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7�ar �• t i - <br /> � EI`1SR international <br /> I C411 Oji P1a^Frvil a Roy d <br /> Suite 210 <br /> August 30, 2004 Sac,amento,CA 95827-2508 <br /> (91 g)362.7104 <br /> FAX (916)362-8,00 <br /> wN v ensr 6om <br /> Ms Margaret Lagorto <br /> County of San ,Joaquin <br /> Environmentat Health Depart, erit <br /> 334 East Weber Avenue, Third Floor <br /> Stockton, CA 95202-2708 <br /> RE- Response to Agency Request for Additional Subsurface Data <br /> i Former Unocal Station No 2859 <br /> 1665 Pacific Avenue, Stockton, California <br /> Dear Ms Lagorio <br /> On behalf of the Union Oil Company of California (Unocal), ENSR Corporation (ENSR) has <br /> prepared this letter in response to the December 30, 2003 letter from the San Joaquin County <br /> Environmental Health Department (SJCEHD) A copy of the above-referenced letter is included <br /> as Attachment A. <br /> As requested by SJCEHD, ENSR conducted an internal file review and found additional soil <br /> data concerning 1,2-Dichloroethane (1,2-13CA) ENSR is presenting additional soil data <br /> concerning lead. As stated in the letter from the SJCEHD, a soil sample was taken from <br /> storage tank following removal activities on <br /> beneath the former waste oil underground <br /> March 29, 1988 The sample was analyzed for 1,2-DCA with a result of less than <br /> 0 03 milligrams per kilogram (mg/kg) An additional soil sample collected on March 30, 1988 <br /> from beneath the former underground storage tanks at a depth of 26 feet was analyzed for <br /> organic lead with a result of less than 10 mglkg The certified analytical report for these <br /> samples is included as Attachment B <br /> A composite soil sample was collected from soil cuttings generated during the drilling operations <br /> related to piezometer well NP-1 on March 31, 1999 NP-1 is located approximately 20 feet to <br /> the east of the former dispenser islands and next to monitoring well MW-10 NP-1 was drilled <br /> and installed from January 4 through January 6, 1999 to a total depth of 90 feet below ground <br /> surface The sample was <br /> of analyzed <br /> 0 l arts pelta an r The certiosal fied analyturposes ical report fwas ar the composrted by the ite <br /> to have a concentrationP <br /> soil sampie is included as Attachment C <br /> A composite soil sample obtained from of soil cuttings from ronitoring ::ells MW-12, MAPI-14, <br /> MW-16, M IV-18, and MW-19, was collected on March 8, 2002 and analyzed for disposal <br /> purposes The previously listed monitoring wells were drilled on May 21 through May 23, 2001 <br /> Monitoring wells MW-12, MW-14, and MW-16 are located onsite while MW-18 and MW-19 are <br /> offsite wells The laboratory reported a total lead concentration of 8 2 mg/kg from the composite <br /> sample No add,tianal soil sample results were found regarding lead or 1,2-DCA The certi;ed <br /> analytical report for the latter composite soil sample is included as Attachment D <br /> Arcec,1Jo940`2gi9 57Fi^ t1(nne^ronds'-r�16556_jr fl8?r'�lddoc <br />