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Dredging the channel

by DEVIN WEEKS
Staff Writer | October 31, 2022 1:08 AM

Sediment is being removed from the channel between Upper and Lower Twin Lakes to improve water quality for wildlife, boaters and the overall community.

The Twin Lakes Improvement Association, a nonprofit formed in 1956 to improve and preserve the historic natural values of Twin Lakes, is working with Idaho Fish and Game, and has retained the services of Envirodredge to remove approximately 8,600 cubic yards of organic material and 330 pounds of phosphorus to improve navigation and water quality in the channel.

The Channel Sediment Removal Project will deepen the navigation corridor to 50 feet wide and up to 7 feet deep, removing 2 feet of sediment on the channel floor. No lily pads or wetlands will be removed.

"It’s really quite fascinating," said Debbie Andrews, president of the Twin Lakes Improvement Association. "They pump the sediment into these filter bags and they drain out. There's a polymer inside that bonds with the organic materials. The water comes out clear and goes back into the lake."

Dredging began Oct. 8 and is expected to be done by the end of this week. The overall project will take up to six weeks to complete, but is expected to be fully finished in the spring. Estimated project costs are approximately $210,000-$250,000.

Boaters who used the channel in recent summers may have noticed plumes of muddy sediment kicked up by boat propellers.

The plumes provided clues to the problem that lie beneath.

"Since dredging was done in the mid-1950s, sediment and aquatic vegetation has filled the channel to the point boats can barely navigate and on occasion pass so close to each other that safety has become an issue," the project is described on the Twin Lakes Improvement Association's website. "The shallow navigation channel is a major concern because it greatly limits boat access between the lakes late in the summer, and it can cause expensive damage to boat propulsion equipment. Also, propellers of each passing boat stir up nutrients that degrade water quality by promoting growth of aquatic vegetation."

No boat traffic will be allowed in the channel until after Nov. 30. The Fish and Game boat launch will be closed throughout the project and will reopen April 1.

"It’s a project that will benefit a whole lot of people," Andrews said.

She said maintaining water quality for future generations is important to the association, which has water rights to Twin Lakes.

"We want to do everything we can to be good stewards of that water right," Andrews said.

The association and Twin Lakes community members have raised the lion's share of funds to pay for the project. About $25,000 is still needed to complete the work.

Visit twinlakesimprovementassociation.org for information.

photo

Courtesy photo

Filter bags containing a special polymer are being used to remove sediment from the channel between Upper and Lower Twin Lakes. The Channel Sediment Removal Project is underway and expected to be completed by spring.

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