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Work Plan for Extended Site ChWcterization: 7500 West Eleventh Street, Tracy,Cif. Page 7 6.3.1 Investigation of Vertical Extent: Affected Groundwater in Pump Island Area It is proposed to locate two new monitoring wells, to be designated well MW-3A and well MW-3B, in close proximity to exiting monitoring well MW-3. (See Figure 2 for locations.) These wells, as requested by the SJCPHS, will be designed to explore the vertical extent to which groundwater was affected by the releases of hydrocarbon fuels that occurred near the former pump islands on the property. Well MW-3A will have a total depth of 36 ft. and its screened interval will be between 30 and 35 ft. BGS. Well MW-3B will have a total depth of 51 ft. and its screened interval will ` be between 45 and 50 ft. BGS. These depths and screened intervals have been selected to provide, in conjunction with existing monitoring well MW-3, information on groundwater quality at discrete depths. The construction details of these wells will be similar to those illustrated on Figure 8. When the well array MW-3, MW-3A, MW-313 is complete, it will be possible to compare water quality in three separate intervals: Water Table to 21 ft. BGS, 35 to 40 ft. BGS, and 45 to 50 ft. BGS. 6.3.2 Definition of Eastern Limit: Principal Plume of Affected Groundwater The San Joaquin Company's (SJC) work plan for the first site characterization program for the 7500 West Eleventh Street site called for small-diameter exploratory soil borings to be drilled on to the east side of Chrisman Road to the south of West Eleventh Street and on both the west and east sides of Chrisman Road to the north of East Eleventh Street. In addition, exploratory borings were planned along the north and south sides West Eleventh Street to the east of Chrisman Road. These were to be used to assist in the selection of the locations of planned monitoring wells in those areas to permit the eastern fringe and the down gradient limits of the plume of affected groundwater to be investigated (The San Joaquin Company Inc., 1999). Unfortunately, the California Underground Storage Tank Cleanup Fund (USTCF) refused to fund the drilling of those exploratory borings or the installation of the planned groundwater- quality monitoring wells in those areas (California Underground Storage Tank Cleanup Fund, 2000). The exploratory boring and groundwater-quality monitoring well proposed in this and the following section of this present pian compensate for the omission of the requisite work that was originally proposed in 1999. As SJC stated in its site characterization report (They San Joaquin Company 2000d), the inexplicable funding decision on the part of the USTCF was apparently made by staff devoid of a basic understanding of hydrogeology and solute transport who proceeded without the requisite oversight of a California-licensed engineer. As is shown on Figure 2, a groundwater-quality monitoring well to investigate the eastern limit of the plume of affected groundwater will now be installed at the north side of West Eleventh Street at a location approximately 125 ft. to the east of its intersection with Chrisman Road. This well will be designated well MW-S. �i SJC