Dredging moves forward with small change

Published 10:46 pm Thursday, July 26, 2018

Water returning to Fountain Lake from CDF


Although progress on dredging Edgewater Bay continues to make headway, recent discoveries will mean changing plans slightly to meet the district’s sediment removal goal for phase one, the Watershed District administrator said at Thursday’s meeting.

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So far, Shell Rock River Watershed District Administrator Andy Henschel said J.F. Brennan, the dredging and marine construction company working with the district to dredge Edgewater Bay, has removed roughly 96,000 cubic yards of sediment from the bay. This number is approximately 16 percent of the district’s total goal for the project, which is 617,000 cubic yards of sediment removed.

“They’re well on their way and somewhat ahead of schedule,” Henschel said.

According to Henschel, as the dredge operated it ran into more sand and gravel than expected in certain areas. Therefore, the dredge would likely not be able to remove the entire volume planned for those areas due to how hard that volume has proven to be.

“We’ll have to make up that volume somewhere else,” Henschel said.

Edgewater Bay’s dredging timeline is divvied up into six areas. The district has already completed dredging area six, located in the southwest corner of the bay, and has started on the fifth. This is the area in which the dredge encountered the sand and gravel.

Henschel said the district should not have to reconvene with the Minnesota Department of Natural Resources to approve shuffling sediment removal around to meet its goal. The bathymetry, or underwater map of the lake, the DNR and the Shell Rock River Watershed District worked from to create the initial agreement on sediment removal was created in 2009. When Brennan was preparing for dredging in the spring, it created a new bathymetric map. Henschel said the bay accrued some sediment between the creation of those two maps; therefore, the district can remove some of that sediment to meet its 617,000 cubic yard benchmark.

Henschel said having a hard bottom in those areas will create better habitat and avoid creating a flat bowl on the bottom of Edgewater Bay.

As the project moves forward, water began returning to Fountain Lake from the confined disposal facility Monday.

“What we are finding is that Monday through Wednesday, we meet those water quality (standards) and can discharge, and then we have to throttle it down Wednesday, Thursday, Friday, because it does get a little more turbid,” Henschel said.

Lower turbidity, or water cloudiness due to suspended sediment, occurs earlier in the week because the water has had a chance to settle while the dredge is not pumping water in on the weekends, Henschel said. As the dredge begins discharging into the confined disposal facility again during the week, the water becomes more turbid.

In other action:

The Shell Rock River Watershed District board approved a move to League of Minnesota Cities as provider of the district’s insurance. Security Insurance owner and principal Andrew Petersen said the initial price with the League would be higher, but would save the district money after an audit from Cincinnati Insurance, the district’s current provider, means future rates would increase thanks to additional premiums charged based on subcontracting costs for projects conducted by the district. The League of Minnesota Cities does not have a specific charge for that subcontracting work, and the insurance premiums would be locked in with a non-audit policy, Petersen said.

“For the staff, it helps us in our budgeting to have a more reliable number other than basing it on projects with Cincinnati’s possible increases every time they do an audit,” Henschel said.

Petersen said the coverages are “very comparable.” Coverage through the League of Minnesota Cities would cost the district approximately $44,500 with an annual approximate $1,800 fee. The annual cost of Cincinnati Insurance is approximately $38,500, but Petersen said last year’s audit produced an additional $13,000 they reversed for this year to reach that number.

“They basically did the district a favor because it kind of hit them out of left field, but that would apply going forward,” Petersen said.

Construction for CDF cells two and three will be put out to bid after approval from the board. Their construction was accelerated after the district found peat soil in part of both CDF locations. To move on to the second contract of the dredging process, the district will need cells two and three ready, Henschel said.

Rather than removing the peat, it will be built on, allowing it to compress over the course of a year and for construction to finish in 2019.

“With this new procedure, none of the plans have changed,” Henschel said. “… It’s just the way we’re going to do the construction is different.”

Board manager Al Baaken requested the board talk about drainage in the Shell Rock River near the border to Iowa. He said landowners requested the district facilitate tree removal in a portion of the river that narrows and where some trees fall.

“This has been a problem area that’s been talked about many a times,” Henschel said. He said staff initiated a meeting with the Minnesota DNR, the Iowa DNR, the U.S. Fish and Wildlife Service and the Natural Resources Conservation Service. One solution could be to pond more of the water flowing through the area into the Grass Lake area to help reduce the volume headed through the problem section. The inter-agency meeting would be an opportunity to see what is viable.

Henschel said Shell Rock River Watershed District conservation technician Scott Christenson has a pending grant application in to purchase property in the area and install pump stations to hold flood water during wet seasons.

About Sarah Kocher

Sarah covers education and arts and culture for the Tribune.

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