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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 V ~ Evaluation of Alternatives <br /> <br />C.1 Spillway Alternatives <br /> <br />A feasibility level probable cost estimate was performed for each of the two spillway <br /> <br /> <br />alternatives. Major construction work items were identified, and unit prices and quantities were <br /> <br /> <br />estimated for these items. The following assumptions were made: <br /> <br />· The spillway weir does not require modifications or rehabilitation. The spillway discharge <br /> <br /> <br />chute requires modifications to safely pass the inflow design flood. <br /> <br />· The cost item "Mobilization/Demobilization" is identified to cover the costs of mobilization <br /> <br /> <br />and demobilization of equipment, temporary construction facilities, and bonds and insurance. <br /> <br /> <br />It was also assumed that there is little overhead construction costs such as construction <br /> <br />supervisory personnel. For this type of construction, mob/demob typically ranges from 5 to <br /> <br /> <br />IS percent of the total construction cost. Ten (10) percent was assumed for this cost estimate. <br /> <br />· The existing riprap in the chute area will not be reused for the new construction. <br /> <br />· Rock excavation would be required in the left abutment for the construction of the new <br /> <br /> <br />training wall extension. The weak sandstone bedrock is assumed to be rippable. Excavation <br /> <br /> <br />rock materials are not suitable as fill, and will be disposed of on site. <br /> <br />The probable construction costs, with 20 percent contingencies, for Alternatives 8 I and <br />82 are $815,640 and $915,420, respectively. The cost estimates are presented in Tables V-2 and <br />V -3 for Alternatives 81 and 82, respectively. <br /> <br />Impacts with respect to the man-made environment, the natural environment and the <br /> <br /> <br />existing social structure are equal for the alternatives. Both alternatives are standard practice and <br /> <br />are technically feasible. Alternative 81 takes advantage of the energy stilling capability of the <br /> <br /> <br />steps to reduce the required size of the terminal stilling basin. The flow characteristics for both <br /> <br /> <br />alternatives are very predicable and therefore technically similar. <br /> <br />The main difference between the alternatives is the construction cost. Based on <br /> <br /> <br />construction cost, Alternative 81 is the least cost and therefore, the best alternative and is the <br /> <br /> <br />recommended alternative. <br /> <br />Monument Lake Dam Feasibility ShIdy <br /> <br />50 <br /> <br />BDVLE <br />