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r <br /> San Joaquin County DIRECTOR <br /> Donna Heran,REHS <br /> °�'" Environmental Health Department <br /> ASSISTANT DIRECTOR <br /> 600 East Main Street Laurie Cotulla,REHS <br /> Stockton, California 95202-3029 PROGRAM COORDINATORS <br /> LliiQi <br /> Carl Borgman, REHS <br /> Website: www.s ov.or /ehd Mike Huggins,REHS, RDI <br /> 4�iF6R� �g g Margaret Lagorio,REHS <br /> Phone: (209)468-3420 Robert McClellon,REHS <br /> Fax: (209)464-0138 .teff Carruesco, REHS,RDI <br /> Kasey Foley, REHS <br /> STEPHEN VALENTINE 0 C T 12 2007 <br /> STEVE & GENES SERVICE <br /> 6232 HEMET AVE <br /> STOCKTON CA 95207 <br /> RE: STEVE&GENES SERVICES SITE CODE: 2080 <br /> 2315 N EL DORADO ST <br /> STOCKTON CA 95204 <br /> San Joaquin County Environmental Health Department (EHD) has reviewed Site Conceptual <br /> Model (SCM), dated June 16, 2006, and Report — Groundwater Monitoring 2"d Quarter 2007, <br /> dated May 30, 2007, prepared by your consultant Geological Technics Inc. (GTI) and has the <br /> following comments: <br /> • Soil boring data indicates that the main mass of soil contamination exists in the former <br /> dispenser area at shallow depth. Shallow soil borings SB-B and MW-3 encountered the <br /> highest levels of soil contamination between 21 and 51 feet below surface grade (bsg). SB-B <br /> contained 13,000 milligrams per kilogram (mg/kg) total petroleum hydrocarbons as gasoline <br /> (TPH-g) at 26 feet bsg, and 61 mg/kg benzene at 31 feet bsg. MW-3 contained 2,700 mg/kg <br /> TPH-g and 50 mg/kg benzene at 55 feet bsg. Deeper soil samples, collected between 60 and <br /> 128 feet bsg near dispenser area, including MW-101, MW-210, and SB-201 contained lower <br /> concentrations of the contaminates. The remaining soil borings, up gradient, cross-gradient, <br /> and down-gradient also encountered less soil contamination. <br /> • The vertical extent of impacted soil has not been convincingly demonstrated. The deepest soil <br /> samples from borings SB-B, SB-201, MW-201, MW-2, and MW-3 in the former dispenser <br /> area contained contamination. <br /> • The most intensely impacted groundwater has been sampled from MW-3 (screened 43 to 63 <br /> feet bsg) which has had as much as 220,000 micrograms per liter (µg/1) TPH-g. Up-gradient <br /> from MW-3, groundwater is impacted in the former underground storage tank (UST) system <br /> area with as much as 3,600 µg/1 TPH-g detected in an MW-1 groundwater sample (screened <br /> 55 to 70 feet bsg). Chemicals of concern (CDCs) were not detected in ground water samples <br /> from cross-gradient wells MW-7, MW-107, and MW-207. More assessment of groundwater <br /> down-gradient toward the northeast is needed. The lithology associated with the CPT-2 grab <br /> water samples is not known and the CPT-3 boring log indicates that that boring had passed <br /> out of the sand before the CPT-3 grab water sample was collected. The thick sand from 70 to <br /> 90 feet bsg, in which MW-208 is completed, appears to thin or is absent toward the northeast <br /> (CPT3). The groundwater sample from CPT-3 was impacted (120 µg/kg TPH-g at 73 feet). <br /> Impacted groundwater in this sand (approximately 70 to 90 feet bsg)must be delineated in all <br /> directions. The contaminant impact on the other sand units at depth is unknown. Additional <br /> wells are needed north of MW-8 and in the CPT-2 and CPT-3 areas, with screens set in <br /> significantly thick or laterally extensive sand units. <br />