SITE INFORMATION AND CORRESPONDENCE

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Sent_ By. RWOCB SACRAMENTO; 916 255 3015; Feb-24-99 14:09; Page 416 1665 Pacific Avenue -3 - 16 February 1994 Petition Summary and Conclusions Regional Board Response (Pages 12- 14 1). There is no evidence of MTBE at this site. MTBE was reported at 21 pg1L(ppb)in MW-2 i during 6118198, and 2.9 ltg1L for MW-3 during 316198 sampling events. Both analytical results used EPA Method 8260.(See 28 October 1998 Groundwater Monitoring and Sampling Report prepared by Gettler-Ryan Inc.) Corrective actions including soil vapor extraction San Joaquin County has documentation for and removal of an estimated 850 cubic yards of disposal of 350 cubic yards of contaminated soil. contaminated soil have removed a significant mass not 850 cubic yards. The duration of SVE system of residual petroleum hydrocarbons at petitioner's operation was limited and influent concentrations site. at the time of system shutdown remained high. Z). The plume of dissolved phase hydrocarbons is Without the deep plume assessment information stable,concentrations of constituents are declining, (vertical characterization),and an estimate of and naturally occurring biodegradation of contaminant mass in soil and groundwater,plume petroleum hydrocarbons adsorbed to soil and stability can not be evaluated. present in groundwater is occurring. 3). Ten years after the release was stopped, Onsitc and offsite groundwater contamination does groundwater meets Basin Plan objectives with not meet basin plan objectives within 70 and 150 respect to 13TEX constituents within about 70 feet feet lateraily of the site with respect to BTEX and of the site; with respect to TPHg,groundwater TPHg. Benzene is reported up to 1.000µg/L(ppb) meets Basin Plan objectives within 150 feet of the and TPHg to 83,000 pg/L(8/31198 sampling). site. No presentation was made for achieving water quality objectives within a reasonable time period. 4). Petitioner's site is located in a California Water Service owns and operates four - comrneicialtresidential area. No water supply wells municipal drinking water production wells within are located within 800 feet and the nearest surface 3,000 feet of the site. The closest well is located water is about 2,000 feet from the site. approximately 800 feet north-northeast and a second well is 2,000 feet north-northwest. 5). Current water supply wells in the vicinity of The four nearby water supply wells have sanitary the site are constructed with sanitary seals which seals extending between 70 to 96 feet below extend to depths of 150 to 200 feet below ground ground surface(based on California Water Service surface for the purpose of excluding poor quality well completion details). The gravel pack on all shallow groundwater. four wells fills the annular space from the total well depth to ground surface. Such well construction may provide preferential pathways for vertical contaminant migration.