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Geosyntec <br /> consultants <br /> • The extent of chemical impacts in the A- and B-Zone downgradient of existing <br /> monitoring wells MW-107A and MW-201B is unknown. <br /> • The extent of chemical impacts in the A-and B-Zone immediately downgradient <br /> of the extraction well network beneath Inglewood Avenue is unknown. <br /> • The extent of chemical impacts in the A-Zone south of the extraction well <br /> network beneath Inglewood Avenue is unknown. <br /> • The injection of the reductant as part of the Phase V IRA has altered the <br /> chemistry of the A aquifer immediately downgradient of Pacific Avenue. As <br /> discussed in Section 2.2.2.1, the area affected by the Phase V must be quantified <br /> and accounted for during the alternative evaluation and selection of the final <br /> remedial action for the site. <br /> Based on the data gaps presented above, additional subsurface information is needed to <br /> achieve the objectives of this Work Plan. The follow provides rationale for each of the <br /> proposed data-collection locations shown on Figures 3, 4, and 5: <br /> • Location EBI (Figure 3): An exploratory boring is proposed at this location to <br /> evaluate the post-Phase V IRA subsurface conditions. During installation of this <br /> boring, soil samples will be collected to establish geochemical characteristics of <br /> the water-bearing materials and groundwater samples will be collected to <br /> develop a vertical profile of COPC distribution throughout the A- and B-Zones <br /> in this area. <br /> • Location Al (Figure 4): An A-Zone monitoring well is proposed at this location <br /> to evaluate the downgradient extent of impacts east of existing well MW-107A <br /> and north of the extraction wells operating beneath Inglewood Avenue. This <br /> monitoring well will also provide data on the performance of the GWETS. <br /> • Location A2 (Figure 4): An A-Zone monitoring well is proposed at this location <br /> to evaluate the distribution of COPCs between the extraction wells on Pacific <br /> and Inglewood Avenues and north of the assumed center-line of the <br /> groundwater plume. This monitoring well will also provide data on the <br /> performance of the GWETS. <br /> • Location A3 (Figure 4): An A-Zone monitoring well is proposed at this location <br /> to evaluate water quality downgradient of the Inglewood Avenue extraction <br /> Pre-Design Investigation Work Plan 12 18.05.12 <br />