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How other cities avoided box girder bridges (08/18/2013)
By Chris Rogers
Plans for the new Winona bridge may be solidified Monday. Citizens will get a chance to voice their opinions at a public hearing prior to what may be the final vote by the Winona City Council on whether to approve the project proposed by the Minnesota Department of Transportation (Mn/DOT). The public hearing is at 6:30 p.m. on Monday, August 19, at city hall.

Mn/DOT has selected a concrete box girder bridge design for the companion bridge to the current structure. Some criticize it as unattractive and note the concrete substructure will block upriver views from the old bridge and change views of the old bridge.

Mn/DOT: Hastings

arch bridge fits historic downtown, river

During the recent replacement of the Highway 61 bridge in Hastings, Mn/DOT chose an arch bridge over a box girder bridge. The conclusions reached on questions of aesthetics, historic impact, and avian risks of arch and cable bridges versus box girder bridges were markedly different in Hastings from Mn/DOT's assertions about the Winona project today.

In Mn/DOT's Findings of Fact on the Hastings project which included input from local residents, the city of Hastings, and others the state transportation agency said it chose the arch design because it was provided "a context sensitive design that fits with the city and river landscapes."

Both cable stay and arch style bridges were lauded because their "distinctive designs fit well with historic downtown Hastings and the unique Mississippi River valley." The Mn/DOT document also noted that construction would be finished six to twelve months sooner if an arch or cable bridge were selected, and the steeper grades of the "haunched" box girder bridge could result in increased engine noise.

In Hastings, a Visual Quality Team, including members of the local Heritage Preservation Commission and the State Historic Preservation Office (SHPO), weighed in on their design preferences prior to bridge type selection, with most voting for an arch or cable bridge. In Winona, Mn/DOT has yet to meet with the Heritage Preservation Commission, and issued historic review findings contradictory to those of SHPO. In Winona, Mn/DOT has assembled a Visual Quality Committee to consider "things like colors," but Mn/DOT officials specified that considering the bridge type is beyond the Winona committee's purview.

An arch bridge was constructed next to an old steel truss bridge similar to the Winona bridge in La Crosse during the Cass Street Bridge project. The Winona Post was unable to obtain Findings of Fact for that project before this issue went to press.

Future skyline: four-lane box girder bridge?

During a recent Winona County Board meeting, Mn/DOT Project Engineer Terry Ward explained that in 30 years after proposed renovations are finished, the existing Winona Bridge may need to be replaced if further rehabilitation is deemed not feasible. When asked, he confirmed that one possibility for replacing the bridge would be to expand the proposed box girder bridge to four lanes.

In 30 years, Winona's historic skyline could disappear, Winona County Commissioner Greg Olson said of the current bridge's uncertain longevity.

In comments outside the meeting, Olson also criticized Mn/DOT's bridge type choice and its historic review process. "What historic view is maintained when you look through the bridge and see a concrete wall?" he asked. He called Mn/DOT's public outreach "a mockery of the process and simply an exercise to justify the lowest-cost structure."

He added, "I honestly believe that the public is being misled." Mn/DOT has issued "veiled threats of project withdrawal, project delay, elevated local costs, and loss of current crossing for extended periods of time" that suggest an "attempt to strong arm" Winona into accepting a bridge that will be a "black eye on our city," Olson said.

The horse's mouth: FWS on birds and bridges

Mn/DOT told Winonans it chose the box girder bridge type because it is has a smaller price tag, what they call a smaller historic impact, and a smaller impact on migratory birds compared to arch or cable bridges. How significant is the bridge type decision to migratory birds? U.S. Fish and Wildlife Service (FWS) officials said that is unclear. The federal conservation agency appeared to be more moderate on the issue than was portrayed by Mn/DOT; in one case the FWS approved an arch bridge in exchange for conservation funds.

According to Mn/DOT, the FWS warned that building an arch bridge next to the existing truss bridge could kill many birds, who might run into the additional obstacle as they attempt to traverse one of North America's most important migration routes.

In a public meeting earlier this month, Mn/DOT Project Engineer Terry Ward told Winonans that FWS concerns about migratory birds running into the superstructure of an arch or cable bridge and dying was one of several reasons for choosing the box girder bridge, which lacks a superstructure. In a letter explaining her agency's decision, Mn/DOT Historian Kristine Zschomler said that FWS regulations "will likely require selection of the lowest bridge profile."

When the Winona Post asked regional FWS officials, they expressed a more moderate stance on the issue. "It's something that we don't understand very well," said FWS Biologist Phil Delphey of the impact of bridges on birds. Delphey represents the FWS in discussions with Mn/DOT about projects that may affect endangered species and migratory birds. "We can't say precisely what the differences are from one bridge structure to another; it's more of a common sense thing: the more structure you throw up in the air, the more concern there might be for migratory birds hitting the bridge."

Delphey did recommend a box girder design as FWS's top choice for that reason. However, Delphey explained that the recommendation was made two years ago. At that time Mn/DOT was still exploring a plan to totally replace the Winona bridge which would have removed the current superstructure there. Delphey said he has not had any significant conversations with Mn/DOT since they decided to keep the existing structure.

When asked what the impact of putting a new bridge superstructure right next to an existing one would be for birds, Delphey said, "I'm not sure anyone can tell you that very precisely. It's intuitive that it would less of an impact than a brand new structure."

Delphey added that bridge superstructures that are close to each other "would be more like one bridge" as far as birds are concerned. "The farther away they are [from each other], it's more like the birds are navigating two separate structures."

FWS eagle biologist Megs Rheude said that objects in the flight path are always bad for birds, but when power lines are proposed to cross the Mississippi River, her agency recommends pairing them with existing lines or other structures. Pairing such structures reduces the cumulative impact on migrating birds, she explained.

Neither FWS biologist could say whether constructing an arch bridge next to the existing Winona Bridge would have a significant impact on birds or not. In meetings with Mn/DOT, Delphey said he made informal recommendations, not demands, that Mn/DOT select the lowest profile bridge.

Apparently the FWS is not inflexible on the issue of superstructure bridges. In the case of the Hastings bridge, where the FWS could have totally removed one avian obstacle by successfully insisting that the old bridge be replaced with a box girder bridge, the FWS approved the arch bridge on the condition that Mn/DOT provide $100,000 for migratory bird conservation programs. 


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