Posted on June 30, 2016
By Mike Brownlee, nonpareilonline.com
With the sun shining and warm temperatures, Lake Manawa in?Council Bluffs was a popular destination Tuesday afternoon.
Kayakers paddled the perimeter, while tubers, water-skiiers and jet-skiiers had fun at higher speeds. And, of course, anglers tried their luck from the shore and from a boat.
One vessel currently on the lake moves slower than the rest, with a purpose that will benefit anyone that stops by the state park in the years to come. A dredging barge is working to remove a large amount of sand from the lake bottom.
“Our goal is to make the lake deeper, with the ultimate goal to improve water quality,” said Bryan Hayes, a fisheries biologist with the Iowa Department of Natural Resources.
Based in Lewis in Cass County, Hayes oversees 10 counties in the region, working on lake improvement projects, among a variety of duties.
Dredging is the first step in a Lake Manawa project that will work on improving water clarity on the lake, while also eliminating the algae blooms that make their unwanted presence felt each summer.
Hayes explained that the lake’s maximum depth is 12 feet, with large areas that are only 6 to 7 feet deep. The current dredging is concentrated on a 60-acre area within the 715-acre lake and will take some sections as low as 16 feet deep. Hayes said that increase in depth will improve lake health.
The dredging project is the first on Lake Manawa since 1982. Before that, an extensive 1960s effort deepened significant portions of the lake. Hayes said dredgings are infrequent because of the cost.
The current project comes with a $4.2 million price tag, paid for by a statewide lake restoration fund created in the mid-2000s.
“We’ll learn a lot about what we can do to Manawa from this,” Hayes said of the project. “After this dredging, we’ll evaluate how it went and move on to the next project. Over the next 10 years we hope to implement more projects. To get to where we want to, it’ll take that long.”
Crews with JF Brennan Co. of La Crosse, Wisconsin, arrived in Council Bluffs in March to get set up, and dredging started on April 15. The project is expected to be completed by mid-July.
At Lake Manawa State Park Tuesday, Casey Evenson, project manager for Brennan, took a group including Hayes and Mark Richardson with the natural resources department out for a look at the dredger.
“This is where the whole process starts, right here,” Evenson said.
The machine uses a piece of equipment called the ladder to lower a rotating cutter, which loosens sand at the bottom. The sand is sucked into a pipeline that takes it to shore. The dredger can cover about 75 feet at each of its anchor locations on the lake.
The sand makes its way to shore through pipes that sink to the bottom of the lake when full of sand. As a precaution (the pipes are almost always at the bottom, Evenson said), there are numerous signs and colored buoys on the lake that warn about the pipe and the dredging project. Hayes and Evenson encouraged boaters to use caution around the machinery and the pipes, even over the weekend when crews aren’t working.
“We want to keep the lake open to boating during this project,” Hayes said. “We caution people to follow signs. We have a busy boating weekend coming up.”
On shore, Brennan has set up what they call “the plant” – an area with machinery that processes the pumped-in sand.
After being cleared of debris, the sand goes through two pieces of machinery that separate as much water from the sand as possible. The water is pumped back into the lake, while the sand is piled high in large hills nearby.
Operating six days per week, 24 hours per day, Brennan is able to pull about 400 cubic yards of sand from the lake every hour. The company is slated to remove 500,000 cubic yards of sand from the lake in all.
According to a release, the DNR plans market the sand for use on construction projects, road projects and the like.
Hayes said one key element of the dredging project is making sure not to alter how much water the lake receives from Mosquito Creek or how much water the lake loses to Indian Creek.
“We want to be less dependent on water from Mosquito Creek, also,” he added.
To help make sure that happens, the dredging project will re-establish an important layer of sediment as the lake floor. Brennan’s equipment punches through the sediment layer, removes the sand, and allows the sediment to settle to the bottom.
Additionally, after sand removal is complete, the contractor will put any removed mud and sediment back onto the floor to balance out water depth.
Hayes noted the department wrapped up a similar water-quality project – which included a dredging – on Prairie Rose Lake in Shelby County last summer.
As the tour rode from the dredging barge back to the natural resources department dock, a few boaters passed. Families had fun on the beach. As he looked out on the lake, Richardson with the DNR was optimistic about the benefit of the water quality project.
“People really want to use this body of water,” he said. “They really want to.” Hayes is just as excited about the future of Lake Manawa.
“For recreation, boating and fishing and more, this is an important resource. This is a great project,” he said. “Lake Manawa is a big one for us.”
Source: nonpareilonline.com
