CLINTON — Unwilling and unable to spend $100 million to replace miles of the city’s oldest sewers, the city of Clinton plans to take an inventory of the infrastructure before starting a significant piece of the long-term control plan.
The city needs to complete sewer separation in the basin six area, which spans from the Mississippi River to Bluff Boulevard and is bordered by Seventh Avenue North and Eighth Avenue South.
“We could just go through and separate everything, but that would cost hundreds of millions so we need to do some studying of the basin,” Craft said.
The long-term control plan stipulates the deadlines for completing projects mandated by the Iowa Department of Natural Resources and Environmental Protection Agency to fix the city’s combined sewer overflow problems.
While the city has the first seven years of the 25-year long-term control plan laid out, the years beyond are uncertain.
“It leaves kind of a big question mark in the years eight through 25, being the basin six separation area,” City Engineer Jason Craft said.
Basin six contains the city’s oldest sewers, which Craft called a “tangled web of failing clay sanitary lines and large brick sewers.”
“Many of the intakes go right into the sewer, right into the system and that means it overwhelms it. Every time there is a significant rainfall, there’s an overflow at the First Avenue pump station,” he said.
Craft estimated there are between 30 and 50 overflows at that pump station annually. The city’s consent decree mandates the city have between four and six at this pump station.
While the city has First Avenue pump station upgrades and reconstruction planned for 2018 that will provide more sewer capacity, staff are unsure how much combined sewer overflow events relief it will provide. It also will need need some extra data to properly size the project.
The basin six sewer separation is scheduled for years 2019 to 2035 and is estimated to cost between $35 million and $50 million.
To plan for the most cost-effective separation, the city will hire an outside contractor to perform an analysis of the basin six infrastructure.
The study would cost no more than $100,000 and entail looking at every manhole and intake, pipe sizes, flow direction, pipe conditions and doing a structural analysis of the infrastructure.
Once the information was gathered, it would be available through a geographic information system so the city would have a computerized database to reference and add to when moving forward.
“It’s the correct way to do things. It’s what any other community would do,” Craft said.
The city has funds available for the project and would like to start no later than this spring in order to be complete by July 1 so the city can determine what sewer projects need to take place to reduce the amount of combined sewer overflows.
Craft will issue requests for proposals and come forward at the second council meeting in October for the City Council to approve.