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3) The dissolved hydrocarbon plume is stable. All off-site weds, except . <br /> MWA,had no detectable concentrations of TPPH-g or benzene during <br /> the most recent groundwater monitoring event. There has been no <br /> MWE 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 argumem <br /> than 32 quarters of groundwater samples. <br /> 4) A well survey completed by Applied Geo Systems in 1990 identified the <br /> nearest municipal water supply well as being approximately$00 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, It is <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 /> contarninati m 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 /> envirormament. 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 /> cancenms, please call me at(510)277-2334. <br /> Sincerely, � <br /> Robert Boust <br /> cc:Andrew Lehane, PEG <br /> Elizabeth Thayer, CVRWQCI3 <br /> Mel Jacobo, SWRCB <br /> S00 A 60£Z LLZ 013:131 ZS 1 i (UM L6 .90- 'D11V <br />