Tag Alder Road Bridge over the Namekagon River

Challenge

Originally built in 1950, the existing Tag Alder Road Bridge in the Town of Lenroot, Wisconsin was severely outdated and unable to meet current structural requirements, posing a safety risk to the residents who relied on it for access. The Wisconsin Department of Transportation and the Sawyer County Highway Department recognized the urgent need to replace the old single-lane, five-span bridge structure with a new and improved design. The bridge crosses the Namekagon River, a protected part of the St. Croix National Scenic Riverway, which required extensive coordination with the National Park Service, the U.S. Fish & Wildlife Service, and the Wisconsin Department of Natural Resources (WDNR).

Solution

SEH was chosen by the County to design a new bridge to replace the outdated five-span structure, P-57-0025. The new two-lane bridge, B-57-0091, is a two-span reinforced concrete flat-slab bridge with a total length of 105 ft., a 24-foot clear roadway width, and a Type M steel railing. The new design reduced the number of in-river piers from five to one, significantly improving recreational navigation and safety on the river.

As the primary consultant, SEH handled several aspects of the project, including project management, surveys, roadway and bridge design, and obtaining permits from the U.S. Army Corps of Engineers and the WDNR. The team also coordinated with utilities, involved the public, prepared environmental and design reports, developed a transportation management plan, and compiled the plans, specifications, and estimate package.

To protect the National Scenic Riverway, the project included several environmental protection measures. A temporary shoreline canoe portage path navigating the construction zone was incorporated into the project. To prevent debris from entering the river, a debris capture system was used during construction. Additional precautions included filling large riprap voids with gravel and installing temporary amphibian and reptile exclusion fencing to protect wildlife such as snakes and turtles. A documented archaeological site within the project limits also required careful management.

By addressing structural deficiencies and environmental concerns, SEH's comprehensive approach ensured the successful completion of the new bridge, enhancing safety and recreational use of the riverway.