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California`Tional Water Quality Control Board :, Y <br /> l\- Central Valley Region <br /> vk <br /> Karl E. Longley,ScD,P.E.,Chair <br /> Arnold <br /> Linda S.Adams <br /> 11020 Sun Center Drive tl200,Rancho Cordova,California 95670-6114 Schwarzenegger <br /> Secretaryfor Phone(916)464-3291 •FAX(916)464-4645 <br /> Environmental http://w .waterbouds.ca.gov/centralvalley Governor <br /> Protection <br /> 13 August 2008 <br /> AUG 14 2008 <br /> Mr. Ed Ralston ENVIRONMENT HEALTH <br /> ConocoPhillips PERMIT/SERVICES <br /> 76 Broadway <br /> Sacramento, CA 95818 <br /> SOIL ASSESSMENT REPORT, FORMER UNION OIL BULK PLANT NO. 788, 8203 EAST <br /> 1I r" STREET, TRACY, SAN JOAQUIN COUNTY <br /> California Regional Water Quality Control Board, Central Valley Region (Regional Water Board) <br /> staff reviewed the 1 July 2008 Soil Assessment Report (Report) prepared by Stantec Consulting <br /> Corporation (Stantec) on behalf of ConocoPhillips for the former Union Oil Bulk Plant at <br /> 8203 East 11th Street in Tracy (Site). <br /> The Site is a former bulk fuel storage facility in the City of Tracy. In 1993, Site operations <br /> ceased, and all the tanks and associated piping and structures were removed. The Site is <br /> currently vacant and no longer in use. Since 1989, Union Oil (now ConocoPhillips) has installed <br /> 13 soil borings, sampled 13 test pits, collected 55 soil samples, and installed and sampled 10 <br /> monitoring wells. <br /> In May 2008, ConocoPhillips drilled six confirmation soil borings adjacent to the historical <br /> maximum concentration locations (U-1, U-2, U-5, U-C, TP-8, and TP-11) and collected soil <br /> samples from five to six feet below ground surface (bgs) and from seven to eight feet bgs. Soil <br /> samples from borings CB-1 through CB-3 contained total petroleum hydrocarbons as gasoline <br /> (TPHg) up to a maximum concentration of 1,300 milligrams per kilogram (mg/kg) in CB-3 at <br /> 7-8 feet bgs. TPHd was detected in all six borings with a maximum concentration of 540 mg/kg. <br /> ConocoPhillips estimates about 270 pounds of TPHg and 168 pounds of TPHd still remain in <br /> soil at the Site. In general, soil concentrations attenuated about 30% from historical levels; <br /> however, soil samples collected from CB-2 (TPHg), CB-3 (TPHg and TPHd), and CB-5 (TPHd) <br /> still contain concentrations above the Region 2 Environmental Screening Levels (ESLs) for <br /> shallow soils. <br /> Our.comments are presented below: <br /> 1. Three soil samples contained TPHg and TPI-Id concentrations above the ESLs for <br /> leachability and gross contamination. The Report states that the effect on groundwater <br /> has been minimal over the last 10 years and that the development of less stringent soil <br /> screening levels is warranted. Regional Water Board staff concurs with this statement. <br /> By 6 October 2008, ConocoPhillips needs to conduct Site specific modeling to show <br /> whether soil concentrations will leach to groundwater. <br /> California Environmental Protection Agency <br /> OvIecycled Paper <br />