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♦4 _ ATC Associates Inc s A%TC 1117 Lone Palm Avenue, Suite B Modesto, California 95351 209-579-2221 fax 209-579-2225 . A S S O C I A T E S I N C 4%011 July 21, 2006 SAN JOAgUIN COUNTY 5425847Q037 ENYIr2014H NTAL l'��, HEALTH DEPX.RTHENT Ms Victoria McCartney �a G San Joaquin County Environmental Health Department 304 E Weber Street, Third Floor Stockton, California 95202 Subject Monitoring Report First Quarter 2006, Former Cheaper Store #37, 15 East Grant Line Road, Tracy, California, Local Oversight Program (LOP) # 1404 Dear Ms McCartney This report presents the results of quarterly groundwater monitoring and sampling performed on March 8, 2006, by ATC Associates Inc (ATC) at the site located at 15 East Grant Line Road, Tracy, California (Figure 1) Sampling was performed to monitor the distribution of petroleum hydrocarbons in groundwater at the site Monitoring was performed to evaluate the groundwater flow direction and the hydraulic gradient in the uppermost aquifer SITE HISTORY On March 3, 1988, two 10,000-gallon underground storage tanks (USTs) were excavated and removed from the site One was used to store leaded gasoline and one was used to store unleaded gasoline Groundwater was encountered in the UST excavation at approximately seven feet below ground surface (bgs) Laboratory analyses of two samples of groundwater collected from within the excavation indicated the groundwater had been impacted by petroleum hydrocarbons r On March 29 and 30, 1988, three monitoring wells (MW1, MW2, and MW3) were installed at the site and a sensitive receptor survey within a 2,000-foot radius of the site was conducted by Kleinfelder Based on Klemfelder's Groundwater Assessment Report dated April 12, 1988, petroleum hydrocarbons were not detected at or above laboratory reported detection limits in the groundwater samples collected from MW 1, MW2, or MW3 The groundwater flow direction was reported to be toward the north r On April 19, 1988, an additional monitoring well (MW4) was installed north of the former location of the USTs Based on Kleinfelder's Additional Monitoring Well report dated April 22, 1998, petroleum hydrocarbons were detected in the groundwater sample collected from MW4 on April 19, 1988 The groundwater flow direction was reported to be toward the northwest on April 20, 1988 In late April 1988, the open excavation associated with the former USTs was expanded by excavating petroleum impacted vadose zone soils As reported in Kleinfelder's Soil Removal Report dated May 3, 1988, approximately 350 to 400 cubic yards of soil were excavated from April 25 to 28, 1988 Laboratory analyses of soil samples collected from the sidewalls of the enlarged excavation indicated low concentrations of petroleum hydrocarbons remained at the south and southeastern portion of the excavation s\enviromental125847\00371reports\1 stQTR-2006 doc 1