As she guns her four-wheel-drive vehicle through the back roads of Minnesota’s biggest active development site, Heather Worthington speaks constantly of “the environment” — but in quite different ways.

One minute, it’s an osprey nest or the re-meandered creek splashing through the massive Arden Hills tract. Then she’s pointing to the pumps and plant that are slowly cleaning billions of gallons of chemical-laced groundwater.

The 427-acre megaproject to be built in Arden Hills has been promised as an environmental superstar in the suburbs, powered by acres of solar panels and clean geothermal heat and linked to both light-rail lines by a stream of high-frequency buses. Plans call for suburban-style homes near a town center with movie theaters, sidewalk tables and coffee spots.

But it also faces an environmental challenge: reassuring the public that the site of the abandoned Twin Cities Army Ammunition Plant (TCAAP), where factory workers dumped harmful solvents for years, is a safe place to live.

The paradox, said Worthington, who manages the project for Ramsey County, is that after decades of work TCAAP’s environmental issues are better known than those of any other contaminated site anywhere — yet “mythologies” abound, given its history and impact on surrounding communities.

Spokeswoman Sara Thatcher said that Ramsey County is following a strategy of forthrightness in telling members of the public everything that can be known about the site’s defects, past or present, via an online cache of documents (ricecreekcommons.com/documents).

“The state told us this site was cleaner years ago, before the cleanup we did, than the Twins ballpark site or the Gophers stadium site,” Worthington said. “We know more about TCAAP than anyone in the metro knows about their property.”

Arden Hills Mayor David Grant doesn’t foresee a problem, given the uniqueness of the site, its location alongside two busy freeways and its lofty views of both downtown Minneapolis and St. Paul.

“We had an open house last fall to show people the latest changes,” he said, “and to our surprise and the developer’s, people showed up — not even from the area — wanting to get on waiting lists to be the first to buy. And it wasn’t an isolated case; there were several people like that.”

Environmental factors

To tour the site, now by Worthington’s cheerful admission still “flat and featureless” and awaiting improvements, is to keep noticing ways in which age-old contamination has affected it. For instance:

• The parcel set aside for a huge solar energy farm — a positive environmental sign — is to be used that way partly because it’s polluted and would be costly to clean to residential standards — an environmental negative.

• The strong hope for clean geothermal energy (positive) is based on the notion that if you must pump warm water to the surface to clean it (negative) you may as well draw off that warmth to heat things above ground.

Worthington conceded that the site’s geothermal promise remains up in the air — or rather, down in the ground. “It’s more of a hope right now,” she said.

Also complicated is the oft-mentioned hope of a rapid-transit busway from Rosedale that would link TCAAP to light rail on University Avenue. A Metropolitan Council study completed last fall threw cold water on that prospect, given limited ridership prospects.

The study, Worthington said, made it “clear that there needs to be substantial improvement in density in that whole corridor. ... We are focused like a laser beam on the under-serving by transit of the north suburbs.”

The county, city and others called a news conference at the site last summer to announce the completion of a soil cleanup that officials said wound up a lot less extensive that one might suppose — just 30 of the entire 427 acres.

Amy Hadiaris, project manager for TCAAP with the Minnesota Pollution Control Agency, affirmed that the soil on the site is clean enough for people to live on.

“Soil is easier than water,” she said. “Soil doesn’t move; dig it out and it’s gone.” Groundwater, on the other hand, “takes a lot of effort and a lot of money” to cleanse.

The Ford plant site in St. Paul, another polluted spot on which thousands of people are to live, is an instructive contrast, Hadiaris said. While the pollution there was largely contained by bedrock, in Arden Hills the sandy soil was a “superhighway” for harmful chemicals, sending them miles to the south in a lazy plume and forcing a cleanup that “has gone on for decades and will go on for decades more.”

Master developer Alatus LLC has referred in meetings to vapors being detected in tests at TCAAP, and that is a headache, officials admit — though nothing that hasn’t been seen in other places.

“There are a couple of areas where, if we were to dig deeper, we’d hit a pocket of water,” Worthington said. “We could drain that and have no vapor, but the alternative is to take steps to protect against vapor.”

Grant stressed that all builders deal with the same thing.

“You have places all over the Twin Cities that were once extremely polluted, so bad you couldn’t even move the soil before treating it first, that are thriving today,” he said. “People are looking for a development like this. ... It’s the right time for us.”