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Extended Site Characterization Report: 7500 West Eleventh Street, Tracy, CA Page 12 and 50 ft. BGS. These depths and screened intervals were selected to provide, in conjunction with existing Monitoring Well MW-3, information on groundwater quality at discrete depths. The boring logs and construction details are included in Appendix A. The 4 well array MW-3, MW-3A, MW-313 permits comparison of groundwater quality in three separate intervals: water table to 21 ft. BGS, 35 to 40 ft. BGS, and 45 to 50 ft. BGS. i 5.3.2 Eastern Limit - Principal Plume of Affected Groundwater Monitoring Well MW-8 was originally included in SJC's work plan for the first phase .:= site characterization program (The San Joaquin Company Inc. 1999), but, as was discussed previously, at that time, funding for its installation was refused by the USTCF. . , Its installation was approved during the second phase of the site characterization program. It is located to the east of Chrisman Road on the northern side of West Eleventh Street at distance from Well MW-7, which was installed during the first phase of site _ characterization and is known to contain floating product. Its purpose is to provide a conservative assessment of the eastern limit of the plume of affected groundwater in that area. The log and construction details of Well MW-8 are included in Appendix A. It has a total depth of 22 ft. and is screened over a 15-ft. interval from just above the groundwater table to a depth of 21 ft. Monitoring Well MW-9 (see Figure 2 for location) was installed at the request of the >> SJCEHD. It has a total depth of 22 ft and is screened from a depth of 7 ft. (at an elevation > above the groundwater table) to the bottom of the well at a depth of 22 ft. (See Appendix A for the boring log and well construction details.) 5.3.3 Down- adient Extent- Principal Plume of Affected Groundwater A groundwater-quality monitoring well designated as Well MW-10 was installed on the eastern side of Chrisman Road approximately 265 ft. north of that street's intersection with West Eleventh Street. (See Figure 2 for location). This well is one of two, the other being MW-11, that were located so as to investigate the distance that groundwater affected by fuel hydrocarbons has been transported down the groundwater gradient from the 7500 West Eleventh Street site. MW-10's location is on a projection of a line from the center of the pump island area of the former fueling station, beneath, which the C ! majority of the fuel hydrocarbons that leaked into the subsurface were released, and Monitoring Well MW-7. Groundwater in MW-7 is heavily affected by components of both gasoline and diesel. Based on the hydrogeology and geochemistry of the site, as it was known following completion of the initial site characterization program, it was concluded that the alignment from Former Pump Island Location to MW-7 to MW-10 closely followed the principal axis of the plume of affected groundwater. MW-10 was sited on this alignment so that any analytes of concern present in the groundwater at that distance from the source would Iikely be detected. Location of that well further to the south would risk sic