When any project seeks to build on a site that was previously occupied, one of the first things to look at is the question of reconditioning the site. Abandoned, idled or underused industrial or commercial properties are known as brownfield sites, and this includes the former bus barn and shopping center space that is now Allianz Field. The goal was not simply to make it functional as the site of a soccer stadium, but to turn 32 acres of flat, unattractive asphalt into a site that would include over six acres of grass, 1.5 acres of plantings and 197 mature trees. Fortunately, the company responsible for the construction of Allianz Field, Mortenson, has had a lot of experience working on brownfield sites.
David Liverseed, Director of Environmental at Mortenson, explains that every brownfield rehabilitation project is first and foremost a real estate deal. If there’s no need or demand for whatever you want to put there, the site doesn’t get rehabilitated. But once the site of Allianz Field had been selected, the process began with an environmental site assessment (ESA).
The first phase of the ESA involves going through everything that’s been on the site that could have had an impact on the property. Once this is completed the second phase — when the actual impacts are assessed — begins. In the case of Allianz Field, this meant looking at the bus barn and the businesses that had been in the Midway shopping center, including a dry cleaner, for possible soil contamination, groundwater quality, free phase petroleum floating on the surface.
Liverseed explained that the site of Allianz Field was very middle of the road. “Not a Superfund site,” he said. “Wasn’t the worst, wasn’t the best.” The biggest hurdle came from the need to get multiple property owners to agree to the necessary steps for cleanup. This meant different parties had to come together in order to get waste cleaned up and shipped off.
Once all the pieces were in place, the actual cleanup could begin. Liverseed explained that this means evaluating the contaminants in the soil both “vertically and horizontally.” That means excavation and offsite disposal, with contaminated soil going to a landfill where it can be used as daily cover, depending on the level of contamination. Whatever is not removed has to be scrubbed and then covered with clean soil or paved over, and all of this is done according to guidelines from the Minnesota Pollution Control Agency and their Voluntary Investigation and Cleanup program.
The watchwords for a process like this are, above all, diligence and coordination. Regulations must be adhered to and there needs to be clarity about what is there and exactly what needs to be cleaned up. Working with MPCA, Mortenson was able to ensure that the reconditioning of the Allianz Field site met the necessary conditions before building got underway. The end result is a site that has not only been improved with cleanup and additional greenspace, but that will continue to make a minimal impact on the environment through many green elements.