MANKATO — By now, people probably think they’ve learned all they can about the Kern Bridge, the 153-year-old wrought iron bowspring bridge undergoing final installation between Sibley Park and Land of Memory Park.
But one person, a Mankato native now working in Minneapolis, no less, is sharing more details. The firm co-owned by Rachel Peterson, a 2007 Mankato West graduate who is an architectural historian, was hired by Mankato to do exactly that. Information will be vital when historic designation is once again sought for the structure.
“We do a whole bunch of different kinds of historical consulting,” said Peterson, who has worked at Hess, Roise & Company for more than 12 years.
“Compliance review is a big part of what we do. So, if there’s federal money involved in a project, we’ll take a look and make sure that historical properties are being treated sensitively, based on its past.”
While Mankato is contributing greatly to the $10.8 million project, about 75% of the funding is coming from state and federal grants, according to city engineer Cory Bienfang.
That brings a firm like Hess, Roise in to look at a variety of factors, Peterson said.
It’s more than just the bridge that is being impacted in such a relocation.
“They had to do some compliance review both to understand if Sibley Park and Land of Memories Park were historic properties, because that was going to be impacted by the project, but then also to do the design review for the bridge reconstruction itself and figure out how we rebuild this thing in a new location in a way that respects its historic character,” she said.
Although a Mankato native, Peterson said she had little first-hand experience with the Kern Bridge when it was located south of the Red Jacket Trestle along what is now County Road 1. What she knew of it came from her dad, Steve Peterson.
She said, “My dad’s a big canoer, and he’s like, ‘Oh, yeah. I’ve noticed that bridge but only from the underside, and only because I canoe down the (Le Sueur) river.’”
But that reflects the type of information she gathers about a historical structure.
She can get solid information from newspapers of the era, but since the Kern Bridge had no name when it was being proposed and then was known as Yaeger Bridge for many years, personal reminiscences, often through diary entries, can supplement that.
The ultimate goal, she said, was to duplicate a final configuration that was as close as possible to the original historic integrity while also utilizing, if necessary, mechanical and design technology that was not available 150 years ago.
“But just figuring out … what the new abutments look like so they kind of reference the original abutments but are going to be different. And make sure that the historic truss has got its pride of place and is important for its engineering,” she said, creating its new home between the parks. “We wanted to make sure that the truss structure was all rebuilt the way it should be, and that it was highly visible so that people could see the historic bridge.”
At the same time, however, there will be changes included to accommodate the bridge’s new use as a pedestrian and bicycle connector as opposed to horses or wagons. In part, this was necessary because this version of the bridge will be so much higher in the air.
“We need to put some new railings to make sure that people who are on bikes are safe when they’re using it because that’s the whole point of this crossing is to make that trail connection. But you want to make sure that those new railings don’t distract from the historic truss, that they are as invisible as they can be,” Peterson said. “So, that’s all part of what we were working on, (it) was more design review pieces, not necessarily engineering.”
Because the goal is to again get it designated on the National Register of Historic Places, all of that needed to be done so as not to change it too much. It’s a balancing act as challenging as getting the correct compression and torsion on the two sets of bridge cords that keep the bridge hanging safely in the air.
Although nearly everyone who attended the reassembly process on Aug. 24 was taking pictures and video, none of that existed for the original bridge. Many who remembered the bridge from the 1950s-1970s remembered it only as being rusty, but it had once been a specifically chosen color, she said.
“There wasn’t really anything from the physical evidence (where) we could tell what the original color would have been,” she noted. “The closest we got (through a lengthy newspaper article from the time), is that when they built it, they put two coats of what they called the best quality metallic paint on the bridge. So, we were pretty confident that it was a neutral color, but couldn’t get any closer than that, unfortunately.”
After it was reassembled on site, the bridge received a gray primer and then black finishing coat. In addition to protecting it from the elements, that will help it stand out from the abutments with a stone appearance, plus the blue sky and green trees that form the backdrop.
When it came down to it, there was probably more reading of dry governmental documents than personal remembrances, she said. But it was in these documents from Blue Earth County that they learned John Kern had been paid small amounts of money to maintain the bridge approaches, for example. Those details are key to bringing the story of the bridge to life.
“For our purposes, we were so focused on what the structure looked like when it was first built. You know, who designed it, what the intent was, how big the crossing is. The social history part wasn’t as much a part of our research on this one. We still came across fun little tidbits, but it’s not the kind of meaty diary reading that I like to do,” she said, laughing.