WATERLOO — The city has hired an engineering firm to help repair its downtown Cedar River dam.
City Council members have authorized up to $27,500 for AECOM Technical Services Inc., of Waterloo, to develop plans for an inspection process to determine why the rubber bladder dam is leaking air.
The problem prevented the city from inflating the dam this summer for the first time since it was installed 10 years ago.
“The issue is we don’t know where it’s leaking air,” said City Engineer Jamie Knutson. “It could be the bladder itself has a hole in it, which you would just patch like a tire.”
But Knutson said the leak also could be in the piping located in the dam itself, or from a flexible piece of metal piping from the internal piping to the bladder. The leak is in the eastern-most of three bays on the dam, located just downstream from Park Avenue.
AECOM will prepare a contract for private contractors to install some temporary gates to keep water from flowing over the third bay. Those gates were part of the city’s purchase of the Obermeyer Hydro Inc. dam in 2007, but have been in storage to date.
Engineers would then inspect the dam to find the leak and prepare plans for the repairs.
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Knutson said plans will include having spare parts on hand to make the repair while the water is diverted for the inspection process.
“We don’t know what the cost is going to be to fix this because we don’t know what the repair is,” he added. “We hope to get it done before the snow flies this winter so it can be inflated next year.”
The bladder dam was part of the city’s Riverfront Renaissance plan, which also included river wall repairs, downtown river walks and the RiverLoop Amphitheater. Construction on the dam started in 2007 but wasn’t complete until 2009 due to record 2008 flooding, which caused delays.
Rubber bladders across the low-head dam are inflated during summer months to raise metal gates, which boost the upstream river level by 4 feet to enhance boating and river recreation.
The bladders can be deflated during high water periods to avoid exacerbating flooding upstream.
Knutson noted the city had avoided any major repairs to the dam until this year.