Stepping lightly amidst nature
Mississippi backwater project requires an extraordinary approach
Sometimes it takes extra effort to do the right thing. And rebuilding an 84-year-old transmission line in the backwaters of the Mississippi River proved deserving of extra effort. It called for specialized equipment, including an airboat to erect more than two miles of transmission line through the pristine Upper Mississippi River National Wildlife Refuge near Nelson, Wisconsin.
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A foundation type called helical pile is being used on the majority of structures for the rebuild. Steel bases weighing nearly 900 pounds support the new transmission towers.
“This foundation type allows installation without excavation using a minimal amount of equipment and crew which is very beneficial from both a cost and environmental perspective in the Refuge’s sensitive terrain,” said Chris Strom, senior engineer transmission. “All foundation materials were able to be transported to the structure locations using the airboat. Underlying soil conditions are poor, so the helical piles are driven to the depths necessary for adequate support.”
The project required working closely with the U.S. Fish and Wildlife Service and the US Army Corps of Engineers because transmission line is on designated federal wildlife refuge land.
“Due to the location of this transmission line rebuild, we had to take into account the environmental aspects in our permitting,” said Ellen Heine, senior siting and land rights agent. “We appreciate the efforts of the Fish and Wildlife Service, the Corps of Engineers, the Wisconsin DNR, and the entire project team to work together to find the best solution possible for now and the future.”
The foundation work was completed in mid-January. Steel H-frame structures will be installed this fall using helicopters and the entire project is expected to be complete by the end of 2019.