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- ' Former Beacon Station No. 12474 March 18,2002 <br /> Stockton,California _ _ _ Problem Assessment Report/Corrective Action Plan <br /> wells were identified or tentatively identified as domestic, and one as municipal supply. The <br /> • locations of the wells are approximately 600 to 2000 feet from the site. <br /> The municipal supply well is owned by the California Water Service and provides public <br /> water supply in the survey area. The municipal well is located approximately 2000 feet east <br /> of the site on Oro Avenue and is screened from 144 to 420 feet bsg. According to California <br /> Water Service, the municipal well has been out of service for 15 years because of solvent <br /> contamination reportedly from lumber treatment operations approximately 0.7 miles north- <br /> northeast of the well. No other California Water Service wells are located within the survey <br /> area. <br /> 5.0 PROBLEM ASSESSMENT <br /> The distribution of petroleum hydrocarbons in soil was evaluated on the basis of soil <br /> Sanalytical data from previous investigations. The distribution of petroleum hydrocarbons in <br /> groundwater was interpreted on the basis of groundwater analytical data from first quarter <br /> 2002 quarterly monitoring. <br /> 5.1 Distribution of Petroleum Hydrocarbon-Impacted Soil <br /> Total petroleum hydrocarbons as gasoline (TPHg) and benzene soil analytical data are <br /> plotted on cross sections (Figures 3 and 4) to illustrate their lateral and vertical distributions <br /> in soil. Available analytical data indicate petroleum hydrocarbon constituents were reported <br /> primarily in soil samples from soil borings B-5 (vapor wells VW-11213), B-6 (vapor wells <br /> VW-4/5/6), MW-6, MW-12, VW-7 and AS-1 at depths ranging from 30 to 112 feet bsg as <br /> shown on the cross sections and summarized in the soil analytical data tables (Appendix A). <br /> The distribution of total petroleum hydrocarbons as gasoline (TPHg) in soil, as shown on <br /> Figure 6 and the cross sections suggests the eastern dispenser island as a source. <br /> 474PARCAP3-02.doc 6 <br /> Project No. 1474.23 HORIZON ENVIRONMENTAL INC. <br />