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1 16 September 10, 1996 AS0 TA Environmental Technology Inc Mr Michaellnfurna ' Senior REHS, Site Mitigation Unit Environmental Health Division Public Health Services ' San Joaquin County 445 N San Joaquin Street Stockton, CA 95201-0388 RE: U-HAUL CENTER # 709-50 2701 N. WILSON WAY, STOCKTON, CALIFORNIA ' SOTA'S PROJECT NO. 94HW021 ' Dear Mr Infurna SOTA Environmental Technology, Inc (SOTA) is pleased to submit the following Quarterly Groundwater Monitoring Report for your review This report ' documents the groundwater sampling program that was conducted on June 26, x„996 at the subject site The site location map is presented in Figure 1 Figure 2, shows the location of the wells, the groundwater elevations, the groundwater ' contours and flow direction for June 26, 1996 sampling event Groundwater concentrations of Total Petroleum Hydrocarbons-gasoline standard (TPH-g) are provided in Figure 3 and a Benzene concentration contour map is presented in Figure 4 SOTA's engineer measured the depth to groundwater at all eight monitoring wells, MW-1, MW-2, MW-3, MW-4, MW-5, MW-6, MW-7, and MW-8 on June ' 26, 1996 The depth to the water level and the corresponding surface elevations, with respect to mean sea level, are presented in Table 1 SOTA's engineer informed San Joaquin County Environmental Health Division of the ' proposed sampling event, in advance, on June 26, 1996 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 and pH, were measured with the water flowing through a continuous flow chamber The pumping was carried on until the temperature ' and pH 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 and pH 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 Dedicatedkailers were used for sampling activities at each of the wells, in order to prevent possible cross contamination 1 r