HOUGHTON – A successful piece of civil engineering can largely fade away.
Infinitely reproduced and photographed, the Portage Lake Lift Bridge avoided that fate better than anyone. But most people who drive through it – as more than 20,000 vehicles do every day – probably don’t realize how innovative it was.
Civil engineers yes. The bridge was honored as a National Historic Civil Engineering Landmark by the American Society of Civil Engineers during a ceremony in Bridgeview Park on Friday.
“It’s an engineering marvel, and I think we should celebrate it accordingly,” said Paul Ajegba, director of the Michigan Department of Transportation.
Plaques recognizing the landmark will be affixed to the Houghton and Hancock sides of the bridges.
The reconnaissance was led by two Michigan Technological University graduate students, Emma Beachy and Michael Prast. Their teacher, Tess Ahlborn, mentioned her work to get the same award for the Mackinac Bridge. In an offhand remark, she mentioned that the Portage Lake Lift Bridge also qualified.
They jumped at the chance to work on it as a graduation project; Ahlborn was also enthusiastic about being a councillor.
“It’s a local landmark,” Beachy said. “It’s what connects the two cities, and it’s really visually arresting. And so to be able to delve into its history, which helped to make it, was really special.
The bridge is the only place vehicles can cross between the Keweenaw Peninsula and the rest of the country.
It had precursors: a pontoon bridge, followed by a wooden bridge and a swing bridge. But it is already the longest crossing between the two cities.
The mining-era bridge was built as a double-decker bridge to accommodate rail traffic. And a sign of the region’s changing economy, the lower deck now handles snowmobile traffic in winter and can also accommodate high-load vehicles.
“Engineers marveled at the bridge which, unusually for lift bridges, was built with an intermediate level. This has reduced the number of lifts needed by 63%,” said Al Anderson, an engineer at the MDOT Transportation Service Center in Ishpeming.
“These guys were really thinking when they built this bridge, to put these intermediate sets in there, so they could get it up and get the majority of the boat traffic under it without having to move the bridge,” he said.
Placing the 260-foot span was its own feat of ingenuity. It was set up with just 4 inches of clearance. The barges were filled with water to weigh down the span, Anderson said. The water was then drained from the barges to bring the span to where it could be connected to the lifting cables.
“Then they pumped water into the barges to drive the lifting span down to put pressure on the cables to lift the hanger counterweights that were in the towers,” he said.
These counterweights, precisely tuned to approximately 2,000 pounds of the 4.584 million pound reach, allow for a rare feature. If necessary, workers can grab a pipe wrench or strap wrench and move the bridge by hand.
“It’s kind of a testament to the engineers, civil and mechanical, who figured out how to make this so easy, so you don’t need giant, powerful motors that lift millions of pounds,” Prast said.
To be eligible for the award, a project must be at least 50 years old, possess unique characteristics, and have contributed to the development of the civil engineering profession and the nation.
The bridge passed the first bar easily, already being close to 60 when Beachy and Prast began their work. And they documented the other two parts during their research. At the Michigan Tech Archives, they found plans for the bridge and read communications between officials from the 1950s about funding and various design options. They also interviewed people who figure prominently in its legend: Tom D’Arcy, the bridge’s design engineer and John Michels, one of the project’s engineers who oversaw construction.
D’Arcy was present for Friday’s ceremony and also read a poem he had composed to honor the bridge. He recalled the long hours spent designing with nothing more advanced than slide rules and Monroe calculators.
“I remember it, and I’m very proud to see how you honor the bridge and how much people in this area love the bridge,” he said. “It warms my heart.”
Dennis Traux, president of the American Society of Civil Engineers, said the award was part of an effort to raise awareness of how civil engineering contributes to quality of life.
“As professionals, as a company, as a community, we are committed to trying to advance what we do,” he said. “I hope this landmark helps facilitate the continued maintenance, continued recognition, continued support for the structure that is going to be so important to this community, to this region, and arguably even to this country.”
Beachy and Prast will also give a free presentation on the history of the Portage Lake crossing and the construction of the current bridge at 10 a.m. today at the Finnish American Heritage Center in Hancock.