I-35W bridge is aging, seven years after collapse

Cracks emerged in concrete girders. A drainage hole on the bridge deck plugged up. Rust showed above piers.

Seven years after the collapse of its predecessor, the new Interstate 35W bridge has been showing its age.

It cuts a handsome profile across the Mississippi River in Minneapolis, but annual state bridge inspection reports describe wear and tear that dropped its rating from "excellent" when it opened in 2008 to "very good" within two years.

While most of the changes are minor, a bridge engineer called one problem "rather major" — a leaky anti-icing system on the bridge deck. Repairs to the system were eventually made under warranty, but not before years of finger-pointing between the state and the lead contractor. Taxpayers also covered some costs.

"Contractors are always very reluctant to give anything," said Tom Styrbicki, bridge construction and maintenance engineer for the Minnesota Department of Transportation (MnDOT). "They always try to drag MnDOT into it: 'We did it per your specifications. If it leaks, it leaks.' "

"We held our ground on this one," Styrbicki said. "And said, 'Hey, we bought a bridge for a significant amount of money and … we want the systems to work.' "

A MnDOT engineer overseeing the warranty recalled a tussle. "They were resistant," David Herzog said. "It took a long time and many phone calls and discussions to get the work done that needed to be done."

Still, MnDOT wound up paying for other repairs to the anti-icing system that it conceded weren't covered under warranty.

The lead contractor, Flatiron Construction of Colorado, declined to comment.

There was urgency to replace the old 35W bridge after it fell into the river on Aug. 1, 2007, killing 13 people and injuring 145. Federal regulators blamed the disaster on improperly designed gusset plates for steel beams that fell when the bridge was heavily loaded with construction equipment. They also cited inadequate attention to the plates by state and federal officials during inspections.

From the beginning, the price tag for the new bridge was controversial.

Flatiron won the job with a bid of $234 million — higher than proposals from competitors who vowed to complete the project sooner. It then got another $25 million in bonuses from the state for finishing the work ahead of the company's scheduled completion date.

At the time, MnDOT officials defended Flatiron's proposal as far superior to the other bids when design, aesthetics and other factors besides price and schedule were considered.

A year after the bridge opened, MnDOT inspectors rated the deck, superstructure and substructure of the northbound span in "excellent condition" and the southbound span as "very good," noting cracking on the deck in a couple of places. They dropped the rating of the northbound span to "very good" in 2010 after discovering cracking on two concrete box girders and a concrete railing, shrunken sealant and small areas of rust stains above the piers.

MnDOT described those changes as common in a new bridge.

"Excellent basically means brand new, out of the box, and the first year you get traffic on it, get it through a winter, it starts to show those little bits of deterioration," Styrbicki said. Cracks were repaired and other flaws monitored.

More deterioration was noted in inspection reports from 2011 through 2013. The 2011 report said deck joints and seals "do not appear to be leaking, but … should be closely monitored during inspection."

"Deck drains are starting to fill with debris," inspectors wrote in 2012. "While there is no evidence of ponding, or drainage-related erosion, the deck drains should be flushed." They expanded on their previous remarks about the two girders: "There are isolated areas of minor rust staining on the exterior of the box girders."

The 2013 report includes pictures of rust, cracks and chipped pavement, and of a pipe that pulled apart under the deck. Styrbicki thinks the pipe may be a remnant of construction that's no longer needed.

One element of the bridge got only a fair rating every year — its clearance. That's because one end of the bridge was designed to be a couple of inches lower than normal over a Minneapolis street. The state didn't want to increase costs by raising the bridge or lowering the street, and the bridge clearance "ended up being somewhat substandard," Styrbicki said.

The 35W bridge is supported by huge concrete box sections from which anti-icing chemicals are piped up into disks on the deck that spray them onto the pavement. The automated system, triggered by temperature and humidity sensors, is an alternative to spreading salt on the deck and is believed to enhance safety. MnDOT says the chemicals are not corrosive.

"We had some real issues with those … rather major," Styrbicki said, adding that the disks weren't installed properly and that the anti-icing fluid was "leaking down into the concrete box superstructure."

The disks are provided by Boschung America, which provided similar systems for other Minnesota bridges. Justin Bruce, vice president of the firm, said it wasn't responsible for the leakage and blamed it on the installation.

"We do not install them," Bruce said. "That was all done for the general contractor …. They had some challenges with following the correct procedures for installation of those disks."

Flatiron spokeswoman Elizabeth Fison Hudson said the firm wasn't going to comment and referred questions to MnDOT.

The agency said the problem was discovered soon after the bridge opened. Herzog, the engineer enforcing the warranty, said, "I would deal with Flatiron. They would deal with their [subcontractor.]" He said both firms did some repair work under warranty, and it took two years to fully correct. "We had them out there so many times."

MnDOT could make a quick fix or use salt on the bridge if necessary.

Much of the time involved haggling over responsibility. "I'd have to review the contract with them and show why they have to come out there and stand behind the warranty," Herzog said.

He said he doesn't know the cost of the repairs done by contractors under the warranty.

But the state ended up paying $130,875 for additional anti-icing repairs because the bridge contract didn't specify them as under warranty.

"I'd have to tell my guys, 'This is on us, because we didn't spec out a perfect contract,' " Herzog said.

Pat Doyle • 612-673-4504