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Enclosure, Sharpe RI Report -2- 8 March 1991 <br /> Sharpe Site <br /> • Concentration versus time graphs were nearly illegible. More of these <br /> graphs (at a larger scale or enlarged) for key wells in each plume would <br /> have been useful . <br /> • Report states that VOCs adsorb to clays. This is incorrect. This <br /> assumption may also have biased the collection of soil samples from the <br /> soils borings. <br /> • The Report does not clearly state in text whether the metals concentrations <br /> were soluble or total concentrations. It is assumed that the metals and <br /> pesticide analyses were usually for total concentrations. <br /> • The Report states that soil moisture is an indicator of the transmissivity. <br /> This is incorrect. <br /> • The Report has a table of the relative moisture content from many soils <br /> borings samples for the years 1984, 1985 and 1986. The tables do not state <br /> the depths of the samples or the depth of the water table. The percentages <br /> of each relative moisture category were used to support the conclusion that <br /> only 26 percent of the subsurface is saturated. <br /> • Regional cross-sections have never been constructed using deep supply wells <br /> and monitor wells from on and off-site. The Report never developed the <br /> "big picture" to determine which sedimentary trends are regionally <br /> correlatable. The conceptual model of the site consists of four zones. <br /> Well installations are assigned to one of the zones or a combination of two <br /> zones (A, AB, B, C, CD, and D) . The site picture is becoming increasingly <br /> complex and not necessarily more accurate or useful for the design of the <br /> extraction system. <br /> • The Report does not provide estimates of the pumpage of the on- and off- <br /> site supply wells (including the SHAD and agricultural wells) yet the <br /> Report acknowledges that agricultural pumpage is affecting plume movement. <br /> • The Report states that the major portion of the subsurface is unsaturated. <br /> This erroneous conclusion was based on seismic reflection reconnaissance <br /> and relative soil moisture contents of soils borings samples. The Report <br /> also states that pumping tests were performed and it was determined that <br /> there was hydraulic connection between the zones. It is unclear how <br /> pumping tests can be performed on unsaturated sediments. <br /> • The Report implies that each aquifer is confined. However, the Report <br /> states that there is hydraulic interconnection between the zones. <br /> Furthermore, some of the values for storage coefficient (S) indicate <br /> unconfined and semiconfined conditions. <br /> • The ground water flow model is based on the three layer concept. Each <br /> layer is non-interactive with the other layers. However, the Report states <br /> repeatedly that there is hydraulic connection between the zones. The <br />