Preliminary Cost Estimation Models for Construction, Operation, and Maintenance of Water Treatment Plants

Abstract

Reliable cost estimation of construction, operation, and maintenance (O&M) of water treatment plants is essential for project planning and design. The authors have developed construction and O&M cost models for different unit operations and processes involved in water treatment plants. These models are developed from historical cost data and can be used to develop preliminary cost estimates for major project components and to screen alternative process trains of a water treatment project during the planning phases of the project. The historical cost data were updated to April 2011 costs by using cost indexes from Engineering News Record (ENR) and Bureau of Labor Statistics (BLS), in addition to April 2011 costs of energy and labor. This paper presents the use of a single cost index to further update construction and O&M costs. This approach has significant advantages over using multiple indexes (such as ENR and BLS indexes) for different cost components. Using the method presented in this paper, future cost updating by ENR construction and building cost indexes becomes simple and straightforward. Actual bid prices for one new water treatment plant construction and two water treatment plant expansion projects were obtained from reputed consulting firms and compared to estimated costs by using the cost models presented in this paper. Further validation is recommended by use of the equations and comparisons of the costs to the detailed estimates and actual bids. Accurate forecasting of the costs of a project is site specific and cannot be generalized. Design plans and specifications are needed to develop accurate cost estimates based on equipment, materials, and labor.