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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />- <br /> <br />found to be a layer of lean clay to sandy clay about 2.5 to 7 feet thick <br /> <br /> <br />overlying a stratified layer of fat clay. The lean clays containing a small <br /> <br /> <br />percentage of basalt cobbles and boulders are believed to be slopewash origin <br /> <br /> <br />while the underlying fat clays are probably of lake sediment origin. The lean <br /> <br /> <br />clay material would provide an excellent source for compacted embankment. Logs <br /> <br /> <br />of the test pits and moisture/density curves are included in Appendix D. <br /> <br />The slopewash materials proposed for use as embankment appear to contain <br /> <br />about 5 to 10 percent basalt cobbles and boulders (larger than 3-inch size). <br /> <br /> <br />The potential borrow area has a vegetative growth of thick grass and would <br /> <br /> <br />require about 6 inches of stripping to remove the roots and organic material. <br /> <br /> <br />The areas near the small drainage channels in the borrow area are wet and would <br /> <br /> <br />have to be avoided during borrowing operations. <br /> <br />This potential borrow area for impervious materials has a surface area of <br /> <br /> <br />about 3 acres. Using an average depth of 3 feet for the lean clays, the area <br /> <br /> <br />would yield approximately 15,000 cubic yards of borrow. <br /> <br />Pervious Materials <br /> <br />Pervious sand and gravel for such uses as concrete aggregate, filter zones, <br /> <br /> <br />or riprap bedding is not available at the Alsbury site and would require hauling <br /> <br /> <br />from the Colorado River deposits near Silt, Colorado. The haul distance would <br /> <br /> <br />be about 25 miles to Silt. Commercial aggregate plants are presently in <br /> <br /> <br />operation in this area. <br /> <br />Riprap <br /> <br />Riprap for erosion protection on the upstream slope of the dam could <br /> <br />probably come from the cobbles and boulders on the surface along the shoreline <br /> <br /> <br />upstream from the left abutment. Some rocks would probably have to be obtained <br /> <br /> <br />above the proposed high water elevation in order to secure sufficient yardage. <br /> <br /> <br />This source could be supplemented by the oversize from processing the materials <br /> <br /> <br />in the impervious borrow area. All the cobbles and boulders are of subangular <br /> <br /> <br />basalt and are very hard and dense. These rocks are up to 8 feet in maximum <br /> <br /> <br />dimension and would provide an excellent riprap material. <br /> <br />-16- <br />