A hefty repair bill is coming due for a group of historic bridges that have spanned the Mississippi River in Minneapolis for about 90 years.
Three local government entities are separately planning major repair projects over the next five years for the Third Avenue, 10th Avenue and Franklin Avenue bridges, with the total price tag possibly exceeding $130 million.
The nearly identical concrete arch bridges are cousins of sorts, built over a 12-year time frame around the 1920s to accommodate the needs of a rapidly growing city.
"You can see that they're similar types of structures," said Steve Kotke, Minneapolis director of public works. "And they're all coming due for major rehabs at about the same time."
Each of them last had a major overhaul in the 1970s. Water and salt seeping through deck joints have taken a toll on the concrete structures, in some cases even exposing the steel reinforcements.
They are safe, engineers say, but need new decks and concrete patches. Hennepin County engineers recently imposed weight restrictions on the Franklin Avenue Bridge, however, after realizing a 1970s decision to remove some columns had compromised its load capacity.
The Franklin Avenue Bridge connecting Seward with Prospect Park will be repaired first, starting in spring 2015 with traffic closures in 2016.
The project's $50 million cost was driven up partly by the scarcity of cement in the area, due to Minnesota Vikings stadium construction and oil traffic on freight tracks, said Hennepin County engineer Jim Grube. County, state and federal governments are all chipping in.
The rehabilitation project includes building a barrier separating motorists from bicyclists and pedestrians. The county also plans to restore historic railing and lighting that originally lined the bridge, which have since been replaced.
Known as the Cappelen Memorial Bridge after its designer, city engineer Frederick Cappelen, the structure was the largest concrete arch bridge in the world when it was completed in 1923.
It earned a listing on the National Register of Historic Places for being "one of the most prominent of the Twin Cities' nationally renowned concrete arch bridges of the 1920s."
The nomination letter notes the Twin Cities had one of the first major programs of concrete highway bridge construction, largely due to the challenges posed by the Mississippi and Minnesota rivers. The 10th Avenue Bridge connecting the Seven Corners area with the East Bank, formerly known as the Cedar Avenue Bridge, is also nationally designated.
Minneapolis officials hoping to repair the 10th Avenue Bridge recently returned $3.3 million in federal funds that were slated to expire back to the Met Council after realizing that the bridge needed more work than initially anticipated. The cost of the project has grown from about $16 million to $42 million, and the construction date moved back from 2014 to around 2018.
City staff had initially considered a partial rehab that did not involve replacing the deck.
"The problem with that is we knew that literally within a number of years we'd be back in again," Kotke said, noting that the full rehab will prove more cost-effective over the long-term life of the bridge.
But the city must now cobble together funds from a number of different sources, including the state and federal governments. Kotke said the city's lobbyists intend to pursue changes at the Legislature that would give the state more responsibility over major river crossings, which are expensive for cities to maintain.
The bridge remains safe today, he said, though leaving it unrepaired for another 10 years could require imposing load restrictions and possibly closing it to traffic.
"We're out there inspecting that bridge on a regular basis," Kotke said. "And even though … you can see some rebar showing here and there, structurally the bridge is safe."
The Minnesota Department of Transportation, which owns the Third Avenue Bridge between downtown and Central Avenue, is in the early stages of planning a rehab project that may begin in 2019. MnDOT spokesman Nick Carpenter said there is not yet funding for the plan, estimated to cost about $40 million.
"It goes beyond just redecking the bridge," Carpenter said. "It's a historic bridge too so there has to be a lot of meticulous work that goes into it as far as being careful to preserve the historic integrity of the bridge."