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PUBLIC 'EALTH SERV'tr<'-TS <br /> SAN JOAQUIN COUNTY <br /> ENVIRONMENTAL HEALTH DIVISION <br /> Ernest M. Fujimoto, M.D., M.P.H., Acting Health Officer o Ct <br /> 445 N. San Joaquin Street • P.O. Box 388 • Stockton, CA 95201-0388 4;� <br /> (209) 468-3420 <br /> STEPHEN POA <br /> MOBIL OIL CORPORATION <br /> 3700 W 190TH BLD TPT-2 � t <br /> TORRENCE CE 90509-2929 <br /> RE: Former Mobil Bulk Plant SITE CODE: 1968 <br /> 500 East Grant Line Road <br /> Tracy CA 95376 <br /> San Joaquin County Public Health Services, Environmental Health Division (PHS/EHD) has completed <br /> review of the "Supplementary Site Assessment Work Plan" dated November 14, 1994 and prepared by <br /> Alton Geoscience. PHS/EHD has the following comments for your consideration. <br /> The work plan proposed to investigate the area to the west of the former bulk plant facility and to access <br /> the feasibility of enhanced biodegradation. Two soil borings were proposed off site to the west to further <br /> investigate the extent of soil contamination. The work plan indicated that a possible remedial alternative <br /> was biodegradation enhanced by the addition of magnesium oxide. Groundwater samples will be <br /> collected from existing wells to determine the dissolved oxygen and mineral content which may affect <br /> enhanced biodegradation's feasibility. Please be aware that the introduction of substances into the aquifer <br /> requires a discharge permit from the Central Valley Regional Water Quality Control Board. <br /> No soil borings were proposed to the north to further define the extent of soil contamination which has <br /> been evidenced. PHS/EHD does not concur with the opinion expressed within the work plan that the soil <br /> to the north side of Grant Line Road apparently was not affected by hydrocarbons from the Mobil site. <br /> Soil contamination was detected during the off site installation of AW6 at 6 and 11 feet below ground <br /> surface. Also, the most northern on site soil borings were 5138 and S89 and there was significant soil <br /> contamination detected up to 6,700 ppm TPH-d and 1.2 ppm benzene in SB8 and 1,100 ppm TPH-d and <br /> 4.1 ppm benzene in SB9. The evidence of significant soil contamination at the site's northern boundary <br /> suggests that off site migration occurred. <br /> Please submit a permit application and $89 permit fee along with an off site encroachment agreement for <br /> the proposed soil borings. Also be aware that additional work may be necessary to comply with the <br /> PHS/EHD directive dated September 9, 1994. If you have any questions or comments, please contact me <br /> at (209) 468-0337. <br /> Donna Heran, REHS, Director <br /> Environmental Health Division <br /> Mary Meays, Senior REHS iane M. Hinson, REHS <br /> Site Mitigation Unit Supervisor <br /> MM/500EGL <br /> cc: Elizabeth Thayer, CVRWQCB cc: Wendy Cohen, CVRWQCB <br /> cc: Gordon Egan, Tracy Venture cc: Greg Schubert, Tracy Venture/Mark III <br /> cc: Kevin Keenan, Alton Geoscience <br /> A Dkision or San Jiiaquin Counly Health Care Service~ <br />