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Report:Groundwater-quality Monitoring—July 14-15,2006, 7500 West Eleventh Street, Tracy, Cit. Page 3 monitoring wells are currently extant at the site. The geological, geotechnical and geochemical data gathered by the site characterization studies were used to develop an understanding of the hydrostratigraphy and groundwater flow regime at the 7500 West Eleventh Street Site and to evaluate the lateral and vertical extent to which the soil and groundwater have been affected by the release of fuel hydrocarbons that occurred on the property. The results of that process are summarized in Sections 1.5 and 1.6 below and synthesized on Figure 3, which shows the plumes of affected groundwater at the site and Figures 4-9, which are hydrostratigraphic cross sections drawn through the area where groundwater is affected by the fuel hydrocarbons. 1.4.1 Groundwater-quality Monitorin Since the first round of groundwater-quality sampling and analysis at the Navarra Site was conducted on May 11, 2000, in association with the initial phase of site characterization (The San Joaquin Company 2001), by March 2006, 20 additional groundwater-quality monitoring rounds had been conducted at the site. The results of the depths to groundwater measurements made during those rounds and the results of analyses of the groundwater samples recovered are compiled in Tables I and 2, respectively. In February, 2005, and again in March 2006, the accumulated data from the groundwater- quality monitoring rounds conducted through each those dates was analyzed using the Monitoring and Remediation Optimization System (MAROS) (United States Air Force 2004), use of which is advocated by both the United States Environmental Protection Agency (US-EPA) and the California Environmental Protection Agency (Cal-EPA) (United States Environmental Protection Agency 2005) to ensure that extended groundwater-monitoring programs are conducted economically but with sufficient rigor to ensure that the monitoring Objectives are met. The results of the MAROS analyses conducted for the Navarra Site demonstrated that an optimal future groundwater- monitoring program would call for recovery of groundwater samples at a frequency not in excess of once per year(The San Joaquin Company 2006a,b). This report documents the 22nd monitoring round, which was conducted on July 14-15, 2006. 1.4.2 Monitoring of LNAPL In April 2002, monitoring of the thickness of light non-aqueous phase liquid (LNAPL), (also known as floating product), was initiated. At that time, the thickness of floating product was measured in Monitoring Well MW-7, but the program was later expanded to include Monitoring Wells MW-13 and MW-14 and floating product Monitoring Wells MWFP-1 through MWFP-5, which were installed in April 2004. This report includes records from a program of monitoring the thickness of LNAPL, present as floating product, in an array of five floating product monitoring wells and three sic