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as the reconfigured dam. Each chute includes grouted boulders 2 to 3 feet in diameter. Smaller boulders and stones line the remaining channel bottom as shown in Drawing 4. A boulder sill, stretching across the width of the channel downstream of the second plunge pool, provides grade control on the downstream end of the structure. Both banks are lined with riprap as shown in Drawing 4 to prevent bank erosion. This alternative results in higher water surface elevations for the 100-year flood between stations 1500 and 1000 when compared to the water surface elevations under existing conditions. This is due primarily to the drop of 5 feet being distributed over a 320-foot length, as proposed, versus a vertical drop occurring at the existing dam face. To protect the adjacent properties to the east, a berm is recommended along the left bank. The existing right bank (west) is sufficiently high to contain floods up to and including the 100-year event. Upstream and downstream of the proposed structure the water surface elevation changes are negligible from existing conditions. Thus the left bank berm extends only the length of the proposed structure. This berm is not designed to meet standards set by the Federal Emergency Management Agency (FEMA) for levee protection. The Delta County FIS FIRM map (panel number 080041 0393C, August 19,1991) shows the Gunnison River overtopping much of its banks during the 1 OO-year flood, between the Highway 50 bridge and cross section 1900 at the upstream limit of the study area. In the vicinity of the Hartland diversion dam the 100-year floodplain width is approximately 1400 feet wide over the left bank, extending 3600 feet upstream. Thus a berm or levee at the fish passage structure, as proposed, serves as flood protection from flows that overtop the river bank immediately adjacent to the berm, but not from flood flows that have reached the overbank areas from upstream flooding. 29 I I I I I I I I I I I I I I I I I I I