Posted on October 24, 2016
By William Morris, Owatonna.com
One year after dredging up an unsightly sandbar below Morehouse Dam, city officials are preparing to go back and do it again.
The sandbar, which City Engineer Kyle Skov blamed on the 2006 reconstruction of the dam and subsequent floods in 2010 and 2014, was removed in September 2015 when city workers used backhoes and dump trucks to haul away approximately 1,600 cubic yards of sediment. The project removed what Skov called an “unsightly” distraction from one of the city’s signature features.
But now, the sandbar is back. When the floods following the Sept. 22 rains receded, they revealed a new deposit of sand and sediment at the foot of the dam.
“It’s basically whatever is pushing down upstream, getting over the spillway and over the dam itself,” Assistant City Engineer Bill Pekuri said. “Every time you get a good rain, it pushes that silt over the dam.”
Pekuri said September’s flooding, which he estimated to be a once in 20- to 50-year event, was particularly to blame, as waters rose nearly to the level of the footbridge above the dam.
“It’s not yearly, but probably after the big events is when it will happen,” he said.
The sandbar is not the only place covered in sediment after the flood. Pekuri said Parks and Recreation workers have been removing sandy deposits from Brooktree Golf Course and the trail just east of Hoffman Drive, among other locations.
“You know, when you’ve got streams running through town, what can you do?” he said.
City officials discussed the sandbar at a supervisor’s meeting in early October, and Pekuri said city workers would again be sent out with a backhoe to scrape the accumulated sediment out of the river. He said the work could take place later this fall or winter, when the ground is harder, and did not immediately know how much it will cost. The 2015 dredging was estimated at about $10,000.
Prior to 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.
“It’s probably going to be an ongoing problem between now and forever,” Pekuri said. “Periodically, when we have these big rain events, we’ll have to go in and dredge it out.”
Source: Owatonna.com
