Avid park-goers may have noticed the Straight River looked a little more “green” this year around the Morehouse Dam — and not from the color of the water.
What many believed was thanks to the drought, the apparent sandbars, dunes and foliage near the dam can also be credited to the way the dam was designed some 15 years ago.
According to City Engineer Kyle Skov, one of the big reasons it appeared you could see the bottom of the river this summer was because of the sediment build up that continues to occur. The build up, he said, is a result of how the dam was designed during its 2006 reconstruction.
“The engineers didn’t want to build [the dam] this way, but the community did,” said Skov. “The community wanted the cascading water and the [Minnesota Department of Natural Resources] wanted the fish passage. Those things result in water slowing down and the sediment deposits we see now.”
Starting Monday, a crew from the city Public Works Department began clearing away the built up sediment, a project Skov said will take two days with cleaning of the area and streets included. Though sediment removal would typically fall under a project for the Parks and Recreation Department, Skov said the obvious reason is his department having the necessary equipment and it falling under his purview.
This is not the first time a backhoe and dump truck have been called to the dam. Skov said the city cleared out sediment about three years ago, too, and a sandbar directly below the dam was notably removed in 2015 and 2016 as a result of major flooding events.
“There is more erosion when we have floods, and more erosion upstream results in more sediment depositions,” Skov said. “We won’t be clearing it out every three years, it will depend on flooding events and when and how they happen.”
Prior ot the 2015 dredging, the city council had considered a much more expensive proposal to create new structures to change the flow of the river through the dam and prevent sediment buildup. In the end, the city settled on dredging as needed, and obtained a Department of Natural Resources permit allowing further maintenance as needed.
At the time of the 2016 sandbar removal, Skov called the sandbar an “unsightly” distraction from one of the city’s signature features.
“The sediment build up isn’t dangerous, it’s just some people in the community don’t like how it looks,” Skov said. “It’s really just cosmetics.”
Though the two days of construction are less than scenic, Skov said the crew will clean up everything by the end of the day Tuesday. He also said this will be an ongoing “issue” for as long as the dam remains designed the way that it is.
“This is not going to go away,” he said. “The design they came up with results in sediment, and they knew that when they designed it.”