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CM0001759 <br />is <br />• <br />t <br />Page 5 <br />4.0 DESIGN EVALUATIONS <br />This section discusses the assumptions, design approaches and results for each of the major Darn <br />design components. <br />4.1 Borrow Areas <br />Figure 2 shows the location of borrow areas to provide earthen materials for the Dam's <br />construction. Figure 3 shows the locations of test pits and boreholes logged within these borrow <br />areas during subsurface investigations to investigate the geotechnical characteristics of the <br />potential borrow area material. Appendix B contains the 1993 preliminary geotechnical report, <br />including borehole logs, by Kumar and Associates (Kumar) and the 1996 test pit logs developed <br />by Titan Environmental Corporation. The borehole and test pit logs were used to delineate three <br />potential borrow areas near the Dam construction site: the Terimile Tunnel Portal Borrow Area; <br />the East Island Borrow Area; and the West Island Borrow Area. A fourth soil borrow area <br />source, the Mosquito Fault Borrow Area, was identified by CMC as an another potential borrow <br />area source of clayey soil and its chemical characteristics are currently being evaluated by CMC <br />to determine if this borrow material is suitable as Dam construction materials. <br />4.1.1 Soil Analysis <br />Samples were collected for geotechnical testing from several test pits in the Tenmile Tunnel <br />Portal and the East Island and West Island borrow areas and for geotechnical and chemical <br />testing from the surface of the Mosquito Fault Borrow Area. Table 2 summaries the geotechnical <br />testing results for the laboratory testing reports included in Appendix B. Table 3 summarizes the <br />chemical analyses results provided by CMC for the Mosquito Fault Borrow Area material. <br />Geotechnical testing classified the soil in the Tenmile Tunnel Portal Borrow Area and both <br />island borrow areas as silty gravels and sands. Visual inspection indicated larger size boulders <br />are also present. The borrow area soils have the necessary geotechnical characteristics to provide <br />all materials required to construct the Dam. However, the soils will have to be processed to meet <br />Dam construction material specifications. Borrow material processing will include screening of <br />the borrow materials to produce the required gradations specified for each zone of the Dam and <br />c: ynn rus Amax am rep . <br />12103/96 <br />_= nvironmenta <br />