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t n� • <br /> ("A-3" , HF-5, & HP-6, ) indicates that the area of impacted water <br /> is restricted primarily to the north & west of the site of the <br /> removed UST. <br /> 2. The hydraulic gradient is very flat, trending slightly to the <br /> north, and the contamination has not migrated far from the UST <br /> site. This is supported by the fact that; (1) there are no water <br /> wells in the area to affect the regional gradient, and (2) the <br /> removed UST has not been in use for several years. if there had <br /> been active movement in the shallow groundwater, the <br /> contamination should have migrated far off site, and possibly <br /> have been diluted below detection levels. <br /> 3. The significant lowering of water levels between January & <br /> April indicates a shallow perched water table which fluctuates <br /> vertically due to rainfall & possibly irrigation. <br /> 4. Irrigation has not significantly affected the defined plume, <br /> which supports the ,above conclusions of a static gradient and a <br /> perched water table. <br /> 5. Visual observation reveals that the current field crop, <br /> alfalfa, is not affected by the low levels of petroleum product <br /> found in the soil or water. <br /> 6. The water in the area has been classified as unsuitable for <br /> domestic use due to the high salt and Boron content; the entire <br /> region is served by treated water piped in from the Tracy area. <br /> In summary, we believe that the plume has been well-defined, the <br /> levels of contamination identified, and the potential impact on <br /> the environment established. Further investigative work does not <br /> appear justified, but at this time we do not have any <br /> recommendations for soil and/or water remediation. Your review <br /> and comments will be appreciated. <br /> Y ur tr y, <br /> Wil J. Hunter <br /> cc: Eliot Appleton <br />