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Walker to Berry <br /> March 30, 1999 <br /> Page 3 of 5 pages <br /> channel (will save the structures that are there too). <br /> Added drop structure <br /> Drop st ture / <br /> Ac <br /> tive erosio equilibrium <br /> undercu� --_____ <br /> Drop I <br /> ructure <br /> 2. Add energy dissipating riprap to protect the base of each drop structure. The purpose of this <br /> work is to protect new structures from, and save existing structures from additional, undercutting. <br /> Geotextile liner underneath, slope of riprap 3 horizontal to 1 vertical. Hides concrete drop <br /> structures. <br /> Drop stn ture♦_ Riprap, 2'minimum diameter <br /> Drop structur <br /> Drop ructure <br /> John suggests riprapping the entire reach between drop structures. <br /> 3. Repair the massive erosion feature (Enclosure 5). Reshape, line with a geotextile fabric, and <br /> riprap (Large, like 2-foot diameter rocks, with filter bedding). The purpose of this work is to <br /> arrest additional erosion at this site (will also make it look better). <br /> 4. Install ford crossings at the road (do not use culverts). An upper cut-off wall, discharge apron, <br /> energy dissipating basin and channel riprap to the main drainage will be required. The purpose <br /> of this work is to arrest erosion at the down stream side of the road, and to reduce road <br /> maintenance at these sites (without them, the roads will wash out continuously—culverts are <br /> avoided due to the large sediment loads from wasting of slopes above). <br /> 5. Arrest the head-of-project main channel erosion. This will require reshaping, lining with <br /> geotextile fabric, and riprap from the vicinity of the sandstone ledge in the main channel level to <br /> the base of the slope. The purpose of this work is to arrest erosion in the backfill area. A <br /> sandstone ledge will likely arrest head erosion up the undisturbed drainageway. <br />