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4 1` 1 • A S S o C IATE S INC The depth to water measurements and the elevations of the well casings (Table 1) of wells MW-1 through MW-5 were used to evaluate the groundwater flow direction and gradient beneath the site The groundwater elevation beneath the site increased an average of 6 46 feet since November 25, 1997 The groundwater gradient for June 3, 1998 showed groundwater flowing to the east at a gradient of approximately 0 004 ft/ft which is consistent with previous groundwater gradients The groundwater gradient for June 3, 1998, is depicted on Figure 3 GROUNDWATER SAMPLING On June 3, 1998, groundwater samples were collected from wells MW-1, MW-2, MW-4, and MW-5 for laboratory analyses Well MW-3 was not sampled at the direction of Mr Jeff Wong of the PHS/EHD and well RW-1 was not sampled because it was inaccessible The field methods used are presented in Attachment 1 Field purge logs are included in Attachment 2 Groundwater samples were analyzed by State-certified 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 ANALYTICAL RESULTS Results of laboratory analyses indicated dissolved TPHg was detected in the sample from well MW-1 at a concentration of 1,100 parts per billion (ppb) No TPHg was detected in any other site monitoring wells that were sampled Benzene, ethylbenzene, and xylenes were also detected in well MW-1 No other BTEX constituents were detected in any of the wells TPHd was detected in wells MW-1, MW-2, and MW-5, at concentrations ranging from 88 ppb in well MW- 2 to 360 ppb in well MW-1 The laboratory results of TPHd were reported as unidentified hydrocarbons in the C9-C24 range Results of laboratory analyses are summarized in Table 2 ADDITIONAL FIELD ACTIVITIES On July 7, 1998, ATC disposed of approximately 1,000 gallons of monitoring well purge water into the City of Stockton sanitary sewer system This work was performed in accordance with the Special Discharge for Wastewater Permit issued by the City of Stockton Department of Municipal Utilities (DML) dated June 12, 1995 and valid through June 12, 2000 In addition, ATC contacted Mr Larry Williams of the DMU on July 6, 1998 to inform him of the scheduled purge water disposal On the morning of July 7, 1998, Mr Williams faxed a letter to ATC approving the purge water disposal w 162574162574 0119436712QSR98doc 2