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Ms Lori Duncan Page 2 of 5 Source Removal: Excavation On November 8, 2000, approximately 165 cubic yards of soil was excavated in the vicinity of the former tank pit in order to to remove contaminated soil from the subsurface; document the completeness of the removal effort with confirmation soil samples, and further investigate the vertical limit of contamination. A total of five confirmation soil samples were collected from the floor and sidewalls of the excavation pit. Detectable concentrations of contaminants were not detected in any sample. No contaminants appeared to extend beyond the limits of the excavation boundaries. Analytical results are summarized in Table 3. The excavation boundaries and soil sampling locations are depicted on Figure 2. Hydrogeological Setting The site is situated in the Lodi South quadrangle, Section 8, T2N, R6E, San Joaquin County, California. Regionally, the property is located in the San Joaquin Valley physiographic province. The valley is a topographic and structural basin bounded on the east by the Sierra Nevada and on the west by the Coast Ranges. Locally the topography slopes gently toward the southwest at approximately six feet per mile. Significant surface water bodies in proximity to the site are Five Mile Creek, Mosher Slough, and the Calaveras River. Mosher Slough and Five Mile Creek, are located approximately 800 feet and 1 mile south of the site, respectively. These two waterways flow in a westerly direction. The southwest flowing Calaveras River is located approximately 4 miles west southwest of the site and is a tributary of the San Joaquin River. The Calaveras River generally exhibits moderate stream flow losses over portions of the year, which contributes to groundwater recharge (USGS Professional Paper 1401-D, 1989). Regional groundwater flow in the site area is generally in an easterly direction toward a regional groundwater depression centered approximately 4 miles east of Stockton (San Joaquin County Flood Control and Water Conservation District, Fall 1998). Drinking water wells in the region are generally completed at depths greater than 100 feet below ground surface (bgs) due to the relatively poor quality of near-surface groundwater. Current depth to first groundwater at the site is approximately 32 feet below grade, and is expected to flow in a northeasterly direction (San Joaquin County PHS/EHD Corresp, 9/6100). Historical data from the San Joaquin County Flood Control and Water Conservation District suggests that water levels are currently at or near a historical high. Historical low water levels are expected to have been between 45 and 50 feet bgs. INVESTIGATIVE PROCEDURES The investigation was conducted in accordance with the approved Workplan dated July 20, 2000 and addendum dated October 6, 2000. On January 12, 2001, one soil boring was advanced at the nsauto/reports/adct,;uhsurfsum.doc