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• ' 11 June 2001 AGE-NC Project No. 96-0232 ' Page 3 of 11 ' by AGE. • 19 January 1996-one soil boring(MW-5)was advanced upgradient of the former UST area to a depth of 70 feet. Soil boring MW-5 was completed as a 2-inch diameter ground water ' monitoring well. Petroleum hydrocarbon impacted soil was encountered at depths of 45 and 50 feet. Dissolved TPH-g was detected in the initial ground water sample from MW-5 at a ' concentration of 23,000 µg/1 (Tables 1 and 2). Results of the December 1995 investigation were reported in the CAP. • 19 January 1996-An 8-hour soil vapor extraction(SVE)pilot test was conducted at the site ' in January 1996. The pilot test was performed to provide vapor extraction data for proper system design of a remediation system. TPH-g and BTEX compounds were detected from influent SVE air flow samples at concentrations as high as 95,000 micrograms per liter ' (µg/1). Results of the December 1995 investigation were reported in the CAP. • 06& 07Apri12000-Five soil borings(CPT-1, CPT-lA, CPT-2,CPT-2A and CPT-3)were ' advanced on- and off- site to approximately 105 feet bsg utilizing cone penetrometer testing (CPT) technology to characterize the geological and hydro-geological framework and to assess preferential migration pathways. Based on soil composition data obtained from the ' CPT soil borings, cross sections A-A'and B-B'(Figures 3 and 4)were constructed depicting the general subsurface soil composition beneath the site. Laboratory analysis of grab water samples detected substantial petroleum-impact from CPT-1Aand CPT-2A to depths of 105 ' feet bsg(Table 3). Results of the April 2000 CPT investigation were reported in Quarterly Report- Second Quarter 2000, dated 31 July 2000,prepared by AGE. ' Between January 1995 and 07 February 2001,twenty-two ground water monitoring events have been performed at the site to monitor dissolved petroleum hydrocarbon concentrations in ground water and to characterize ground water flow direction and gradient on the site (Table 3). Based on ground water data depicted in cross sectional views A -A'(Figure 3) and B-B'(Figure 4), ' the vertical extent of petroleum-impacted ground water extends to at least 105 feet bsg beneath the site and is not fully defined;based on an isoconcentration map(Figure 5) depicting the approximate horizontal extent of dissolved TPH-g at the site on 07 February 2001, the horizontal extent is not fully delineated in any direction. The purpose for the drilling and installation of the proposed multi- level wells are to characterize and delineate the vertical extent of hydrocarbon-impact soil and ' ground water beneath the site. 2.4. REGIONAL GEOLOGIC SETTING The property is situated within the Great Valley Geomorphic Province of California, a large, ' Advanced GeoEnvironmental,Inc.