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— � 1117 lone Palm Avenue, Suite B <br /> - -- Modesto, CA 95351 <br /> http llvwwv atcassociates com <br /> 209 579 2221 <br /> Fax 209 579 2225 <br /> A a a O C 1 A 4 L' a I M C <br /> September 26, 2005 <br /> 54 14885 0001 SEP 9 2005 <br /> EfNVIrRDP��P EjE i HM'Th <br /> Ms Margaret Lagorio ������T/�ErtUf <br /> San Joaquin County <br /> Environmental Health Department <br /> 304 E Weber Street, Third Floor <br /> Stockton, California 95202 <br /> Subject Second Quarter 2005 Groundwater Monitoring Report for Three Palms Grocery, <br /> 6732 East Highway 88, Stockton, California, Site Code 1830 <br /> Dear Ms Lagono <br /> This letter report summarizes field activities conducted on April 11, 2005 by ATC Associates <br /> Inc (ATC) at the subject site (Figure 1) Monitoring was performed to evaluate the groundwater <br /> flow direction and magnitude in the uppermost aquifer Sampling was performed to monitor the <br /> distribution of petroleum hydrocarbons in groundwater at the site <br /> • SITE HISTORY <br /> The site is located on the south side of Highway 88 (Waterloo Road) and on the east side of <br /> Fairchild Lane, Stockton, California, as shown on Figure 1 The site is presently occupied by <br /> Three Palms Grocery (a convenience store), a beauty salon, and an adjacent residence A <br /> domestic well, which provides water to the site, is located north of the residence (Figure 2) <br /> Prior to July 1984, one 550-gallon waste oil underground storage tank (UST), identified as Tank <br /> #4, was emptied of product, filled with sand, and capped with concrete In November 1986, one <br /> 1,000-gallon regular gasoline UST, identified as Tank #3, was removed and disposed of A soil <br /> sample collected during the removal of Tank #3 contained elevated concentrations of petroleum <br /> hydrocarbons In May 1989, one 1,000-gallon unleaded gasoline UST, identified as Tank #1 was <br /> filled with five cubic yards of concrete Currently, two other USTs remain in place and are in <br /> operation at the site These USTs are located approximately 40 feet east of the tanks which were <br /> closed in place <br /> On June 18, 1998, an ATC geologist supervised the advancement of two soil borings (SBI and <br /> S132) to 86 5 feet below ground surface (bgs) to assess subsurface conditions at the site <br /> Petroleum hydrocarbon constituents were detected in soil samples collected from borings SBI <br /> and SB2 The highest reported constituent concentrations were observed in soil samples <br /> collected at 25 5 feet bgs in each of the borings The highest concentrations of petroleum <br /> constituents at this depth were detected in SBI and include total petroleum hydrocarbons as <br /> gasoline (TPHg) (9,500 mg/kg), toluene (65 mg/kg), ethyl benzene (82 mg/kg), and xylenes (470 <br /> ENVIRONMENTAL, GEOTECHNICAL AND MATERIALS PROFESSIONALS <br />