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Ms Rebecca Setliff <br /> Page 2 of 4 <br /> The potentiometric surface was above the top of the screened intervals in all wells except monitoring wells <br /> ' MW1, MW2, MW3, MW13 and MW14 and vapor wells VW2, VW3, VW5 and VW6 Groundwater <br /> flowed in an east-northeasterly direction, with an average gradient of approximately 0 002 —0 003 feet per <br /> foot A groundwater gradient map generated using the monitoring data from all site wells is shown on <br /> Figure 2 Groundwater monitoring data are summanzed in Table 1 Monitoring data sheets are included <br /> in Attachment A <br /> ' On February 20 and February 21, 2002, a Ground Zero technician collected groundwater samples from <br /> monitoring wells MWl through MW5, MW7, MW8, MW9, MW12 and MW14 and vapor wells VW2 <br /> and VW3 A minimum of three well casing volumes was purged from each well prior to sampling <br /> ' During the purging process, physical parameters (pH, electrical conductivity, and temperature) were <br /> monitored Subsequent to parameter stabilization and a minimum of 80% recovery of initial depth to <br /> groundwater measurements, groundwater samples were collected and placed in an iced cooler for <br /> ' transport to Argon Laboratories (FLAP #2359) under chain of custody Purge water was contained in <br /> labeled 55-gallon drums approved by the Department of Transportation (DOT), which are stored onsite <br /> within a secured area Purge logs are included in Attachment A <br /> Analysis consisted of gasoline oxygenates, EDB and 1,2-DCA by EPA Method 8260, TPHg by EPA <br /> Method 8015 modified and BTEX by EPA Method 8020 <br /> ' MonitoringWell Survey <br /> Y <br /> As required by AB 2886, all momtonng wells were surveyed by a Registered Surveyor to a horizontal <br /> ' <br /> accuracy of less than one meter and a vertical accuracy of 0 01 feet In January 2002, Morrow Surveying <br /> accu y Y <br /> surveyed the latitude and longitude of the site wells relative to the North American Datum (NAD83), and <br /> surveyed the wellhead elevations relative to North American Vertical Datum (NAVD88) A site map <br /> showing monitoring well locations, latitude and longitude coordinates and wellhead elevations is included <br /> in Attachment B <br /> 1 <br /> Purgewater Disposal <br /> ' On March 15, 2002, American Valley Waste Oil removed and transported approximately 800 gallons of <br /> purgewater to Seaport Environmental located in Redwood City, CA for disposal Documentation is <br /> ' included in Attachment A <br /> i <br /> ' GROUNDWATER ANALYTICAL RESULTS <br /> Groundwater Monitoring Wells <br /> ' TPHg was detected in all sampled wells except MW7 and MW9, and benzene was detected in all <br /> sampled wells except MWI, MW7 and MW9 Concentrations of TPHg and BTEX were generally stable <br /> to decreasing relative to the concentrations present during the previous sampling event, however, in wells <br /> ' MW2, MW12 and MW14 TPHg and benzene levels increased Overall, the extent of the plume of <br /> groundwater contamination associated with the onsite release is stable and concentrations are decreasing <br /> ' TPHg and BTEX concentrations are summarized m Table 2 Attachment C contains laboratory reports <br /> ' roeklgmr11gm2002 <br />