|
- t
<br /> San Joaquin County DIRECTOR
<br /> Donna Heran,REHS
<br /> �oP
<br /> 5, Environmental Health Department° ,co p ASSISTANT DIRECTOR
<br /> 2: ` ? 600 East Main Street Laurie Cotulla,REHS
<br /> Stockton, California 95202-3029
<br /> PROGRAM COORDINATORS
<br /> ;: '• Carl Borgman, REHS
<br /> !' Mike Huggins,REHS,RDI
<br /> Cq�/FOR ;P Website: www.sjgov.org/ehd
<br /> 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 /> June 13, 2008
<br /> Mr. Den and Ms.Betty Ueda
<br /> 626 East Galin Road
<br /> French Camp, California 95231
<br /> Subject: Den's Auto Repair
<br /> 308 South El Dorado Street
<br /> Stockton,California 95203-3404
<br /> San Joaquin County Environmental Health Department (EHD) has reviewed historical analytical
<br /> data from previous investigations and quarterly groundwater sampling events through the year
<br /> 2007, for the above-referenced site, prepared and submitted by Advanced GeoEnvironmental, Inc.
<br /> (AGE) on your behalf. High concentrations of petroleum hydrocarbon contamination are present in
<br /> groundwater samples collected from monitoring wells MW-lA and MW-2A, screened between 60
<br /> and 65 feet below surface grade (bsg), and MW-2B, screened between 25 and 45 feet bsg. Low
<br /> concentrations of petroleum hydrocarbon contamination have also been detected intermittently in
<br /> groundwater samples collected from monitoring wells MW-4 and MW-7, the two deepest wells
<br /> screened between 110 and 120 feet bsg. Also grab groundwater samples collected from cone
<br /> penetration test (CPT) borings CPT-1, CPT-2, CPT-3 and CPT-4 indicate that contaminants of
<br /> concern are present in all four borings at depth of 115 to 125 feet bsg. Additional investigation is
<br /> needed to define the impacted groundwater plume based on these results. Submit a work plan to
<br /> the EHD by August 29, 2008, to address the petroleum hydrocarbon plume at your site. The
<br /> submitted work plan should be presented in the context of a preliminary site conceptual model
<br /> (SCM).
<br /> An SCM that incorporates findings from the last eleven years of site characterization is needed to
<br /> evaluate present site conditions. The general purposes of an SCM are to demonstrate where the
<br /> contaminants came from, where they are at the present time, how they move through the
<br /> subsurface,how they will respond to changes in the groundwater flow characteristics or to potential
<br /> remediation efforts, what the contaminants' ultimate environmental fate will be, and to help
<br /> evaluate the risk posed by the contaminants to groundwater supplies and sensitive receptors. In
<br /> addition, the SCM may demonstrate data gaps, thereby illustrating where additional investigation is
<br /> needed. To be sure that the SCM will adequately address the assessment, remediation and,
<br /> ultimately, final closure requirements for this site,please include the following in the SCM:
<br /> • Local and regional plan view maps showing locations of sources, boring and monitoring
<br /> well locations, lines of cross section, extent of contaminants in each media (i.e., an
<br /> interpretive drawing — not merely a plot of laboratory results), direction and rate of
<br /> groundwater flow, and receptor locations, including water supply wells within 2,000 feet of
<br /> the site;
<br /> I
<br /> I
<br />
|