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San Joaquin Cou ity DIRECTOR <br /> Donna Hera RENS <br /> Environmental Health Department M ASSISTANT DIRECTOR <br /> 600 East Main Stre t Laurie Cotulla, REHS <br /> T Stockton, California 952 23029 PROGRAM COORDINATORS <br /> • is• Carl Borgman,REHS <br /> Mike Huggins, REHS, RDI <br /> �gLl ��P Website: www.sjgov.org ehd Margaretgagorio,REHS <br /> Phone: (209) 468-3420 :Robert McClellon,REHS <br /> Fax: (209) 464-0138 Jeff Carruesco, REHS,RDI <br /> Ur <br /> h 15 <br /> 200 Kasey Foley,REHS <br /> DENIS L. BROWN <br /> AUG L ALI AWNALLAH <br /> SHELL OIL PRODUCTS US 211 EAST CENTURY BLVD <br /> HSE — ENVIRONMENTAL SERVICES LODI CA 95240 <br /> 20945 SOUTH WILMINGTON AVENUE <br /> CARSON CA 90810-1039 <br /> RE: Former Shell Service Station SITE CODE: 000592 <br /> 1313 East Charter Way <br /> Stockton, California 95205 <br /> San Joaquin County Environmental Health Departm nt (EHD) has received and reviewed <br /> Site Investigation Work Plan dated July 19, 2007, prepared and submitted by Conestoga- <br /> Rovers & Associates (CRA) on your behalf for the above-referenced site. In the work <br /> plan, CRA proposes to advance three cone penetration testing (CPT) borings to <br /> approximately sixty feet below surface grade (bsg) on the south side of East Charter Way <br /> to electronically log soil conditions and assess the extent of the 1,2-dichloroethane (1,2- <br /> DCA) groundwater plume south of the above-referenced site. <br /> EHD has reviewed groundwater flow direction at t is site and although recent quarterly <br /> groundwater monitoring reports indicate variable .flow direction, historically, groundwater <br /> flow direction at the source area has been toward t e southAoutheast. This tendency is <br /> supported by analytical data demonstrating the highest concentration for 1,2-DCA is <br /> detected in groundwater samples collected from mon toring well .MW-1. 1,2-DCA has not <br /> been detected in groundwater samples collected frm MW-3 located southwest of the <br /> source area, but 1,2-DCA has consistently been detected at low concentrations in <br /> groundwater samples collected from MW-2 and igh concentrations in groundwater <br /> samples collected from MW-6, both located south/southeast of the source area. For this <br /> reason, EHD believes that either soil boring SB-10 should be relocated east of SB-12 at a <br /> distance equal to the distance between SB-11 and S13-12, or an additional boring be <br /> installed. EHD conditionally approves the work plan with either revision; otherwise, <br /> submit a technical argument demonstrating that the original proposal should be <br /> implemented over the EHD-recommended change. <br /> Soil samples will be collected at ten and thirty feet below ground surface (bgs), and <br /> groundwater samples will be collected from the "bottom of the first saturated coarse- <br /> grained zone" at approximately fifty feet bgs, each liorn separate borings adjacent to the <br /> three CPT borings. Soil and groundwater samples will be analyzed for'total petroleum <br /> hydrocarbons quantified as gasoline (TPH-gas); benzene, toluene, ethyl benzene, and total <br />