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1995 Technical Memorandum on Soil Boring Investigation

Section 1 - Introduction

As part of an ongoing investigation to determine the origin of groundwater contamination in Camp Stanley Storage Activity (CSSA) wells 2, 3, 4, 16, and D, drilling and soil sampling for chemical analysis were performed at seven potential source areas (Figure 1.1). Six areas, B-1, B-2, B-3, B-4, B-19, and B-28, were historically classified as burn areas. The seventh site was a lined and bermed oxidation pond, O-1. These sites are discussed in detail in the "Camp Stanley Storage Activity Environmental Assessment" (Parsons ES, 1993a). The burn sites and oxidation pond are located within a 0.4-mile radius of well 16, which preliminary results indicate to be near the central area of groundwater contamination within the middle Trinity aquifer.

Chlorinated hydrocarbons were first detected in well 16 at concentrations above the drinking water limits in April 1991. CSSA retained Parsons Engineering Science (Parsons ES) in October 1992 under the Armstrong Laboratory/OEB (AL/OEB) contract F33612-89-D-4003 to perform a preliminary evaluation of the groundwater contamination. Quarterly groundwater monitoring of all wells at CSSA began in October 1992 and has continued to the present. Additional tasks of the investigation included a downhole camera survey (December 1992), a downhole geophysical survey (August 1994), discrete interval sampling (September 1994), well upgrades to seal off perched zones for monitoring of the middle Trinity aquifer, and well plugging and abandonment of four wells (September 1994). These actions are addressed in two reports - the "Hydrogeologic Report for the Evaluation of Groundwater Contamination at Camp Stanley Storage Activity, Texas, March 1993" (Parsons ES, 1993b) and the Technical Memorandum on geophysical Well Logging, Discrete Interval Sampling, and Well Upgrades and Plugging, Camp Stanley Storage Activity, Texas" (Parsons ES, 1995a).

The source characterization began with surface geophysical tasks. Geophysical surveys were performed during January and March 1995 to locate any subsurface anomalies associated with the potential source areas. The results of the surveys are discussed in depth in the Parsons ES "Technical Memorandum on Surface Geophysical Surveys, Well 16 Source Characterization, Camp Stanley Storage Activity, Texas, June 1995" (Parsons ES, 1995b). Source characterization drilling activities began on February 21, 1995 and ended March 16, 1995 and is the subject of this report.

A total of thirty-four soil borings were drilled at the seven potential source areas mentioned above (Figure 1.1). These potential source areas are considered solid waste management units (SWMUs). The location of the soil borings were based on the surface geophysical survey results. Table 1.1 provides a summary of the geophysical survey results and drilling activities that are further discussed in this report.

Table 1.1 - Summary of Geophysical Surveys ad Drilling Activities

¹ An additional sample was collected and only analyzed for asbestos, which was not detected.

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