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_/ L.N111 V1 I.A" l• G/Vllu• f I <br /> \\ O Central Valley Region <br /> Karl E. Longley,ScD.P.E., Chair <br /> Linda S.Adams 11020 Sun Center Drive#2O0,Rancho Cordova,California 95670-6114 Arnold <br /> Secretaryfor Phone(916)464-3291 •FAX(916)464-4645 Schwarzenegger <br /> Environmental http:// waterboards.ca.gov/centralvallcy Governor <br /> Protection <br /> t,n <br /> , <br /> v, <br /> To: Antonia K.J. Vorster FROM: Kristi Shelton <br /> Site and Groundwater Cleanup Water Resources Control Engineer <br /> Program Manager Abovegrou d Tanks Cleanup Unit <br /> jL <br /> SIGNATURE: F <br /> Wendy Cohen, P.E. <br /> Chief, Aboveground Tanks Unit <br /> t � o <br /> i <br /> DATE: 4 March 2009 SIGNATURE: <br /> SUBJECT: RATIONALE FOR CONSIDERING NO FURTHER ACTION REQUIRED ON <br /> VOLP/FARM PROPERTY, 14210.WEST STATE ROUTE FOUR, STOCKTON, <br /> SAN JOAQUIN COUNTY <br /> Rationale: Soil removal activities conducted in 1998 and 1999 removed petroleum <br /> hydrocarbon contamination from the Site. Following the 1999 soil removal action and the <br /> subsequent groundwater monitoring, concentrations of petroleum hydrocarbons in soil and <br /> groundwater have declined significantly. <br /> Issues: In 2005, MW-3 contained 100 micrograms per liter (pg/L) of MTBE. Downgradient <br /> wells MW-1 and MW-7 have not contained petroleum hydrocarbons above water quality <br /> objectives since 2003. In 2008, the MTBE concentration in MW-3 was 27 pg/L, and it.is <br /> expected to continue to decline to water quality objectives <br /> Setting: The Site is in an agricultural region about 13 miles west of Stockton on Highway 4. <br /> The Site includes two maintenance buildings. An irrigation ditch runs along the southern <br /> portion, and one domestic well is north of the Site (see attached Site Plan). <br /> Source: Spills and/or leaks from two aboveground tanks (ALTs). In September 1999, Volpi <br /> removed the AGTs and dispenser. <br /> Actions: Investigation commenced in 1998. <br /> • Site investigations showed three areas of concern: the area around the 7,500-gallon diesel <br /> AGT that appeared to be leaking fuel from the dispenser onto the pad; the 1,000-gallon <br /> gasoline AGT with a portion of its system lines buried; and an area used for waste oil <br /> handling and possibly disposal. <br /> • In July 1998, Volpi removed about 52.5 tons of contaminated soil from four trenches and <br /> encountered groundwater in two of them at about eight feet below ground.surface (bgs). <br /> Volpi collected grab groundwater samples from the irrigation ditch and the onsite domestic <br /> well. The domestic well sample did not contain petroleum hydrocarbons above reporting <br /> limits. <br /> California Environmental Protection Agency <br /> �d Recycled Paper <br />