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a Mr.Nuel Henderson >✓ " Re: 102 S. Wilson Way–Petition for Closure Page 2 caused by an unauthorized release occurring at another site located along this single groundwater plume. Based on available evidence, it is not reasonable to designate the Knowles Family Trust as a responsible party for any further contaminant remediation. The parry which is responsible for the unauthorized release of fuel containing MTBEs and other oxygenates must be identified as the responsible parry for any further monitoring and remediation. Groundwater Migration Measurements of groundwater elevation show that the groundwater declines in elevation as it moves from the 101 S. Wilson Way site(Top Filling Station)toward the 102 S. Wilson Way site(previous Knowles Family filling station). This indicates that the site is down gradient of the release that occurred at 101 S. Wilson Way(Top Filling Station). In addition,there is also an Arco filling station located at 130 S. Wilson Way, which is adjacent to the site in question. Evidence suggests that the Arco station may also be contributing to the contaminants found in the groundwater at 102 S. Wilson Way. MTBE and Oxygenate Contamination MTBE MTBE was first used as a fuel additive in the late 1970s; during the 1980s, oxygenates, including MTBE,came into wider use.' At least one other California county has acknowledged that the large-scale use of MTBE as a gasoline additive first began during the winter of 1992? The underground storage tanks at 102 S. Wilson Way were removed prior to these dates and never stored fuel containing MTBE. Since the underground storage tanks were removed from the site prior to introduction of MTBE and the groundwater beneath the site contains a significant presence of MTBE, logic dictates that the majority, if not all, of the groundwater contaminants, including all presence of MTBE, is the result of unauthorized release(s)occurring at a different site. Site monitoring began long after the storage tanks were removed—approximately 17 years after the tanks were removed. Yet during the course of monitoring at the site, at least 84 percent of the monitoring and vapor extraction wells have registered increases of at least 100 percent in MTBE contaminants. Even after all of the remediation actions undertaken to date,of the original 13 monitoring wells, six currently show a higher presence of MTBE than initially recorded in 1997. For example, several wells which in 1997 indicated the presence of MTBE of less than 5 parts per billion,now show readings of over 500 parts per billion. http://www.ep&gov/otaq/regs/ftiels/ostpexec.pdf (page 6) 2 Acknowledged by Alameda County;contained in a petition presented at the November 2002 meeting of the State Water Resources Control Board,Item 13. Available at http://www.waterboards.caLgov/agendas/2002/november/I I 19-13.doc.