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r i Navarra Site:Potable Wate�upply Well Program Page 3 of 7 recommending modifications to, but not elimination of, the potable water-quality monitoring program for the Navarra site. This letter has been prepared in response to that request. Well Logs As was reported to the SJCEHD in our report, Extended Site Characterization - Former Fueling Station at 7500 West Eleventh Street, Tracy, California, submitted on October 22, 2002, which document included, in Appendix D, all available well construction data for wells in or near the contaminant plume emanating from the Navarra Site, logs are available only for three of the six potable water supply wells in the array being monitored. Exhaustive research, including searches made by electronic searches of United Stares Geological Survey(USGS) records and the Federal Reporting Data System (FRDS), by visits to the SJCEHD well record archive in Stockton and the California Department of Water Resources (DWR) archive in Sacramento produced no information beyond that compiled in attached Table 1, which has been abstracted from the information provided in our October 2002 report. Three Well Completion Reports with simplified well logs were found for the wells at 7601 West Eleventh Street (Gowan), 13950 Chrisman Road (BCNC) and at the Carmelo Business Park. As was requested by SCEHCD at the January 18, 2005 meeting, those logs, which, as noted above, were also included in Appendix D of the above-cited 2002 Extended Site Characterization Report, are submitted again as attachments to this letter. Results of Potable Water-quality Monitoring_Program The analytical results of the completed water-quality monitoring program that included quarterly rounds of sampling and analysis from each of the six potable water wells over the period April 2, 2004 to February 25, 2005 are compiled in attached Table 2. As can be seen by inspection of that table, no analytes of concern were at any time detected in samples of potable water recovered from any of the wells. Revised Potable Water-quality Monitoring Program The total absence of any detectable concentration of any analyte of concern in any of the samples recovered from any of the potable water supply wells over the completed one- year monitoring period demonstrates that the risk of future contamination by any chemical of concern released at the 7500 West Eleventh Street site, where leaks of fuel hydrocarbons occurred over a period of at least some 60 years, and where the groundwater flow regime and the hydrogeology indicate that any risk of contamination of groundwater in the potable-water supply wells, is extremely low. However, in response to the SJCEHD request to continue monitoring water quality in selected potable water supply wells, SJC proposes that a revised program of potable water-quality monitoring be implemented based on the following recommendations.