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i • Ms. Margaret Lagorio Page 2 Prior to sampling, monitoring wells MWI and MW2 were purged of a minimum of three well casing volumes. During the purging process temperature, pH and electrical conductivity parameters were measured. Samples were collected after parameter stabilization and an 80% minimum water level recovery of pre-purge levels. The samples were subsequently placed into an ice chest refrigerated to a temperature of approximately 4°C. Purge water was contained in appropriately labeled DOT- approved 55-gallon drums. Purge logs are included in Attachment A. Groundwater samples were delivered under chain of custody protocol to Argon Laboratories (ELAP ##2359). Analysis consisted of gasoline oxygenate additives, EDB and 1,2 DCA using EPA method 8260, BTEX using EPA method 8020, and TPHg using EPA method 8015 modified. I Monitoring Well Survey As required by AB 2886, all monitoring 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 surveyed the latitude and longitude of the site wells relative to the North American Datum (NAD83), and surveyed the wellhead elevations relative to San Joaquin County Benchmark No. HS0393. A site map showing monitoring well locations, latitude and longitude coordinates and wellhead elevations is included in Attachment B. Purgewater Disposal On March 15, 2002, American Valley Waste Oil (EPA ID No. CAL000827878) removed and transported approximately 100 gallons of purgewater to Seaport Environmental (EPA ID No. CAL000032058) for disposal. Documentation will be forwarded upon receipt. GROUNDWATER ANALYTICAL RESULTS TPHg and BTEX constituents were not detected in either well. MTBE was not detected in well MW2 for the third consecutive event. MTBE was detected at a concentration of 42 parts per billion (ppb) in well MWL No other gasoline compounds, oxygenate additives, EDB or 1,2 DCA were detected in either well. Analytical data are summarized in Table 2. Laboratory reports and chain of custody documentation are included in Attachment C. SUMMARY Wells MWI and MW2 were monitored and sampled for TPHg, BTEX, gasoline oxygenates, EDB and 1,2 DCA. Depth to water measurements indicated a rise in the potentiometric surface since the last monitoring event. TPHg and BTEX constituents were not detected in the groundwater sample collected from well MWI; however, the level of MTBE increased since the last monitoring and sampling event. No analytes • were detected in the sample from well MW2 for the third consecutive event. G:IData1GROUNDZEIVALLEY V WIQM R11 QM2002,doc