The Fourmile Sewer Interceptor project extended from the Wastewater Treatment Facility to the constructed Fourmile Interceptor Extension project at Broadway Avenue. This was an expansion project to serve the communities of Ankeny, Altoona, Bondurant, Des Moines, and Polk County. Design capacities for the projects are from approximately 50 MGD to approximately 80 MGD. Allowable infiltration of new sewers was reduced to 100 gal/in dia./mile/day for this project, and final testing results averaged around 25 gal/in dia./mile/day.
The project was separated into five segments with four construction contracts. The project included construction of approximately 16,700-feet of 72-inch and 20,100-feet of 60-inch sanitary sewer through a mix of industrial, commercial, residential, and agricultural areas within the City of Des Moines and Polk County at depths up to 25-feet including open cut and trenchless installation methods. The new sewer primarily paralleled an older sewer/s and an additional project was performed to investigate and evaluate the condition of existing sewers and manholes. This project also included two active railroad crossings requiring significant coordination with the railroad.
With the exception of geotechnical engineering, Snyder & Associates completed all aspects of the project including comprehensive facility planning, wetland delineation, right-of-way acquisition and negotiations, construction documents, construction observation, construction staking, and construction administration.