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Second Quarter 2002 Monitoring and Sampling Report 3 7-Eleven Inc Store No 17334,4501 North Pershing Avenue, Stockton CA July 29,2002 ' An additional site assessment(IT Corporation, April 25, 2002) was Implemented at the site on April 3 and 4, 2002, per a workplan (IT Corporation, October 2002) and addendum (IT Corporation, April 5, 2002) approved by SJCPHS A soil boring (S13-1) was advanced to a depth of 5 feet bg, and grab groundwater samples collected by Hydropunch at 50 feet bg Two double-nested SVE/AS wells (SPV-1 and SPV-2) were Installed to 30 feet bg, and soil samples were collected at total depth in the borehole of each well ' The deep well segments were screened from 25 to 30 feet bg The shallow well segments were screened from 12 to 22 feet bg TPH-G was detected in a soil sample from SPV-1 at 30 feet bg MTBE was not ' detected in soil samples from either well boring Dissolved benzene, TPH-G, and MTBE were detected in groundwater samples from SB-1 @ 50' bg, at concentrations of 28 pg/L, 7,100 µg/L, and 67 µg/L, respectively ' Geology/Hydrogeology ' The relatively level site Is located at an elevation of approximately 8 feet above mean sea level The site is underlain by Quaternary alluvial deposits assigned to the Modesto Formation (Fluor Daniel GTI, ' Additional Site Assessment Report, January 15, 1998) Materials encountered during previous drilling at the site generally consisted of clayey silt and sandy silt to approximately 24 feet bg, followed by interbedded clayey silt and silty fine sand to maximum exploratory drilling depths ranging from 35 to 40 feet bg ' The depth to groundwater in MW-9 has ranged from 30 feet bg in 1990 to 20 feet bg in 1996 During the ' current sampling event, equilibrated depth to groundwater in sampled wells at the site ranged between 16 04 to 17 40 feet below top of casing (TOC) Seasonal water table fluctuations average 2 to 3 feet Historically, groundwater flow direction at the subject site and adjacent facilities has been to the northeast Sensitive Receptors Previous reports on sensitive receptors indicate that there are no public supply wells within 4,000 feet downgradient of the site The nearest crossgradient/upgradient water supply well is of unreported status ' and lies about 1,500 feet away Other wells within 2,000 feet of the site are not in hydraulic communication with shallow groundwater at the site ' Groundwater Monitoring Data t Before monitoring, the well caps were opened to allow the water in each well to stabilize to atmospheric pressure The DTW was measured to the nearest 0 01 foot from the top of the well casing using an Interface probe • 17334Q22 OUR DOC