150-year-old Kern Bridge on pace for 2025 rebirth

Aug. 5—MANKATO — The one-of-a-kind Kern Bridge is spending its 150th birthday disassembled and packed in shipping containers, but it remains on track for a dramatic rebirth in two years as a keystone element of Mankato's park system and of the regional trail network.

Design and financing plans are coming together for a late-2024 construction of the piers to support the unique wrought-iron bridge, along with the connecting trails and bridge approaches on both sides of the Blue Earth River in Sibley Park and Land of Memories Park. In 2025, the dismantled 1873 bridge is to rise again as a pedestrian bridge connecting not only the parks but a trail system stretching from Faribault to Mankato to Minneopa State Park.

"We are wrapping up the preliminary design with many of the plans having been sent to various agencies for review and comment," said Assistant City Engineer Michael McCarty. "Final design is anticipated to start this fall. Currently, the plan is to bid the project in late June or early July of 2024."

A 190-foot bowstring arch bridge, the Kern is the last of its kind in Minnesota and the longest of its type remaining in America. Despite its length, it's not quite long enough to cover the entire width of the Blue Earth River that divides two of Mankato's biggest parks. In addition, the Land of Memories side includes low-lying land in the floodplain near the riverbank.

The result is a design that includes plans to construct a series of six smaller spans — one on the Sibley Park side and five on the Land of Memories side — to support elevated trail sections leading to the Kern Bridge and to keep the trail grades gradual enough to meet accessibility standards. Those added spans are to be intentionally low-profile so that the historic structure remains the focal point of the river crossing.

People will be about 30 feet above the river's normal water level when walking or biking across the bridge.

The location of the bridge has been shifted a bit closer to the confluence of the Blue Earth and Minnesota rivers than originally planned. That will allow the Minnesota River Trail to remain entirely on the river side of Sibley Park Road rather than crossing the road twice as initially contemplated.

The new layout means Sibley Park Road will need to be shifted a few feet to the east near the intersection with CHS Pergola Way — the short sideroad that climbs up the knoll in the center of the park. But the change will make the trail safer and less steep as it approaches the bridge, according to a memo from SEH, the engineering consultant on the project.

The City Council last month authorized staff to seek a grant to cover some of that trail and road work from the Greater Minnesota Regional Parks and Trails Commission, which allocates a percentage of the funding from the state's Legacy Act sales tax that's dedicated to projects in outstate Minnesota.

The city has also obtained federal and state Department of Natural Resources grants for a planned trail through Land of Memories Park to provide a connection from the bridge to Blue Earth County's existing Minneopa Trail, which runs along Highway 169/60 near the park's entrance. That trail continues along Highway 68 to near Minneopa State Park.

And the city successfully sought a federal grant earlier this year to make repairs and safety improvements to the Minnesota River Trail, a municipal path that runs from Sibley Park to the Sakatah Singing Hills State Trail. The state trail connects Mankato to Madison Lake, Elysian, Waterville and Faribault, and a future offshoot is planned between Mankato and St. Peter along Highway 22.

The construction of the Blue Earth River crossing itself, expected to cost more than $4.5 million, will be mostly funded by federal funds dedicated to the preservation of historic bridges.

The Kern Bridge definitely met the definition of historic, built less than a decade after the Civil War over the Le Sueur River southwest of Mankato. It was also very much in need of preservation a decade ago.

After a modern bridge was constructed nearby to carry local township traffic, the old bridge was closed in 1991 and left to deteriorate. With its stone piers crumbling, the span in danger of collapsing into the river and liability concerns rising, the township supervisors who owned the bridge voted in 2018 to dismantle and scrap it.

The regional office of the Minnesota Department of Transportation, with assistance from Blue Earth County, cobbled together funding to dismantle the bridge and put it in storage, later obtaining the federal funding necessary to cover its reassembly at a yet-to-determined new location.

The successful effort resulted in a statewide competition between cities and counties looking to reuse an elegant piece of history as a pedestrian amenity. Although Mankato's proposal was named the winner 31 months ago, the complexity of the project — including the multiple funding sources and the regulations surrounding historic preservation — made it impossible to complete the work in time for the bridge's sesquicentennial.

But the marathon effort remains on track to culminate in 2025, according to McCarty.

"We would anticipate construction starting in late fall (of 2024) as the river conditions allow," he said.

If the project remains on schedule, the hundreds of iron pieces of the old bridge will be reassembled in 2025 with the bridge possibly open for use by the fall of that year.