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w Report;Groundwater-quality Monitoring—October 27,2003; 7500 West Eleventh Street, Tracy, CA. Page I 1.0 INTRODUCTION This groundwater-quality monitoring report has been prepared for the site of a former fueling station at 7500 West Eleventh Street, Tracy, California. The fueling station ceased operation in 1998 and, in December of that year, eight underground fuel tanks were removed from the property. At that time, it was found that soil and groundwater .. beneath the site were affected by fuel hydrocarbons. A site characterization investigation completed in May 2000 included installation of seven groundwater-quality monitoring wells (The San Joaquin Company 2001d). A second phase of site characterization was conducted in March and April 2002 during which eight additional groundwater-quality monitoring wells were installed (The San Joaquin Company 2002c). �.. The first round of groundwater-quality sampling and analysis was conducted on May 11, 2000 using the seven wells that were initially installed on the site (The San Joaquin Company 2001d). Ten additional rounds of sampling and analysis were conducted between that date and July 30, 2003, with the rounds conducted in April, July and October 2002 and January and April 2003 involving recovery of groundwater samples from all 15 wells that had been installed at the site by that time (The San Joaquin w- Company 2001c, 2001b, 2001a, 2002d, 2002c, 2002b, 2002a, 2003c and 2003b). The July 2003 sampling round (The San Joaquin Company 2003a) was reduced at the direction of the San Joaquin County Environmental Health Department (SJCE11D) to the sampling of seven of the 15 monitoring wells. This report presents the results of the twelfth sampling round, which was conducted on October 27, 2003, and is comprised of sample analysis data from 11 of the 15 wells, together with a compilation of the data obtained from the earlier rounds of groundwater-quality monitoring, 1.1 Site Location The subject property is situated at 7500 West Eleventh Street, Tracy, California, at the intersection of Chrisman Road and West Eleventh Street. That location is shown on Figure 1. Its elevation is between 48 and 51 feet above mean sea level (MSL). A map of the site and neighboring areas is presented on Figure 2. 'N' Note: Figure 2 has been updated since it was last issued in July 2003 to show a new .� water supply well at Piedmont Lumber, 7675 West Eleventh Street. The new well, which is currently being commissioned, is to the north of the existing water supply well at that site. The old well will no longer serve to provide potable +^� water due to the excessive concentrations of nitrates present in the aquifers down to approximately 200 ft. below the ground surface (BGS). The new well is 640- ft. deep and draws water from formations beneath the Corcoran aquitard, which ... has an extensive presence beneath the San Joaquin Valley. �, sic