Designing a Cost-effective Wastewater Collection System

Marco Island, Florida currently in the third year of a seven-year septic tank replacement program (STRP). The STRP will connect approximately 5,000 new customers to the island's centralized wastewater collection system. Success of STRP is highly dependant on the cost of the project, which is funded by assessments paid by the residents. This study discusses a design methodology developed for STRP aimed to minimize the cost of the project with an efficient design that could be timely implemented. The developed methodology includes a custom-developed spreadsheet that enables accurate calculation of sanitary sewer pipe and manhole quantities, which compose approximately 75 percent of the overall cost. Plan and profile drawings were streamlined through the use of the custom spreadsheet, topographic data obtained from aerial mapping, and Autodesk Civil 3D drafting software. The developed methodology has proven successful with low and accurately predicted costs, few change orders, and on schedule implementation.