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,6 <br /> Hydrogeology is summarized by flow direction that is regionally south to southwest bsed on <br /> DWR data(Figures 11 and 12). Local flow direction from nearby sites has also been to south <br /> to southwest. <br /> Well and Conduit Study: All wells identified to a distance of 2,000 foot .radius of site. <br /> 6. y <br /> Nearest well is located on ST&E property 300 feet west of former UST. Well has been tested <br /> for TPH-d and volatile organic compounds and found to be non-detect. <br /> 7. Estimation of Release Mass:Initial volume of impacted petroleum hydrocarbon soil at the site <br /> was estimated to be approximately 400 to 700 cubic yards with an average concentration of <br /> TPH-d ranging from 100 to 500 mg/kg. This suggests that the initial TPH-d contaminant <br /> Ilf <br /> mass was approximately.16,000 pounds. <br /> Source has been stopped with UST removal in 1998 and cessation of onsite fueling <br /> operations since then. <br /> 8. Source Removal Activities: Leaking UST was removed in 1998. <br /> 9. Remediation Activities: None. <br />`r <br /> 10. Areal extent of petroleum hydrocarbon groundwater plume: Maximum (400 square feet) <br /> 11. Concentration of Chemicals vs Distance: Detectable TPH-d degrades to zero line no greater <br /> than 100 feet horizontal from remaining soil contaminant mass. <br /> 1.2. Concentration of Chemicals vs Time: Degredation of petroleum hydrocarbons is estimated <br /> to go to below detectable limits by approximately 2018 (ten years). <br /> 13. Spread of Constituents in Groundwater: Not applicable. <br /> Environmental\STET ARSCR09102008.wpd 19 <br />