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• Closure Report - Chevron Station#9-1848 January 18, 1999 - - ppm) and benzene (0 010 ppm), and the soil sample from well boring C-2 at 16 feet bgs contained TPHg (13 ppm) and benzene (0 11 ppm) also These borings appear to define the lateral and vertical extent of petroleum hydrocarbon impacted soil beneath the site Furthermore, soil samples from the four off-site soil borings did not contain detectable petroleum hydrocarbons, thus delineating the soil cast, northeast, noith, and west of the site Groundwater impacted by petioleum hydrocarbons appears to be confined to wells C-1 and C-2 Moreover, it appears the groundwater plume has not migrated off-site and is stable as evidenced by the grab gioundwater samples collected from borings 13-1 through B-4 Based on these data, additional investigation or remediation of soil or groundwater is not wai ranted, and the site should be closed In support of the closure request, we summai ize the infoimation requested in Appendix B of the CRWQCB Request For Closure guidelines This information is presented point by point as outlined in the document I Background history of the case The case history is Summarized above • II Investigative methods Based on our review of available documentation, work performed at the site to date appears to have followed the appropriate San Joaquin County Department of Public Health Services (SJCDPHS) and RWQCB guidelines foi the investigation and remediation of hydrocarbon-impacted sites, and the accepted methods and practices in general use at the time the work was performed III Extent of soil and groundwatei pollution The lateral and vertical extent of hydrocarbon impact has been defined Impacted soil from the former gasoline UST pit, associated product lines, waste oil UST, hydraulic lifts and fluid tank, grease traps, and oil water separator had been excavated until only low levels of petroleum hydrocarbon concentrations were left in place Approximately 960 cubic yards of soil was transpoited to Forward Landfill in Stockton, California Appi oximately 30 cubic yards of soil containing waste oil were transpoi ted to Browning Ferris Industries in Livermore, California Approximately 450 cubic yards of soil were used to backfill the former UST excavation Impacted groundwater appears confined to on-site wells C-1 and C-2 Free-phase hydrocarbons have never been measured or observed in the any of the thiee wells at this • 346302 02-0 4