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Phase II Tasks <br />Utilizing the drainage inventory conducted in Phase I, along with the cleaning of one <br />small drainage system, complete the benefitJcost analysis of system-wide rehabilitation, <br />utilizing the U.S. Bureau of Reclamation's economic analysis guidelines for drainage <br />systems.' Such benefiticost analysis incorporates information on land class, the amount <br />of acres to be drained, and estimated capitalized direct net benefit per acre. The land <br />class usually determines the dollar value of capitalized direct net benefit per acre. This <br />benefiUcost ratio analysis would be performed for three scenarios: <br />a. Rehabilitation. Rehabilitation of the existing drainage system layout and lands <br />served, with only cleaning and selected improvements to existing drainage <br />system features. This would include replacement of existing drains where it is <br />clearly needed, replacement of all existing manholes, re-excavating of the surface <br />drainage system where clearly needed, and installation of drainage pumps for <br />closed basins. <br />b. Replacement. Rehabilitation of the existing drainage system layout and lands <br />served, replacing all subsurface drains, installing manholes as needed under new <br />design criteria, re-excavating all surface drains/wasteways, and installation of <br />dr�iina�a numps i:,• closed basins. � <br />Re-desit?m. Complete re-design and installation of a new Lower Arkansas Valley <br />drainage system, including additional lands to be served by the drainage system, <br />utilizing new information on water contours and the hydrologic conductivity of <br />soils. <br />i. Re-design would include a new drain system layout based on an updated <br />understanding of the hydrologic conductivity of soils, the required <br />spacing of drains, and whatever depth of the drainage system is needed <br />for current and anticipated crop production in the Lower Arkansas <br />Valley. <br />d. A benefit-cost analysis that discounts the benefits and costs to present value will <br />be undertaken. Appropriate life expectancies of three rehabilitation scenarios <br />will be determined. The output of the analysis will take the form of a benefit-cost <br />ratio of the three scenarios in the context of present value. A critical and careful <br />analysis of the costs will be performed: engineering, installation, operating and <br />maintenance. The benefits will be analyzed by ascertaining the ongoing benefits <br />to the different classes of land under the project. <br />i. Most economic analysis and decision making fails to take into account <br />uncertainty. However, many of the components of feasibility analyses of <br />projects are subject to the inability to predict what will happen in the <br />future with certainty. Rather that using single point estimates as inputs <br />to the model, distributions can be used that more accurately reflect <br />� Part of this economic analysis will be informed by traditional U. S. Bureau of Reclamation methodology. <br />See, Drainage Manual: A Water Resources Technical Publication. Bureau of Reclamation, U.S. <br />Department of Interior (1993). <br />