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<br />. <br /> <br />. <br /> <br />- <br /> <br />Greeley and Loveland Irrigation Company <br />January 22.23, 2003 <br /> <br />Agenda Item 19c <br /> <br />some holes and leaks, as well as substantial sediment accumulation. Downstream of the <br />embankment the existing pipe is collapsing in some areas, preventing efficient delivery of water. <br /> <br />In addition, SEa reservoir evacuation criteria requires that outlets for Class I dams be capable of <br />draining the top 5 feet of the reservoir in 5 days. Currently, with the existing pump system, high- <br />level diversion, and low-level outlet it would take 10 days to drain the top 5 feet. With the proposed <br />project the evacuation time would be reduced to 6-7 days. The SEa has indicated a willingness to <br />work with the GLlC on this matter, but they will have a to formally request a waiver of the standard <br />criteria and document their reasons. GLlC cites downstream capacity constraints and high cost as <br />obstacles to fully meeting the SEa criteria. <br /> <br />Proiect DescriDtion <br /> <br />Boyle Engineering Corporation has determined that complete replacement of the low-level outlet <br />works is required due to its deteriorated condition. Three alternatives were considered: <br /> <br />1. Cut and Cover Alternative ($1,204,000) <br />2. Cut and Cover Variation ($1,218,000) <br />3. Microtunneling Option ($1,135,200) <br /> <br />Alternative No.1, Cut and Cover - The proposed low-level outlet works would consist of 300 feet of <br />48" diameter pipe through the dam embankment, constructed in traditional cut and cover operation. <br />This would include 220 feet of 48" diameter CML (concrete mortar-lined) steel pipe, encased in <br />concrete, including the 50 feet of inlet pipe leading into the sluice gate chamber. The remaining 80 <br />feet under the embankment would be 48" RCP (reinforced concrete pipe) installed using <br />microtunneling technology to get under City of Greeley water lines. Downstream of the <br />embankment, RCP would extend an additional 1600 feet before discharging into a stilling basin. <br />The water would then conveyed by open channel for 200 feet and through then discharged into the <br />existing culvert under U.S, Highway 34. <br /> <br />Alternative No.2, Cut and Cover Variation, is a variation of Alternative 1 using more open channel <br />than pipe to discharge below the dam. This reduces theRCP pipe below the dam from 1600 to 800 <br />feet and increases the open channel portion from 200 feet to 1000 feet. <br /> <br />Alternative No.3, Microtunneling, is very similar to Alternative No.1, but 250 feet of CML would be <br />installed using microtunnelling technology, instead of 80 feet of RCP. <br /> <br />Selected Alternative. Alternative NO.3" While all alternatives were deemed to be technically <br />feasible, and have equal environmental impacts, Alternative No.3 allows the most flexibility <br />regarding cost and disturbance of surrounding areas. The proposed low-level outlet works will <br />consist of 300 feet of 48" diameter concrete mortar-lined (CML) steel through the dam <br />embankment. The outlet would be controlled by a 48" sluice gate, located in a gate chamber. The <br />50 feet of CML steel pipe leading into the chamber would be encased in concrete, and the <br />remaining 250 feet of CML steel pipe installed using microtunneling technology. Downstream of the <br />embankment, the steel pipe would transition into 1600 feet of 48" reinforced concrete pipe (RCP), <br />discharging into a stilling basin 200 feet upstream of U.S. Highway 34. <br /> <br />The Total Project cost is estimated to be: <br /> <br />1. <br />2. <br /> <br />Construction Cost <br />Engineering Fees <br /> <br />$1,135,000 <br />210,000 <br />$ 1,345,000 <br /> <br />TOTAL <br /> <br />Page 3 of 6 <br />