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ENVIRONMENTAL HEALT&EPARTMENT <br /> SAN JOAQUIN COUNTY <br /> 2.. iUnit Supervisors <br /> Q, Donna K.Heran,R.E.H.S. 304 East Weber Avenue, Third Floor Carl Borgman,R.E.H.S. <br /> Director <br /> AlOlsen,R.E.H.S. Stockton, California 95202-2708 Mike Huggins,R.E.H.S.,R.D.I. <br /> - Douglas W.Wilson,R.E.H.S. <br /> • c4t�Foa:''p • Program Manager Telephone: (209) 468-3420 Margaret Lagorio,R.E.H.S. <br /> Laurie A.Cotulla,R.E.H.S. Fax: (209) 464-0138 Robert McClellon,R.E.H.S. <br /> Program Manager Mark Barcellos,R.E.H.S. <br /> DENIS L BROWN APR 2 8 2005 <br /> HSE — ENVIRONMENTAL SERVICES <br /> 20945 S WILMINGTON AVE <br /> CARSON CA 90810-1039 <br /> RE: Former Texaco Service Station SITE CODE: 1055 <br /> 440 Charter Way <br /> Stockton CA 95206 <br /> San Joaquin County Environmental Health Department (SJC/EHD) has reviewed <br /> Groundwater Monitoring Report— Fourth Quarter 2004 (Report) dated March 14, 2005, <br /> submitted on your behalf by Cambria Environmental Technology, Inc. (Cambria) and has <br /> the following comments. <br /> The report documents a routine quarterly groundwater monitoring and sampling event <br /> conducted on November 15, 2004. The report recommends discontinuing sampling of <br /> MW-14, noting that the well is located offsite and there are two wells without detections <br /> of contaminants located between the well and the onsite contaminant source. <br /> Concentrations of methyl tertiary butyl ether(MtBE) are increasing in MW-14. The <br /> report also recommends reducing the analyses for 1,2-dichloroethane (1,2-DCA), <br /> ethylene dibromide (EDB) and tertiary butyl alcohol (TBA) in selected wells. <br /> SJC/EHD approves discontinuing analysis for TBA in monitoring wells MW-2, MW-6, <br /> MW-8, MW-15 and MW-17. Monitoring well MW-7 has had detections of methyl tertiary <br /> butyl ether (MtBE) in the past year. TBA is a breakdown product of MtBE; analysis for it <br /> must continue until there is an established history of non-detect for MtBE in this well. <br /> SJC/EHD approves discontinuing analysis for 1,2-DCA and EDB in monitoring wells <br /> MW-2, MW-6, MW-7, MW-13, MW-15, MW-17 and MW-19-120. These are the only <br /> wells that have shown a consistent history of non-detect at an appropriate detection limit <br /> for over one year. <br /> SJC/EHD agrees that the MtBE currently impacting monitoring well MW-14 is not likely <br /> to have originated from the subject site, but has requested Mr. Denis Brown of Shell to <br /> continue monitoring for MtBE in that well. As the well itself is still useful for groundwater <br /> elevation data and for tracking the advancing plume should it actually impact the Shell <br /> site, Mr. Brown has agreed to continue quarterly analysis for MtBE in MW-14. SJC/EHD <br /> will attempt to identify the proper responsible party for the MtBE plume and make them <br /> responsible for monitoring the MtBE plume. SJC/EHD appreciates Shell's assistance <br /> with this issue. <br />