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Donna Gardner 3 - 29 September 2006 <br />26056 Thornton Rd Thornti <br />Associates Inc. and approved by SJCEHD. From April 2002 to August 2004 groundwater <br />monitoring ceased at the Site. In July 2003, the SJCEHD issued a Notice of Responsibility for <br />the USTs case to Ronald J Barber Jr and Bonnie J Barber, the new owners. Groundwater <br />monitoring resumed in August 2004 but ceased again in October 2005. Only MW-3 and MW- <br />4 were sampled although water levels were recorded for all six monitoring wells. Maximum <br />groundwater concentrations (MW-4) in October 2005 were: TPHg, 830 pg/L; benzene, <br />1.5 pg/L; toluene, 1.6 pg/L; ethylbenzene, 2 pg/L; xylenes, 2.3 pg/L; and fuel oxygenate <br />Methyl tert-Butyl Ether (MtBE), 0.65 pg/L. Note that during the previous event in July 2005 the <br />fuel oxygenate Tertiary Butyl Alcohol (TBA) was detected at 2 pg/L. The fuel oxygenate <br />Di-Isopropyl Ether (DIPE), 3.4 pg/L was detected in January 2005. <br />The following graph of MW-4 of TPHg groundwater concentrations from March 2004 through <br />October 2005 does not show a declining concentration trend: <br />MW-4 TPHg concentration in ug/L 3000 <br />2500 <br />2000 <br />1500 <br />1000 <br />500 <br />0 <br /> <br />MW-4 TPHg <br /> <br />—Linear (MW-4 <br />TPHg) <br />,c4), <br />ec) coe' <br />date <br />Although maximum concentrations have declined since 1990, threats from the petroleum <br />hydrocarbons release to Well #2 remain. The driller's logs for Well #2 show a potential <br />conduit for groundwater pollution below 70 feet bgs. The pumping effects of Well #2 have <br />never been demonstrated on the monitoring wells. <br />I have conducted a preliminary case review and agree with some of the previous directions <br />given by SJCEHD. Therefore, you need to comply with the following Regional Board staff <br />directives: <br />By 31 October 2006, resume quarterly monitoring of monitoring wells MW-1 through <br />MW-6 and Well #2 for all petroleum hydrocarbon constituents of concern reported to <br />date, including TPHg, benzene, toluene, ethylbenzene, xylenes, the five fuel <br />oxygenates, lead scavengers 1,2-dicholorethane and ethylene dibromide, methanol and <br />ethanol. Analytical Method Detection Limits shall be sufficiently low for comparison of