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•- 15 - <br />Slope Protection: The on-site clays and fine sands and silts are • <br />susceptible to water erosion. Therefore, slopes and channels <br />subjected to beach or stream type action will require protection. <br />Several types of protection are possible. Riprappin9 can be used but <br />due to the large difference between gradation of the fine-grained <br />embanlanent materials and riprap, use of a filter bed or fabric below <br />the riprap will be required as a transition. well cemented sandstone <br />excavated from the steep slope along the haul road would be a poten- <br />tial source of riprap. A suitable riprap bedding material may be <br />obtainable from granular borrow along the river; however, processing <br />the material to proper gradation will be required. If water level <br />fluctuation is confined to a relatively narrow range, partial proteo- <br />tion of the slope can be provided. For this case, a minimum 10 foot <br />wide bench should be provided at the tce of the riprap. <br />we understand that spillways throuc~s the embanlanent will also be <br />provided. Due tc the erodibility of the on-site fine rained soils in <br />their natural as well as cre~r.scted condition, the spillway should be <br />protected by use of riprap, slope mattress, grasses, etc. Protection <br />should be adequate tO prevent head cuttirg of the channel into the <br />reservoir. well cemented sandstone material could also be used for <br />energy dissipaters. If water velocities are below erosion levels or <br />periodic repair of spillways is conducted after periods of flow, the <br />riprap can be eliminated. <br />Instrumentation: Instrumentat:~~n in the form of settlement ~mnuments <br />and open end observation wells should be provided to evaluate the <br />performance of the structures during operation. we recommend a <br />reference point monument be provided near maximum section on the crest • <br />