A proposed expansion of Sioux Center’s wastewater collection system could cost between $6.9 million and $9.9 million under three alternatives reviewed by the City Council last week.
The East Interceptor Improvements would replace and enlarge two lift stations, construct new forcemains and redirect wastewater away from smaller mains running through central Sioux Center. The preliminary schedule calls for construction to begin in late 2027 and finish in October 2028.
The improvements are part of the city’s 2022 Sanitary Sewer Collection System Master Plan. Some of the smaller mains in central Sioux Center date to the 1920s, when the community had approximately 1,500 residents.
Bolton & Menk engineer Wes Boyer said the master plan identified a series of projects needed throughout the collection system.
“It really gets flow loading off of that center core, as we call it, through the center of town. And at the same time, understanding future development, particularly in the northern end of town and the northeastern side of town,” Boyer said.
Two Lift Stations and New Forcemains
The project would relocate the current GCC lift station from along Highway 75 to the northeast corner of GCC’s property. A new 10-inch forcemain would run east along 12th Street Northeast and connect with an existing unused 10-inch pipe near the high school.
The existing four- and six-inch GCC forcemains would be taken out of service. Boyer told the council the GCC lift station is currently at or even over capacity.
The city would also replace and significantly enlarge the lift station near Sioux Center High School. Boyer said the new station likely would use three pumps, allowing the pumps to alternate and providing backup capacity.
A new 12-inch forcemain would then carry wastewater south along the Harrison Street and 13th Avenue East corridor toward the wastewater treatment plant. Combined, the proposed improvements would involve approximately three miles of forcemain.
Wastewater Department Head Zeke Ellis said the additional capacity also would benefit established portions of Sioux Center.
“Trying to protect the community…is really what this is all about,” Ellis said. “(It’s about) protecting what we already have here and accommodating for growth.”
Forcemains are pressurized pipes that use pumps at lift stations to move wastewater through areas where gravity alone cannot carry it toward the treatment plant.
Three Alternatives Under Consideration
The primary difference among the three alternatives is how far south the new high-school forcemain would extend before wastewater transitions into a larger gravity sewer.
Planning-level estimates are:
- Alternative One: $7.4 million to $9.9 million
- Alternative Two: $7.2 million to $9.7 million
- Alternative Three: $6.9 million to $9.4 million
The council did not select an alternative during the update.
Boyer said extending the 12-inch trenchless forcemain farther south is estimated to cost less than constructing a longer 21- to 30-inch gravity sewer. However, a gravity line could provide additional options if development eventually moves farther east.
Construction Could Begin in Late 2027
The city planned to submit its facility plan and State Revolving Fund application to the Iowa Department of Natural Resources by September 1.
The preliminary schedule anticipates DNR approval in December, engineering continuing through May 2027, and the project being bid in July 2027. A construction contract could be awarded in September, with work beginning in November 2027 and concluding in October 2028.
Officials cautioned that the schedule could change depending on the length of the DNR’s environmental review.
The city expects to finance the improvements through Iowa’s low-interest State Revolving Fund. The planning and design loan would eventually roll into a construction loan based on the project’s final bid costs.
