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Show region and provides daily passenger service via Amtrak as part of an east/ west rail corridor. In 1983, the rising lake began to effect the railroad track structure. Union Pacific raised the track in this area to protect it from the rising water. The elevation ( top of the rail) through most of this area is 4221.0 feet, with the sub- grade ( top of the embankment) at 4218.5 feet. Flooding Impacts on the Northern Railroad Causeway In 1906 Southern Pacific Transportation Company ( SPTC) constructed the Rambo Fill, a wooden trestle and the Saline Fill between Lakeside and Promontory Point, to shorten the time required to go north around the lake. In 1959, SPTC completed the replacement of the original wooden trestle across the lake with a rock- fill and earthen causeway. ( See Figure 4.) The causeway was designed and constructed to have a minimum freeboard ( vertical distance from maximum water level in the lake to the top of the causeway slope protection) of 10 feet. The slope protection design was based on the COE Shore Protection Manual, and was provided by utilizing very large one to three ton stones placed on a 1.5 to 1 slope. The thickness of the large stone layer was five feet. The causeway began to settle 10 years after construction and settles an average of two to four inches per year. Several areas of the causeway have experienced more settlement than the average, up to a half foot per year with a total settlement of up to 17 feet. GSL is subject to sudden and violent storms, with winds over 70 mph. The winds generate waves that can reach eight feet in height and have 20 percent more energy than the ocean due to the higher density of lake waters. The height, length and period of wind- generated waves are determined by wind speed. The calculated " design wave," which is the average of the highest one- third of all waves, is 7.2 feet for the northern railroad causeway. High winds and waves can occur year round. However, most of the damaging wind and waves occur from the north, from April to July, and from the south, from July to August. Prior to completion of the northern railroad causeway, the surface elevation throughout the lake was uniform. After completion of the causeway, however, an elevation difference began to develop between the two arms of the lake, with the south arm being higher. This elevation difference is due to two factors; the majority of the tributary inflow enters the south arm of the lake and the causeway restricts the movement of water from the south to the north arm of the lake. From 1959 to 1982 the freeboard varied from 8 to 17 feet. During periods of the higher water elevations and low freeboard, the slope protection had some isolated areas that eroded and required repair. In January 1983, the average elevation of the crest of the causeway fill areas crossing the lake was 4209 to 4210 feet with some isolated areas as low as 4207 feet. There were approximately 30 miles of fills crossing the lake and 60 miles of exposed slopes. By 1987, the fills crossing the expanding lake increased to 60 miles with over 105 miles of slopes to protect. The decision was made to utilize surplus and scrap box cars to create a " boxcar sea wall" on the north side of the causeway, which allowed the tracks and fill to be raised from about 4206 to 4217 feet. 31 |