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California Regional Water Quality Control Board <br /> Central Valley Region <br /> ion <br /> 0 <br /> Karl E. Longley, ScD.P.E..Chair <br /> Linda S.Adams n'for Arnold <br /> Secreta 11020 Sun Center Drive N200,Rancho Cordova,California 95670-6114 <br /> Phone(916)464-3291 •FAX(916)464-4645 Schwarzenegger <br /> Environmental http:// waterboards.ca.gov/centralvalley Governor <br /> Protection <br /> p A <br /> t v �. . <br /> To: Antonia K.J. Vorster FROM: Kristi Shelton <br /> Site and Groundwater Cleanup Water Resources Control Engineer <br /> Program Manager Aboveground Tanks Cleanup Unit <br /> SIGNATURE: K <br /> Wendy Cohen, P.E. <br /> Chief, Aboveground Tanks Unit <br /> M <br /> DATE: 4 March 2009 SIGNATURE: v'�i �nr � � <br /> SUBJECT: RATIONALE FOR CONSIDERING NO FURTHER ACTION REQUIRED ON <br /> VOLPI 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 (Ng/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 /> �a Recycled Paper <br />