FLOOD10335 - Laserfiche WebLink

Home Browse Search

. ( " ( '. L ) 16 . : r'o!!:.!'.': :. J i" ."~ '.:- !.. _.,.~_._... ......-o--._:..._~ Th~- -total' -Sf;;~g~ - ca~~bi ~y~~~f.th.e~--.struc1:~;; . ~ii.'~'be 1',615. acre- feet, of which 1,045 acre-feet will be allott'ed to flood detention storage. In addition, 570 acre-feet of storage wj,11'.be provided.~for-. the accumulation of sediment estimated to occur over a 50-year period. This is equivalent to 1.64 inches of sediment. The principal spillway is an ungated concrete outlet conduit installed through the d~ at channel grade and no storage other than sediment will occur in the reservoir. The remaining 36 percent of the watershed area above the High Line Canal contains 3.75 square miles. The High Line Canal presently has adequate freeboard capacity below the crest of the high spoil bank to have a retarding effect on the runoff fram this area in all stor.ms up to about a lOO-year frequency storm. The sponsors have been working since the flood of 1958 to eliminate all channel restrictions in the.Indian Wash channel and provide a unifonn capacity equal to that of the culvert under the Denver and Rio Grande Western Railroad bridge. This capacity is about 1,000 cubic feet per second. . The release rate fram the structure through the principal spillway when the reservoir is full to the level of the west emergency spillway .' is 211 c.f.s. However, the average release rate is 169 c.f.s. This rate will empty the floodwater-retarding pool frem such a storm in three days. . The structure will be a rolled earth-fill dam with an ungated concrete principal spillway. Emergency spillway release will be provided by shaped earth section through the west abutment. I~ will be seeded to grass and designed to carry the maximum six-hour storm. (See Table 3 and additional data in Section 2). The total estimated cost of installing the structural works of improvement is $389,036. The cost distribution is shown in Table 2. A typical floodwater-retarding structure is shown on Figure 3. .