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Background Information Report

Summary of Previous Investigations at CSSA

This section gives a summary of previous studies (as of 1999), concentrating on aspects which relate specifically to the units subject to closure submittal in this work plan.

Routine water well testing by the Texas State Department of Health detected the presence of dissolved tetrachloroethene (PCE), trichloroethene (TCE), and 1,2-dichloroethene in well 16 above the respective constituent maximum contaminant levels (MCLs).  Additional testing of other wells for halogenated volatile organics has been performed since August 1991 (ES, 1993b).  Results of monitoring conducted approximately quarterly is reported in quarterly groundwater monitoring reports (listed in Volume 5).

U.S. Army facilities are required to perform an environmental baseline and overall environmental assessment of installation properties.  An environmental assessment (EA) was developed for CSSA, identifying, describing, and evaluating potential and known environmental impacts associated with current and past operations.  Thirty-four potential solid waste management units (SWMUs were identified following a review of records, interviews with CSSA personnel, and field observations.  This report recommended further study at sites where past releases could pose a threat to human health and the environment.

One of the sites identified during the EA was site F-14.  The F-14 site was a less-than-90-day accumulation site submitted for closure under TNRCC Risk Reduction Standard 1.  Parsons ES conducted preliminary and verification sampling of surface and subsurface soils to demonstrate the absence of constituents above background levels for Standard 1 closure (Parsons ES, 1995e).

In conjunction with the F-14 and B-20 investigations, samples of background surface soils and subsurface rock were collected from undisturbed areas of CSSA and statistically evaluated.  Per direction from TNRCC, each of the eight soil types occurring at CSSA, and the Glen Rose Limestone bedrock, were evaluated separately,   Ten samples of each of the limestone soil types were collected and analyzed for arsenic, barium, cadmium, chromium, copper, lead, nickel, mercury, and zinc.  A background concentration for each metal in each soil/rock type was then determined by calculating the 95 percent upper tolerance limit.  A report entitled “Evaluation of Background Metals Concentrations in Soil Types at Camp Stanley Storage Activity” was submitted in June 1997 and approved by TNRCC in September 1997.  Volume 2 includes further information on background studies.  

According to CSSA records, an open burning/open detonation site (B-20) was used for the detonation of explosive ordnance, static firing of rocket motors, disposal of scrap metal, and disposal of small arms ammunition from 1946 to 1987. In 1992, under the jurisdiction of the Resource Conservation and Recovery Act (RCRA) enforcement, the  EPA (Region VI) required CSSA to immediately cease operation of the site and prepare a closure plan.  The closure plan was prepared in 1994 (ES, 1994a) and has had numerous amendments (Parsons ES, 1995f, 1995g, 1996b).  Investigations at B-20 have been ongoing since 1995 and have included environmental sampling and removal of unexploded ordnance (UXO) and scrap metal.

Surface geophysical surveys were conducted at seven SWMUs, which were identified as potential sources of groundwater contamination at Well 16 (Parsons ES, 1995a).  These were units B-1, B-2, B-3, B-4, B-19, B-28, and O-1.  Geophysical surveys identified subsurface anomalies potentially related to sources of contamination prior to drilling and subsurface sampling.

In the summer of 1995, surface geophysical surveys were conducted at eight additional SWMUs to determine the nature and extent of potential ground disturbances (Parsons ES, 1995c).  The methods used to identify the anomalies included electromagnetic induction (EMI) and ground penetrating radar (GPR).  Results indicated one or more anomalies at units B-8, B-15/16, B-23, and B-24, and are presented in the “Technical Memorandum on Surface Geophysical Surveys at High Priority SWMUs”.  

In June 1995, drilling and sampling was conducted to further determine the source of groundwater contamination in five water wells at CSSA (Parsons ES, 1995b).  Seven potential source areas, SWMUs B-1, B-2, B-3, B-4, B-19, B-28, and the oxidation pond (O-1) were investigated.  These potential source areas are located within a 0.4 mile radius of well 16.  In relation to the potential for Well 16 contamination source study, B-2, B-3, B-4, B-28, and O-1 were categorized as high priority units and B-1 and B-19 as low priority units.  For the purpose of SWMU closure investigations, B-1 and B-19 have been recategorized as medium priority sites due to additional drilling necessary for data.  At each source area, field observations of potential sources of contaminants, such as waste, metal scraps, and topographic expression, were recorded in a field logbook.  Additionally, soil/rock samples were taken at or around depths of 5 feet, 10 to 20 feet, and 30 feet.  Groundwater grab samples were taken where sufficient volume was available, but no monitoring wells were installed. The results of this study were presented in the “Technical Memorandum on Soil Boring Investigation, Well 16 Source Characterization” (Parsons ES 1995b).

In conjunction with the other investigations to identify the source or sources of contamination in Well 16, soil gas surveys were performed at thirteen sites at CSSA.  The samples were tested for the chlorinated hydrocarbon compounds identified in well 16 as well as for benzene, toluene, ethyl benzene, and xylenes (BTEX) to test for fuel contamination.  Results strongly indicate that unit O-1 is one of two source areas of PCE groundwater contamination at CSSA.  The other potential source of groundwater contamination is SWMU B-3.  A technical memorandum of the soil gas surveys was submitted in the “Groundwater Investigation and Associated Source Characterizations”  (Parsons ES, 1996d).

Since 1996, investigations addressing SWMUs and groundwater contamination at CSSA have continued under the direction of CSSA and the Air Force Center for Environmental Excellence (AFCEE).  These investigations include the following:  

Scoping documents for these investigations are included in this volume of CSSA’s environmental encyclopedia, and results from these investigations will be provided in subsequent volumes.