Culver authorizes Lake Delhi sediment control project

Gov. Chet Culver signed an emergency proclamation Wednesday that will allow remedial work to control erosion from the silt-laden bed of the former Lake Delhi.

Since the July 24 breach of the Lake Delhi dam, the 6-foot layer of sediment that had accumulated during the past 80 years has been exposed and is eroding into the Maquoketa River, degrading both water quality and aquatic habitat.

The proclamation will allow officials to use emergency bidding procedures for the construction of two rock erosion-control structures – one at the dam and another just below the Hartwick bridge about 2 miles upstream – to impede the downstream movement of sediment.

Officials hope the emergency stabilization project, with an estimated cost of $800,000, can be completed by the end of October.

Project manager Nate Hoogeveen, river programs coordinator for the Department of Natural Resources, said it's critical to stop the head cut – the site of the greatest erosion, where the river is cutting a channel through the silt – at a point below the Hartwick Bridge.

That area has a bedrock outcropping that will provide favorable construction access, he said.

Much of the lakebed is too remote for heavy equipment to gain access, and the layers of sediment remain dangerously unstable in many locations, he said.

The head cut has traveled about 1.9 miles upstream in the 81 days since the dam failed, Hoogeveen said.

The installation of heavy rocks that make up the riffle structures can be accomplished without diverting the river's flow, he said.

Interim DNR Director Pat Boddy said the top immediate priority is stabilizing the existing river channel.

“This is not a silver bullet. We won't suddenly have clear water in the river down below, but it is at least a start at reducing the impact of the sediment until a longer term solution can be found,” Boddy said.

Culver earlier established the Lake Delhi Recover and Rebuild Task Force to develop strategies to aid the rebuilding of the Lake Delhi area and to determine if, and under what conditions, the Lake Delhi Dam should be rebuilt. Its report is due Dec. 1.