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2011 Annual Groundwater Monitoring and Evaluation Report <br /> Full-Scale In Situ Hexavalent Chromium Reduction Treatment Implementation <br /> Former Marley Cooling Tower Site, Stockton,California January 2012 <br /> 9.0 ACTIVITIES PLANNED THROUGH 2012 <br /> • Groundwater monitoring and sampling will continue quarterly. The next sampling event <br /> is anticipated in late January 2012. <br /> • The list of wells and analytes may be reduced with DTSC and CVRWQCB concurrence <br /> based on the successful and lasting reduction in Cr and Cr+6 concentrations in the 2008 in <br /> situ treatment area. <br /> • Groundwater data evaluation will continue through 2012, including the use of the <br /> decision logic diagram (Figure 5). <br /> • The effect of the full-scale (2008) and supplemental injection (2010) programs will be <br /> monitored. If data from upcoming quarterly sampling events indicate Cr concentrations <br /> have decreased to below the established WQO (50 gg/L), recommendations may be made <br /> to shut down groundwater extraction wells. <br /> • Additional supplemental injection(s) may be executed dependent on the mutual <br /> understandings reached during a February 1, 2012 meeting between CVRWQCB, DTSC, <br /> SPX, MWH, and Dudek. <br /> MWH, <br /> 9-1 <br />