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<br />I- <br />II <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 />stem will be a rising stem type sloped to match the slope of the dam. The stem will be supported <br />by a concrete grade beam and will be protected by being inserted into a schedule 80 galvanized <br />steel pipe attached to the concrete grade beam. <br /> <br />5. Spillway. The emergency spillway proposed consists of a concrete grade beam wall <br />located in the dam crest. The grade beam will control the spillway crest elevation and will provide <br />a cutoff for water flow and inhibit undercuttmg during discharges, The grade beam and the dam <br />face will be protected from erosion by 30-inches of rip rap with a maximum stone size of 24- <br />inches. The riprap on the dam face will be grouted to prevent the riprap from being dislodged and <br />carried downstream. The spillway will control the flows down the dam face on the right side of <br />the dam and will end in a plunge pool lined with grouted riprap. <br /> <br />Drainaee and SeeDage. There do not appear to be any special drainage problems above th,e dam in the <br />reservoir area. However, the spillway discharges downstream of the dam will present challenges that need <br />to be addressed due to development downstream of the dam. <br /> <br />Seepage from the reservoir is not expected to significantly impact the proposed residential construction on <br />the north and west side of the reservoir, Basement construction however, should be planned to be above <br />the normal hig~ water level if the residence is within approximately 100 feet of the reservoir. <br /> <br />Downstream of the reservoir, there most likely will be an increase in the groundwater level due to the <br />reservoir. Even if the reservoir is lined with a PVC liner, all seepage can not be contained and the area <br />below the dam will increase in moisture conditions. <br /> <br />Sedimentation. Estimates of sediment yield are complex and involve numerous assumptions and <br />laboratory determination of site-specific parameters. However, due to the nature of the soil in the drainage <br />basin above the reservoir, we would not expect excessive siltation of this reservoir. The siltation of the <br />reservoir would be expected to be similar to that experienced in Carter Lake and other front range <br />reservoirs located in the foothills. <br /> <br />COST ESTIMATE <br /> <br />A summary of the estimated constructions costs, engineering fees, and contingencies are shown in Table <br />4. The complete breakdown of the cost of the work proposed for each alternative is shown in Table 5, <br />The costs are based on our past experience with similar projects and also from data supplied by local <br />contractors and suppliers. Quantities were based on a topographic map of the reservoir site provided to <br />us by the Town of Lyons in conjunction with additional cross section surveying conducted at the dam sites <br />during this study. <br /> <br />1. Construction Cost <br />2. Engineering Fees <br />3. Contingency @ 20 % <br />4. Total Project Cost <br /> <br />TABLE 4 <br />ESTIMATED PROJECT COST SUMMARY <br />J3ilt~:r~El~f <br /> <br />$ 1,846,809 <br />$ 184,681 <br />$ 369,362 <br />$ 2,400,852 <br /> <br />$ 0 <br />$ 10,000 <br /> <br />AgST:e:RNRmNE;5i~{ <br />'--' "- "'---------' . ,~^' --__,___'-,. _ .;.,,~0 '. <br /> <br />$ 1,880,208 <br />$ 188,021 <br />$ 376,042 <br />$ 2,444,271 <br /> <br /> <br />$ 10,000 <br /> <br /> <br />Stone Canyon Dam Feasibility <br /> <br />Page 11 <br />