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San Joaquin County DIRECTOR <br /> Pp U iN Donna Heran, REHS <br /> Environmental Health Department ASSISTANT DIRECTOR <br /> 600 East Main Street Laurie Cotulla, REHS <br /> Stockton, California 95202-3029 PROGRAM COORDINATORS <br /> — -- Carl Borgman, REHS <br /> C, Mike Huggins, RENS, RDI <br /> 4��Fo.R(4, Website: www.Sjgov.org/ehd Margaret Lagorio, REHS <br /> Phone: (209) 468-3420 Robert McClellon, REHS <br /> Fax: (209) 464-0138 Jeff Carruesco, REHS, RDI <br /> Kasey Foley, REHS <br /> 06 February 2008 <br /> Remo Canepa <br /> Canepa's Car Wash <br /> 1536 N Hunter <br /> Stockton, CA 95204 <br /> Subject: CANEPA'S CAR WASH <br /> 248 PARK STREET <br /> STOCKTON CA 95202 <br /> The San Joaquin County Environmental Health Department (EHD) has received and <br /> reviewed Additional Soil and Groundwater Investigation Report and Workplan <br /> Addendum (WPA) dated July 12, 2004, and Third Quarter Groundwater Monitoring <br /> Report July 2007 (OMR), dated 31 August 2007, both prepared by your consultant <br /> Condor Earth Technologies, Inc. (Condor). In addition, the EHD met with you and <br /> Condor at the EHD office on 15 January 2008 and briefly discussed this site with you. <br /> The EHD comments as follows: <br /> Currently there are seven groundwater monitoring wells on site, MW-1 through MW-7; all <br /> are screened from 40 to 60 feet below surface grade (bsg) or 45 to 65 feet bsg. Each <br /> monitoring well screen interval intersects sand at 40 to 50 feet bsg, most commonly at <br /> 40 and 45 feet bsg; soil in the lower portions of the screen interval was generally not <br /> sampled. Groundwater has been approximately 15 to 20 feet over the tops of the screen <br /> intervals since approximately 1997, so shallowest groundwater is not being monitored. <br /> The contaminant concentrations in monitoring well MW-5, the most down-gradient <br /> monitoring well located along the northern property boundary, were initially low in 1994, <br /> then increased significantly up to 2005, and have been elevated since. This indicates to <br /> the EHD that the plume has been and is likely still migrating off-site. Concentrations in <br /> MW-2 and other monitoring wells have declined. Monitoring wells MW-1, MW-3, MW-4, <br /> MW-6 and MW-7 have not had significant contaminant concentrations detected for up to <br /> two years, most have undetectable concentrations of the chemicals of concern (CDCs). <br /> This may be due in part to migration of the contaminants, natural attenuation, and a <br /> reduced flux rate from the sorbed to the dissolved state with the increase of groundwater <br /> elevation since 1997. The sampling schedule for the currently existing wells should be <br /> changed from quarterly to annually, with the exceptions of MW-2 and MW-5, which <br /> should remain on a quarterly sampling schedule. <br /> Condor presented the findings of the 2004 cone penetration testing (CPT) investigation <br /> in WPA in terms suggestive of a vertically segmented hydrogeologic model, but cross <br /> sections displaying the relationships were not provided. During the 2004 investigation, <br /> petroleum hydrocarbon contaminants were detected in grab groundwater samples <br /> collected from all five CPT borings (CPT3 to CPT7) on the above-referenced site as well <br /> Work Plan C'nmment 1 Ptter WOR <br />