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