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' 1.3 Geology <br /> II ' The subsurface geology of the site was determined by logging soil samples collected at <br /> various intervals during the initial and supplemental site investigations, and the remedial <br /> soil excavation. <br /> Dark brown silty clay dominates the stratigraphy from within one foot of the surface to <br /> ' the bottom of the borings. In general, fine sand was found within the silty clay unit near <br /> the bottom of the borings at an approximate depth of 20 feet bgs. The moisture content <br /> increased with depth and reached saturation between 12 and 16 feet bgs. During the <br /> ' remedial excavation a highly plastic brown clay layer was encountered at a depth of <br /> approximately 18 feet bgs. <br /> ' 1.4 Hydrology <br /> ' Groundwater at the site is contained in a semi-confined or unconfined aquifer typically 10 <br /> to 15 feet bgs. However, ground water was measured at an approximate depth of 8 feet <br /> bgs during the spring of 1998. Historically, groundwater at the site demonstrates a <br /> ' shallow gradient that slopes to the northwest. <br /> • 2.0 PURPOSE <br /> The purpose of this report is to present analytical data collected during the June 15 and <br /> 22, 1999 quarterly sampling event. Sample collection methodology, laboratory analytical <br /> methods, analytical data and an evaluation of the data are described in subsequent <br /> sections of this report. In addition to providing this information, a request for case <br /> closure has also been incorporated into this document. <br /> 3.0 SCOPE OF WORK <br /> The following tasks were conducted in order to meet the objectives of this phase of the <br /> ' investigation at this site: <br /> • Collect ground water elevation data accurate to 0.01 feet. <br /> Purge and sample two ground water monitoring wells to obtain representative <br /> 1 samples on June 15, 1999. <br /> • <br /> 1 <br /> American Geological Service, Inc. <br /> ' CA95DE-029 5 <br />