Everyone attending a football game in the $1 billion New Minnesota Stadium, home to the Minnesota Vikings football team, will walk and sit on precast concrete provided by Wells Concrete of Maple Grove, Minnesota. 

The stadium broke ground in December 2013 and is rising on the site of the former Metrodome, built in 1982 for the Vikings. The state legislature tasked the Minnesota Sports Facilities Authority in 2012 to oversee design and construction of this project, and the authority will operate the new multipurpose stadium. Private funds will pay for more than half the stadium costs, $529 million, with the balance split between the City of Minneapolis, $150 million, and the state at $348 million. 

HKS Sports and Entertainment Group of Dallas received the architectural contract and designed a bold, iconic structure, with a fixed, transparent roof system. Mortenson Construction of Minneapolis was awarded the contract to build the 1.75 million-square-foot stadium, with 65,400 seats, expandable to 72,000 for the 2018 Super Bowl.

Hanson Structural Precast, which Wells Concrete acquired in 2014, established budgets to provide the structural precast for the stadium project three years before submitting the bid in the fall of 2013.

Bringing a New Type of Precast to the Project

Family-owned Wells Concrete, founded in 1951, has grown through the years, organically and through acquisitions. The company employs about approximately 850 people. It maintains more than 2 million square feet of manufacturing space and serves clients throughout the upper Midwest and Canada.

Wells Concrete enjoys a long history of providing concrete for large stadium and arena projects, including the Vikings' Metrodome; the Minnesota Twins stadium, Target Field, in Minneapolis; TCF Bank Stadium in Minneapolis, home of the Minnesota Golden Gophers; and the Xcel Energy Center, where the Minnesota Wild play. 

HKS originally designed the Vikings stadium with the intent of using double and triple risers, as is standard in the industry. Well Concrete proposed to pour single risers upside down in the forms. When the form is vibrated, the rock and sand naturally are pushed to the surface. That produces a dense and durable finish. The harder, more consolidated concrete is on the face of the risers.

Wells Concrete strips the forms and rotates them using vacuum lifts. The innovative lifting devices hang from a crane and use suction from a vacuum reservoir to lift precast components in the plant, and then lift and place them in the field.

The vacuum lifts eliminate the need for traditional rigging and lifting lugs, which require manual patching and can remain visible to the public, explains Gary D. Pooley, Sales Manager for Wells Concrete. On a stadium the size of this one being built for the Vikings, he estimates there would have been 24,000 patches, if not for the vacuum lifts.

Wells Concrete hoped to reuse as many forms and vacuum lifts as possible from prior projects on the Viking stadium. However, the company needed to buy additional vacuum lifts, because some of the pieces were heavier than on the prior jobs.

The company has found success with its single-riser technology on two prior stadiums completed with general contractor, Mortenson. The design team expressed concerns that by using single risers there would be more caulk joints. 

"We came in with something different," says Steve Olson, Sales Representative with Wells Concrete. "Even though it was a proven system in the past, we had to do it again."

During the discussions, it was determined that the additional caulking would be in a vertical plain and less susceptible to traffic.  There would be no additional caulking on the walking surface. 

Installing the Concrete

Wells Concrete runs two shifts at the stadium and is providing the precast for the structural seating area. The upper bowl precast consists of stadia risers, closure walls, vomitory walls, stairs, and miscellaneous pieces for TV platforms, press box and wheelchair accessible areas. A cast-in-place column and beam frame supports these upper bowl precast components. The lower bowl consists of the same precast components, supported by precast columns and raker beams. The upper bowl is constructed first, the lower bowl is constructed next using all precast components to allow the heavy cranes access to the upper bowl.

The Vikings stadium contains more than 5,000 pieces of precast, weighing altogether 60.5 million pounds. Approximately 14,957 cubic yards of concrete are required. More than 102,000 linear feet of precast concrete stadia will support the spectator seats. During the day shift, crews perform detail work and surveying.

"We need to survey the structure our product is bearing on," Pooley says. "Lets say one of the bearing seats is off, we need to report that in a timely fashion, so the trade that did that work has time to repair it."

Due to more than 1,200 people working on the site and the crane activity during the day shift, the precast elements are set during the second shift. The start of each shift requires significant planning to set equipment, verify positions of the tower cranes to ensure no one is working beneath one, Pooley explains. 

Work continues through the winter. The team lost several days in 2014 to cold weather but just a handful this year.

In early June, Wells Concrete had set 2,600 precast concrete pieces, with 400 remaining to be placed in the upper bowl and 2,200 pieces in the lower bowl. It expects to complete its portion of the project by year-end. The stadium is on schedule to open in time for the 2016 football season.