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Has the site been adequately characterized? <br /> Yes. Based on investigations associated with the tank removal and product line overexcavation <br /> (1989), groundwater well installations (1990), septic tank and leach field removal (1992) and <br /> additional soil borings (1992), the site has been adequately characterized. All environmental <br /> work, including well installation and soil boring work was requested and approved by your <br /> department. <br /> There is little or no impact to groundwater, or the plume is not migrating? <br /> True. Attached is a copy of the most recent groundwater monitoring and sampling report. <br /> Petroleum hydrocarbon concentrations of all groundwater samples collected from this site have <br /> been either non-detectable or below MCL's for approximately two years.t' <br /> I <br /> Are they any potential receptors? <br /> No. Based on groundwater,analytical data,potential receptors would not be exposed to <br /> hydrocarbon concentrations above MCL levels. Additionally,two domestic wells located onsite <br /> have been previously destroyed under the supervision of you department. A well survey <br /> conducted in June 1996 indicates that no domestic wells are located within a 500 foot radius of <br /> the site. <br /> } Is there a significant risk to human health or the environment? <br /> No. Based on site specific data,humans or potentially sensitive environmental receptors will not <br /> be exposed to any remaining hydrocarbons. Additionally,based on known natural biodegradation <br /> processes, any remaining hydrocarbons should rapidly degrade. <br /> To date,Unocal has spent approximately $712,000 investigating and remediating sthe <br /> Imse subject <br /> Based on all the available information,our efforts have proven successful. A lease feel <br /> requests that you review this case for closure. If you have any questions or concerns,p <br /> free to call me at(510) 277-2311. I look forward to your response. <br /> Sincerely, <br /> Edward C. Ralston <br /> Senior Environmental Geologist <br /> cc: Bob Kezerian, KEI,w/o <br /> File SS#5421 : 3 <br /> 2401 Stanwell Drive;Suite 3o0,Concord,CA 94520 <br /> TEL:(510)602-5120 FAX:(510)689-1916 <br /> f <br />