Stillwater bridge repairs may harm rare mussels
Repairs of the existing lift bridge at Stillwater, Minn., could result in the incidental take of some rare mussels from the St. Croix River, under a permit the Wisconsin Department of Natural Resources proposes to issue for the 2012 project.
Incidental take refers to the unintentional loss of individual endangered or threatened animals or plants that does not put the overall population of the species at risk.
The lift bridge connects Wisconsin State Highway 64 and Minnesota State Highway 36 over the St. Croix River in St. Croix County. The Minnesota Department of Transportation in coordination with the Wisconsin Department of Transportation, proposes repairs to stabilize the existing bridge and piers.
The presence of the state threatened Rock Pocketbook (Arcidens confragosus) and Buckhorn (Tritogonia verrucosa) mussels has been confirmed at the bridge site, no other state or federally listed mussel species were found in the project area. DNR staff determined that the proposed project may result in the incidental taking of some mussels.
To minimize impacts to the river bottom, temporary floating cofferdams will be placed around the piers. Although the cofferdams are floating, materials will be used to anchor them at the base of the piers, and some excavation may be required. Barges will be used to access the piers and structure of the bridge, and will require spudding to anchor the barges along both sides of the bridge. The spud poles will be set in an area limited to two 200-by-600 foot strips on either side of the existing bridge. The spudding could result in the loss of some mussels. Once removed, the project will not result in the destruction or adverse modification of habitat that is necessary for these state threatened mussels.
DNR staff concluded that the proposed project will minimize the impacts to the mussels by adhering to conservation measures; is not likely to jeopardize the continued existence and recovery of the state populations of these species or the whole plant-animal community of which they are a part; and has benefit to the public health, safety or welfare that justifies the action.
The conservation and mitigation measures to minimize the adverse effect on the threatened species will be incorporated into the proposed Incidental Take Authorization. Copies of the jeopardy assessment and background information are available by searching "incidental take" on the DNR website or upon request from Rori Paloski at 608-264-6040.
Public comments will be taken through April 20 and should be sent to Rori Paloski, DNR Bureau of Endangered Resources, P.O. Box 7921, Madison, Wis. 53707-2971.