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3) The dissolved hydrocarbon plume is stable All off-site wells, except <br />' MW-4, had no detectable concentrations of TPPH-g or benzene dunng <br /> the most recent groundwater monitoring event There has been no <br /> MtBE detected at this site Groundwater will continue to be impacted <br />' by capillary fringe or smear zone soils However, eight years of <br /> monitoring data strongly suggests the groundwater plume is naturally <br />' attenuating Additional data could not provide any stronger argument <br /> than 32 quarters of groundwater samples <br />' 4) A well survey completed by Applied GeoSystems in 1990 identified the <br /> nearest municipal water supply well as being approximately 800 feet <br /> north of the site (crossgradient) <br />' 5) Soil contamination has been defined on site Groundwater has <br /> historically been at depths of 35 to 50 feet below ground surface Itis <br />' highly unlikely that any basements or utility trenches extend to these <br /> depths <br />' In conclusion, the majority of the source material has been removed, the extent of <br /> contamination is defined, the groundwater plume has been stable for several years, and <br /> there are no drinking water wells near the site Given these facts, it is Unocal's technical <br /> opinion that this site poses no significant threat to human health and safety or the <br /> environment Further site assessment and active corrective action are not needed, and the <br /> site is suitable for closure as a low-risk groundwater case If you have any questions or <br /> concerns, please call me at (510) 277-2334 <br /> Sincerely, <br /> Robert Boust <br /> cc Andrew Lehane, PEG <br /> Elizabeth Thayer, CVRWQCB <br /> Mel Jacobo, SWRCB <br />