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I I I I I I I i I I I I I I I I I I I I borrow soils are available within the area for construction of the proposed dam embankment. It is also envisioned that an adequate supply of riprap will be available at the site. Based on limited testing, rock used for riprap can be obtained by excavating into the existing hillside along the southern end of the reservoir. However, a more detailed testing program will be required for final design to further determine if the rock will be suitable for construction purposes. According to past records, the top 5 feet of the existing dam was added to the original structure in the 1960's and is made up of finer material suitable for use on the upstream surhce of the proposed embankment raise. Below this layer of materials lies a layer of coarse material approximately 1 foot thick. It is possible that this coarse material was the crest of the original structure before it was raised in the 1960's. As a part of the proposed rehabilitation, the top 5 feet of the dam will be excavated, stockpiled and incorporated into the upstream face of the new embank- ment. In addition, a 15-foot wide section of the upstream face of the dam will be excavated down to the existing water surface elevation to ensure that the unsuit- able coarser materials below the top 5 feet of the dam are removed (refer to Figure 5.6). In order to complete this excavation, the water level of the reservoir will have to be lowered about 4-feet. The dam will then be reconstructed with 2.25H:1V sideslopes with a 16 foot crest width to an elevation of 10,404 feet. The upstream face of the dam will be protected from wave action by a 2- foot layer of riprap (sized for a D50 of 15-inches) on a I-foot layer of bedding. The finer material that originally made up the t~ 5 feet of the old embankment will be placed 3-feet thick on the upstream face of the raised section. This is to provide an impervious layer along the upstream slope. Random on-site fill will make up the remainder of the extended embankment. A layer of coarse material will be placed on the crest of the dam as a road base for maintenance vehicles. The downstream face of the dam will be covered with topsoil, seeded and held in place by an erosion control netting. In addition, all of the areas disturbed by construction will also be seeded. According to the geotechnical report, the random fill material which will make up most of the dam embankment is well draining and therefore a toe drain in the new 39