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COST ESTIMATING EQUATIONS FOR BEST MANAGEMENT PRACTICES
Citation:
Koustas*, R, R. Raghavan, AND S. Liao. COST ESTIMATING EQUATIONS FOR BEST MANAGEMENT PRACTICES. Presented at ASCE Urban Water Resources Research Council/Engineering Foundation Conference, Snowmass, CO, August 19 - 24, 2001.
Impact/Purpose:
To inform the public.
Description:
This paper describes the development of an interactive internet-based cost-estimating tool for commonly used urban storm runoff best management practices (BMP), including: retention and detention ponds, grassed swales, and constructed wetlands. The paper presents the cost data, cost estimating procedures, and cost equations associated with these BMP. A systematic cost-estimating approach was used to integrate capital costs (construction costs) and operational and maintenance (O&M) costs of individual BMP with inflation and regional costs. Cost per total basin volume (total BMP volume) was used to predict the overall construction costs. Cost per total basin surface area (total BMP surface area) was used to predict the overall O&M costs. The average inflation rate and the CPI were used to determine the cost in year 2000 dollars. Total capital costs were adjusted from the dollar-base year of the cost equation used to the calculations. The total capital BMP costs were multiplied by the CPI for each year after the base year and then summed to obtain the total BMP cost increase resulting from inflation. Total capital costs for the construction of a BMP facility may vary significantly depending upon the region. Regional-cost differences are the result of variabilities in the cost of living, labor costs, and materials costs of a particular location. Regional-cost variations were calculated based on a methodology presented by the American Public Works Association. To adjust for these costs, the total capital costs were divided by an adjustment factor based on regional rainfall zones. The cost functions of the determination of BMP costs typically follow the single determinant equation: C = aPb, where a and b are a constant coefficient and exponent, respectively, and P is the determinant variable.