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• A S S O C I A T E S I N C GROUNDWATER MONITORING AND SAMPLING ATC performed quarterly groundwater monitoring and sampling on January 7, 2004 Field work included measuring the depth-to-water in wells MW 1 through MW3 and purging and sampling the water from these wells and the site's domestic well The samples were analyzed for the presence of dissolved petroleum hydrocarbons Depth to water measurements were recorded on January 7, 2004 from monitoring wells MW1 through MW3 The water table elevation has decreased an average of 4 63 feet in the monitoring wells since the last monitoring event in March 2003 Groundwater beneath the site generally flows in a northeasterly direction at an average gradient of 0 004 f1/ft, or approximately 21 feet/mile Historically, groundwater beneath the site generally flows in a northeasterly direction Groundwater monitoring data are summarized In Table 1 A groundwater gradient map for the January 2004 monitoring event is shown on Figure 3 Groundwater samples were collected from wells MW1 through MW3 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 SJEHD Monitoring well purge logs are included in Attachment 1 Furthermore, ATC collected • a water sample from the sampling port of the on-site Domestic Well Collected groundwater samples were placed on ice and transported under chain-of-custody to State-certified Argon Laboratories, Inc , (DHS Certification No 2359) Samples were analyzed for BTEX by EPA method 8021B, TPHg by EPA method modified 8015, and oxygenate fuel additives, including 1,2-dichloroethane (1,2-DCA), and 1,2-dlbromoethane (EDB) by EPA method 8260B RESULTS Laboratory analyses detected petroleum hydrocarbon constituents in the sample collected from well MW 1 The constituent concentrations detected include TPHg (310 pbb), benzene (1 2 ppb), toluene (0 7 ppb), ethyl benzene (1 1 ppb), and xylenes (1 7 ppb) Groundwater samples collected from well MW2 contained low levels of TPHg (210 ppb), but contained no detectable concentrations of BTEX Groundwater samples collected from wells MW3 and the Domestic Well contained no detectable concentrations of BTEX or TPHg 1,2-DCA was detected In wells MW i through MW3 in concentrations of 30 ppb, 2 3 ppb, and 5 5 ppb, respectively Analytical results are summarized in Table 1 Laboratory reports and chain-of-custody documentation are presented in Attachment 2 w 1148851reports\1 gtr2004 doc 3