Architects Use Drones to Digitally Map Historic Bridge

Drones have captured images of bridges, mansions, lighthouses and other historic structures across Wisconsin and the Midwest in recent years, gathering data before the sites are razed and gone.

A drone flying over a city.
(TNS) — William Krueger said it is important to have a digital record of the Cobban Bridge, so it can be preserved forever.

Krueger, an instructor at the UW-Milwaukee School of Architecture & Urban Planning, used a drone on Tuesday to map out every fine detail of the century-old bridge, located halfway between Jim Falls and Cornell. It is slated to be torn down next year.

Krueger said he took about 30 scans of the bridge from all sides, using the drone to take footage from a sky view as well as underneath.

“It takes just under a million data points per second,” Krueger said. “It’s a laser-range finder. I can take it into the computer and I can make a virtual model. It’s vastly superior to running around with a tape measurer.”

Krueger and his classes have captured images of bridges, mansions, lighthouses, and other historic structures across Wisconsin and the Midwest in recent years, gathering data before the sites are razed and gone.

“With this, we have this snapshot in time, we can archive forever,” Krueger said. “These kinds of (structures) are thoughtfully done; this has a beautiful assembled work to it.”

Matt Jarosz, executive director for the Advocates for Wisconsin Historic Places, stood near the bridge and observed the work. Like Krueger, he considered it important to preserve the history of the bridge.

“The technology of scanning and documenting is advancing so quickly,” Jarosz said. “It’s a fairly efficient operation.”

Jarosz agreed that too much of the area’s history has been lost when buildings with unique architecture are torn down.

“We’ve taken down rail stations in Milwaukee, and there are almost no images,” Jarosz said. “We want to document it properly.”

Chippewa Falls resident Chuck Nagle, founder of Cobban Bridge Preservation Inc., contacted Krueger and Jarosz, seeing their interest in coming to the area and scanning the bridge. They jumped at the opportunity.

“They saw the value in it,” Nagle said. “This thing is going away. It will be like a lost family member. This is an icon.”

Nagle and his group had submitted a proposal to the state’s Department of Transportation to relocate the bridge onto a nearby cornfield in the town of Sigel, with the idea of placing the quarter-mile long bridge on a cement slab. The idea was to make it part of a roadside park. However, WisDOT rejected the plan.

When it was built in 1908, the Cobban Bridge crossed the Yellow River in the town of Anson. It was moved to its current location sometime between 1917 and 1919.

There have been plans to replace it for years. The new bridge design has been finalized and approved by the state. Bids will be let this winter, with the goal of beginning work in summer 2022 with it completed in spring or summer 2023.

The 484-foot-long bridge is a single-lane, steel “Pennsylvania Truss” bridge. However, it is now considered “fracture critical.” The county reduced the weight limit on the bridge in 2007 from 10 tons to 6 tons, meaning that vehicles like school buses and fire trucks could no longer use it. However, as the bridge continued to decay, the Highway Department closed it entirely in August 2017, placing barriers in front of it, to stop vehicles from illegally crossing it.

The bridge wasn’t used frequently; the last traffic count study in 2006 showed only 240 vehicles crossed it daily. However, proponents of constructing a new bridge said the replacement will be used far more often because it will be safer and open to all types of vehicles. The new bridge is designed as 30 feet across, with 11-foot lanes and room for bike and pedestrian lanes.

Proponents of the new bridge also have pointed out that going to the nearest bridge, either in Cornell or Jim Falls, is an 11-mile detour.

The entire bridge replacement is expected to cost almost $6 million, with the state picking up 80% of the construction costs. Overall, the county will pay about $1.8 million in its share for the bridge replacement, between 20% of the construction costs and 100% of the design costs.

© 2021 the Leader-Telegram (Eau Claire, Wis.). Distributed by Tribune Content Agency, LLC.
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