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3-30 <br />3.9.4 RECLAIMED EPHEMERAL CHANNELS <br />• LOWER ROAD CHANNELS <br />The reclamation of the mine site and road will include establishing stable ephemeral channels <br />across the reclaimed area. Two major channels cross the lower portion of mine road, Munger <br />Creek near the topsoil stockpile and the channel draining the major canyon south of the road <br />near where the waste rock disposal area was proposed. Both channels are now diverted under <br />the road with culverts. When the culverts are removed, dry fords will replace the culverts. The <br />reclaimed configuration of each is shown on Fgure 3.1-10. <br />Calculations for the size of the reclaimed channels on the lower road are contained on Table <br />3.9.5. These calculations are based upon previous surface water hydrology studies for the two <br />lower channels. The calculations are shown in Appendix M(v) for the 100 year event at the 72 " <br />culvert and Appendix M() for the 10 year event at the 42 "culvert. Pages 3 and 4 of Table <br />3.9-5 show the drainage area, flow calculations and channel design for the 18"culvert near the <br />topsoil stockpile. <br />Although the channels have been designed for non erosive water velocities, rip rap will be <br />installed in the channels to protect the fords and gravel on the road surface will minimize rutting <br />of the channel with wheeled traffic and the ensuing erosion. Rip-rap keys will be installed at the <br />upstream and downstream edges of the ford. The rip-rap keys will be a two foot wide by two <br />foot deep slot dug into the channel bottom on both sides of the reconstructed channel. The keys <br />will be filled with one foot top size rip -rap. These rip rap keys will ensure that the fords will not <br />be washed out during high flow , The gravel will be reclaimed from the existing road where the <br />road base is excavated in the process of building the ford. The gravel is a coarse "pit -run" <br />gravel with a top size of about 10 inches and will protect the channel bottom between the rip rap <br />keys. The some of the gravel recovered from the existing road will be placed upon the road <br />surface for the ford to help maintain a firm road base that will not erode or wash out. <br />The fords will be constructed by excavating the existing road surface to create a 15% slope <br />into the stream channel where the slope will be 20% below the high water level of the design <br />storm. Although this is steep, the fords are only intended to provide occasional access to the <br />area and are not intended for daily access. The general design includes an eight foot wide road <br />surface and 1 H to 1 V side slopes. <br />MU Volume I 12 - 18 - 96 <br />