The Lower Yahara River is a shared-use trail extending from McDaniel Park in McFarland to the Capital City Trail in Madison. Phase 1, a 2.5-mile section, is the initial segment of a planned 11-mile bicycle/pedestrian trail planned to connect Madison to Stoughton. Due to sensitive site discoveries, the Lower Yahara River Trail required a floating boardwalk, a helical pile supported boardwalk and prefabricated steel bridge structures placed on concrete piers. 

The centerpiece of the 2.5-mile section is a nearly one-mile-long boardwalk and bridge structure. Investigations of the site revealed Native American burial sites along the trail corridor, so engineer Graef redesigned the original 1,600-ft-long, at-grade path as an elevated boardwalk to avoid artifacts. 

The boardwalk uses a spread footing that distributes the load and “floats” on the ground surface to limit impact. Discovery of other burial sites during construction required redesign of two bridge spans. Crews had to work within a 50-ft-wide construction zone.

The team moved 2,300 linear ft of prefabricated steel bridge spans into place, including a 100-ft-long, 35-ton span. Two 500-gallon pea boiler steel drums from an old food processing plant were repurposed into a floating structure to carry and place the span. 

Janke and SEH worked with state and city agencies and the Ho Chunk Nation to ensure the burial sites weren’t disturbed.