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Groundwater Investigation and Associated Source Characterization
Section 1 - Introduction
This project was conducted to evaluate groundwater contamination by chlorinated hydrocarbons detected in a decommissioned drinking water well, well 16, located at Camp Stanley Storage Activity, Boerne, Texas. This report is intended to summarize all reports to date, and to present data not discussed in any prior reports prepared.
Previous reports prepared under AL/OEB order 067 include a hydrogeologic report (ES, 1993a), plans of action (ES, 1993b and c), work plan for soil vapor extraction pilot testing (Parsons ES, 1996a), work plan for monitoring well installation (Parsons ES, 1996b), technical memorandum on initial actions (Parsons ES, 1995a), surface geophysical surveys (Parsons ES, 1995b and c), soil boring investigations (Parsons ES, 1995d and e), a well packer test (Parsons ES, 1995h), quarterly and annual groundwater monitoring reports (July 1994 through February 1996), and subcontractor reports on ground penetrating radar profiling (Young, 1996) and seismic reflection (Blackhawk Geoscience, 1996). Reports prepared for other environmental projects at CSSA such as the environmental assessment (Parsons ES, 1993d) were also utilized.
As a branch of the Department of Defense, CSSA is subject to federal and state environmental laws. Specifically, the Safe Drinking Water Act (SDWA) applies to wells that serve at least twenty-five people. When in active use, well 16 was subject to SDWA rules. Under Section 120 of the Comprehensive Environmental Response, Compensation, and liability Act (CERCLA), CSSA is obliged to characterize and remediate the groundwater contamination. 40 Code of Federal Regulations (CFR) Part 260, promulgated under the Resource Conservation and Recovery Act (RCRA) establishes requirements and standards for groundwater protection. Upon verification of solvent contamination in well 16 (August 23, 1991) CSSA inactivated well 16 and notified water users, as required by state and federal regulations. CSSA then voluntarily initiated a groundwater evaluation.
In January 1993, the preliminary evaluation data was presented to the Texas Department of Health (TDH), Texas Natural Resource Conservation Commission (TNRCC), and EPA Region VI RCRA Permitting Section at a technical interchange meeting. The project plans of actions were submitted to EPA and TNRCC in May 1993. In fall 1993, CSSA and EPA Region VI RCRA Enforcement Section discussed the June 30, 1993 EPA compliance order regarding the closure of CSSA hazardous waste management unit B-20. It was agreed that EPA would have primacy over this groundwater evaluation project. The 1993 project plans were submitted to EPA and TNRCC.
This project is authorized on September 30, 1992, under AL/OEB Contract F33615-89-D-4003, Delivery Order 067. The work was conducted by Parsons ES under the technical supervision of AL/OEB and has also been overseen by EPA Region VI RCRA Enforcement Section since October 1993. The scope of work defined preliminary evaluation actions such as record reviews, groundwater sampling, and preparation of project plans. The scope of work was modified on September 20, 1993, to include phase II investigation actions to define the possible contaminant source areas and the installation of monitoring wells. Due to reasonable delays in work schedule, the project period of performance was extended twice, in 1994 and in 1995. The final delivery order schedule date in June 22, 1996.
1.4 - Investigation Objectives and Scope
The 1992 scope of work defined phase I technical actions. Because previous groundwater samplings and analyses had confirmed groundwater contamination in inactive water wells (well 16, D, and 4), the objective of the phase I evaluation was to define the possible extent of the problem without drilling and to establish plans of actions. The phase I evaluation included a records review, a field geologic survey, inventory, sampling, and surveying of existing wells, laboratory analysis, downhole camera surveys, and the preparation of a hydrogeologic report, a phase II work plan, sampling and analysis plan (SAP), and a health and safety plan (HASP).
The phase II scope of work was defined in the first modification to delivery order 067 in September 1993. The objective of the phase II site investigation was to evaluate potential source areas and define the groundwater contamination, with efforts focused on obtaining data to support recommendations for remediation, if necessary. Site investigation actions included borehole geophysical logging, groundwater sampling of perched zones, upgrade or plugging of wells, and installation of groundwater monitoring wells. Source characterization actions included cluster well installation, electromagnetic induction surveys and soil borings drilled and sampled at potential source areas. Other actions were aquifer testing, quarterly groundwater monitoring, assessment of waste disposal actions, and closure plans for solid waste management units (SWMUs).
Additional deliverables included a technical memorandum on waste disposal associated with the project, prepared under the National Pollutant Discharge Elimination System (NPDES) draft and final permit for CSSA (Parsons ES, 1995g), and this groundwater investigation report.
This report is organized in ten sections. Section 1 describes the project purpose, authorization and objectives. Section 2 discusses geographical and historical information of the post and the environment. including regional hydrogeology. Section 3 presents the methodologies and procedures of actions undertaken to characterize groundwater contamination source areas and to define the site hydrogeology.
Section 4 summarizes the preliminary evaluation and resulting deliverables submitted in 1993. Section 5 presents characterization actions at potential source areas. Section 6 and Section 7 discuss additional source characterization and testing at CSSA solid waste management units O-1 (the oxidation pond) and the B-3 burn/landfill area, respectively. Section 8 discusses the hydrogeologic evaluation which involved 2 years of data collection in groundwater monitoring, geologic mapping, geophysical surveys, and installation of groundwater monitoring wells. Section 9 presents project conclusions and remedial alternatives, and Section 10 lists references.