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1 <br /> Environmental Technology fnc <br /> ' October 30, 1996 <br />' Mr MichaelInfurna <br /> Senior REHS, Site Mitigation Unit <br /> Environmental Health Division <br />' Public Health Services <br /> San Joaquin County <br /> 445 N San Joaquin Street <br /> Stockton, CA 95201-0388 <br />' RE: U-HAUL CENTER # 709-50 <br /> 2701 N. WILSON WAY, STOCKTON, CALIFORNIA <br />' SOTA'S PROJECT NO. 94HWO21 <br /> Dear Mr Infurria <br />' SOTA Environmental Technology, Inc. (SOTA) is pleased to submit the following Quarterly <br /> Groundwater Monitoring Report for your review This report documents the groundwater <br /> sampling program that was conducted on September 26 and 27, 1996 at the subject site <br />' The site location map is presented in Figure 1 Figure 2, shows the location of the wells, the <br /> groundwater elevations, the groundwater contours and flow direction for September 26-27, <br /> 1996 sampling event Groundwater concentrations of Total Petroleum Hydrocarbons- <br /> gasoline standard (TPH-g) are provided in Figure 3 and a Benzene concentration contour map <br /> is presented in Figure 4 <br /> SOTA's engineer measured the depth to groundwater at all eight monitoring wells, MW-1, <br /> MW-2, MW-3, MW-4, MW-5, MW-6, MW-7, and MW-8 on September 26, 1996 The depth to <br /> the water level and the corresponding surface elevations, with respect to mean sea level, are <br /> presented in Table 1 SOTA's engineer informed San Joaquin County Environmental Health <br />' Division of the proposed sampling event, in advance, on September 17, 1996 <br /> The sampling program was conducted as described below A minimum of 4 well casing <br /> volumes, which was calculated to be approximately 16 gallons, was purged from each of the <br /> eight wells During purging operations the temperature, conductivity, and pH, were <br /> measured with the water flowing through a continuous flow chamber The pumping was <br /> carred on until the temperature, conductivity, and pH values stabilized within at least 5% of <br />' previous readings MW-1, MW-2, MW-3, MW-4, MW-5, MW-6, MW-7, and MW-8 were purged <br /> of approximately 25 gallons of water per well using a 2-inch submersible pump Copies of <br /> the field observation which includes temperature and pH values are enclosed in Appendix-A. <br />' Proper decontamination procedures which included flushing the pump and hose with a <br /> solution of detergent and water, followed by clean tap water, with a final rinse using <br /> deionized water were employed The purged water is stored in 55-gallon DOT approved <br /> drums which have been labeled and stored on-site for subsequent treatment/disposal <br />' Adequate time was allowed for recovery after purging All monitoring wells were allowed to <br /> recover to 95 percent or more of their static water level condition At the time of groundwater <br /> sampling, neither free product nor sheen was noticed in any of the monitoring wells <br /> Dedicated bailers were used for sampling activities at each of the wells, in order to prevent <br /> possible cross contamination <br />' l <br /> 16980 Via Tazon, Suite 130 1571 E Cherry Lynn Road <br /> San Diego CA 92127-1633 Phoenix, AZ 85014 <br /> 619 485 8100 FAX 619 485 0812 602 265 8554 FAX 602 265 8457 <br />