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Louisville District, Army Environmental Command assess environmental impacts of Old Timbers Lake Dam

Published Dec. 2, 2020

The U.S. Army Corps of Engineers Louisville District is currently working with Army Environmental Command to assess the environmental impacts associated with the Old Timbers Lake Dam at Jeffersonville Proving Ground in Indiana.  

The Old Timbers Lake Dam has been classified as a high hazard dam; therefore, some action is required to reduce the hazard classification and to comply with Army and state of Illinois dam safety regulations. 

As the dam no longer serves any mission purpose for the Army, the Army is looking at several options and their associated impacts, including reducing its impounding capacity, modifications to the dam, or removal of the dam.  

According to Louisville District Environmental Engineer Sandy Gruzesky, “OTLD does not meet Indiana, nor Army Dam Safety Management Program dam safety standards, and it does not function to support any U.S. Army mission requirements. The project is to develop an Environmental Impact Statement to analyze the effects to human health and the environment that may result from removing the dam or reducing its water impounding capacity.”

According to the U.S. Environmental Protection Agency, federal agencies prepare an Environmental Impact Statement if a proposed major federal action is determined to significantly affect the quality of the human environment. 

“It is a document required by the National Environmental Policy Act for certain actions significantly affecting the quality of the environment,” Gruzesky said. “It describes the positive and negative environmental effects of a proposed action, and it usually also lists one or more alternative actions that may be chosen instead of the action described in the EIS.”

Old Timbers Lake supports significant biodiversity, which may be identified as threatened or endangered by the Endangered Species Act or by the Indiana Department of Natural Resources. 

According to Gruzesky, the EIS will look at the potential impacts of removing the dam or reducing its impounding capacity to the biodiversity that Little Otter Fork and Old Timbers Lake Dam support.  

The dam currently limits the release of sediments and contaminants to Little Otter Fork that are present within the watershed. Additionally, bald eagles and other migratory birds have been observed at Old Timbers Lake.

Thus, it is important for the Army to evaluate potential impacts and avenues to mitigate effects to make informed decisions, as stated by Gruzesky. 

“While the removal of the dam will not impact military missions, it may impact recreational opportunities, such as fishing within the Big Oaks National Wildlife Refuge,” Gruzesky said. “The dam does not serve as a water supply nor a flood retaining structure.”

The team is evaluating environmental impacts using various studies of current lake and stream conditions, along with hydraulic modeling associated with a controlled dam breech. Lake sediment was sampled and analyzed for explosives, pesticides and metals. Stream hydraulics will be evaluated to anticipate transport of sediment and how downstream habitats are affected as well as any safety concerns regarding flooding. Impacts to specific bird species are also investigated as per the Endangered Species Act, Bald and Golden Eagle Protection Act, and the Migratory Bird Treaty Act, according to Gruzesky.

After the studies are completed, a Description of Proposed Action and Alternatives will be provided to the public and public input sought to further evaluate alternatives and inform future decisions. The public will have an additional opportunity to comment after the EIS is drafted.