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Ms Vicki McCartney Page 2 of 3 • After groundwater parameters had stabilized and water levels had recovered to at least 80% of pre-purged levels, groundwater samples were collected using dedicated disposable bailers and transferred into appropriate containers The samples were stored in an ice-chest refrigerated to approximately 4°C, for subsequent transport to Argon Laboratories (ELAP #2359) under chain of custody protocol Field notes and purge logs are included in Attachment A GROUNDWATER ANALYTICAL RESULTS Argon Laboratories analyzed all groundwater samples for total petroleum hydrocarbons as gasoline (TPHg) using EPA method 8015M, for benzene, toluene, ethylbenzene, xylenes (BTEX) using EPA method 8021B, and for oxygenated gasoline additives, including the lead scavengers EDB and 1,2-DCA, using EPA method 8260B Wells MW 1 and MW3 contained TPHg at 72 parts per billion (ppb) and 1,200 ppb, respectively At the request of Ground Zero, the laboratory director reviewed the chromatograph of the analysis for well MW3 and indicated that the chromatograph pattern appeared to be typical of degraded gasoline Very low levels of toluene, ethylbenzene, and xylenes were also detected in well MW3 No benzene or MTBE was detected in either well No gasoline constituents were detected in well MW2 Groundwater analytical results are summarized in Table 2 Laboratory reports are included in Attachment C SUMMARY AND CONCLUSIONS • The depth to groundwater beneath the site ranged from 10 82 to 11 33 feet btoc Groundwater flowed north with a gradient of approximately 26 feet per mile • TPHg was detected in wells MW 1 and MW3 at 72 ppb and 1,200 ppb, respectively • Minor concentrations of toluene, ethylbenzene and xylenes were detected in well MW3 at levels below their respective primary Maximum Contaminant Levels (MCLS) • No benzene, MTBE, or any other oxygenated gasoline additives were detected in any site well No gasoline constituents were detected in well MW2 l RECOMMENDATIONS Ground Zero recommends that San Joaquin County Environmental Health Department (EHD) consider closing this site as a low-nsk groundwater contamination case based upon the following • The current levels of gasoline constituents in site wells remain below applicable primary MCLS • No oxygenated gasoline additives, including MTBE, has ever been detected m any site well, • The nearest known active water supply well is located approximately 1,100 feet upgradient of the site and is screened from depths greater than 340 feet(Ground Zero, August 23, 2002) G 1GROUNDZE15ouza\Reports\IQMR 2003 doc