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ENVIRONMENTAL HEALTA DEPARTMENT <br /> oPp��N c SAN JOAQUIN COUNTY <br /> UO <br /> ' ' Unit Supervisors <br /> Donna K.Heran,R.E.H.S. Carl 8or pan,R.E.H.S. <br /> Director304 East Weber Avenue, Third Floor <br /> Mike Huggins,R.E.H.S.,R.D.I. <br /> AI Olsen,R.E.H.S. Stockton, California 95202-2708Douglas w-Wilson,R.E.H.s. <br /> Program Manager Telephone: (209) 468-3420 Margaret Laprio,R.E.H.S. <br /> Laurie A.Cotulla,R.E.H.S. <br /> Program Manager Fax: (209) 464-0138 Robert McClellon,R.E-HS. <br /> Mark Barcellos,R.E.H.S. <br /> BOB HOPKINS D E C 3 0 2003 <br /> UNION OIL COMPANY <br /> 276 TANK FARM ROAD <br /> P O BOX 1069 <br /> SAN LUIS OBISPO CA 93406 <br /> RE: Former Unocal #2859 SITE CODE: 1213 <br /> 1665 Pacific Avenue <br /> Stockton, CA <br /> San Joaquin County Environmental Health Department (EHD) has reviewed the "Evaluation of . <br /> 1,2-Dichloroethane in Groundwater and Proposed Changes to the Monitoring and Sampling <br /> Program" dated November 26, 2003, prepared by ENSR International for the above referenced <br /> site. <br /> EHD approves of discontinuing groundwater sample analyses of MTBE, TBA, DIPE, ETBE and <br /> TAME in monitoring wells MW12 through MW19 and of discontinuing groundwater sample <br /> analyses of 1,2-DCA and EDB in monitoring wells MW12 through MW16. <br /> To evaluate the site as a potential source of 1,2-DCA in the groundwater, ENSR proposes to <br /> analyze for 1.2-DCA using EPA Method 8260 on groundwater samples collected from MW1 <br /> through MW 10 for a period of one year. EHD approves this proposal but requires that <br /> groundwater samples from NP1 also be analyzed for 1,2-DCA and EDB. In addition, soil data <br /> from past investigations should be reviewed to see if analysis for 1,2-DCA was performed. EHD <br /> reviewed its file and found that the soil sample collected beneath the waste oil underground <br /> storage tank removed from this site in 1988 was analyzed for 1,2-DCA with a result of less than <br /> .03 mg/kg. if soil data cannot be found other investigation may be required to determine the <br /> source of the 1,2-DCA. Waiting for a year of groundwater sample results to determine <br /> appropriate action is not acceptable. <br /> If you have any questions contact me at (209)468-3449. <br /> Donna Heran, REHS, Director <br /> Environmental Health Department <br /> =M: Supervising REHS <br /> Unit IV <br /> c: Jim Barton—CVRWQCB <br /> David Irey— SJCADA <br /> Ms. Helen McCrary <br /> Ben Heningburg - ENSR <br />