MINNEAPOLIS (KMSP) - As construction crews work on the new billion dollar U.S. Bank Stadium, re-securing its outer skin, emails released to Fox 9 detail how the problem of falling panels was diagnosed and how it would be fixed.
Crews are currently remediating more than 4,000 of the zinc panels on the northwest side of the stadium, which faces downtown Minneapolis. It is the part of the building most exposed to wind and rain.
“We have experienced leaks in three or four parts of the building, not severe leaks,” said John Wood, a senior vice president for Mortenson Construction, the General Contractor for the stadium.
He blamed the problem on the design and engineering of the connections holding the panels in place.
“These connections are not adequate to resist the 90 mph winds,” Wood added.
Workers are removing the panels and placing 4,000 additional fasteners to a scaffold system, known as e-gerts, which hold the panels in place.
The problems with the panels began a couple weeks before the stadium opened, when 24 panels at different locations came loose during a summer rainstorm with 45 mph wind gusts. The stadium is designed to resist wind speeds double that, above 90 miles per hour.
On December 24, 2016, it happened again when eleven panels came loose.
During construction, the exterior panels were only fastened at the bottom. The top was clipped into the panel above it.
The solution, agreed to last year by the design and construction teams, was to install additional fasteners at the top of all the panels, all 55,000 of them.
THE PROBLEM SPELLED OUT
The blame game that followed was revealed in thousands of pages of documents, reports and emails, the Fox 9 investigators obtained in a public records request with the Metropolitan Sports Facilities Authority (MSFA), the public agency in charge of the stadium.
The structural engineer for the project, Thornton Tomasett, warned in a July 7, 2016 letter to MSFA, “..we must question the integrity of the metal panel system as installed.”
Fingers pointed at Mortenson and two of its subcontractors, MG McGrath, which designed and installed the metal panels, and Custom Drywall, which was responsible for the design and construction of the structure underneath those panels. That included the framing, insulation, and water barrier.
Custom Drywall has yet to be paid $3.3 million for the work.
An attorney for the company, David Hammargren, blamed the water for the panels falling off. “Excessive water is getting through McGrath’s panels and saturating the insulation..” wrote Hammargren on September 30, 2016.
In the letter to MSFA and Mortenson, Hammargren points to the icicles that developed in December below the northwest elevation which caused water to drip on to the walkway below.
“This creates a risk of panels popping and ice falling. This is a life/safety issue that will not be fixed by McGrath’s proposed repair. In fact, the repair clearly is not even intended to fix this problem,” wrote Hammargren.
Former MSFA Chair Michele Kelm-Helgen wrote in an email: “This is taking us down a path I never discussed or heard about…” “Custom is saying the entire building should be re-skinned,” she wrote on September 7, 2016.
Consultant Raths, Raths, & Johnson, blamed the wind, “differential shear movement,” that caused supporting panels underneath the exterior metal panels to shift in different directions. Monitors placed on the exterior of U.S. Bank Stadium have not detected any significant movement, according to multiple sources. However, internal documents also reveal those monitors are unreliable.
Wood of Mortenson responded in a February 23, 2017 letter that “shear movement’ is yet another red-herring, in this case advanced by a consultant and...the mutual trust and respect… is being eroded by consultants who, frankly, are not vested in the continued success of the project.”
Wood told the Fox 9 Investigators all the consultants made the process more difficult, but it was likely necessary.
“It made it more time consuming, but I would give everybody the benefit of the doubt," he said. "We chased down a few cul-de-sacs in terms of theories of what was going on, but ultimately proved to be not what was happening."
Other consultants pointed to the screws holding the panels in place, questioning if they were the right kind, whether some screws were missing, or if through continued remediation the screw holes were becoming too big.
Mortenson, McGrath and Custom Drywall are in arbitration to determine who pays for the remediation.
“That unfortunately is subject to a current litigation process and I’m not at liberty to comment about that,” Wood said. “Taxpayers should not pick up the tab.”
The warranty on the panels is good for two years, but MSFA and Mortenson agreed that the clock won't start running on those two years until MSFA is satisfied with the work.
WORK PROGRESSING ON PANELS
New MSFA Board Chairperson, Mike Vekich, went up on a crane to look at the re-installation of panels.
“I’ve been watching it as it has been unfolding and these things are on really tight,” he said. “I feel very confident those panels are on secure."
But MSFA is on the sidelines, as long as they don’t get the bill.
“I would describe it as an abundance of caution. The fact is you have an iconic structure here, it’s with unique design, there are going to be issues,” Vekich added.