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CAMBRIA <br /> 4 Stockpiled soil remaining on-site or off-site disposal(quantity); <br /> There is no stockpiled soil remaining on-site An unknown amount of soil was stockpiled on-site <br /> following the 1987 waste oil tank removal This stockpile was sampled, but its final disposition is <br /> unknown Approximately 70 cubic yards of soil were removed during the 1990 fuel UST removal <br /> activities This soil was removed from the site and disposed of at West Contra Costa Class III landfill <br /> S Monitoring wells remaining on-sate,fate, <br /> All site monitoring wells (MW-1 through MW-4) and vapor wells (VEW-1 and VEW-2) will be <br /> properly destroyed once Shell receives a No Further Action Required letter <br /> 6 Tabulated results of all groundwater elevations and depths to water, <br /> Tabulated historical depth to groundwater and groundwater elevation data are presented in <br /> Attachment C <br /> • 7 Tabulated results of all sampling and analyses; <br /> Tabulated historical soil data are presented in Table 1 and tabulated groundwater analytical data are <br /> presented in Attachment C <br /> 8 Concentration contours of contaminants found and those remaining an soil and groundwater, <br /> both on-and off-sate; <br /> Soil iso-concentration contour maps are included in Attachment F Each map shows TPHg and <br /> benzene concentrations,respectively, in the top 20 feet of soil from samples collected between 1989 <br /> and 1991 These maps show concentrations in the UST and dispenser areas Three soil samples were <br /> also collected in the vicinity of the waste oil tank in 1987 One of these samples contained 298 ppm <br /> TPHg and 0 044 ppm benzene The two other samples from this location did not contain detectable <br /> concentrations of TPHg or benzene, indicating that impact to soil is localized in this area No soil <br /> samples have been collected at the site since December 1991, so current TPHg and benzene soil <br /> concentration data are not available No iso-concentration maps for groundwater were prepared, <br /> because TPHg and benzene were not detected during the most recent sampling event (first quarter <br /> 2002) and MTBE concentrations were below 5 ppb Further, initial groundwater samples collected <br /> • from MW-1 through MW-3 in 1990 did not contain detectable concentrations of petroleum <br /> hydrocarbons All detections in groundwater at this site have been sporadic and low-level <br />