ARVADA — For Michelle Gabrieloff-Parish, learning that one of her neighbors, the 6,500-acre Rocky Flats National Wildlife Refuge, had been a nuclear weapons production plant was like falling down the rabbit hole.

More than 70,000 fission cores or “triggers” for nuclear weapons were manufactured there over four decades.

By the time the plant 16 miles northwest of Denver was shut down in 1989, its environmental legacy included plutonium fires in 1957 and 1969 that wafted toxic smoke over the metro area. Leaking barrels of radioactive waste and other small accidents had contaminated downstream communities to the south and east.

Now, nearly 25 years after the shutdown, most of Rocky Flats is considered safe, and the vast open spaces at its edge are among the few large areas still available for development on the west side of metro Denver.

A massive residential and commercial development called Candelas is underway. And a major toll road to complete the 470 beltway, though mired in litigation, has been proposed to slice through the area.

Gabrieloff-Parish argues — along with longtime activists at the Boulder-based Rocky Mountain Peace and Justice Center — that ground disturbances, such as September’s floods, homebuilding, construction of the proposed Jefferson Parkway on the eastern edge of the refuge, and planned development of biking and hiking trails will kick up plutonium-laced dust, increasing the risk of leukemia and bone, lung and liver cancers for those who breathe it.

And they worry that the memory of the site’s toxic legacy has faded to the point that people will move into what Gabrieloff-Parish describes as the “plutonium dust bowl,” without understanding the potential risk.

“I only found out recently how close we are to Rocky Flats. The kids’ schools are about a mile and a half away,” said the mother of two, who moved to the Rock Creek neighborhood of Superior six years ago. “The more I learned about it, the more horrified I became.”

Industrial sites often are reclaimed for new uses. In Denver, the old Stapleton International Airport was transformed into a 4,700-acre neighborhood in the heart of Denver. Farther south, defunct Lowry Air Force Base, including asbestos-filled buildings that were demolished and buried decades ago, has been repopulated with homes and commercial development.

But the Cold War machine shop, Rocky Flats, has a more harrowing history.

After the Rocky Flats fires, levels of radioactive plutonium in soils just east of the plant ranged up to hundreds of times higher than levels outside the plume of the airborne plutonium, according to a 1970 report by the U.S. Atomic Energy Commission.

If 1970 sounds like ancient history, Gabrieloff-Parish said, consider that the half-life of the most common radioactive isotope or form of the element released, Pu-239, is 24,000 years.

Federal, state and local governments say the public has nothing to worry about.

The U.S. Environmental Protection Agency, U.S. Department of Energy, Colorado Department of Public Health and Environment, U.S. Department of Health and Human Services’ Public Health Service and U.S Fish and Wildlife Service — in stacks of reports — say the public’s exposure to the contaminants has not posed any significant risks.

Scott Surovchak, the Rocky Flats site manager with the DOE Office of Legacy Management, says naturally occurring radioactive uranium and other heavy metals in Colorado soils present more of a health risk than the minuscule amounts of plutonium remaining around Rocky Flats. Plutonium is also present in soils because of fallout from nuclear bomb tests elsewhere.

“I think the bottom line is that anything outside the Central Operable Unit (a 1,308-acre core of the plant retained by the Department of Energy) is now available for any and all uses,” Surovchak said.

The EPA says Rocky Flats and other Superfund cleanup sites, formerly among the most hazardous waste sites in the country, are continually monitored to safeguard public health.

Colorado has 21 Superfund sites. There are 11 along the Front Range, including Rocky Flats and Rocky Mountain Arsenal in Commerce City, which also has been cleaned up and made into a national wildlife refuge.

Rocky Flats’ history came to a climax in 1989, after years of calamities and protests, when a raid by the FBI and EPA halted production by the DOE’s private contractor at the time, Rockwell International.

The raid also kicked off Rocky Flats’ transformation — first to a Superfund site and eventually, in 2007, to a 4,000-acre national wildlife refuge. The site now is a beautiful vista of tallgrass prairie not yet opened for public use.

Critics contend that the truth about the health effects on workers and nearby residents that eventually came out is now hidden from newcomers behind Rocky Flats’ re-branding as a wildlife refuge.

Gabrieloff-Parish and her group Candelas Glows have held protests at the development over the last year to increase awareness of the “outrageous radioactive history” of adjacent Rocky Flats.

“There’s nothing we can say or do — no facts — to change some people’s minds,” DOE’s Surovchak said. “Professional protesters have an agenda. We’ve got loads of data.”

The Rocky Flats cleanup was declared complete in 2005, after more than 10 years and at a cost of $7 billion. Some 800 buildings were demolished. More than 120 tons of material were transported to nuclear waste storage facilities around the country, and some contaminated soil was buried on- site, according to the Rocky Flats Stewardship Council, which includes representatives of local governments.

Rocky Flats’ Central Operable Unit is the permanently closed area of the former plant that has required additional remediation and testing.

“We’re protecting what’s out there (equipment) from the public,” Surovchak said.

Now, the mostly empty acreage at Rocky Flats forms a stunning backdrop for bordering residential development, including the 2,000-acre Candelas neighborhood in west Arvada, about 1.3 miles south of where the plant once stood. It could one day have more than 4,000 homes — priced from $300,000 to $1 million — developers’ literature says.

“What really horrifies me is that they’re building houses around Rocky Flats, and nobody even knows what it was,” said artist Jeff Gipe, who now divides his time between Colorado and Brooklyn.

In December, Gipe put the finishing touches on a slightly larger-than-life-size horse sculpture wearing a respirator, brilliant magenta hazmat suit and black booties. Gipe thinks of the horse as a fitting memorial to the Rocky Flats legacy.

His father started working at Rocky Flats in the 1980s. Gipe, now 29, was a few months old when his family moved to Arvada, just south of the plant.

“He was there for 20 years, a supervisor at the plant,” Gipe said. “He couldn’t talk about anything. Even today he won’t talk about it. He doesn’t remember (because of neurological problems).”

Gipe began digging into Rocky Flats history for himself about four or five years ago.

“It’s been coverup after coverup after another coverup of all the accidents and illnesses,” he said. “There is no (adequate) marker saying it was ever a nuclear-arms facility, even though a lot of the contamination is buried there and can never be cleared out. It’s going to be dangerous for a really long time.”

Gipe spent about seven months constructing the as-yet-unnamed Cold War horse he envisions as a warning to future residents of the area around Rocky Flats.

“It has a lot of personal symbolism for me — the sacrifices of all the people who worked there,” he said. “Now my major concern is finding a permanent site for it. When I originally started, it was going to be a renegade piece. I was just going to put it out there. But it probably would have been destroyed within a day.”

Electa Draper: 303-954-1276, edraper@denverpost.com or twitter.com/electadraper

Candelas

Candelas is marketed as a green community, with homes built by Richmond American, Ryland and Village Homes, priced from $300,000 to $1 million. Developers are Terra Causa Capital and GF Properties, partnered with landowner Arvada Residential Partners. CBRE Commercial is designing commercial spaces, partnering with landowner Cimarron LLC.

Each home must obtain an Energy Star score of 3.

CDPHE

Communities in the general vicinity of Rocky Flats had cancer incidence during a 1980-89 study period comparable to the rest of the Denver metro area, said state health department research scientist Margaret Ruttenber. But lung cancer risk for plutonium workers employed at Rocky Flats employed between 1951 and 1989 was elevated, a 2003 state study found.

Cancer and Rocky Flats

Before: Lung cancer risk for plutonium workers employed at the Rocky Flats nuclear-weapons production facility employed between 1951 and 1989 was elevated, a 2003 state study found.

After: Communities in the general vicinity of Rocky Flats had cancer incidence during a 1980-89 study period comparable to the rest of the Denver metro area, state health department research scientist Margaret Ruttenber says.

There are 21 Superfund sites in Colorado, including Rocky Flats and Rocky Mountain Arsenal