The watchdogs of the bridges

A closer look at the city’s Bridge Maintenance and Inspection Unit  

In a city dotted with lakes and bound by waterways, traveling over a bridge had, for a long time, been commonplace — something taken for granted.

That is until the failure of one last August led Minneapolitans to note the importance of the other 649 in the city. 

The Minneapolis Bridge Maintenance and Inspection Unit’s (BMIU) is responsible for more than half of them. The system used by city inspectors to inspect and maintain bridges is small in scale, relatively small in funding, but nonetheless efficient.

“It’s better than OK,” said the city’s Transportation and Maintenance Inspection Engineer Mike Kennedy. “We’re confident we have a good system.”

City Council Member Elizabeth Glidden (8th Ward), a member of the Transportation and Public Works Committee, said that Public Works’ infrastructure is analyzed and prioritized by safety first. The question of whether there is a large enough budget for maintenance and inspection of bridges is debatable.

Glidden said while the city has good safeguards in place, safety and funding issues are always on the Council’s radar.

“There is no question, in general, that our budget to support infrastructure issues isn’t what it should be,” she said. “In Minneapolis, and statewide, funding has been slashed and burned.”

While federal regulations require the annual inspection of bridges more than 30 years old, BMIU must — by city statute — inspect every city-owned bridge at least once each year.

However, to oversee all these multijurisdictional bridges, it takes collaboration among city, county and state leaders.

The city of Minneapolis owns the vast majority of bridges in the City of Lakes — 382. Additionally, Hennepin County owns 32, joined by a number of state, railroad and Park Board bridges, totaling 650. Some 411 are meant to support vehicles, and city inspectors are responsible for 119 of them.

Every Downtown skyway is counted as a bridge, as are the rickety, century-old structures buried under Bassett Creek. Some of the spans are simple footbridges in city parks; others are thousand-plus-foot-long behemoths. 

The task of keeping them in good shape is a decidedly small, yet efficient undertaking.

“We are inspecting at a higher level than what industry and federal standards [require],” Kennedy said. 

In the summer, bridge inspection and maintenance personnel grows slightly to 25 people, up from about 20 in the winter. However, there are only two full-time inspectors and one part-time inspector. The remaining employees are charged with maintenance. This includes mowing near the bridges, replacing railings, removing graffiti, flushing salt and sealing surfaces of bridges.

City bridge maintenance funding is ‘adequate,’ seen as a priority

Cuts in Local Government Aid (LGA) have resulted in cutbacks to the streets and bridges divisions of Public Works, but bridge inspections have not seen budget reductions. 

“We still believe we’re able to do an adequate job on the bridges, maintaining them, preserving them,” said Jeff Johnson, a bridge maintenance and inspections engineer for the city. 

As of 2005, the average age of a city-owned bridge was 60. 

“When we say age, I think of a car — five years, 10 years and it’s shot,” Johnson said. “You think of a road, 30 years and it’s gone. For a bridge, you figure 75 years for its life, then repairs. At 67 years, a bridge could just be getting into middle life.”

Kennedy, director of transportation maintenance and repair, said that the nearly $2 million annually allotted to staff, maintenance and inspection of 382 bridges is sufficient — for now. 

“If we have to start taking more [money away from inspections], that’s going to start cutting into the bone a little bit,” Kennedy said. “There is plenty of work we could do if we had more of a budget.”

Kennedy said they’ve made bridge inspection a priority.

“We’ve cut less there, but we recognize the higher level of potential problems we’d have with bridges,” he said. 

Currently, the department is funded only to keep bridges in the condition they are in. 

“Over time, that’s going to be harder and harder to do,” Kennedy said.

While funding has been cut to Public Works, there was still funding for a $500,000 Under Bridge Inspection Unit. The unit, purchased in 2003, allows inspectors to get up close and personal with bridges from the relative comfort of a lowered basket. That apparatus is still used today to perform inspections on a number of bridges 10 to 15 times a year, Johnson said. 

“[Public Works] has treated my little group better than anyone else,” Johnson said. “I’ve always got the equipment I’ve needed.”

After the bridge fell

The Aug. 1 collapse of the Interstate 35W bridge led to the infusion of an extra $100,000 (totaling $300,000) this year from the city budget, to be used for additional deck sealing on city bridges. 

While the 35W bridge is state owned and inspected, city staff had to sign off on its design, ensuring there was room for light-rail transit. The catastrophe naturally heightened awareness in the city’s bridge maintenance unit.

“The bridge collapse did raise an awareness on everybody’s part,” 
Kennedy said. “There was a recognition that we wanted to keep our program up and running.”

Soon after the collapse, the city’s bridge inspections department re-inspected the 10th Avenue bridge just east of the 35W bridge site. The city also commissioned an independent review of inspection procedures by St. Paul-based TDKA, which, 
Kennedy said, found they were inspecting bridges “appropriately.” 

“It made us look a little harder, take an independent look, and we determined we we’re doing [inspections] well,” Kennedy said. 

The 2007 Minneapolis Bridge Inspection Report listed 20 vehicular bridges as deficient at the end of 2006. This means that they have a Bridge Sufficiency Rating (BSR) rating of 50 or less, therefore qualifying them for federal funding for replacement. Those with a rating of 51 to 70 — some 33 city-owned vehicular bridges — could qualify for renovation, however. Of those that qualify for replacement, only two are overseen by the city — both buried in the Bassett Creek tunnel system. 

Of the remaining bridges deemed deficient, many were nearing 100 years old and half were in Downtown and Southwest Minneapolis. 

Of those deemed deficient, six are along the Midtown Greenway, which runs from Lake of the Isles one block north of Lake Street, east along 29th Street. Seven deficient bridges were counted in Southwest and three, including the 35W bridge, in Downtown, according to the 2007 Minneapolis Bridge Inspection annual report. Replacement of a bridge usually takes five years to approve and begin, Kennedy said. However, 35W was fast-tracked and is scheduled to be complete and reopen by Christmas 2008.

Most recently, Minneapolis inspectors closed a Park Board pedestrian bridge April 7 at Bryant Avenue and Minnehaha due to deterioration of the 78-year-old bridge. 

‘God bless the Roman arch’

During his decade of experience overseeing city bridges, Johnson has had the opportunity to inspect bridges of varying designs. 

He said many of the city-owned bridges are arch bridges, an ages-old Roman design he said is not only proven to be reliable, but beautiful.

“God bless the Roman arch,” Johnson said. 

The majority of these are located along the Midtown Greenway and are approaching 100 years old. 

“Again, they all get inspected every year,” Johnson said. But many of those along the Greenway “flake,” meaning bits of superficial concrete are known to chip and fall off. And particularly since 35W bridge fell, those at the city have had an increase in calls regarding bridges, Kennedy said. 

“We inspect every bridge in the city of Minneapolis that is our responsibility to inspect,” Johnson said.

City–owned bridges are replaced at about one a year, however none will be replaced this year.

Upcoming projects

State-owned bridges

• The new Interstate 35W bridge is slated for completion by the end of the year;

• The 50th Street bridge will re-open in the fall; and

• The 46th Street bridge will son be demolished and replaced.

County-owned

• Hennepin County closed the Lowry Avenue Bridge on April 25 due to structural issues with one of the bridge’s piers. Contruction on a replacement bridge is scheduled to begin in 2009 with a planned completion in 2011.

• The Glenwood Bridge over Bassett Creek, the Lowry Avenue Bridge over the Mississippi and the bridge at Lyndale Avenue and 50th Street over Minnehaha Creek are scheduled to be replaced by year’s end; and

• Main Street between 1st and 3rd avenues over the Burlington Northern Santa Fe Railroad is scheduled to be replaced by October with a more pedestrian-/bike-friendly bridge. 

City-owned

Within the next five years, 
Kennedy and Johnson said the following bridge projects are expected to move forward:

• Major rehabilitation of bridges along the Midtown Greenway — a bike and pedestrian corridor that stretches from the Uptown area to the Mississippi River just north of Lake Street; 

• Repairs to the 1st Avenue bridge over I-35W at the exit just north of Lake Street; and

• $200,000 worth of repairs to the 10th Avenue Southeast/Cedar Avenue bridge, which Johnson called “the most beautiful bridge in the city.”

From 2002 to 2006, the city constructed 37 new bridges, 15 of which were skyways. 

While the city has a high number of aging bridges, it also has an experienced staff and resources to keep a close eye on all 382.

“Our bridges have good ratings, and we have a reasonable program to support it,” Johnson said. “We believe we have a relatively good system.”