SITE INFORMATION AND CORRESPONDENCE

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San Joaquin County. DIRECTOR o N Donna Heran,REHS oP Environmental Health Department I' ASSISTANT DIRECTOR 600 East Main Street Laurie Cotulla,REHS Stockton, California 95202-3029 PROGRAM COORDINATORS Carl Borgman,REHS Mike Huggins,REHS,RDI Website: www.Sjgov.org/ehd Margaret Lagorio,REHS /FOR Phone: (209)468-3420 Robert McClellon,REHS Fax: (209)464-0138 Jeff Carruesco,REHS,RDI Kasey Foley,REHS June 10,2008 I� Mr. John Johnson J'';C1-' Former Cheaper Store Number 37r4` 7 E ba 4457 R d � o ks Bicia;rk lifornia 9424 VaeavIe, uYnI^ 95688 Subject: Former Cheaper Store Number 37 15 East Grant Line Road Tracy,California 95376-2720 The San Joaquin County Environmental Health Department (EHD) has reviewed current quarterly groundwater monitoring reports for.the above-referenced site submitted by ATC Associates Inc. (ATC)on your behalf and believes additional investigation is needed to define the methyl tertiary-butyl ether (MTBE) plume both vertically, at the source area, and toward the north and west of your site in the deeper aquifer zones. Although laboratory analytical results indicate that MTBE concentrations have generally declined during the first quarter 2008 groundwater monitoring event in March 2008, significant concentrations of MTBE still exist in groundwater samples collected from monitoring wells MW-1, MW-4, and MW-5. Soil litho,logy interpreted from the two cone penetration test (CPT) borings is primarily gravelly sand and sand between approximately thirty-seven and forty-five feet below surface grade (bsg), and between sixty-five and seventy feet bsg. Also groundwater samples collected at sixty-seven feet bsg from CPT-2 indicate significant concentrations of contaminants of concern (COC) are present in this deepest grab groundwater sample collected at your site. Submit a work plan to the EHD by August 20, 2008, that will include the installation of one monitoring well screened between sixty- five and seventy feet bsg to verify groundwater results collected from CPT-2, and will address the delineation of the impacted groundwater plume both vertically, and laterally to the north, northwest, and west of your site. The EHD also directs you to provide a trend analysis of monitoring wells impacted with MTBE; and include an explanation for the periodic spikes in MTBE concentration found in monitoring wells MW-1, and MW-4 through MW-8. Submit the information to the EHD by September 19, .2008. A list of domestic, municipal, and irrigation wells located within and outside a 2,000-foot radius of your site were submitted to the EHD in 1998; however, the EHD directs you to submit a more . comprehensive sensitive receptor survey that includes updated well locations, as well as surface water, hospital, and school locations. Submit the updated sensitive receptor survey to the EHD by September 19, 2008.