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r� [ <br /> Mr Jeffrey Wong <br /> Page 2 <br /> The hydraulic gradient at the site was essentially flat(;z�0 001 ft/ft) A potentiometric surface map generated <br /> using the March 15, 2002 monitoring data is shown on Figure 2 Groundwater monitoring data are <br /> summarized in Table 1 Monitoring data sheets are included in Attachment A <br /> Wells MWl through MW4 were purged and sampled on March 15 and U-Haul well MW7 was purged and <br /> sampled on March 18 Each well was purged of approximately 3 well casing volumes During the purging <br /> process, physical parameters (temperature, pH and electrical conductivity) were measured Groundwater <br /> samples were collected after physical parameter stabilization, and a minimum of 80% water level recovery <br /> Subsequently the samples were placed in an ice chest cooled to a temperature of approximately 4°C <br /> Purgewater was contained in appropriately labeled DOT-approved 55-gallon drums Purge logs are <br /> included in Attachment A <br /> Groundwater samples were delivered under chain of custody protocol to Argon Laboratories (ELAP <br /> #2359) Analysis consisted of gasoline oxygenate additives, 1,2-DCA and EDB using EPA method <br /> 8260, BTEX using EPA method 8020, and TPHg using modified EPA method 8015 <br /> Morutonng Well Survey <br /> As required by AB 2886, all monitoring wells were surveyed by a Registered Surveyor to a horizontal <br /> accuracy of less than one meter and a vertical accuracy of 0 01 feet In January 2002, Morrow <br /> Surveying surveyed the latitude and longitude of the site wells relative to the North American Datum <br /> (NAD83), and surveyed the wellhead elevations relative to City of Stockton Benchmark No 85 A site <br /> map showing monitoring well locations, latitude and longitude coordinates and wellhead elevations is <br /> included in Attachment B <br /> Soil and Purgewater Disposal <br /> On January 15, 2002, approximately four cubic yards of waste soil was removed and transported by <br /> Jim Thorpe Oil to Forward Landfill in Manteca, CA for disposal On March 15, 2002, approximately <br /> 425 gallons of purgewater was removed and transported by American Valley Waste Oil to Seaport <br /> Environmental in Redwood City, CA for disposal Documentation is included in Attachment A <br /> GROUNDWATER ANALYTICAL RESULTS <br /> Gasoline oxygenate additives and EDB were not detected in the samples from any monitoring well, and <br /> benzene was not detected in monitoring well MW3 for the second consecutive time TPHg was <br /> detected in the samples from each site monitoring well Benzene was detected in the samples from <br /> monitoring wells MWI, MW2, and MW4 TPHg concentrations ranged from 160 parts per billion <br /> (ppb) to 180,000 ppb, and benzene concentrations ranged from <0 5 ppb to 13,000 ppb in wells MW3 <br /> and MWl, respectively 1,2-DCA was detected in all wells except MW3 Concentrations of 1,2-DCA <br /> ranged from 110 ppb m well MW4 to 900 ppb in well MWl U-Haul well MW7 contained dissolved <br /> TPHg, benzene, and 1,2-DCA at concentrations of 1,800 ppb, 16 ppb and 17 ppb, respectively <br /> Analytical results are summarized in Table 2 Attachment C contains laboratory reports and chairs of custody <br /> documentation <br /> 11GZA_PSISYS011Data1GROUNDZEULkRRYS\RepozU\IQM2002 doe <br />