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Section 6 DESALTING SYSTEM DESIGN PARAMETERS FOR SELECTED COMMUNITIES INTRODUCTION A preliminary estimate of the cost of desalting for each of the selected communities cannot be made until a number of design parameters have been quan- tified. The parameters requiring quantification include economic factors, water quality information, and statistics covering the magnitude of water usage for the cities concerned. ECONOMIC FACTORS In the process of examining the candidate desalting systems, the economic comparison base is the cost of product water in cents per 1000 gallons. This involves determining the total annual costs for producing water by the various methods. To calculate the annual costs associated with the capital costs of equipment elements in desalting systems, the years of amortization and interest rate for financing must be specified. For purposes of this study, a 30-year amortization period and 6 percent interest rate are used. Other economic factors which must be taken into account include items which update building and labor costs to reflect the most recent figures and items which indicate the local economic situation for the selected communities. All capital costs derived from the Office of Saline Water Desalting Cost Calcu- lating Procedures were updated with a building cost correction factor of 1.03 which is based on the most recent building cost index of Engineering News- Record (July 1970h All labor cos ts were updated by a factor of 1.075 from the most recent U.S. Department of Labor cost index (April 1970). In addition, the labor costs were corrected by multiplying by a factor of 0.8 to show the relation of the Denver area labor cost to the U.S. average figure.* Land costs have been assumed to be $400 per acre fo~ the South Platte River Valley and $100 per acre for the Arkansas River Valley. * From Dodge Estimating Guide for Public Works Construction, 1970 annual edi- tion, McGraw-Hill Information Systems Co., New York. 33 0188