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Rito Seco FER 4 In addition, about 10 critically eroded areas will be treated with structural measures. The remaining 21 will be treated under the land treatment program at an 80-20 cost share rate. The total lnsrallation cost of the 21 areas treated under the land treatment program is esti- mated to be $994,600. The local sponsors share of [he cost for treat- ment of 21 critically eroded areas is $200,000. An estimated $5,300 annual operation, maintenance and repair cost will be required. The total structural measure installation cost including construction, engineering, pro}ect administration and land rights would be $787,300. The local share of the $787,300 total installation cost is an estimated $78,600. In addition, the sponsors will incur operation, maintenance and repair cost of $10,600 annually. The total average annual cost is $58,900. Average annual benefits are estimated to be $68,500. This results in a benefit-cost ratio of 1.2:1.0. Alternative ~3: A proposed floodway would begin near Highway 159, pass below Salazar Reservoir, cross Rito Seco Creek channel, a county road, Highway 152, Peoples Ditch and outlet into Culebra Creek south of San Luis. The floodway would be approximately 2.7 miles long. The first 0.85-mile would have a bottom width of 300 feet, and a dike on the town side of the floodway with a depth of flow including freeb~~ard of 5 feet. The next 0. 7$-mile would have a bottom width of 300 feet, and a dike on the town side of [he floodway with a depth of flow including free- board of 4 feet. The last 1.02 miles, beginning at the county road, would have a bottom width of 780 feet, and dikes on each side with a depth of flow plus freeboard of 4 feet. A total of 2$0 acres ~+ould be inundated with this alternative. [See Figures 3, 4, and 5l• There would be two siphons under [he floodway. The first below Salazar Reservoir - a 600-foot 36" diameter reinforced concrete siphon to carry approximately 25 cfs of irrigation water. The second would be for the Peoples Ditch - an 800-foot, 36" diameter reinforced concrete :siphon to carry approximately 25 cfs of irrigation water. Where the floodway crosses the county road and Highway 152, reinforced concrete box cul- verts and dip sections would need to be constructed. The proposed floodway is described as follows: Station 0+00: A bottom width of 300 ft. with a flow depth of 3 feet, plus 2 feet of freeboard. At a velocity of 4.4 fps, the capacity is 4,000 cfs. The floodway dike (35,000 cu. yds. of fill) is on the town side of the structure. Station 45+00 to 86+00: A bottom width of 300 ft. with a flow depth of 2 feet, plus 2 feet of freeboard. At a velocity of 5.4 fps, the capacity is 6,800 cfs. The floodway dike (21,85C cu. yds of fill) is on'the town side of the structure.