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CVkVA 1117 Lone Palm Avenue, Suite B <br /> ` Modesto, CA 95351 <br /> f http//www atcassociates com <br /> 209 579 2221 <br /> 110 A 8 a 0 C I A T E 3 1Nc Fax 209 579 2225 <br /> September 13, 2005 <br /> 54 22493 0001 SEP f' 0 2005 <br /> Mr Jeff Wong ENVIPONN;1 NT HE-ki�31 <br /> San Joaquin County PERM41T/W-R1110E8 <br /> Environmental Health Department <br /> 304 East Weber Street, Third Floor <br /> Stockton, California 95202-2708 <br /> Subject Monitoring Report Third Quarter 2005, Eggiman Property, 1112 East Harding Way, <br /> Stockton, California <br /> Dear Mr Wong <br /> This report presents the results of the third quarter 2005 groundwater monitoring and sampling <br /> performed on July 5, 2005, by ATC Associates Inc (ATC) at the site located at 1112 East Harding <br /> Way, Stockton, California (Figure 1) Monitoring was performed to evaluate groundwater flow <br /> direction and the hydraulic gradient in the uppermost aquifer Sampling was performed to monitor <br /> the petroleum hydrocarbons in the groundwater at the site <br /> BACKGROUND <br /> In April 1987, SEMCO removed and disposed of two 1,000-gallon regular gasoline underground <br /> storage tanks (USTs), associated piping, and fuel dispenser from the locations shown on Figure 2 A <br /> soil sample was collected from beneath the end of each tank at approximately 17 feet below ground <br /> surface (bgs) Analytical testing indicated the collected samples contained detectable concentrations <br /> of petroleum hydrocarbon constituents The excavation was subsequently backfilled to the ground <br /> surface <br /> On July 24, 1997 six soil borings were advanced to depths ranging from approximately 16 to 31 feet <br /> bgs to investigate the extent of residual soil contamination at the site Detectable concentrations of <br /> total petroleum hydrocarbons as gasoline (TPHg), total petroleum hydrocarbons as diesel (TPHd), <br /> and benzene, toluene, ethylbenzene, and xylenes (BTEX) were observed in soil samples collected <br /> from the site The distribution of petroleum constituents beneath the site has been evaluated and <br /> appears to be limited laterally to the immediate vicinity of the former tank pit The highest <br /> concentrations were reported between 10 and 20 feet bgs and generally attenuate rapidly with depth <br /> Only low concentrations of toluene (0 064 mg/kg) and xylenes (0 012 mg/kg) were detected at <br /> approximately 30 feet bgs in one boring, the maximum depth explored Attempts were made to <br /> further advance the Geoprobe® unit in several of the borings, however probe refusal was encountered <br /> at depths ranging from approximately 16 to 30 feet bgs due to the hardness of the formation The <br /> results of the subsurface investigation were summarized in Smith Technology's Summary Report, <br /> Subsurface Investigation, dated December 22, 1997 <br /> In April 1999, at the request of Public Health Services/Environmental Health Division (PHS/EHD) of <br /> San Joaquin County, ATC completed a receptor survey for the subject property ATC reviewed <br /> ENVIRONMENTAL, GEOTECHNICAL AND MATERIALS PROFESSIONALS <br />