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V 1117 Lone Palm Avenue, Suite B Modesto, CA 95351 www atc-enviro coni 2095792221 w °�'Ir'rlt�UMMi �-tFAI 711 Fax 209 579 2225 ASSOC 1 A 7 e s INC03 J0 JO pM+ v 52 June 26, 2003 54 14885 0001 Ms Margaret Lagono San Joaquin County Environmental Health Department 304 E Weber Street, Third Floor Stockton, California 95202 Subject First Quarter 2003 Groundwater Monitoring Report for Three Palms Grocery, 6732 East Highway 88, Stockton, California, Site Code 1830 Dear Ms Lagono This letter report summarizes field activities conducted during the First Quarter 2003 by ATC Associates Inc at the subject site (Figure 1) Monitoring was performed to evaluate the groundwater flow direction and magnitude in the uppermost aquifer Sampling was performed to monitor the distribution of petroleum hydrocarbons in groundwater at the site BACKGROUND The site is located on the south side of Highway 88 (Waterloo Road) and on the east side of Fairchild Lane, Stockton, California, as shown on Figure 1 The site is presently occupied by Three Palms Grocery (a convenience store), a beauty salon, and an adjacent residence A domestic well, which provides water to the site, is located north of the residence (Figure 2) Prior to July 1984, one 550-gallon waste oil UST, identified as Tank#4, was emptied of product, filled with sand, and capped with concrete In November 1986, one 1,000-gallon regular gasoline UST, identified as Tank 93, was removed and disposed of A soil sample collected during the removal of Tank #3 contained elevated concentrations of petroleum hydrocarbons In May 1989, one 1,000-gallon unleaded gasoline UST, identified as Tank #1 was filled with five cubic yards of concrete Currently, two other USTs remain in place and are in operation at the site These USTs are located approximately 40 feet east of the tanks which were closed in place On June 18, 1998, an ATC geologist supervised the advancement of two soil borings (SB1 and S132) to 86 5 feet below ground surface (bgs) to assess current subsurface conditions at the site Petroleum hydrocarbon constituents were detected in soil samples collected from borings SB 1 and S132 The highest reported constituent concentrations were observed in soil samples collected at 25 5 feet bgs in each of the borings The highest concentrations of petroleum constituents at this depth were observed in SBI and include total petroleum hydrocarbons as gasoline (TPHg) (9,500 mg/kg), toluene (65 mg/kg), ethyl benzene (82 mg/kg), and xylenes (470 mg/kg) The petroleum hydrocarbons appear to attenuate rapidly with depth as indicated greatest w 1148851ieports\1 gtr2003 doc I ENVIRONMENTAL, GEOTECHNICAL AND MATERIALS PROFESSIONALS