The need for a method of accurate and rapid preliminary design, and cost estimating for wastewater treatment plant construction projects has long been recognized. Various models have been developed which purport to prepare planning or design level cost estimates. Few of these models are responsive to the requirements of the planner or engineer responsible for accurately projecting construction costs for the purpose of alternative evaluation. The CAPDET model was developed with the specific intent of assisting personnel responsible for wastewater treatment planning in the evaluation of wastewater treatment alternatives based primarily on life cycle costs and degree of treatment provided. This cost estimating procedure uses both parametric and unit cost estimating techniques. (Author).