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Extended Site Characterization Report: 7500 West.Eleventh Street, Tracy, CA, Page 3 the installation of groundwater-quality monitoring wells to the east of Chrisman Road and to the north of West Eleventh Street to assess the full lateral extent of the contamination could not be performed at that time. This work was identified as clearly necessary by the California-licensed Engineer in Responsible Charge of the f characterization program (The San Joaquin Company Inc. 2001f,pp 7-8, 12, 27). The initial, restricted phase of site characterization work was completed in May 2000. It included the drilling of 14 exploratory borings (Nos, PP-1 through PP-14) and 7 groundwater-quality monitoring wells (Nos. MW-1 through MW-7) at the locations shown on Figure 2. The results of that program were presented in an engineering report submitted to San Joaquin County Environmental Health Department (SJCEHD) in January 2001 (The San Joaquin Company Inc. 20011), Including the rounds conducted at the time of the initial site characterization work, five rounds of groundwater-quality monitoring were conducted at the site over the period May 2000 to December 2001. r Those were performed in May 2000, November 2000, May 2001, September 2001 and December 2001 and the results were reported to the SJCEHD (The San Joaquin Company Inc. 2001f, 2001g, 2001e, 2001c and 2002). The SJCEHD, in a letter dated July 3, 2001, requested installation of additional groundwater-quality monitoring wells to: 1) improve understanding of the down-gradient extent of the contaminant plume; 2) investigate the environmental condition of the subsurface beneath an area close to the southern boundary of the property, which appears either to have been affected by petroleum hydrocarbons migrating from an up-gradient source or emanating from a Iocal, on-site source; and 3) improve definition of the vertical extent of contamination of groundwater, particularly in the area where the principal releases of hydrocarbon fuels to the subsurface had occurred prior to the cessation of fuelling operations at the property (San Joaquin County Environmental Health kd Department 2001c). In response to the SJCEHD request, SIC prepared a work plan for an extended site characterization program and submitted it to the SJCEHD for review (The f San Joaquin Company Inc. 2001d}• The primary objective of the work plan was to extend !- the investigation of the lateral extent of plume of affected groundwater emanating from the 7500 West Eleventh Street site in areas to the east of Chrisman Road and to the north i _ of West Eleventh Street, where authorization to install exploratory borings and groundwater-quality monitoring wells had been denied by the SJCEHD and the USTCF when originally recommended by SIC in 1999. The locations of the proposed groundwater-quality monitoring wells were carefully selected, using a synthesis of the =' hydrogeological and groundwater chemistry data, so as to detect the northward advance of the plume of groundwater emanating from the 7500 West Eleventh Street site. -- In response to the submitted work plan for the extended site characterization program, the SJCEHD requested inter alia the repositioning to the south of a well that SJC proposed to locate on the east side of Chrisman Road (San Joaquin Public Health Services 2001a). SIC had selected the location of the well based on a thorough evaluation of the hydrogeology and geochemistry of the site to ensure that any components of hydrocarbon fuels that had migrated down the groundwater gradient from the source beneath the former pump islands at 7500 West Eleventh Street as far north as what, on Figure 2, is SJC :d