OCR Text |
Show If the salt water does not mix with the fresh water, as is actually found at present, a stratified condition, then the heavier salt water remaining on the bottom will be the first to pass cut of the submerged gates, and freshening practically accomplished the first year. In actual operation, some combination of the two theories might be expected, and the freshening would be accomplished in not to exceed four years. Several types of dike have been considered, among which were the typical railroad fill of earth, sand, gravel, and roek » This type of dike in the opinion of most of the engineers making the study, applied its weight or downward pressure on a restricted area, with a probable resultant displacement of the unstable materials below, in lateral directions on either side and thence upward until equalized. Another objection to this type was the high maintenance due to erosion by wave action and inability to maintain materials en steep side- slopes. The Lucin Cut- off, Western Pacific and Saltair Railroads have demonstrated that such a type fill can be maintained under conditions much mere severe than encountered on the proposed unit east of Antelope, as to bottom conditions, unrestricted wave- action and extremely heavy loading with a pounding reaction. These railroad fills across the Lake are feasible. They are operative and have been for many years. As to their economy, which is a different consideration, they are comparable to this project in no way since they are built for a different purpose, and under very much different conditions. Another type dike considered was piling and lining with lumber, both entirely of lumber, and earth- fill between lines of piling. In such a type, the forces, reactions, weight and loads are transmitted through piles into the bottom materials of the lake, the resultant of all these stresses and strains being to produce stability. This type of structure only for different loading conditions, has proved feasible not only on part of the Lucin Cut- off, but also at Saltair, and if feasible at those places, then under conditions more favorable as to bottom materials, protection from wave action and 1/ 10 , of the loading should also be feasible. These existing structures together with an observance of what nature sets down for us in the form of beach slopes, lead us to the bread, flat- sloped type of dike for increased stability, and less cost of maintenance. In other words, it is building more in tune with nature. This type of dike ( 1^: 1) side- slopes, for a fill of 14 feet, is 460 feet wide • n the base, contains 130 cubic yards per running foot, and fcr present lake stage would have 2 feet of salt water against it on the outside and 7 feet of fresh water on the inside, the distance between water- edges being 325 feet. The top of the gravel roadway was figured to be at elevation 4211, six feet higher than the high lake stage for the past 40 years, and 12 feet higher than present stage. The south dike from mainland to Antelope Island is 2,5 miles, has an average fill of 10.5 feet, all on dry ground at present and contains 1 million yards. The north dike from Antelope Island to Syracuse point is 5.2 miles, has an average fill cf 14 feet, ( average depth salt water 2 ft., maximum 7 feet for 1/ 2 mile) and contains 3* 5 million yards. The cost of this project, including gravel roads on top of dike, - 19 - |