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6.0 CORRECTIVE ACTION MONITORING The existing monitoring program under the WDR Order No. R5-2004-0157 includes a groundwater evaluation monitoring network where groundwater sampling is conducted semi- annually and water levels are measured quarterly. The evaluation monitoring network is comprised of 9 wells for groundwater sampling purposes, including 5 wells completed in the shallow zone and 4 wells completed in the deep zone. Groundwater samples are analyzed for field parameters and also eleven other parameters (Table I of the WDRs), including the two constituents of concern (TDS and chloride). This chapter describes the purpose of the corrective action monitoring that will be conducted in coordination with the existing evaluation monitoring program. The purpose of corrective action monitoring(Title 27, Section 20430 (d)) is to demonstrate the effectiveness of the corrective action program. Particularly, the water quality and water level data gathered from the combined networks will be used to evaluate the effectiveness of the corrective action program toward achieving compliance with the WQPS. As described above, groundwater remediation actions (extraction) are planned to focus on restoring the shallow zone to the WQPS concentrations of 89 mg/L for chloride and 600 mg/L for TDS. Correspondingly, the corrective action monitoring network below has a similar focus. Remedial actions occurring through pond closure and also shallow zone extraction are anticipated to result in improved groundwater quality in the deep zone. Progress made toward improved conditions in the deep zone will continue to be assessed using the data generated from the existing evaluation monitoring program. 6.1 Corrective Action Monitoring Well Network The corrective action monitoring network for the shallow zone incorporates the four existing shallow dedicated monitoring wells MW 1, MW2, MW3A, and MW4A, and also Well A, a shallow production well (Figure 6-1). The test well/extraction well (EWl) constructed for groundwater remediation will also be included in this network. The objectives for monitoring at each corrective action monitoring well are: a. MW2 (Background water quality in the shallow zone): Continued assessment of water quality trends in shallow zone; b. MW 1 (Groundwater quality in the shallow zone immediately west of the ponds): Monitor progress toward achieving the WQPS near the salt source area(former ponds; pond closure will be completed in Fall 2005); © LUHDORFF & SCALMANINI CONSULTING ENGINEERS 12