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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />Chapter IV - Formulation of Alternatives <br /> <br />Chapter IV - Formulation of Alternatives <br /> <br />Boyle has developed alternatives, which meet the project purpose of rehabilitating! replacing <br />the outlet system for Boyd Lake Dam while complying with SED guidelines. The proposed <br />alternatives were formulated to address the problems described in Chapter ill of this report. The <br />existing facilities are shown in Figure N-I <br /> <br />As described in Chapter ill, Boyle determined that complete replacement of the low-level <br />outlet works is required due to its deteriorated condition. The proposed alternatives are presented <br />below. Elevations for the figures are based on the City of Loveland 1995 Datum. <br /> <br />/ <br /> <br />A.I Alternative I - Cut and Cover <br /> <br />The Cut and Cover Alternative includes demolishing and removing the existing 400-foot long <br />approach box culvert and replacing it with a 400-foot long open channel, which matches the size and <br />shape of the existing approach channel. An inlet structure with a trashrack would be constructed and <br />50 feet of 48-inch mortar-lined steel pipe encased in concrete would convey water into a gate <br />chamber. A 48-inch sluice gate would control the discharge into a 48-inch mortar-lined steel pipe, <br />encased in concrete, that conveys the discharge under the Canal into an access manhole. The pipe <br />transitions to a 48-inch RCP pipe within the access manhole. 80 feet of RCP would be installed <br />under the City of Greeley water lines using microtunneling technology. The RCP would then extend <br />1,600 additional feet and discharge into a USBR Type N stilling basin. The existing discharge <br />channel would be reshaped for the final 200 feet before entering the existing box culvert under <br />Highway 34. This alternative is presented in Figures N -2 and N -3. <br /> <br />A.2 Alternative 2 - Cut and Cover Variation <br /> <br />A variation of the proposed alternative includes shortening the section of RCP pipe from <br />1,680 feet to 880 feet and increasing the open channel portion from 200 feet to 1,000 feet. This <br />variation was analyzed to determine if an open channel would be less expensive than the RCP. <br /> <br />Boyd Lake Dam Outlet System Feasibility Study <br /> <br />12 <br /> <br />BOVLE <br />