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FLOOD06450
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Last modified
1/25/2010 7:09:02 PM
Creation date
10/5/2006 2:17:53 AM
Metadata
Fields
Template:
Floodplain Documents
Designation Number
92
County
Jefferson
Community
Arvada
Stream Name
Ralston, Leyden Creeks
Basin
South Platte
Title
Major Drainageway Planning - Ralston/Leyden Creek, Arvada, Jefferson County, CO
Date
8/1/1977
Designation Date
1/1/1978
Floodplain - Doc Type
Floodplain Report/Masterplan
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<br />I <br /> <br />VI-l <br /> <br />I <br /> <br />I <br /> <br />SECTION VI <br /> <br />Unit Costs <br /> <br />PHASE A BENEFIT/COST ANALYSIS <br /> <br />The costs of land were determined by entity input as to reasonable market <br />value of developed and undeveloped lands. The costs of bridge additions and <br />replacements were obtained through the Colorado Department of Highways and <br />reflected the Phase A cost of construction. <br /> <br />I <br /> <br />GENERAL <br /> <br />I <br /> <br />The alternatives selected to be investigated under the Phase A benefit/cost <br />analysis were designated by the local entities and through engineering <br />judgment to be the best choices considering limited right-of-way, construction <br />costs, and operation and maintenance costs, The alternative selected in each <br />reach is based upon: <br /> <br />Total cost of construction, land acquisition and maintenance for each alter- <br />native was determined for each on M reach-by-reach basis. The life of most <br />structures associated with drainage works is estimated to be forty years; <br />therefore, initial costs were amortized over a forty year period using a 7 <br />percent interest rate. Construction costs used in the Phase A analysis may <br />be found in Table VI-I, <br /> <br />I <br /> <br />I <br /> <br />1. The most suitable alternative for each entity. <br /> <br />2, The optimized design frequency in 1 ight of the damages resulting <br />from the frequency chosen. <br /> <br />Operation and Maintenance Costs <br /> <br />I <br /> <br />3. Detailed design facts and cost estimates. <br /> <br />Operation and maintenance (O&M) include the daily, monthly, and yearly <br />operations by city or county forces to maintain the hydraulic and aesthetic <br />qualities of the flood channel. This would include, but not be limited to: <br /> <br />I <br /> <br />4. Intangible benefits, <br /> <br />Deb r is Remova 1 <br />Removing Sediment <br />Trimming Trees and Brush <br />Mowi ng <br />Access Path Repair <br />Ferti I izing <br />Weeding <br />Amortization of Equipment <br />Wages and Benefits of Employees <br />Reseeding of Damaged Areas <br />Bank Stabilization <br />Repair of Erosion Damage <br /> <br />I <br /> <br />Each of the alternatives chosen was designed and evaluated using three <br />design frequencies (2,10 and 100-year) with three rainfall frequencies <br />for each design giving nine distinct design variations to be considered <br />for each alternative of each reach. <br /> <br />I <br /> <br />The tocl used to determine the relative merit of the alternatives, as required <br />by the engineering agreement with the Urban Drainage and Flood Control District <br />is "Benefit/Cost Analysis." The important consideration in such an analysis <br />is that all estimates must be mutually consistent. In each evaluation, the <br />same basis for estimating prices, calculation methods, and economic factors <br />was used. This continuity in calculation methods results in an ability to make <br />comparisons between alternatives. The comparison is in the form of benefit <br />to cost ratios, as well as the probable annual costs. The anticipated annual <br />costs include the damage dollars to be paid. It is important to realize <br />that the figures calculated may not be the actual dollars to be paid, but <br />that this analysis will indicate the best comparative alternative and its <br />aDDroximate cost ranqe. Only a final engineering design plan would provide <br />the detailed cost and financing strategy, <br /> <br />The unit costs in Table VI-2 were used to determine annual costs for the various <br />alternative solutions, <br /> <br />I <br />I <br /> <br />SECONDARY BENEFITS <br /> <br />I <br /> <br />The secondary or auxiliary benefits are not easily measured in terms of <br />dollars, but they can be so measured if time is taken to get the facts, <br />utilizing suitable experts in many disciplines. <br /> <br />I <br /> <br />In order to realize what future costs represent today or what annual costs <br />may be realized in the future, a 7 percent interest rate has been used which <br />is sufficiently representative of various municipal bond interest rates. <br />The costs have been annualized on a 40-year basis which is a real istic compro- <br />mise between structural and other improvement lives. The effects of inflation <br />have uniformly not been considered in annual damage costs, operation and <br />maintenance charges, and intangible benefits. The inflation rate is and <br />has been quite unpredictable, and with the comparative effect to increase <br />benefit cost ratios, it would not serve a good purpose other than emphasizing <br />the present need for the improvements. <br /> <br />Auxiliary benefits are numerous. A significant list can be prepared for <br />most urban areas by engineers, urban planners, and sociologists, The <br />following partial tabulation is presented for Ralston and Leyden Creeks. <br /> <br />I <br /> <br />I <br /> <br />I <br /> <br />I <br />
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