U.S. Labor Secretary Tom Perez toured U.S. Bank Stadium on Tuesday with a handful of women who showed off the work they did on the $1 billion project.

The women installed plumbing throughout the stadium, wired loft skyboxes with energy-efficient lighting and ensured the cooling and heating systems in the Minnesota Vikings locker room were up to snuff.

“Are you cool enough?” April Williams, a 39-year-old heating and air conditioning installer, asked Perez as he walked through the Vikings locker room.

Perez swung through Minnesota making his pitch for expanded apprenticeships in blue-collar trades he said would ensure more women and minorities enter the workforce. He visited the stadium with Democratic U.S. Sen. Al Franken, even throwing around a football with him, and held up the project as an example of a public and private partnership that succeeded in hiring large numbers of women, minorities and veterans.

Perez and Franken also visited MGC Diagnostics, a medical-device maker in Vadnais Heights. There they learned about partnerships between businesses and educators to train workers for high-skilled jobs.

“The real stars today are the workers that we met,” Perez told reporters after the stadium tour, adding that programs aimed at beefing up the skills of underemployed women and minorities will expand the middle class, much like a college diploma. “Apprenticeship is the other college — except without the debt.”

Perez, 54, has served as the country’s top official for workforce and economic development since 2013. Formerly an assistant attorney general in the Justice Department’s civil rights division, he emerged earlier this year as a potential vice-presidential pick for Hillary Clinton. He’s also a staunch supporter of labor unions, highlighting the role they have played in ensuring that publicly financed projects have diverse workforces.

“Not only have we constructed, through a project labor agreement in coordination and collaboration with our union brothers and sisters, a remarkable state-of-the art facility … we’re building the middle class,” he said.

Perez commended Minnesota’s strong economy, saying its low unemployment rate gives state officials the opportunity to address long-standing racial disparities in the workforce. “What this project is getting at is that we want to make sure every person in every ZIP code of this community has access to those career ladders.”

The U.S. Bank Stadium project easily surpassed its hiring goals for women, minorities and veterans, a feat made possible in part by the project’s location in downtown Minneapolis and various public transit options, including light-rail and bus. Projects located in less accessible areas have struggled to reach minority hiring goals, a barrier Perez and Franken said is surmountable.

“That has been a challenge,” Franken said. “We have to recognize that and build that infrastructure.” He added that “we need a quality child care system” to ensure more women take advantage of well-paid, skilled jobs.

“If the next project is in an area that is not transit accessible, you bake that into the financing and into the whole plan,” Perez said.