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A A S S O C I A T E S I N C In order to assess the site's current subsurface conditions, Mr Harlin Knoll of PHS/EHD requested that all six project monitoring wells, in addition to the municipal well, be sampled during this reporting period Further more, PHS/EHD requested the samples undergo chemical analysis for TPHg and BTEX by EPA method 8015/8020, and oxygenate fuel additives by EPA method 8260B QUARTERLY MONITORING ACTIVITIES ATC performed quarterly groundwater monitoring and sampling on September 27, 2000 Feld work included measuring the depth-to-water in wells MW1 through MW6 and purging and sampling the water from these wells in addition to the nearby Thornton No 2 Municipal Supply Well (Supply Well) The samples were analyzed for the presence of dissolved petroleum hydrocarbons Depth to water measurements were collected on September 27, 2000 from monitoring wells MW 1 through MW6 Groundwater beneath the site generally flows in a westerly direction at an average gradient 0 001 ft/ft, or approximately 5 28 feet/mile, with apparent mounding in vicinity of MW3 Historically groundwater beneath the site generally flows in a southwesterly direction Groundwater monitoring data are summarized in Table 1 A groundwater gradient map for the September 27, 2000 monitoring episode is shown on Figure 2 Groundwater samples were collected from wells MW1 through MW6 after purging and stabilization of physical parameters (pH, electrical conductivity, and temperature) The monitoring wells were purged and sampled according to ATC's Field Procedures on file with FHS/EHD Monitoring well purge logs are included in Attachment 1 Furthermore, ATC coordinated with San Joaquin County Utility Maintenance Division personnel and collected a water sample from the sampling port of the Supply Well Collected groundwater samples were placed on ice and transported under chain-of-custody to State-certified Argon Laboratories (ELAP #2359) Samples were analyzed for TPHg, and BTEX by EPA method 8015/8020, and oxygenate fuel additives by EPA method 8260B RESULTS Laboratory analyses detected only concentrations of TPHg at 6,000 parts per billion (ppb), toluene at 7 4 ppb, ethylbenzene at 84 ppb, and xylenes at 51 ppb in the sample collected from well MW4 The water sample collected from MW4 reported benzene was below the laboratory detection limit of 1 0 ppb Groundwater samples collected from wells MW1, MW2, MW3, MWS, MW6, and the nearby Supply Well contained no detectable concentrations of TPHg, • BTEX, or fuel oxygenate additives, including methyl tertiary butyl ether (MTBE) These analytical results are generally consistent with historical levels w%625821quan1yl3gr-2000 doe 4