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• 66 the existing channel alignment and will require excavation to attain these chan- nel slopes. In addition, these two alternatives would require that the Magpie Creek diversion channel be riprapped on the channel banks and bed where PM-CH-15 joins the Magpie Creek diversion channel. Alternative 15-C and 15-D require that the channel alignment of PM-CH-15 be changed to make a smooth transition into the Magpie Creek diversion channel. This alignment is shown on Hydrology ' Hap 2, Appendix A. The channel slope vas estimated from the 1" 200' scale, five-foot contour mapping (1979). Alternative 15-C uses side elopes of 2:1 • and alternative 15-D uses side slopes of 3:1. The first two alternatives for PM-CH-17 use the existing channel slope. Alternative 17-A utilizes side slopes of 3:1 and alternative 17-B uses side [, slopes of 4:1. At the end of this channel is a depression storage area. Runoff will leave this channel, floc across the depression storage area and through the ~• existing nine-foot culvert under the haul road. when the haul road and culvert are removed, these two alternatives will require that the riprap lined channel • be extended downstream so that it may make a smooth transition into the existing channel. The last two alternatives (17-C and 17-D) reduce the amount of work that will be required when the haul road and nine-foot culvert are removed. Both of these alternatives require that the existing channel slope be flattened. Starting at the boundary of G.E.C. and Dorchester, the channel should be graded to a uniform slope to a location 60 feet upstream of the existing nine-foot culvert. This slope vas estimated from the 1" 200' scale, five-foot contour mapping (1479). A smooth riprapped transition between the channel ridth and the culvert ridth is made in the last 60 feet. These two alternatives rill require that the depression storage area be partially filled and compacted so the milder channel slope can be attained. When the culvert and haul road are removed, the transition section will be widened and the riprap lined channel extended downstream to make a smooth transition with the existing channel (PM-CH-10). This channel alignment is shown on Hydzology Map 3, Appendix A. Alternative 17-C uses side slopes of 3:1 and alternative 17-D uses side slopes of 4:1. The hydraulic calculations for each alternative were calculated by normal • depth using the Manning's equation. The channel slopes for all alternatives are large enough to allow normal depth to be a good approximation. The summary of the hydraulic calculations for each alternative is presented in Table 18. Included in this table is the required riprap size. These calculations are based on the 10-year storm peak discharge.