Major Wastewater Infrastructure Projects Nearly Complete

The City of Sioux Falls is investing $25 million in wastewater infrastructure in northeast Sioux Falls. These four miles of huge sanitary sewer pipes will convey more than 90 percent of the City’s wastewater, and the two-year project is scheduled to be complete in the fall.

The project includes the replacement of a 66-inch-diameter pipe with approximately 1.8 miles of 72-inch-diameter gravity sewer line from west of Cliff Avenue and Chambers Street to the Main Pump Station near I-229 and East Rice Street. The project required boring a tunnel under I-229 where the new pipe will reside. The trenchless construction (tunnel boring) under I-229 was completed using a 96-inch-diameter earth pressure balance machine. A cutting face at the head of the machine cuts and ingests soil and rocks into a crushing chamber and auger system, which transports the excavated material from the face of the machine back out the tunnel for disposal. Steel casing pipe is welded behind the machine and hydraulically pushed forward at a constant pressure. On average, the machine can move roughly 1 foot per hour.

The crossing underneath I-229 is 350 feet long and took approximately one month to complete. Tunneling began on July 10 on the east side of I-229 and emerged on the west side of I-229 on August 8. The 72-inch pipe will be placed within the 96-inch casing pipe on rails to ensure the sewer pipe is on the correct line and grade.

“This project has gone extremely smoothly, even including the risks associated with tunneling under a major interstate. Our wastewater infrastructure will be stronger than ever and ready for the continued growth expected for our city,” says Dustin Posten, Civil Engineer.

Another ongoing project includes the installation of 2.3 miles of 42-inch-diameter force main pipe connecting the new gravity sewer line to the Water Reclamation Facility. The two projects will accommodate future flows and reduce the risk of backups and sewer overflows. The new pipes also are manufactured using state-of-the-art materials and should last nearly a century.

These projects are possible using dedicated funding from Water Reclamation revenues. The rates that homeowners and businesses pay for sanitary sewer services are invested back into the infrastructure that serves the system.