Clamshell Mechanical Dredge Production and Cost Estimation

Abstract

Mechanical clamshell dredges are a versatile platform for performing dredging operations. The relative mobility, suitability of use for a variety of sediment types, and deep dredging capability result in the use of mechanical clamshell dredges for a variety of dredging projects. Accurate estimates of overall dredging project costs are important for both dredging contractors and entities soliciting dredging projects. This thesis presents a method for determining the production rate and dredging project duration for a mechanical clamshell dredge. The production rate is combined with cost inputs to determine an overall project cost.

The methods and cost inputs are developed with a Microsoft Excel-based estimating program. The program utilizes methodologies for estimating digging production rate and hauling production rate, and utilizes cost inputs from a variety of sources. The program allows for reasonably accurate estimates when limited information about the project or dredge specifics is known. At the same time, the program allows the user to incorporate project-specific knowledge in order to refine the project estimate.

The results of the estimating program are compared with actual winning bids from eight recently completed dredging projects in the United States as well as independent government estimates performed by the United States Army Corps of Engineers. The estimating program generated a mean absolute percentage difference of 23.8% from the winning bids, compared to 33.5% for the government estimates. When compared with a previously developed clamshell dredge estimating program, the mean absolute percentage difference was 14.0%.