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Environmental Technology Inc = �_ ' The sampling program was conducted as described below A minimum of 4 well casing volumes, which was calculated to be approximately 16 gallons, was purged from each of the eight wells During purging operations the ' temperature, pH, and conductivity were measured with the water flowing through a continuous flow chamber. The pumping was carried on until the temperature, pH, and conductivity values stabilized within at least 5% of previous readings MW-1, MW-2, MW-3, MW-4, MW-5, MW-6, MW-7, and MW- 8 were purged of approximately 25 gallons of water per well using a 2-inch submersible pump Copies of the field observation which includes temperature, pH, and conductivity values are enclosed in Appendix-A Proper ' decontamination procedures which included flushing the pump and hose with a solution of detergent and water, followed by clean tap water, with a final rinse using deionized water were employed. The 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 eight 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, and new data for MW-7 and MW-8 The groundwater level observations (Table 1) indicated a consistent increase of ' approximately 0 48 to 0 85 feet during the reporting period (08/14/95 and 10/24/95) It should be noted that the fluctuation in groundwater level is a common occurrence in the Stockton area as reported by Applied Consultants ' Data, April 9, 1994 Figure 2 presents the groundwater contour map. It ��f appears that the general groundwater flow direction is toward th Southwes during the reporting period ' During the reporting period 08/14/95 through 10/24/95, TPH (gasoline) l concentrations in MW-1, MW-2, MW-4, MW-5 and MW-6 have reduced from 8.600, 1,800, 66,000, 540, and 3,500 to 270, 130, 40,000, <50, and 790 ' respectively TPH concentrations in MW-3 has increased from non-detect to 54 ppb The newly installed monitoring wells MW-7 and MW-8 showed TPH concentrations of 5,900 and 130 ppb respectively A TPH concentration contour map is presented in Figure 3