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tr r The depth to water measurements and the elevations of the well casings (Table 1) were used to evaluate the groundwater flow direction and gradient beneath the site Groundwater elevation beneath the site decreased an average of 1 19 feet since July 8, 1996 Groundwater flow direction was generally to the east at a gradient of approximately 0 003 ft/ft as depicted on Figure 3 On October 21, 1996, groundwater samples were collected from wells MW-1 through MW-5 for laboratory analyses The field methods used are presented in Attachment 1 Field purge logs are included in Attachment 2 Groundwater samples were analyzed by Sequoia Analytical for total purgeable petroleum hydrocarbons (TPHg) using Environmental Protection Agency (EPA) Method 8015 modified, total extractable petroleum hydrocarbons (TPHd) using EPA Method 8015 modified, and benzene, toluene, ethylbenzene, and total xylenes (BTEX) using EPA Method 8020 Copies of the laboratory reports and chain of custody documentation are included in Attachment 3 Results of laboratory analyses indicated dissolved TPHg was detected in the samples from well MW-1 at a concentration of 20,000 parts per billion (ppb) No TPHg was detected in any other site monitoring wells BTEX constituents were detected in well MW-1, most notably benzene at 3,100 ppb No other BTEX constituents were detected in any of the wells TPHd was detected in wells MW-1, MW-2, MW-3 and MW-5 at concentrations ranging from 66 ppb in MW-3 to 1,700 ppb in MW-1 The laboratory results of TPHd were reported as unidentified hydrocarbons No TPHd was detected in monitoring well MW-4 Results of laboratory analyses are summarized in Table 2 OTHER FIELD WORK On October 21, 1996, Ms Linda Turkatte of San Joaquin County Public Health Services Environmental Health Department was on site to witness the collection of groundwater samples Ms Turkatte noted that the grout in well MW-5 was low by three to four feet and requested that the grout be brought up Smith Technology returned to the site on October 22, 1996 and grouted up well MW-5 SUMMARY AND RECOMMENDATIONS The groundwater flow direction and gradient was generally consistent with those evaluated during previous events Dissolved gasoline hydrocarbons were detected in the samples from well MW-1 Dissolved hydrocarbons in the diesel range were detected in wells MW-1, MW-2, MW-3 and MW-5 during the reporting period Dissolved TPHg and TPHd concentrations were below laboratory detection linuts in monitoring well MW-4 w 19436719436714QSR96 dm 2 • SMTN