Laserfiche WebLink
<br />New Storage Facili- <br />ties, On-Channel <br />(Alternative I-A) <br /> <br />Potential water development under <br />this alternative is illustrated hy the <br />Two Forks reservoir, which would <br />be located just downstream from the <br />confluence of the North Fork and <br />mainstem South Platte River. The <br />total design capacity of the Two <br />Forks project would be about 450,000 <br />acre-feet to include flood control, <br />sediment storage, water supply. and <br />surcharge storage. <br /> <br />Supply <br /> <br />The average dependable municipal <br />water supply provided hy such a <br />project would be 30,800 acre-feet. <br />The estimated return flows from the <br />municipal use of this additional water <br />would be about 20,600 acre-feet an- <br />nually. Agricultural reuse of return <br />flows four times downstream would <br />provide an additional 7,600 acre-feet <br />of irrigation water deliveries. <br /> <br />Costs <br /> <br />The 1980 cost estimate for construc- <br />tion of the assumed project is $239 <br />million. The interest cost during the <br />period would be over $99 million by <br />the time construction would be com- <br />pleted in 1992. The annual costs for <br />operation. maintenance. and replace. <br />ment would be $4.7 million. <br /> <br />Impacts <br /> <br />The investment required would total <br />over $338 million in construction <br />costs and interest during construc- <br />tion. Net economic benefit would be <br />about -$161 million. <br /> <br />Some water quality benefits would <br />occur from releases of water in this <br />part of the basin during periods of <br />normal low flows downstream. The <br />projected impacts on wildlife and <br />fisheries would cause a large negative <br />change from present conditions. The <br />creation of lake fisheries could re- <br />duce some of the large negative im- <br />pacts caused by the loss of riverine <br />fisheries. <br /> <br />New Storage Facili- <br />ties, Off-Channel <br />(Alternative I-B) <br /> <br />To illustrate water resources devel- <br />opment under this alternative, the <br />project considered was the proposed <br />West Plum Creek Reservoir located <br />in Douglas County. The proposed <br />project would consist of a diversion <br />dam on the South Platte River, a dam <br />and reservoir on West Plum Creek to <br />store South Platte River flows, and a <br />tunnel connecting the Foothills Fil- <br />tration Plant to the West Plum Creek <br />Reservoir. <br /> <br />Supply <br /> <br />The average dependable municipal <br />water supply provided by the design <br />project would be 30,800 acre-feet. <br />The return flows from the municipal <br />use of the additional wa ter would be <br />20,600 acre-feet annually. Agricul- <br />tural reuse ofretum flows four times <br />downstream would provide an addi- <br />tional 7,600 acre-feet of irrigation <br />water deliveries. <br /> <br />Costs <br /> <br />The 1980 cost estimate for construc- <br />tion of the design project is $793 <br />million. The interest cost during con- <br />struction would be $329 million. The <br />annual costs for operation. main- <br />tenance. and replacement would be <br />$4.7 million. <br /> <br />Impacts <br /> <br />A total investment of$1.12 billion in <br />construction costs and interest during <br />construction would be necessary in <br />this alternative. Net economic bene- <br />fits would be nearly -$542 million. <br /> <br />The reservoir site is on a stream <br />where no threatened. endangered, <br />or high interest species are found. <br />Moderate positive change to the fish- <br />ery could occur as a result of project <br />construction. Wildlife impacts would <br />be a negative change from present <br />conditions. <br /> <br />Management Changes <br />of Existing Facilities <br />(Alternative I-C) <br /> <br />This alternative would consider the <br />reallocation of flood control and water <br />conservation storage in Chatfield <br />Reservoir to water supply storage. <br />Chatfield Reservoir is located on the <br />mainstem South Platte River. about <br />2 miles south of the City of Denver. <br />and is operated by the U.S. Army <br />Corps of Engineers as a flood control <br />project. The reservoir includes 20,000 <br />acre-feet for sediment storage and <br />215,000 acre-feet for flood control. <br />If operational procedures for flood <br />control were changed, the reservoir <br />could provide up to 54,000 acre-feet <br />for project water supply. <br /> <br />Supply <br /> <br />The average dependable municipal <br />water supply provided by the design <br />project would be 6,000 acre-feet. <br />The return flows from the municipal <br />use of the 6,000 acre-feet of water <br />would be 4,000 acre-feet annually. <br />Agricultural reuse of the return flows <br />four times downstream would pro- <br />vide an additional 1.500 acre-feet of <br />irrigation water deliveries. <br /> <br />Flood Control <br /> <br />Additional use of these existing facil- <br />ities for water supply storage might <br />be expected 10 reduce their flood <br />control value. <br /> <br />Costs <br /> <br />New construction costs have not <br />been estimated, as this alternative <br />involves only changes in operation. <br />Annual costs have not been esti- <br />mated. for the facilities are now <br />being operated and maintained. <br /> <br />Impacts <br /> <br />It was assumed that no additional <br />investment costs would be required <br />in order to implement this alter- <br />native. The present value of project <br />benefits less the present value of <br />project costs would be $6.3 million. <br /> <br />The projected impact on the fisheries <br />and wildlife would be a moderate <br />positive change from existing con- <br />ditions. <br /> <br />3 <br />