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California*gional Water Quality Contr*Board <br /> Central Valley Region x <br /> Katherine Hart Chair <br /> Arnold <br /> 11020 Sun Center Drive 4200,Rancho Cordova,California 9567M114 Schwarzenegger <br /> Phone(916)464-3291 •FAX(916)464-4645 Governor <br /> hupllwww.waterboards.ca.govlcentralvalley <br /> 1 February 2010 <br /> Mr. Ed Ralston <br /> ConocoPhillips <br /> 76 Broadway <br /> Sacramento, CA 95818 <br /> SOIL GAS SAMPLING REPORT, FORMER UNION OIL BULK PLANT NO. 788, 8203 EAST 11TH <br /> STREET, TRACY, SAN JOAQUIN COUNTY <br /> California Regional Water Quality Control Board, Central Valley Region (Central Valley Water Board) <br /> staff reviewed the 15 December 2009 Soil Gas Sampling Report (Report) prepared by Stantec <br /> Consulting 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 ceased, <br /> and all the tanks and associated piping and structures were removed. The Site is currently vacant <br /> and no longer in use. Since 1989, Union Oil (now ConocoPhillips) has installed 13 soil borings, <br /> sampled 13 test pits, collected 55 soil samples, and installed and sampled 10 monitoring wells. In <br /> the first half of 2009, ConocoPhillips properly abandoned all Site monitoring wells, excavated <br /> contaminated soil to depths of up to 10 feet below ground surface (bgs), installed five temporary soil <br /> gas vapor probes, and collected soil gas samples. <br /> In November 2009, ConocoPhillips installed five temporary soil gas probes near the June 2009 <br /> locations and collected soil gas samples. Soil probe SG-8 was the only location to have detections <br /> above the California Regional Water Quality Control Board — San Francisco Bay Region <br /> Environmental Screening Level (ESL) for commercial/industrial and residential land use. The soil gas <br /> sample from SG-8 contained total petroleum hydrocarbons as gasoline and benzene at <br /> concentrations of 350,000 micrograms per cubic meter (ug/m) and 91 pg/m3, respectively. SG-8 is <br /> about 20 feet east of the excavation and is near an area of remaining soil concentrations. <br /> Central Valley Water Board staff concurs with ConocoPhillips' recommendation to resample the soil <br /> gas near SG-8 in six months. By 30 June 2010, ConocoPhillips needs to resample the soil gas near <br /> SG-8 and submit a report of findings. <br /> If you have any questions, you may contact me by phone at (916) 464-4819 or by email at <br /> kshel on waterboards.ca. ov. T r M r <br /> XKRISTI SHELTON, P.E. pl� JFEB 0 3 2010 D <br /> Water Resources Control Engineer <br /> Aboveground Tanks Cleanup Unit By--__----__ <br /> cc: Ms. Margaret Lagorio, San Joaquin County Environmental Health Department, Stockton <br /> Mr. Mark Bare, Stantec Consulting Corp., Rancho Cordova <br /> California Environmental Protection Agency <br /> Orecycled Paper <br />