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--' - Report: Groundwater-quality Monitoring—June 23-28,2005, 7500 West Eleventh Street, Tracy, CA. Page • ,. _:::.� that analyte actually present in that groundwater sample E By April 11, 2002, it was clear that floating product was present in the surface of the groundwater in Monitoring Well MW-7. It continued to be present at various apparent LNAPL-purging program in that well was initiated on thicknesses up to 0.58 ft. until an -�; November 8, 2003. As part of the further extension of the site characterization program in five floating product monitoring wells were installed at the locations shown on Figure 2 to investigate the down-gradient extent to which LNAPL may have migrated April 2004, in the interior of the plume of affected groundwater emanating from the 7500 West s was Eleventh Street property. The tereaso made toess of td floating roduct in the presence of LNAPLthose five Ion the checked at that time and tests w MW-13 and MW-14. The water table in groundwater-quality monitoring wells MW-7, an July 26 same array of wells was again checked for the presence of floating pro t of LNAPL and October 27, 2004, and on February 24, 2005. The historical record k>! thickness measured in the array of floating product monitoring wells through February 24, 2005 is presented in Table 3. r 1.3.4 Testin of Water in Potable Water-su 1 wells r At the direction of the SJCEHD, the quality of water in six potable water-supply wells in Site was analyzed in April 2004. Second, third and the neighborhood of the Navarra fourth rounds of sampling and analysis of the water produced from those wells were conducted on July 27 and October 28, 2004 and on February25, 2005. This report fifth quarterly monitoring round of that program. includes the results of the 1.3.5 Evaluation of Natural Attenuation In addition to the groundwater-quality monitoring round that was conducted in February and March 2005, an extensive program of field testing, laboratory analysis and geochemical and engineering studies was completed to investigate the progress of natural attenuation processes that are reducing the contaminant load in groundwater beneath the t ' Navarra Site. That work demonstrated that there is strong primary and secondary evidence that natural attenuation is aggressively reducing contaminant concentrations in the subsurface and that those processes alone will be sufficient to adequately remediate the groundwater within a reasonable time, which is estimated to be on the order of 10 to fr> 20 years (The San Joaquin Company Inc. 2006). 1.4 Geology and Hydrogeology The subject property and the surrounding area are situated on level terrain on the distal, northern slope of an alluvial fan. The shallow underlying alluvial sediments are of Quaternary to Recent age. The site and the immediately adjacent property along the south side of West Eleventh i ' Street and the west side of Chrisman Road have been extensively excavated and backfilled during prior filling station construction and remodeling, utility installation, and -' sic