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Mnn+nx`Honxio.a: <br /> Water Boards <br /> Central Valley Regional Water Quality Control Board <br /> TO: Case File: Flag City Chevron FROM: James L.L. Barton, P.G. <br /> 6421 Capitol Avenue Engineering Geologist <br /> Lodi, San Joaquin County YA <br /> DATE: 20 March 2012 SIGNATURE: ' <br /> SUBJECT: UST CASE CLOSURE, FLAG CITY CHEVRON #9-0302, <br /> 6421 CAPITAL AVENUE, LODI, SAN JOAQUIN COUNTY, <br /> CLEANUP AND ABATEMENT ORDER 5-00-700 (CASE 390782) <br /> Site Background: <br /> Flag City Chevron (Site) currently leases a Chevron-branded retail fueling station to an <br /> independent operator near the intersection of Interstate 5 and Hwy 12, west of Lodi <br /> (Attachment 1). Operations at the Site began in 1984. The current underground <br /> storage tank (UST) complex consists of six fuel dispensers, three 12,000-gallon <br /> gasoline USTs and one 12,000-gallon diesel UST. Prior to 1995, the site utilized four <br /> 12,000-gallon gasoline USTs and one 12,000-gallon diesel UST. <br /> During vent system repairs/upgrades in June 1990, Benzene (B), Toluene (T), <br /> Ethylbenzene (E), and Xylenes (X) were reportedly detected at concentrations up to <br /> 25 micrograms per kilogram (ug/kg) in soil samples collected from borings advanced <br /> below the UST pit. Specific concentrations for individual constituents are unavailable, <br /> as a copy of the individual results was never submitted. In 1991, three monitoring wells <br /> (MW-1 through MW-3) were installed near the original underground storage tank <br /> complex for a property transfer (Attachment 2). Dissolved petroleum hydrocarbons <br /> were not detected in initial groundwater samples collected from MW-1 through MW-3. <br /> However, in May and August 1993, benzene was detected in MW-1 and MW-3 at <br /> concentrations up to 9.4 micrograms per Liter (ug/L). In May 1993, San Joaquin County <br /> Environmental Health Department (SJCEHD) filed an unauthorized release form, <br /> opened a USTs case, and provided oversight for investigation and remediation activities <br /> until February 2000, when SJCEHD transferred oversight to the Regional Water Quality <br /> Control Board (Regional Board). <br /> In March 1995, the five USTs were removed from the site (Attachment 3). Soil samples <br /> collected from the bottom and sidewalls of the tank pit following over-excavation <br /> identified no impacts from constituents of concern (CDCs). Soil sampling from below <br /> the product dispensers and piping identified total petroleum hydrocarbons as gasoline <br /> (TPHg) at a concentration of 1,500 ug/kg at approximately 5.0 feet below ground <br /> surface (' bgs). The product-piping trench was subsequently over-excavated vertically <br /> one additional foot. Confirmation soil samples collected from the bottom and sidewalls <br /> KnRL E. Lonc-_Ex S:'.D, RE. cunin Patsc_a C. CRc EaD,c c+.rculy[ ,,rc" <br /> 11020 Swr Ceme,Dnve 6804 Rancho Domnva,.9 n56]0 vrww waerOOares c,povice,,,nlvaieV <br /> Li• ui.i ...a,u, <br />