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San Joaquin County DIRECTOR <br /> PQ u N Donna Heran,REHS <br /> Environmental Health Department ASSISTANT DIRECTOR <br /> Z.-' =i 600 East Main Street Laurie Cotulla,REHS <br /> �. Stockton, California 95202-3029 PROGRAM COORDINATORS <br /> Carl Borgman,REHS <br /> ' Mike Huggins,REHS,RD[ <br /> Website: www.sjgov.org/ehd Margaret Lagorio,REHS <br /> Phone: (209)468-3420 Robert McClellon,REHS <br /> Fax: (209) 464-0136 Jeff Carruesco,REHS,Rol <br /> Kasey Foley,REHS <br /> SERGIO MORESCALCHI AUG 2 4 2007 <br /> ATLANTIC RICHFIELD COMPANY <br /> P O BOX 1257 <br /> SAN RAMON CA 94583 <br /> RE: ARCO Service Station No. 2186 <br /> 3212 North California Street <br /> Stockton, California 94570 <br /> San Joaquin County Environmental Health Department (EHD) has reviewed Work Platt <br /> for Soil Vapor Survey dated August 9, 2007, prepared by SECOR International <br /> Incorporated (SECOR) on your behalf. The work plan was submitted in response to the <br /> EHD letter dated June 7, 2007, directing you to evaluate the potential for vapor intrusion <br /> into existing onsite and offsite buildings. <br /> In the work plan SECOR proposes to install three permanent soil vapor probes at the site <br /> by advancing three borings to total depth of approximately six feet below ground surface <br /> (bgs) and installing soil vapor probes screened between approximately 5`/4 to 53/4 feet bgs. <br /> To evaluate the potential threat of soil vapor petroleum hydrocarbon concentrations, <br /> SECOR proposes to collect soil gas samples in Summa canisters from each soil vapor <br /> probe and analyze the soil gas samples for total petroleum hydrocarbons quantified as <br /> gasoline (TPH-g) between carbon ranges C4 and C20; benzene, toluene, ethyl benzene, <br /> and total xylenes (BTEX); methyl tertiary-butyl ether (MTBE), ethyl tertiary-butyl ether <br /> (ETBE), tertiary butyl alcohol (TBA), di-isopropyl ether (DIPE), tertiary-amyl methyl <br /> ether (TAME), naphthalene, 1,2-dibromoethane (EDB), isopropyl alcohol, and 1,2- <br /> dichloroethane (1,2-DCA). <br /> SECOR proposes to install one soil vapor probe (VP-1) along the east property line <br /> approximately 25 feet north/northeast of monitoring well MW-2; one probe (VP-2) <br /> adjacent to the sidewalk directly north of the station building approximately 65 feet <br /> southeast of MW-3; and one probe (VP-3) adjacent to the north side of the canopy <br /> approximately 30 feet south of MW-1. EHD approves the location for soil vapor probes <br /> VP-2 and VP-3; however, EHD believe VP-1 should be relocated along the east property <br /> line between MW-1 and the residential home adjacent to the east side of this site at 522 <br /> East Alpine Avenue. Because groundwater samples collected from MW-1 have the <br /> highest concentrations for TPH-g, BTEX, MTBE, and TBA, and groundwater flow <br /> direction tends to be toward the east-northeast, EHD believes a soil vapor probe located <br /> between MW-1 and the adjacent home will provide the most relevant information <br /> concerning the potential for soil vapor intrusion into the closest residential structure. <br /> EHD conditionally approves the work plan with this revision; otherwise, <br />