake to groundwater is not likely to significantly affect surface water elevations in the lake, as discharge measured at the diversion canal weir, which measures discharge coming primarily from the lake, averages approximately 6 to 7 cfs. Based on the results of this model, the induced groundwater recharge from Sequalitchew Lake and the wetlands will attenuate groundwater drawdown to less than 0.1 feet approximately ½ mile west of the Fort Lewis Sequalitchew Springs.

Table 10 provides a comparison of current conditions model results to measured groundwater elevations. The data match reasonably well except in the area of CHMW-3S and D, which is located within the western portion of the mine expansion area, and is the well that is furthest away from the wetlands and lake that are being evaluated with these additional model runs. The match is best in the area of Sequalitchew Lake (MW-SL-1 and SRC-MW-2).

Sensitivity Analyses Consideration of a drought year condition and substitution of the upgradient constant head with a constant flux boundary condition were selected as sensitivity analyses to be performed on the Sequalitchew Lake Model, in discussion with the Fort Lewis engineers. Appendix C presents water level and drawdown contours for the dry year sensitivity analysis and drawdown contours for the constant flux boundary condition sensitivity analysis. Tables 8 and 9 summarize the water balance for these sensitivity runs.

The dry season current conditions analysis indicates groundwater elevations significantly lower than with the Sequalitchew Lake Model. For example, the 210-foot contour extends all the way to the east end of Sequalitchew Lake, while in other model runs this contour is near the middle or west end of the lake. The modeled drawdown however, is virtually identical to the modeled drawdown for the Sequalitchew Lake Model, with 0.2 feet of drawdown predicted at the west end of the lake and 0.1 feet of drawdown predicted near the middle of the lake. The water balance for this sensitivity analysis (Table 8) shows increased recharge of groundwater from the wetlands and Sequalitchew Lake, and increased groundwater discharge to Sequalitchew Lake. The water balance also shows increased inflow across the constant head boundary between American Lake and Sequalitchew Lake.

For the constant flux boundary condition sensitivity analysis the current condition model run was unchanged from the Sequalitchew Lake Model. In the future condition model run the constant head boundary condition between American Lake and Sequalitchew Lake was replaced with a constant flux boundary. Modeled drawdown is similar to the modeled drawdown for the Sequalitchew Lake Model, although the 0.1-foot drawdown contour forms a narrower envelop around Sequalitchew Lake. Inspection of the water

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balance shows essentially no change in the losses of water from Sequalitchew Lake to groundwater relative to the Sequalitchew Lake Model.

Conclusions The modeling analysis indicates groundwater drawdown upgradient of the project area will be minor because changes in the groundwater elevation (i.e. drawdown) will be offset by induced recharge from the area surface water bodies. This will occur primarily in areas where there is direct hydraulic connection between the surface water and groundwater; for example, the area between the Sequalitchew Lake outlet and DuPont Steilacoom Road. In this area, monitoring data indicate the diversion canal gains flow due to groundwater discharge. Taken together, the monitoring data and modeling analyses indicate that drawdown propagating towards Sequalitchew Lake will be offset by a reduction in the groundwater discharge to the diversion canal at the west end of the lake. The induced recharge near the lake outlet will also help to maintain the lake level desired to prevent backflow to the water supply system at the springs.

The monitoring data and modeling indicate the amount of induced recharge will be small, roughly one-tenth of the current natural surface water recharge rate. This amount is less than the natural variability seen due to seasonal and annual precipitation patterns.

The hydrogeologic cross section provides perspective on the groundwater level changes expected to occur from construction of the new Sequalitchew Creek tributary. The cross-section uses monitoring data to show current conditions and the modeling analysis to show the predicted drawdown under future conditions. The vertical scale on the hydrogeologic cross section is exaggerated 40 times over the horizontal scale in an attempt to show the change in water level (drawdown) expected from the project. Even at this great exaggeration it is virtually impossible to show the small amount of change expected to propagate into the upgradient groundwater-surface water system beyond about ½-mile from the east edge of the project area.

References Aspect Consulting, 2004a, Technical Memorandum, Surface Water and Groundwater

System with Predictions on Effect to Wetland Hydrology Upstream of Proposed North Sequalitchew Creek, July 21, 2004.

Aspect Consulting, 2004b, Supplemental Report, Surface Water and Groundwater System, North Sequalitchew Creek Project, Prepared for Glacier Northwest, December 13, 2004.

Aspect Consulting, 2007, 2005-2006 Water Resource Monitoring Data Report, North Sequalitchew Creek Project, Prepared for Glacier Northwest, May 2007.

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CH2M Hill, 2000, Groundwater Investigation Report, North Sequalitchew Creek Project, DuPont, Washington, June 2, 2000.

CH2M Hill, 2003, Draft Final Groundwater Modeling and Analysis Report, North Sequalitchew Creek Project, DuPont, WA, Prepared for Glacier Northwest, May 2003.

City of DuPont, 2007, Final Supplemental EIS (SEIS), Glacier Northwest DuPont Area Expansion and North Sequalitchew Creek Project, May 2007.

Hart Crowser, 1994, Draft Remedial Investigation, Former DuPont Works Site, DuPont, Washington, Volume 1, Prepared by Hart Crowser, Inc., for Weyerhaeuser Company & E.I. DuPont de Nemours &Co., December 22, 1994.

Northwest Hydraulic Consultants, Inc., Sequalitchew Springs Source Water Protection Project, Performed by AHBL, Inc. (project 204689) and. (project 21380), Prepared for the USACE Seattle District in cooperation with Fort Lewis Public Works, August 2007.

Pacific Groundwater Group, 2006, Groundwater Impact Analysis, Expansion of Glacier Northwest’s Pioneer Aggregate Mine, DuPont, Washington, Prepared for Huckell Weinman and Associates, technical report supporting the SEIS, April 27, 2006.

Shapiro and Associates, Inc., 1997, Lake-Level Management Plan for Sequalitchew Lake.

Truex, M.J., Johnson, C.D., Cole, C.R., 2006, Numerical Flow and transport Model for the Fort Lewis Logistics Center, DSERTS No. FTLE-33, Fort Lewis Public Works, Building 2102, Fort Lewis, WA.

Vaccaro, J.J., Hansen, A.J. Jr., Jones, M.A., 1998, Hydrogeologic Framework of the Puget Sound Aquifer System, Washington and British Columbia, USGS Professional Paper 1424-D.

Woodward-Clyde Consultants, 1991, Fort Lewis Landfill No. 5 RI/FS, Remedial Investigation Report, Volume 1, Submitted to the Corps of Engineers Seattle District, October 1991, Draft Final.

Limitations Work for this project was performed and this report prepared in accordance with generally accepted professional practices for the nature and conditions of work completed in the same or similar localities, at the time the work was performed. It is intended for the exclusive use of CalPortland for specific application to the referenced property. This report does not represent a legal opinion. No other warranty, expressed or implied, is made.

Table 1 - Wetland and Diversion Canal Monitoring DataNorth Sequalitchew Creek, Dupont, WashingtonProject 040001-012

Wetland Monitoring DataWater Level Elevations in Feet

Wetland Minimum Maximum AverageEdmond Marsh 209.64 211.37 211.03 211.14Sequalitchew Creek Marsh 210.57 212.67 212.09 212.27Hamer Marsh 211.67 215.05 213.64 214.24McKay Marsh 213.57 217.35 215.54 215.95Bell Marsh 215.63 219.11 217.57 218.43

Period of Record is March 2004 through February 2009

Diversion Canal Monitoring DataChange in Flow along Diversion Canal in cfs1

Year Range Average2004 -3.1 to -0.6 -1.92005 -3.1 to -0.2 -1.52006 -4.3 to 1.1 -0.62007 -0.6 to 3.3 0.62008 -1.7 to 3.0 0.5

Period of Record -4.3 to 3.3 -0.5Values summarized from monthly flow measurements between March 2004 and December 2008.Negative values indicate decrease in flow, positive values indicate increase in flows.The original EIS model included 2.5 cfs of recharge from the diversion canal.1 Change recorded as difference in flow between gaging station DC-1 and DC-3.

Value used in Original EIS Model

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Table 2 - Recharge EstimatesNorth Sequalitchew Creek, Dupont, WashingtonProject 040001-012

Parameter Average (1942 - 2008) Minimum (1952)Precipitation 41.5 22.1Recharge by Land Use Type

Undeveloped 25.0 8.7Residential 18.7 6.5Built Up 12.5 4.4Urban 0.0 0.0

All values are in inches per year.Recharge calculated using Equation (6) from Vacarro, et al. (1998) for recharge to coarse-grained deposits.Average and minimum precipitation from precipitation data for McMillan Reservoir, with period of record of 1942 through 2008.

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Table 3 - Boundary Conditions and Hydraulic ConductivitiesOriginal EIS ModelNorth Sequalitchew Creek, Dupont, WashingtonProject 040001-012

Boundary Condition Parameter Value UnitsAreal Recharge

Diversion Canal Leakage Recharge rate 740 inches/yrWetland Areas Recharge rate 0 inches/yrAll other areas Recharge rate 19.8 inches/yr

Constant HeadUpgradient Boundary Head 211 feetDowngradient Boundary (current conditions only) Head 184.1 to 190.2 feet

RiverEdmond Marsh Head 211.14 feet

Vertical conductivity 0.08 ft/dSequalitchew Creek Marsh Head 212.27 feet

Vertical conductivity 0.08 ft/dHamer Marsh Head 214.24 feet

Vertical conductivity 0.08 ft/dMcKay Marsh Head 215.95 feet

Vertical conductivity 0.08 ft/dBell Marsh Head 218.43 feet

Vertical conductivity 0.08 ft/dConstant Flux (Wells)

Layer 1 Flux 123,316 ft3/dayLayer 2 Flux 7,672 ft3/dayLayer 3 Flux 3 ft3/dayLayer 4 Flux 341 ft3/dayLayer 5 Flux 341 ft3/dayLayer 6 Flux 337 ft3/dayLayer 7 Flux 515 ft3/dayLayer 8 Flux 505 ft3/day

Hydraulic ConductivityLayer 1 Horizontal conductivity 1,800 ft/dLayer 2 Horizontal conductivity 1,800 ft/dLayer 31 Horizontal conductivity 0.3 ft/dLayer 41 Horizontal conductivity 50 ft/dLayer 51 Horizontal conductivity 50 ft/dLayer 61 Horizontal conductivity 50 ft/dLayer 7 Horizontal conductivity 50 ft/dLayer 8 Horizontal conductivity 50 ft/d

Notes:See Attachement 4 for model output.Horizontal to vertical hydraulic conductivity anisotropy in all layers is 10:11 Higher hydraulic conductivity values were applied at the west corner of the model near Old Fort Lake. In layers 3 through 5 the hydraulic conductivity in this area is 1,800 ft/d andin layer 6 the hydraulic conductivity is 500 ft/d. Hydraulic conductivity values for other model layers were applied uniformly throughout each layer.


Table 3Page 1 of 1

Table 4 - Boundary Conditions and Hydraulic ConductivitiesUpdated ModelNorth Sequalitchew Creek, Dupont, WashingtonProject 040001-012


Diversion Canal Leakage Recharge rate 19.8 inches/yrWetland Areas Recharge rate 0 inches/yrAll other areas Recharge rate 19.8 inches/yr

Constant HeadUpgradient Boundary Head 211 feetDowngradient Boundary (current conditions only) Head 184.1 to 190.2 feet









Notes:See Attachement 5 and Table 5 for model output.Horizontal to vertical hydraulic conductivity anisotropy in all layers is 10:11 Higher hydraulic conductivity values were applied at the west corner of the model near Old Fort Lake. In layers 3 through 5 the hydraulic conductivity in this area is 1,800 ft/d andin layer 6 the hydraulic conductivity is 500 ft/d. Hydraulic conductivity values for other model layers were applied uniformly throughout each layer.


Table 4Page 1 of 1

Table 5 - Boundary Conditions and Hydraulic ConductivitiesSequalitchew Lake ModelNorth Sequalitchew Creek, Dupont, WashingtonProject 040001-012


Diversion Canal Leakage Recharge rate 19.8 inches/yrWetland Areas Recharge rate 0 inches/yrAll other areas Recharge rate 19.8 inches/yr

Constant HeadUpgradient Boundary Head 211.25 to 212.05 feetDowngradient Boundary (current conditions only) Head 184.1 to 190.2 feet






Vertical conductivity 0.08 ft/dSequalitchew Lake Head 211 feet




Notes:See Attachement 6 and Table 6 for model output.Horizontal to vertical hydraulic conductivity anisotropy in all layers is 10:11 Higher hydraulic conductivity values were applied at the west corner of the model near Old Fort Lake. In layers 3 through 5 the hydraulic conductivity in this area is 1,800 ft/d andin layer 6 the hydraulic conductivity is 500 ft/d. Hydraulic conductivity values for other model layers were applied uniformly throughout each layer.


Table 5Page 1 of 1

Table 6 - Water Balance Summary, Updated ModelNorth Sequalitchew Creek, Dupont, WashingtonProject 040001-012

Inflows - Current ConditionsComponent Layer Rate (ft3/d) Rate (cfs) Percent of Total

Recharge 1 953,999 11.0 62%River (wetlands) 1 434,868 5.0 28%Upgradient Constant Head 1 8,896 0.1Upgradient Constant Head 2 3,300 0.0Upgradient Constant Head 3 2 0.0Upgradient Constant Head 4 269 0.0Upgradient Constant Head 5 269 0.0Upgradient Constant Head 6 265 0.0Upgradient Constant Head 7 410 0.0Upgradient Constant Head 8 397 0.0

Total 13,808 0.2 1%Wells (Constant Flux) 1 123,316 1.4Wells (Constant Flux) 2 7,672 0.1Wells (Constant Flux) 3 3 0.0Wells (Constant Flux) 4 341 0.0Wells (Constant Flux) 5 341 0.0Wells (Constant Flux) 6 337 0.0Wells (Constant Flux) 7 515 0.0Wells (Constant Flux) 8 505 0.0

Total 133,031 1.5 9%Total Inflows 1,535,705 17.8 100%

Outflows - Current ConditionsComponent Layer Rate (ft3/d) Rate (cfs) Percent of Total

Downgradient Constant Head 1 -53,195 -0.6Downgradient Constant Head 2 -208,260 -2.4Downgradient Constant Head 3 -3,727 0.0Downgradient Constant Head 4 -475 0.0Downgradient Constant Head 5 -805 0.0Downgradient Constant Head 6 3,554 0.0Downgradient Constant Head 7 3,395 0.0Downgradient Constant Head 8 -18,954 -0.2

Total -278,468 -3.2 18%Drains 1 -31,061 -0.4Drains 2 -38,271 -0.4Drains 3 -15,214 -0.2Drains 4 -32,289 -0.4Drains 5 -88,941 -1.0Drains 6 -104,318 -1.2Drains 7 -159,912 -1.9Drains 8 -761,316 -8.8

Total -1,231,322 -14.3 82%Total Outflows -1,509,789 -17.5 100%


Table 6Page 1 of 2

Table 6 - Water Balance Summary, Updated ModelNorth Sequalitchew Creek, Dupont, WashingtonProject 040001-012

Inflows - Future ConditionsComponent Layer Rate (ft3/d) Rate (cfs) Percent of Total

Recharge 1 953,999 11.0 61%River (wetlands) 1 479,365 5.5 31%Upgradient Constant Head 1 3,151 0.0Upgradient Constant Head 2 260 0.0Upgradient Constant Head 3 1 0.0Upgradient Constant Head 4 183 0.0Upgradient Constant Head 5 184 0.0Upgradient Constant Head 6 183 0.0Upgradient Constant Head 7 280 0.0Upgradient Constant Head 8 277 0.0



Outflows - Future ConditionsComponent Layer Rate (ft3/d) Rate (cfs) Percent of Total

Drains 1 -81,235 -0.92 -105,412 -1.23 -6,910 -0.14 -14,276 -0.25 -41,801 -0.56 -88,108 -1.07 -200,802 -2.38 -1,028,192 -11.9



Table 6Page 2 of 2

Table 7 - Water Balance Summary, Sequalitchew Lake ModelNorth Sequalitchew Creek, Dupont, WashingtonProject 040001-012


Recharge 1 953,999 11.0 61%River (wetlands) 1 414,537 4.8River (Sequalitchew Lake) 1 37,661 0.4

Total 452,197 5.2 29%Upgradient Constant Head 1 11,354 0.1Upgradient Constant Head 2 5,323 0.1Upgradient Constant Head 3 2 0.0Upgradient Constant Head 4 370 0.0Upgradient Constant Head 5 371 0.0Upgradient Constant Head 6 363 0.0Upgradient Constant Head 7 566 0.0Upgradient Constant Head 8 543 0.0




River (Sequalitchew Lake) 1 -26,114 -0.3 2%Downgradient Constant Head 1 -55,899 -0.6Downgradient Constant Head 2 -212,660 -2.5Downgradient Constant Head 3 -3,765 0.0Downgradient Constant Head 4 -683 0.0Downgradient Constant Head 5 -1,063 0.0Downgradient Constant Head 6 3,298 0.0Downgradient Constant Head 7 3,001 0.0Downgradient Constant Head 8 -19,423 -0.2




Table 7Page 1 of 2

Table 7 - Water Balance Summary, Sequalitchew Lake ModelNorth Sequalitchew Creek, Dupont, WashingtonProject 040001-012







River (Sequalitchew Lake) 1 -22,154 -0.3 1%Drains 1 -84,255 -1.0

2 -109,672 -1.33 -8,762 -0.14 -15,088 -0.25 -43,033 -0.56 -88,990 -1.07 -204,505 -2.48 -1,041,958 -12.1



Table 7Page 2 of 2

Table 8 - Water Balance Summary, Dry Year Sensitivity AnalysisNorth Sequalitchew Creek, Dupont, WashingtonProject 040001-012



Total 514,938 6.0 46%Upgradient Constant Head 1 114,661 1.3Upgradient Constant Head 2 47,135 0.5Upgradient Constant Head 3 16 0.0Upgradient Constant Head 4 2,044 0.0Upgradient Constant Head 5 2,043 0.0Upgradient Constant Head 6 1,995 0.0Upgradient Constant Head 7 3,113 0.0Upgradient Constant Head 8 2,980 0.0




River (Sequalitchew Lake) 1 -86,472 -1.0 8%Downgradient Constant Head 1 -10,136 -0.1Downgradient Constant Head 2 -138,035 -1.6Downgradient Constant Head 3 -3,092 0.0Downgradient Constant Head 4 3,355 0.0Downgradient Constant Head 5 3,233 0.0Downgradient Constant Head 6 8,406 0.1Downgradient Constant Head 7 10,465 0.1Downgradient Constant Head 8 -10,296 -0.1


Total -906,836 -10.5 80%Total Outflows -1,129,406 -13.1 100%


Table 8Page 1 of 2

Table 8 - Water Balance Summary, Dry Year Sensitivity AnalysisNorth Sequalitchew Creek, Dupont, WashingtonProject 040001-012



Total 555,685 6.4 47%Upgradient Constant Head 1 117,610 1.4Upgradient Constant Head 2 48,353 0.6Upgradient Constant Head 3 16 0.0Upgradient Constant Head 4 2,107 0.0Upgradient Constant Head 5 2,107 0.0Upgradient Constant Head 6 2,057 0.0Upgradient Constant Head 7 3,209 0.0Upgradient Constant Head 8 3,072 0.0





2 -41,809 -0.53 -5,598 -0.14 -9,824 -0.15 -23,491 -0.36 -62,413 -0.77 -150,427 -1.78 -782,639 -9.1



Table 8Page 2 of 2

Table 9 - Water Balance Summary, Constant Flux Sensitivity AnalysisNorth Sequalitchew Creek, Dupont, WashingtonProject 040001-012







River (Sequalitchew Lake) 1 -26,114 -0.3 2%Downgradient Constant Head 1 -55,899 -0.6Downgradient Constant Head 2 -212,660 -2.5Downgradient Constant Head 3 -3,765 0.0Downgradient Constant Head 4 -683 0.0Downgradient Constant Head 5 -1,063 0.0Downgradient Constant Head 6 3,298 0.0Downgradient Constant Head 7 3,001 0.0Downgradient Constant Head 8 -19,423 -0.2




Table 9Page 1 of 2

Table 9 - Water Balance Summary, Constant Flux Sensitivity AnalysisNorth Sequalitchew Creek, Dupont, WashingtonProject 040001-012



Total 503,456 5.8 31%Wells (Constant Flux) 1 134,700 1.6Wells (Constant Flux) 2 12,997 0.2Wells (Constant Flux) 3 5 0.0Wells (Constant Flux) 4 712 0.0Wells (Constant Flux) 5 712 0.0Wells (Constant Flux) 6 700 0.0Wells (Constant Flux) 7 1,081 0.0Wells (Constant Flux) 8 1,048 0.0




2 -109,540 -1.33 -8,748 -0.14 -15,058 -0.25 -42,977 -0.56 -88,924 -1.07 -204,325 -2.48 -1,041,173 -12.1



Table 9Page 2 of 2

Table 10 - Calibration ResultsNorth Sequalitchew Creek, Dupont, WashingtonProject 040001-012

Observed Water Levels Modeled ResidualWell ID Minimum Maximum Average Water Levels (Average - Modeled)

CHMW-1 188.65 198.43 192.50 191.70 0.80CHMW-2-D 190.08 196.89 192.87 187.09 5.78CHMW-2-S 190.00 196.84 192.93 187.46 5.47CHMW-3-D 189.58 200.15 194.40 180.77 13.63CHMW-3-S 181.35 200.83 194.67 183.07 11.59CHMW-4-D 190.88 205.07 195.14 192.73 2.41CHMW-4-S 193.04 202.87 197.34 193.00 4.35MW-EM-1D 201.69 208.86 205.87 199.26 6.61MW-EM-2D 209.17 211.29 210.74 205.98 4.76MW-EM-3 210.34 212.83 212.07 209.27 2.80MW-SL-1 209.82 212.56 211.39 209.41 1.98SRC-MW-2 210.67 217.28 213.74 211.90 1.84

Water level data collected approximately monthly from 2003 through 2008.Model results are for the Sequalitchew Lake Model.

Modeled Versus Observed Water Levels

170

175

180

185

190

195

200

205

210

215

220

170 175 180 185 190 195 200 205 210 215 220

Observed Water Level in Feet

Mod

eled

Water Level in

Feet


Table 10Page 1 of 1

2000+00

-50

50

0+00 4000+00

250

0

200

-100

150

100

6000+00 8000+00 10000+00 12000+00 14000+00 16000+00 18000+00 20000+00

300

22000+00 24000+00 26000+00 28000+00

LF

4-M

W4

American Lake

Can

al R

oad

Exi

stin

g M

ine

Pug

et S

ound

QpogPre-Olympia glacial unit 2

(Sea Level Aquifer)

VashonOutwash

Qob - Olympia Beds (Aquitard)

Qpon - Pre-Olympia aquitard unit

2

SequalitchewLake

SequalitchewCreek Marsh

EdmondMarsh

Qpog - Pre-Olympia aquifer unit

Sea Level Aquifer

Proposed Mining

For

t Lew

is S

prin

gs

LF

4-M

W-1

6B

DuP

ont-

Ste

ilaco

om R

oad

Foo

t Brid

ge T

rail

Cen

ter

Driv

e

SL

-1

EM

-3

EM

-2

EM

-1

TW

-4

Qs Silty Peat

Fill

?

?

??

?

-50

50

250

0

200

-100

150

100

300

Pro

pose

d fu

ture

N

orth

Seq

ualit

chew

C

reek

FIGURE NO.

PROJECT NO.DATE:

REVISED BY:

DRAWN BY:

DESIGNED BY:

ear th+water

www.aspectconsulting.com

a limited liability company

Hydrogeologic Cross Section showingCurrent and Predicted Water Levels

North Sequalitchew Creek ProjectDuPont, Washington

June 2009

LJH

PMB

-

040001

2

Q:\_

Tem

p\F

rom

_SE

A\N

orth

Seq

ualit

chew

Cre

ek\2

009-

06\0

4000

1-A

A.d

wg

Scale: 1" = 2000' Horiz1" = 50' Vert

West East

Vertical Exaggeration = 40X

Ele

vatio

n in

Fee

t (N

GV

D 1

929)

Feet

0 10050

Data Legend

Feet Vertical

Feet

0 40002000

Feet Horizontal

Ele

vatio

n in

Fee

t (N

GV

D 1

929)

Predicted water table change updated model (2009)

Water table elevation Feb 2008 (range at TW-4shown for 2003-2008)

Beaverdam

Monitor well location and name

range in measured water levels (2003-2008)

Geologic data from USGS 2005 (adapted Borden and Troost, 2001)

Average surface water elevation

EM-2

APPENDIX A

Model Configuration and Boundary Conditions

ASPECT CONSULTING

PROJECT NO. 040001-012 JUNE 10, 2009 A-1

Current and Future Conditions The current and future conditions model configurations are shown in the attached figures for each of the 8 layers used to construct the model of the Vashon Outwash. The Sequalitchew Lake Model is shown because only that model explicitly includes Sequalitchew Lake using river boundary cells. The Original EIS Model and Updated Model represent the Sequalitchew Lake area the same as the other outwash plain, with area recharge of 19.8 inches/yr. As such, these models are conservative in estimating drawdown beneath and east of Sequalitchew Lake, as it does not provide a source of recharge in the model.

The 8 model layers representing Current Conditions are shown first in the attached maps, followed by the 8 model layers for the Future Conditions. The principal difference between the Current and Future Conditions is how the mine site and future North Sequalitchew Creek are represented. For the current conditions, the proposed future location of North Sequalitchew Creek is represented by constant head cells. For the future conditions, North Sequalitchew Creek is represented by a drain type boundary (CH2M Hill, 2003).

Key to Colors on Map Layers The key to the colors on the attached maps is provided below. See Tables 2, 3 and 4 for the parameters for each of the layers and boundary conditions for each of the Original EIS Model, Updated Model, and Sequalitchew Lake Model.

• White are cells representing the basic aquifer layer

• Blue represents constant head cells

• Red represents constant flux cells

• Green represents river boundaries. As discussed above, only the Sequalitchew Lake Model is shown on the attached maps

• Yellow represents drain cells

Model Boundary Conditions - Layer 1Sequalitchew Lake Model - Current Conditions

EM-1

EM-2 & EM-2D

CHTW-3\PCHMW-3S\PCHMW-3D


CHTW-1\PCHMW-1

FORT LEWIS DIVERSION CANAL

EDMOND MARSH

BELL MARSH

OLD FORT LAKE

MCKAY MARSH

HAMER MARSH

{125}{125}

{150}

{175}

{200}

{125}

{125}

{150}

{175}

{200}

LAKE SEQUALITCHEW

Sequali

tchew

Creek

{125}{125}

{150}

{175}

{200}

{125}

{125}

{150}

{175}

{200}

{150}

{175}

{200}

{125}

{150}

{175}

{200}

{50}

{75}

{100}

{50}

{75}

{100}

{125}

{150}

{175}

{200}

{125}

{150}

{175}

{200}

{140}

2500 feet


EM-1

EM-2 & EM-2D



CHTW-1\PCHMW-1


EDMOND MARSH

BELL MARSH

OLD FORT LAKE

MCKAY MARSH

HAMER MARSH

{125}{125}

{150}

{175}

{200}

{125}

{125}

{150}

{175}

{200}

LAKE SEQUALITCHEW

Sequali

tchew

Creek

{125}{125}

{150}

{175}

{200}

{125}

{125}

{150}

{175}

{200}

{150}

{175}

{200}

{125}

{150}

{175}

{200}

{50}

{75}

{100}

{50}

{75}

{100}

{125}

{150}

{175}

{200}

{125}

{150}

{175}

{200}

{140}

2500 feet

Model Boundary Conditions - Layer 1Sequalitchew Lake Model - Future Conditions

EM-1

EM-2 & EM-2D



CHTW-1\PCHMW-1


EDMOND MARSH

BELL MARSH

OLD FORT LAKE

MCKAY MARSH

HAMER MARSH

{125}{125}

{150}

{175}

{200}

{125}

{125}

{150}

{175}

{200}

LAKE SEQUALITCHEW

Sequali

tchew

Creek

{125}{125}

{150}

{175}

{200}

{125}

{125}

{150}

{175}

{200}

{150}

{175}

{200}

{125}

{150}

{175}

{200}

{50}

{75}

{100}

{50}

{75}

{100}

{125}

{150}

{175}

{200}

{125}

{150}

{175}

{200}

{140}

2500 feet


EM-1

EM-2 & EM-2D



CHTW-1\PCHMW-1


EDMOND MARSH

BELL MARSH

OLD FORT LAKE

MCKAY MARSH

HAMER MARSH

{125}{125}

{150}

{175}

{200}

{125}

{125}

{150}

{175}

{200}

LAKE SEQUALITCHEW

Sequali

tchew

Creek

{125}{125}

{150}

{175}

{200}

{125}

{125}

{150}

{175}

{200}

{150}

{175}

{200}

{125}

{150}

{175}

{200}

{50}

{75}

{100}

{50}

{75}

{100}

{125}

{150}

{175}

{200}

{125}

{150}

{175}

{200}

{140}

2500 feet

APPENDIX B

Modeling Results

PROJECT NO. 040001-012 JUNE 10, 2009 B-I

Modeled Groundwater Elevations and Modeled Drawdown

The following figures provide a model-produced groundwater elevation contour map for the current condition run, and a calculated drawdown map for the future conditions run, for each of the model run series—The Original EIS Model, the Updated Model, and the Sequalitchew Creek Model—in that order.

All groundwater elevations and drawdown values are in feet. The drawdown map is calculated as the difference between the groundwater elevations determined in the current conditions and future conditions model runs.

Modeled Groundwater ElevationsOriginal EIS Model - Current ConditionsLayer 1

126

128 130

132

134 136

138 14

0

142 14

4

146 14

8 15

0 15

2 15

4 15

6

158 160

162 164

166 168 170 172 174

176

178

178

180

180

182

182

184

184

186

186

188

188

190

190

192

192

192

194

194

194

196

196

196

198

198

198

200

200

200

202

202

202

204

204

204

206

206 208

208

210

210

210

212

EM-1

EM-2 & EM-2D



CHTW-1\PCHMW-1


EDMOND MARSH

BELL MARSH

OLD FORT LAKE

MCKAY MARSH

HAMER MARSH

{125}{125}

{150}

{175}

{200}

{125}

{125}

{150}

{175}

{200}

LAKE SEQUALITCHEW

Sequali

tchew

Creek

{125}{125}

{150}

{175}

{200}

{125}

{125}

{150}

{175}

{200}

{150}

{175}

{200}

{125}

{150}

{175}

{200}

{50}

{75}

{100}

{50}

{75}

{100}

{125}

{150}

{175}

{200}

{125}

{150}

{175}

{200}

{140}

2500 feet

Modeled Groundwater ElevationsUpdated Model - Current ConditionsLayer 1

120 126

128 130

132

134 136

138 140

142 14

4

146 148 15

0 15

2 15

4

156

156

158

158

160

160

162

162

164

164

166

166

168

168

170

170

172

172

174

174

176

176

178

178

180

180

182

182

184

184

186

186

188

188

190

190

19 2

192

192

194

194

194

196

196

196

198

198

198

200

200

200

202

202

202

204

204

204

206 206

208 208

208

210

210 212

EM-1

EM-2 & EM-2D



CHTW-1\PCHMW-1


EDMOND MARSH

BELL MARSH

OLD FORT LAKE

MCKAY MARSH

HAMER MARSH

{125}{125}

{150}

{175}

{200}

{125}

{125}

{150}

{175}

{200}

LAKE SEQUALITCHEW

Sequali

tchew

Creek

{125}{125}

{150}

{175}

{200}

{125}

{125}

{150}

{175}

{200}

{150}

{175}

{200}

{125}

{150}

{175}

{200}

{50}

{75}

{100}

{50}

{75}

{100}

{125}

{150}

{175}

{200}

{125}

{150}

{175}

{200}

{140}

2500 feet

Modeled DrawdownUpdated Model - Future ConditionsLayer 1

0.10

0.20

0.20

0.30

0.30

0.30

0.40

0.40

0.40

0.40

0.50 0.50

0.50 0.50

0.50

0.60

0.60

0.60 0.60

0.60

0.70

0.70

0.70 0.70

0.7

0

0.70

0.8

0

0.80

0.80

0.80

0.80

0.80 0.80

0.9

0

0.90

0.90

0.90 0.90

0.9

0

0.90

1.00 1.00 1.00

1.00 1.00

1.00

1.00

1.10

1.10 1.10

1.10 1.10

1.10

1.10

1.20

1.20 1.20

1.20 1.20

1.20

1.20

1.30

1.30

1.30 1.30

1.30

1.30

1.40

1.40

1.40

1.40 1.40

1.40

1.50

1.50 1.50

1.50 1.60

1.60 1.60

1.70

1.70

1.70 1.80

1.80

1.80

1.80

1.90

1.90

1.90

1.90

2.00

2.00

2.00

2.00

2.00 2.10

2.10

2.10

2.10 2.20

2.2

0

2.20

2.20

2.30

2.3

0 2

.30

2.30

2.30

2.30

2.4

0

2.40

2.40

2.5

0

2.5

0

2.50

2.50

2.6

0

2.6

0

2.60

2.60

2.7

0

2.7

0

2.70

2.70

2.70

2.8

0

2.80

2.80

2.80

2.9

0

2.90

2.90

2.90

EM-1

EM-2 & EM-2D



CHTW-1\PCHMW-1


EDMOND MARSH

BELL MARSH

OLD FORT LAKE

MCKAY MARSH

HAMER MARSH

{125}{125}

{150}

{175}

{200}

{125}

{125}

{150}

{175}

{200}

LAKE SEQUALITCHEW

Sequali

tchew

Creek

{125}{125}

{150}

{175}

{200}

{125}

{125}

{150}

{175}

{200}

{150}

{175}

{200}

{125}

{150}

{175}

{200}

{50}

{75}

{100}

{50}

{75}

{100}

{125}

{150}

{175}

{200}

{125}

{150}

{175}

{200}

{140}

2500 feet

Modeled Groundwater ElevationsSequalitchew Lake Model - Current ConditionsLayer 1

120 126

128 130 132

134 136

138 14

0

142 14

4

146 148 15

0 15

2 15

4

156

156

158

158

160

160

162

162

164

164

166

166

168

168

170

170

172

172

174

174

176

176

178

178

180

180

182

182

184

184

186

186

188

188

190

190

192

192

192

194

194

194

196

196

196

198

198

198

200

200

200

202

202

202

204

204

204

206

206 208

208

210

210

210

212

212

EM-1

EM-2 & EM-2D



CHTW-1\PCHMW-1


EDMOND MARSH

BELL MARSH

OLD FORT LAKE

MCKAY MARSH

HAMER MARSH

{125}{125}

{150}

{175}

{200}

{125}

{125}

{150}

{175}

{200}

LAKE SEQUALITCHEW

Sequali

tchew

Creek

{125}{125}

{150}

{175}

{200}

{125}

{125}

{150}

{175}

{200}

{150}

{175}

{200}

{125}

{150}

{175}

{200}

{50}

{75}

{100}

{50}

{75}

{100}

{125}

{150}

{175}

{200}

{125}

{150}

{175}

{200}

{140}

2500 feet

Modeled DrawdownSequalitchew Lake Model - Future ConditionsLayer 1

0.10

0.20

0.20

0.20

0.30

0.30

0.30

0.30

0.40

0.40

0.40 0.40

0.50

0.50

0.50 0.50

0.50

0.6

0

0.60

0.60

0.60 0.60

0.60

0.7

0

0.70

0.70

0.70 0.70

0.70 0.80

0.80

0.80

0.80

0.80

0.90

0.90

0.90

0.90

0.90

0.90 1.00

1.00 1.00

1.00

1.00

1.00

1.00

1.10

1.10 1.10

1.10

1.10

1.10

1.10

1.10 1.20

1.20

1.20 1.20

1.20

1.20

1.20

1.20

1.30

1.30

1.30

1.30

1.30

1.30

1.30

1.40

1.40

1.40

1.40 1.40

1.40

1.40 1.50

1.50

1.50

1.50

1.50 1.60

1.60

1.60

1.60 1.70

1.70

1.70

1.70

1.70 1.80

1.80

1.80

1.80 1.90

1.90

1.90

1.90 2.00

2.00

2.00

2.00 2.10

2.10

2.10

2.10

2.10 2.20

2.20

2.20

2.30

2.30

2.30

2.30

2.40

2.40

2.40

2.40

2.50

2.50

2.50

2.50

2.5

0

2.60

2.60

2.60

2.60

2.6

0

2.70

2.70

2.70

2.7

0

2.80

2.80

2.80

2.80

2.8

0

2.90

2.90

2.90

2.90

2.9

0

EM-1

EM-2 & EM-2D



CHTW-1\PCHMW-1


EDMOND MARSH

BELL MARSH

OLD FORT LAKE

MCKAY MARSH

HAMER MARSH

{125}{125}

{150}

{175}

{200}

{125}

{125}

{150}

{175}

{200}

LAKE SEQUALITCHEW

Sequali

tchew

Creek

{125}{125}

{150}

{175}

{200}

{125}

{125}

{150}

{175}

{200}

{150}

{175}

{200}

{125}

{150}

{175}

{200}

{50}

{75}

{100}

{50}

{75}

{100}

{125}

{150}

{175}

{200}

{125}

{150}

{175}

{200}

{140}

2500 feet

APPENDIX C

Sensitivity Analyses

ASPECT CONSULTING

PROJECT NO. 040001-012 JUNE 10, 2009 C-1

Sensitivity Analyses The following figures provide the model-generated groundwater elevation contour maps for the current condition model run, and a calculated drawdown map for the future conditions model run, for each of the assumed conditions. The sensitivity analyses runs were conducted for a worst-case dry year condition, and to look at the effect of replacing the upgradient constant head boundary condition with a flux boundary condition.

All groundwater elevations and drawdown values are in feet. The drawdown map is calculated as the difference between the current conditions groundwater elevations and the future conditions groundwater elevations.

Modeled Groundwater ElevationsDry Year Sensitivity - Current ConditionsLayer 1

120 124 128 132 136 140

144

148

152

152

156

156

160

160

164

164

168

168

172

172

176

176

180

1

80

180

184

1

84

184

188 188

188

192

192

192

196

196

196

200

200

200

204

204 204

208

208

208

EM-1

EM-2 & EM-2D



CHTW-1\PCHMW-1


EDMOND MARSH

BELL MARSH

OLD FORT LAKE

MCKAY MARSH

HAMER MARSH

{125}{125}

{150}

{175}

{200}

{125}

{125}

{150}

{175}

{200}

LAKE SEQUALITCHEW

Sequali

tchew

Creek

{125}{125}

{150}

{175}

{200}

{125}

{125}

{150}

{175}

{200}

{150}

{175}

{200}

{125}

{150}

{175}

{200}

{50}

{75}

{100}

{50}

{75}

{100}

{125}

{150}

{175}

{200}

{125}

{150}

{175}

{200}

{140}

2500 feet

Modeled DrawdownDry Year Sensitivity - Future ConditionsLayer 1

0.10 0.10

0.20

0.20

0.20

0.30

0.30

0.30

0.40

0.40

0.40 0.40

0.50

0.50

0.50 0.50

0.60

0.60 0.60

0.60

0.70

0.70 0.70

0.70

0.80

0.80

0.80

0.80

0.80 0.90

0.9

0

0.90

0.90 0.90

0.90

1.00

1.0

0

1.00

1.00 1.00

1.00

1.10

1.1

0

1.10

1.10

1.10 1.10

1.20

1.2

0

1.20

1.20

1.20 1.20

1.20

1.3

0

1.30

1.30

1.30

1.30

1.40

1.4

0

1.40

1.40

1.40 1.40

1.40

1.50

1.5

0

1.50

1.50

1.50

1. 6

0

1.60

1.60

1.60

1.60 1.60

1.60

1.7

0

1.70

1.70

1.70

1.70 1.70

1.70

1.8

0

1.80

1.80

1.80

1.80

1.9

0 1

.90

1.90

1.90

1.90

1.90

2.0

0

2.00

2.00

2.00

2.00

2.1

0

2.10

2.10

2.10 2.10

2.2

0

2.20 2.20

2.20

2.20

2.20

2.20

2.3

0

2.30 2.30

2.30

2.30 2.30

2.30

2.4

0

2.40 2.40

2.40

2.40 2.40

2.40

2.5

0 2

.50

2.50

2.50

2.50 2.50

2.50

2.6

0 2

.60

2.60

2.60

2.60 2.60

2.60

2.7

0 2

.70

2.70

2.70

2.70 2.70

2.70

2.8

0 2

.80

2.80

2.80

2.80 2.80

2.80

2.9

0 2

.90

2.90

2.90

2.90 2.90

2.90

EM-1

EM-2 & EM-2D



CHTW-1\PCHMW-1


EDMOND MARSH

BELL MARSH

OLD FORT LAKE

MCKAY MARSH

HAMER MARSH

{125}{125}

{150}

{175}

{200}

{125}

{125}

{150}

{175}

{200}

LAKE SEQUALITCHEW

Sequali

tchew

Creek

{125}{125}

{150}

{175}

{200}

{125}

{125}

{150}

{175}

{200}

{150}

{175}

{200}

{125}

{150}

{175}

{200}

{50}

{75}

{100}

{50}

{75}

{100}

{125}

{150}

{175}

{200}

{125}

{150}

{175}

{200}

{140}

2500 feet

Modeled DrawdownConstant Flux Sensitivity Analysis - Future ConditionsLayer 1

0.20

0.20

0.20

0.30

0.30

0.30

0.40

0.40

0.40 0.40

0.50

0.50

0.50 0.50

0.50

0.60

0.60

0.60 0.60

0.60

0.7

0

0.70

0.70

0.70 0.70

0.70

0.80

0.80

0.80

0.80

0.80

0.90

0.90

0.90

0.90

0.90

0.90

0.90 1.00

1.00 1.00

1.00

1.00

1.00

1.00

1.10

1.10

1.10

1.10

1.10

1.10

1.10

1.20

1.20 1.20

1.20

1.20

1.20

1.20

1.20 1.30

1.30

1.30

1.30

1.30

1.30 1.40

1.40

1.40

1.40 1.40

1.40

1.40 1.50

1.50

1.50

1.50

1.50

1.50

1.60

1.60

1.60

1.60

1.60 1.70

1.70

1.70

1.70

1.70 1.80

1.80

1.80

1.80 1.90

1.90

1.90

1.90

1.90 2.00

2.00

2.00

2.00 2.10

2.10

2.10

2.10

2.10 2.20

2.20

2.20

2.20

2.30

2.30

2.30

2.40

2.40

2.40

2.50

2.50

2.50

2.50

2.5

0

2.60

2.60

2.60

2.6

0

2.70

2.70

2.70

2.70

2.7

0

2.80

2.80

2.80

2.80

2.8

0

2.90

2.90

2.90

2.90

2.9

0

EM-1

EM-2 & EM-2D



CHTW-1\PCHMW-1


EDMOND MARSH

BELL MARSH

OLD FORT LAKE

MCKAY MARSH

HAMER MARSH

{125}{125}

{150}

{175}

{200}

{125}

{125}

{150}

{175}

{200}

LAKE SEQUALITCHEW

Sequali

tchew

Creek

{125}{125}

{150}

{175}

{200}

{125}

{125}

{150}

{175}

{200}

{150}

{175}

{200}

{125}

{150}

{175}

{200}

{50}

{75}

{100}

{50}

{75}

{100}

{125}

{150}

{175}

{200}

{125}

{150}

{175}

{200}

{140}

2500 feet

modeling analyses for fort lewis jblm drinking water system, aspect 2009

Education

model boundary conditions

sequalitchew lake model

current conditions model

conceptual model

future conditions model

original eis model

original model inputs

sequalitchew springs