COMPLIANCE INFO_FILE 7 - Laserfiche WebLink

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SECTION 2 SUMMARY OF SITE CHARACTERIZATION AND EXISTING REMEDIAL ACTIVITIES This section summarizes site characteristics, including site hydrogeology and the distribution and occurence of VOCs in soil and ground water. The existing ground water extraction system is also described in this section. Site Characterization Site characteristics are summarized in the following discussions. Hydro eog� logy Soil at the site, to a depth of approximately 100 feet below ground surface (bgs), is comprised primarily of clay and silt with varying amounts of sand and fine gravel. Three water-bearing zones have been designated at the site: A-Zone, B-Zone and, C-Zone. The A-Zone is designated as the first 10 feet of the uppermost water-bearing zone and primarily consists of silty to sandy clay. This unit occurs at approximately 10 feet bgs to 25 feet bgs and appears to be laterally continuous across the site. The upper portion of the B-Zone is usually identified as a clayey sand which may contain poorly graded gravel to silty sand and is approximately 5 to 10 feet thick. The B-Zone is laterally discontinuous across the site and is generally encountered between 25 to 45 feet bgs. The lower portion of the B-Zone is similar to the A-Zone and consists predominately of silty clays. The upper C-Zone varies from a silty sand to a poorly graded gravel, but generally consists of a poorly graded to well graded sand which is typically 10 to 15 feet thick. This unit is typically encountered between 65 to 75 feet bgs. The lower portion of the C-Zone typically consists of clayey sediments. Drawing 2-1 presents a geologic cross section of the site. These materials become saturated at an approximate depth of 8 to 10 feet bgs. Since 1990, the maximum ground water fluctuation measured in the A-Zone was 2.89 feet (measured at MW-13A). Ground water flow is 2-1