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ARCADIS Ms. Kathy Amaru <br /> May 26, 2011 <br /> Suggested-No-Adverse-Response Level Taste and Odor Threshold (Taste and Odor <br /> Threshold), included in the Central Valley Regional Water Quality Control Board's <br /> (CVRWQCB's) Compilation of Water Quality Goals(CVRWQCB 2008). No other <br /> constituents were detected above laboratory reporting limits. <br /> The results of soil sampling, groundwater sampling, and soil removal activities were <br /> presented in the Excavation and Sampling Workplan, dated June 1, 2010, and the <br /> Excavation and Sampling Report, dated October 19, 2010. The CVRWQCB <br /> responded with a letter dated March 11, 2011 requiring submittal of a workplan for <br /> groundwater monitoring well installation and sampling to evaluate groundwater <br /> quality in the vicinity of the excavation. <br /> Proposed Sampling Activities <br /> To address the CVRWQCB's request for the installation of a groundwater monitoring <br /> well, ARCADIS proposes to install one monitoring well to confirm the grab <br /> groundwater sampling results from temporary well point TW-01. Because grab <br /> groundwater sampling can often result in elevated turbidity levels that affect <br /> analytical results, samples collected from properly installed and developed <br /> groundwater monitoring wells are likely to be more representative of actual <br /> groundwater conditions. One groundwater monitoring well will be installed in <br /> approximately the same location as TW-01 and sampled to assess groundwater <br /> conditions in the immediate vicinity of the excavation and evaluate if further sampling <br /> activities are warranted. A detailed description of the sampling activities is provided <br /> below, and the proposed well location is shown on Figure 3. <br /> Pre-Field Activities <br /> Prior to initiating field activities, the site-specific health and safety plan will be <br /> updated in accordance with state and federal requirements, and a monitoring well <br /> installation permit will be obtained from San Joaquin County. An Underground <br /> Service Alert(USA)ticket will be issued for the site, and a private third-party utility <br /> locator will screen the proposed well location to identify potential conflicts with <br /> underground utilities. Additionally, per PG&E requirements, all sampling activities will <br /> be conducted in the presence of a qualified PG&E electrical observer. <br /> Page: <br /> McD Island Well Insta9 Wakplan_FinaI.DOC 318 <br />