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SOFA il Environmental Technology Inc , ZiA purged water is stored in 55-gallon DOT approved drums which have been labeled and stored on-site for subsequent treatment/disposal Adequate time was allowed for recovery after purging All monitoring wells were allowed to recover to 95 percent or more of their static water level condition At the time of groundwater sampling, neither free product nor sheen was noticed in any of the monitoring wells Dedicated bailers were used for sampling activities at each of the wells, in order to prevent possible cross contamination The six water samples collected were stored in an ice chest maintained at 4 degrees Celsius Appropriate chain of custody was prepared prior to transporting to a State certified laboratory Del Mar Analytical, Irvine, CA performed the laboratory analyses All the water samples were analyzed for Total Petroleum Hydrocarbons (TPH) as gasoline (Volatile Fuel Hydrocarbons) and Benzene, Toluene, Ethylbenzene, and Xylenes (BTEX) following EPA Methods 8015/8020 The test data are presented in Table 2 All laboratory analytical results including QA/QC are enclosed with this letter report Table 2 also includes the historical data for wells MW-1 through MW-6 The groundwater level observations (Table 1) indicated a consistent increase of approximately 6 25 to 6 46 feet during the reporting period (2/22/95 to _ �¢ 5/16/95) Groundwater elevations in all six monitoring wells have been abovel� the screened intervals of the respective wells for the last two quarters In order • to minimize the effects due to this situation, the purging was conducted at the maximum possible pumping rate using the 2-inch GRUNDFOS pump, which was about 4 to 4 5 gpm However, it was unable to depress the water table below the top of the screen, which was at about 68 to 70 feet BGS for the wells Other possible pumping mechanisms were explored, but were found to be unfeasible This situation was discussed with San Joaquin County personnel on May 16, 1995 Figure 2 presents the groundwater contour map The general groundwater flow direction at the site is towards the west The gradient for the monitoring event conducted on May 16, 1995 is [-39 79-(-39 91)) / 131 25 = 0 000914 feet/feet During the reporting period 2/95 through 5/95, TPH (gasoline) concentrations in MW-1 decreased from 2,100 to 1,100 parts per billion (ppb) MW-2 decreased from 480 ppb to 55 MW-3 decreased from 630 to 88 ppb MW-4 decreased from 24,000 ppb to 8,200 MW-5 decreased from 630 to 50, and MW-6 decreased from 78 ppb to N D (<50 ppb) A TPH concentration contour map is presented in Figure 3 During the reporting period 2/95 through 5/95, Benzene concentrations in MW-1 increased from 47 to 85 ppb MW-2 decreased from 9 2 to 1 6 ppb MW- 3 decreased from 97 to 4 ppb MW-4 decreased from 4,700 to 1,900 ppb MW- 5 decreased from 17 to 5 ppb, and MW-6 decreased from 11 to 3 ppb. Generally, a consistent decrease in all six monitoring wells was evidenced during this reporting period \