2011-03-14_REVISION - M1977493 (65)

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CM0001765 • Page II Brief provided in Appendix E) is required for Zone 2 construction. The quantity required to produce the Zone 2 material gradation was checked against the quantity available from the borrow areas as detailed in the `Soil Quantity Required and Available by Particle Size' calculation brief provided in Appendix E. 4.7 Zone 3 - Rockfill The rockfill in Zone 3 is provided to relieve excess pore pressures and provide a stable Dam cross-section. Zone 3 must be more permeable than Zone 2 while having a gradation specification that is compatible with the Zone 2 gradations. Based on the slope stability analyses performed, a permeability of 10'3 cm/sec was selected to provide a stable Dam cross-section. As with the zones 1 and 2 gradation specification, the Zone 3 gradations identified in the Specifications was selected based on laboratory testing of borrow area soils and the filtration criteria evaluation performed in the `Zone Particle Size by Filtration Analysis' calculation brief provided in Appendix E. Table 4 identifies that approximately 9,000 cy of in-place material (as calculated in the `Summary of Construction Materials Calculation Brief provided in Appendix E) is required for Zone 3 construction. The quantity required to produce the Zone 3 material gradation was checked against the quantity available from the borrow areas as detailed in the `Soil Quantity Required and Available by Particle Size' calculation brief provided Appendix E. 4.8 Riprap Face and Crest Surfacing The final layers of the Darn cross section are the riprap face and crest surfacing. As with the gradation designs for zones 1 through 3, the riprap face gradations identified in the Specifications are more permeable than the adjacent Zone 3 and are compatible with the Zone 3 gradations. The riprap face gradations were developed based on the filtration criteria detailed in the `Zone Particle Size by Filtration Analysis' calculation brief provided in Appendix E. Total riprap required for the Dam face and the spillway and headwall aprons is approximately 10,000 cy. The quantity required to produce the riprap material gradation was checked against the quantity available from the borrow areas as detailed in the `Soil Quantity Required and Available by Particle Size' calculation brief provided in Appendix E. This evaluation indicated that to produce the gradations specified for all riprap required for the Dam, fractured bedrock must be quarried. c:ULynn%L-nm\ciimuMoldun%6104repldoc IL03/W --_ ,aw ? ? - ° _ _ = Environmental