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Groundwater Well Installation Work Plan Sharpe Army Depot <br /> Lathrop, California <br />Ahtna Environmental, Inc. Page 6 of 6 <br /> <br /> <br />Reviewer Marcus Pierce Organization Central Valley Water Board Date July 27, 2020 <br />Item Reference Review Comment Response <br />Specific Comment <br />1. Figure 5 The Army is proposing to construct new extraction well <br />EWNC7 with a 10-foot screen from 120 to 130 feet <br />below ground surface (bgs). Based on the lithology <br />depicted on Figure 5, the proposed design may be <br />unsuitable for an extraction well as the screen may be <br />placed in fine-grained materials. Although the screened <br />interval should be based on the actual soils <br />encountered during drilling, we recommend targeting a <br />20-foot screen interval from approximately 120 to 140 <br />feet bgs or a 10-foot screen interval from <br />approximately 130 to 140 feet bgs. These deeper <br />screens correlate better with the screen interval of <br />MW505C and will likely penetrate more transmissive <br />materials. <br />Revised. Sections 3.2 and 3.2.1, Table 1, and Figures 5 <br />and 13 have been updated to reflect installation of a 10- <br />foot screen from 130 to 140 ft bgs. <br />2. Table 2 Table 2 has useful construction information on wells <br />near the proposed new extraction and monitoring <br />wells. However, some of the wells are missing on the <br />figures. Please check the figures in the Draft Work Plan <br />and add any of the well that may be missing. <br />Revised. Figures were checked for completeness and <br />details have been added to Table 2 to direct the reader <br />to specific figures.