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M. Preliminary Opinion of Probable Costs <br />A preliminary cost estimate was developed using current construction costs for the Colorado area. <br />The estimate is divided into sections to identify costs for rehabilitating the GASP wells, reservoir <br />construction, land acquisition, and permitting costs. <br />A 20% contingency was used for items not identified in this estimate. A more refined cost estimate <br />at the preliminary design stage will allow better identification of project components and a resulting <br />reduction in the contingency item. The largest cost in construction will be the embankment for the <br />dam. Approximately 520,000 c.y of material will need to be moved. <br />Phasing of the project may be possible. The connection of the GASP wells could be deferred as a <br />second phase. This would postpone the expenditure of approximately $275,000 in construction costs <br />for the pipeline /manifold system. The elimination of this part of the project would reduce the <br />allowable diversions down to the capacity of the reservoir that could be filled by gravity from the <br />Peterson Ditch. It would also require increased construction costs of an open channel connection to <br />the South Platte River from the reservoir. There is a slough that flows towards the river, but loses <br />definition once it crosses under the railroad tracks. The proposed pipeline /manifold could be <br />reversed to allow for gravity releases to the South Platte. <br />The release structure from the Peterson Ditch would be a concrete headwall with low head diversion <br />gates. The structure would allow the damming of the canal to create adequate headwater for <br />diversion into the reservoir. A short reach of a trapezoidal open channel canal would be constructed <br />from the ditch to the dam. The water would then be routed through a concrete or steel pipe under the <br />dam embankment into the reservoir. A shutoff gate on the downstream side of the pipe would be <br />installed to allow for topping off the reservoir from other supplies. <br />There are no provisions in this cost estimate for rehabilitating the Peterson Ditch upstream of this <br />project or the Peterson Ditch diversion structure on the South Platte River. <br />The cost estimates show that the proposed project could be constructed for a cost of between $750 to <br />$800 per acre -foot. <br />An amortization schedule was compiled for the project on a 40 year payback period. A $1,600,000 <br />project capital cost was amortized at 4% interest. Annual costs were included for project <br />maintenance, and project operating costs such as pumping energy and carriage charges for the <br />Peterson Ditch. The total annual .ost for the project was divided by 2,200.acre -feet which is the <br />present capacity estimate for the reservoir. The average cost per acre -foot for the 50 year return <br />period is $47. Table 6A is the amortization schedule that was developed for the assumptions stated. <br />If the project is amortized under more favorable conditions such as a 0% or 1% interest rate, the cost <br />per acre -foot is significantly improved. Table 6B and 6C show the costs associated with these <br />scenarios. <br />• <br />16 <br />