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San Joaquin County DIRECTOR <br /> Donna Hera REHS <br /> Environmental Health Department <br /> ASSISTANT DIRECTOR <br /> a _ 600 East Main Street Laurie cotuua, REHS <br /> Stockton, California 95202-3029 PROGRAM COORDINATORS <br /> ' Carl Borgman,REHS <br /> Mike Huggins,REHS,RDI <br /> 4 /F ORS\ Website: www.sjgov:org/ehd 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 /> October 30, 2008 <br /> Mr.John Johnson <br /> Former Cheaper Store Number 37 <br /> 765 Eubanks Drive, Suite D <br /> Vacaville, California 95688 <br /> Subject: Former Cheaper Store Number 37 <br /> 15 East Grant Line Road <br /> Tracy,California 95376-2720 <br /> The San Joaquin County Environmental Health Department (EHD) has reviewed Work Plan for <br /> Vertical and Lateral Subsurface Investigation dated July 17, 2008, and Mass Calculations dated <br /> September 18, 2008, prepared by ATC Associates Inc. (ATC) on your behalf for the above- <br /> referenced site. In the work plan, ATC proposes to install seven groundwater monitoring wells, <br /> three screened within"Zone A"identif ed as the gravel/sand units from 5 to 25 feet below.surface <br /> grade (bsg), one screened within "Zone B" identified as the gravel/sand units from 35 to 45 feet <br /> bsg, and two screened within "Zone C"identified as'the gravel/sand units-from 65 to 75 feet bsg. <br /> In Mass Calculations, ATC concludes that approximately 2,090 pounds of total petroleum <br /> hydrocarbons quantified as gasoline (TPH-g), 7.4 pounds of benzene, and 0.26 pounds of methyl <br /> tertiary-butyl ether (MTBE)remain cumulatively in soil and groundwater beneath the site. By <br /> letter dated June •10, 2008,the EHD had directed submittal of the work plan to verify groundwater <br /> results collected from cone penetration test (CPT) boring CPT-2, and address the delineation of <br /> the impacted groundwater- plume; and submittal of contaminant mass estimates, supported by <br /> calculations. <br /> The EHD approves the installation of two proposed monitoring wells screened within "Zone A", <br /> one located.on the west side of Holly Street, west of monitoring well MW-8, and one located at <br /> the northwest corner of the property, as illustrated in Figure 11 of the work plan. The EHD <br /> believes the two shallow wells should be screened at a total depth of approximately twenty-five <br /> feet bsg, instead of the proposed twenty feet bsg. This decision is based on soil lithology from <br /> previous bore logs that indicates the presence of a. sand layer (and potentially a migration <br /> pathway for contaminants) at- approximately twenty to twenty-five feet bsg. However, the <br /> decision for total well depth trust be based on litholo,gical evaluation of soil samples collected <br /> from each borehole that targets the sand unit,if present. { <br /> The EHD does not approve installation of the proposed monitoring well at the northeast corner of <br /> the site. This decision is based on low concentrations of MTBE detected in groundwater samples <br /> collected from monitoring well MW-7 between August 2007 and September 2008. MW-7 is <br /> screened in "Zone A" between five and fifteen feet bsg. Groundwater samples collected from <br />