Arch completed on Lowry Avenue bridge, predicted to last 500 years

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Anyone who regularly uses the new Lowry Avenue Bridge better get used to it. Some predict the steel structure will stand for centuries if it’s well-maintained.

The last section of the two arches that support the bridge’s main span was hoisted into place Wednesday in Minneapolis, marking a milestone for a two-year construction project due to finish in late summer.

As construction workers bolted the 73,000-pound piece of steel into the top of the structure, Hennepin County Commissioner Mark Stenglein predicted it could stand as long as 500 years. That’s about five times longer than its predecessor, which spanned the Mississippi River until 2009.

Expectations are comparatively high for the Lowry Bridge. Consider that it’s just upriver from the 43-year-old Interstate 35W bridge that collapsed in 2007, killing 13 people and injuring 145. And part of the Plymouth Avenue Bridge, two crossings from the Lowry, is being rebuilt after just 26 years of service because of corrosion in its support cables.

The 1883 Stone Arch Bridge is the only Minneapolis span over the Mississippi River that is more than 100 years old.

The predicted life span for the Lowry is possible, according to a bridge engineer who served on the forensics team representing victims of the I-35W bridge collapse. Sam Schwartz, who closed 17 city bridges over maintenance issues during his tenure as New York City’s chief transportation engineer in the late 1980s, said a well-built bridge will last.

“A steel bridge can last up to 500 years,” Schwartz said. “I personally inspected portions of the Brooklyn Bridge that were in great condition 140 years later.”

Even so, his assessment of the Lowry Bridge’s life span comes with one caveat.

“You have to maintain the bridge well,” Schwartz said.

Standard engineering parlance labels the Lowry Avenue Bridge as having a “100-year service life.” Hennepin County project engineer Paul Backer said modern construction materials and techniques could extend its life.

Stenglein proclaimed the Lowry will “last 500 years” while congratulating the county’s engineering team at Wednesday’s event.

If the bridge stands five centuries, Backer said, it will be because of dense concrete, multiple support systems and close construction supervision.

He has a team of seven engineering technicians inspecting bridge materials and construction methods daily. “We have pretty rigorous quality control on site,” he said.

The 1,575-foot bridge is supported by two piers in the river, steel cables running through the bridge deck and 36 cables connecting the bridge’s main span to 90-foot-high steel arches. This cable-stayed, tied-arch design relies on support from above and below.

Due to open in late summer, the Lowry project is expected to cost $13 million less than its $104 million budget, Backer said. The Black River Falls, Wis.-based Lunda Construction Co. is the general contractor.

The Lowry Avenue Bridge is near the midpoint of Lowry Avenue, which runs from France Avenue near North Memorial Medical Center in Robbinsdale to Stinson Boulevard in Columbia Heights.

The previous Lowry Avenue Bridge was closed in 2008 after one of its piers shifted. The 104-year-old steel truss bridge, known for the open metal bridge deck that cars traveled over, was imploded in 2009.

See below for a slideshow by photographer Bill Klotz taken on Wednesday: