SITE INFORMATION AND CORRESPONDENCE

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} San Joaquin Qcy Air Pollution Control District Page 3 (intermittently), MW12, and EW2. In addition, deeper zone well MW13C has also contained MTBE in the past. M W 1 previously contained free-phase gasoline and V W 1 typically contains a strong odor of gasoline. The impacted area measures approximately 28,000 square feet and the leading edge of the main plume extends approximately 140 downgradient of the source area. The volume of impacted groundwater and the mass of dissolved contaminant was estimated by assuming an affected saturated interval of 20 feet (70-90 ft bgs), a total porosity of 30% and estimating the areas of various concentration Ievels. It is estimated that approximately 1.25 million gallons of groundwater was affected by MTBE in the main plume and that the mass of dissolved MTBE contained therein was approximately 39 pounds prior to treatment. The TPHg plume apparently impacted an area of approximately 11,300 square feet, with and estimated volume of approximately 500,000 gallons of groundwater affected, with the mass of TPHg contained therein of 52 pounds prior to treatment. Groundwater analytical results are summarized in Table 3. The volume and mass of free product was estimated by assuming an average product thickness of 0.29 feet (prior to groundwater extraction), an affected area of 315 square feet and a porosity of 30%. It is estimated that approximately 205 gallons (1,365 pounds) of product was present on the groundwater surface beneath the site prior to groundwater extraction. Assuming the MTBE comprises approximately 15% of gasoline, the free product was estimated to contain up to 205 pounds of MTBE. Groundwater extraction appears to have reduced contaminant concentrations signficantly in wells MW1, MW3 and MW4, and no measurable free product is present in well MW1. There does not appear to be any free product remaining in the subsurface. Table 4 summarizes free product monitoring and removal conducted at the site. Free product Removal and Groundwater Extraction Approximately 180 gallons of product/water mixture was removed from monitoring/extraction well MW1 through the use of a passive skimmer and actively bailing the well prior to beginning groundwater extraction in November 2003. Through October 26, 2004, more than 378,000 gallons of groundwater has been extracted from well MWl and remediated through the groundwater treatment system. Ground Zero has estimated that approximately 58 pounds of TPHg and 21.9 pounds of MTBE was removed from groundwater between November 2003 and October 2004. The groundwater treatment system is currently operating, with an average extraction rate from well MW1 of approximately 1.2 gallon per minute (gpm). Downgradient extraction well EW2 was installed in July 2004. Ground Zero has estimated that approximately 58 pounds of TPHg and 21.9 pounds of MTBE was removed from groundwater between November 2003 and October 2004 as a result of groundwater extraction and treatment. Soil Vapor Extraction Test On October 22, 2003 Del-Tech Geotechnical performed short-term vapor extraction tests (VETS) " on wells MWI and VW1. The VET equipment consisted of an internal combustion (IC) engine equipped with a catalytic converter; instrumentation for measuring air flow, air G'1GRnI1Nn7E1Ti SLE'B[JRG1.Vannr Eetrartinn nr it0VfNr r1tr nnr'