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Stockton Taxi Cab/Sunland Gasoline September lb,2003 <br /> 2085 Fremont Street,Stockton, California Page 9 <br />' Report of Findings: Lateral and Vertical Extent <br /> of Soil and Groundwater Contamination <br /> - Based on the laboratory analysis on B-1 (Feb, 2000 investigation) and the data <br />' collected during this investigation, it seems likely that the source of the contamination <br /> is located at the southeast corner of the former UST field, in the vicinity of B-1 and <br /> ' MW-4. Additionally, based on the data collected at B-2 (Feb, 2000 investigation) and <br /> the data collected during this investigation, it is likely that another source of the <br /> contamination is in the vicinity of Island # 2, near B-2 and B-5. Contamination cross- <br /> sections can be found in Figures 4a and 4b of this report. <br /> B-5 showed the presence of lead at a depth of seven feet (7') and at forty feet(40'). <br /> ' Lead was also present in the soil samples collected from MW-4 and B-4. The lead <br /> levels are below the action levels of 25 mg/Kg. <br /> ' - The lateral and vertical extent of the soil contamination has not been defined. The <br /> deepest soil sample was collected at 100' below ground level and showed significant <br /> contamination in the form of MTBE and benzene. <br /> ' 8.0 Recommendations <br /> After reviewing the site data obtained from the February, 2000 investigation and this <br /> Ile <br /> investigation, WHF recommends the following actions to monitor and mitigate the effects <br /> of the release: <br /> ' - Perform quarterly groundwater sampling and measurements for one year-to determine <br /> the site-specific groundwater flow direction and rate and to determine the lateral <br /> extent of the groundwater contamination. <br /> ' - Install an additional monitoring well to the east of MW-1,near the property line, in an <br /> attempt to define the lateral and vertical extent of soil and groundwater contamination <br /> ' to the east. Install a monitoring well to the east of B-4, near the property line, in an <br /> attempt to define the lateral and vertical extent of soil and groundwater contamination <br /> ' to the southeast. Complete a soil boring to the north of the tank excavation in the <br /> vacant field to determine the lateral and vertical extent of soil contamination. This <br /> boring may be converted to a monitoring well if the water sample from the <br /> ' termination point is contains petroleum hydrocarbon constituents. <br /> 1 , <br /> 1 <br />