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[Volume 5 Table of Contents]

Hydrogeologic Conceptual Site Model for CSSA (January 2006)

Table of Contents

Report Introduction

Section 1 - Introduction

Section 2 - Background

Section 3 - Source Characterization and Potential Exposure

Section 4 - Conceptual Site Model Development

Section 5 - Contaminant Distribution and Occurrence

Section 6 - Summary and Conclusions

Section 7 - Glossary of Terms

Appendices

Appendix A   Potentiometric Maps

Appendix B   Groundwater Analytical Summary

Appendix C   Contaminant Plume Maps

Appendix D   Multi-Port Well Analytical Summary

Appendix E   Multi-Port Well Plume Maps

Figures

Figure 1.1   Site Location Map

Figure 2.1   Camp Stanley and Surrounding Area

Figure 2.3   Stratigraphic and Hydrostratigraphic Section of the Hill Country Area

Figure 2.4   Surface Geologic Map

Figure 2.5   Geologic Cross Section through the Study Area

Figure 2.6   Approximate Thickness of the Middle Trinity Aquifer

Figure 2.7   Elevation of the Base of the Middle Trinity Aquifer

Figure 2.8   Approximate Thickness of the Upper Trinity Aquifer

Figure 2.9   Elevation of the Base of the Upper Trinity Aquifer

Figure 3.1   SWMU Location Map

Figure 3.2   Soil Gas Plume Map

Figure 4.1   USGS Geologic Surface Map

Figure 4.2   Watersheds of the San Antonio River Basin

Figure 4.3   Hydrogeologic Conceptual Site Model Bounding Limits

Figure 4.4   Water-level Elevations in the Upper Trinity Aquifer

Figure 4.5   Water-level Elevations in the Middle Trinity Aquifer

Figure 4.6   Combined Stratigraphic Model of CSSA

Figure 4.7   Exposed Surface of the Upper Glen Rose Limestone

Figure 4.8   Base of Upper Glen Rose Limestone

Figure 4.9   Exposed Surface of the Lower Glen Rose Limestone

Figure 4.10   Base of Lower Glen Rose Limestone

Figure 4.11   Geologic Fence Diagram at CSSA

Figure 4.12   Geologic Cross Section A-A^ı (North-South)

Figure 4.13   Geologic Cross Section B-B^ı (Southwest-Northwest)

Figure 4.14   Geologic Cross Section C-C^ı (Northwest-Southwest)

Figure 4.15   Base of the Bexar Shale

Figure 4.16   Hydrograph of Wells with Open Borehole Completions

Figure 4.17   Hydrograph of Wells with Lower Glen Rose Completions

Figure 4.18   Hydrograph of Wells with Bexar Shale Completions

Figure 4.19   Hydrograph of Wells with Cow Creek Completions

Figure 4.20   Hydrograph of Average Water Level Elevations by Geologic Unit

Figure 4.21   Range of Groundwater Elevations in Selected Wells 1992-2004

Figure 4.22   Seasonal Groundwater Fluctuations in Selected Wells 1992-2004

Figure 4.23   Hydrograph of Well CS-MW16-LGR and Precipitation Data

Figure 4.24   Comparison of Groundwater Elevations within Well Clusters

***Figure 4.25   Flow Net of Potential Hydraulic Head, June 2003 (North to South Profile)

Figure 4.26   Flow Net of Potential Hydraulic Head, June 2003 (North to South Profile)

Figure 4.27   Flow Net of Potential Hydraulic Head, June 2003 (Northwest to Southeast Profile)

Figure 4.28   CS-WB01 Hydraulic Profiling Data (January - August 2004)

Figure 4.29   CS-WB01 and CS-MW8 Datalogging Event (April 22 - August 12, 2004)

Figure 4.30   Conceptualized Recharge Scenario based upon June 7, 2004 Precipitation Event

Figure 4.31   Model Area Watershed Subunits Based on USGS Digital Elevation Model (2001)

Figure 4.32   Figure 4.32 Recharge Coefficients (Percent of Rainfall that Recharges the Aquifer) for the Trinity Aquifer in the Hill Country Area

Figure 4.33   Fate of Recharge within the Aquifer for CSSA and Conceptual Site Model Area

Figure 5.1   Maximum Extent of VOC Contamination within the Middle Trinity Aquifer (December 2002 through June 2003)

Figure 5.2   VOC Concentrations at CS-D since 1991

Figure 5.3   VOC Concentrations at CS-16-LGR since 1991

Figure 5.4   CS-MW7 Cluster Discrete Interval Groundwater Sampling

Figure 5.5   CS-MW8 Cluster Discrete Interval Groundwater Sampling

Figure 5.7   Geology and Construction of the Multi-Level Monitoring System

Figure 5.8   CS-WB01 Combined Concentration Data

Figure 5.9   CS-WB02 Combined Concentration Data

Figure 5.10   CS-WB03 Combined Concentration Data

Figure 5.11   CS-WB04 Combined Concentration Data

Figure 5.13   Horizontal and Vertical Extent of PCE within the Middle Trinity Aquifer above 0.05 µg/L

Figure 5.14   Horizontal and Vertical Extent of PCE within the Middle Trinity Aquifer above 1.0 µg/L

Figure 5.15   Horizontal and Vertical Extent of PCE within the Middle Trinity Aquifer above MCL (5.0 µg/L)

Figure 5.16   Horizontal and Vertical Extent of PCE within the Middle Trinity Aquifer above 25.0 µg/L

Tables

Table 4.1   Summary of Geological Data from Model-Area Well Logs

Table 4.7   Summary of Hydrophysical Data at AOC-65

Table 4.8   Summary of Off-Post Hydrophysical Data at WB-04

Table 4.10   Volume of Annual Precipitation within CSSA and Surrounding Watersheds (Based upon 1971-2000 Precipitation Normals for Boerne, TX)

Table 4.11   Volume of Annual Precipitation within CSSA and Surrounding Watersheds (Based upon 1999 Precipitation at CS-16 Weather Station)

Table 4.12   Volume of Annual Precipitation within CSSA and Surrounding Watersheds (Based upon 2000 Precipitation at CS-16 Weather Station)

Table 4.13   Volume of Annual Precipitation within CSSA and Surrounding Watersheds (Based upon 2001 Precipitation at CS-16 Weather Station)

Table 4.14   Volume of Annual Precipitation within CSSA and Surrounding Watersheds (Based upon 2002 Precipitation at CS-16 Weather Station)

Table 4.18   Annual Groundwater Discharge from CSSA Wells (1980-2002)

Table 4.19   Water Balance for CSSA Using Precipitation Minimum, Maximum, and Normals

Table 4.20   Water Balance for Conceptual Site Model Area Using Precipitation Minimum, Maximum, and Normals

Table 5.4   Cumulative Results from the Selected Intervals within CS-WB04

Table 5.6   Ratio of PCE and TCE in Multi-port Zones (January 2004 through September 2004)