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Californiawgional Water Quality Cor A Board <br /> Central Valley Region r ;i <br /> Karl E. Longley. ScD.P.E..Chair `«° <br /> Linda S.Adams Arnold <br /> Secreran�far Sacramento Main Office Schwarzenegger <br /> Se <br /> Environmental 11020 Sun Center Drive 0200.Rancho Cordova.California 95670-6114 Governor <br /> Protection Phone(916)464-3291 -PAX(916)464-4645 <br /> httpi//ws\'w.waterboards.ca.gov/centraivalley <br /> To: Wendy Cohen' FROM: Kristi Shelton <br /> Senior WRC Engineer WRC Engineer <br /> Aboveground Tanks Cleanup Unit Aboveground Tanks Cleanup Unit <br /> DATE: 15 November 2007 SIGNATURE: - <br /> SUBJECT: NO FURTHER ACTION REQUIRED, FORMER MOBIL OIL COMPANY BULK <br /> PLANT 04-343, 500 GRANTLINE ROAD, EAST TRACY, SAN JOAQUIN <br /> COUNTY <br /> I reviewed the 14 April 1997 Formal Site Closure Report prepared by Alton Geoscience (Alton) <br /> on behalf of Mobil Oil Corporation (Mobil) for the former Mobil Bulk Plant at 500 East Grantline <br /> Road, Tracy in San Joaquin County (Site). The report outlines the site assessment activities <br /> and recommendations for site closure. The site history and rationale for issuing a No Further <br /> Action Required letter are summarized below. <br /> BACKGROUND <br /> Mobil operated a bulk fuel distribution facility at the Site. Plant operations were discontinued <br /> in 1988 and all structures were removed from the property. Site structures included a <br /> 1,000-gallon underground storage tank (UST), four 10,000-gallon aboveground storage tanks <br /> (ALTs), and associated piping. The site is currently a paved vacant lot owned by Leprino <br /> Foods Company (Leprino), which uses it for employee parking. Leprino is remediating <br /> groundwater on its property from a separate release with a groundwater extraction and <br /> treatment system downgradient of the Site. A Site Plan of the Site is shown on Figure 1. <br /> SOIL INVESTIGATIONS <br /> In 1988 and 1989, Mobil collected soil samples at 10 and 12 feet below ground surface (bgs) <br /> beneath the UST and around the AGTs. Maximum soil concentrations of total petroleum <br /> hydrocarbons as gasoline (TPHg), TPH as diesel (TPHd), and benzene were 240 milligrams <br /> per kilogram (mg/kg), 3,600 mg/kg, and 2.2 mg/kg, respectively. One grab groundwater <br /> sample was also collected and contained 1,700 micrograms per liter (pg/L) of TPI-Ig and <br /> 130 pg/L of benzene. Soil boring locations are shown on Figure 2. <br /> In 1990, Mobil excavated about 6,000 cubic yards of contaminated soil down to the water table <br /> at 10 feet bgs. The excavated soil was shipped offsite for disposal and clean fill was imported <br /> and compacted to grade. The extent of the excavation is shown on Figure 2. Soil samples <br /> collected from the floor of the excavation contained maximum concentrations of TPI-Ig and <br /> TPHd at 1,900 mg/kg and 1,200 mg/kg, respectively. The lateral extent of the excavation was <br /> limited to the property boundary and no samples were collected along the sidewalls. <br /> California Environmental Protection Agency <br /> prd� Rec,rc/ed Paper <br />