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ARVADA, Colo. — The Rocky Flats Wildlife Refuge is set to open to the public in summer 2018, but a group of critics is hoping that day never comes.

Rocky Flats was a nuclear weapons production facility from the 1950s until the 1990s. During that time, plutonium was leaked into the air, soil and water.

“With a half life of 24,000 years, the smallest particle that you can think of that gets inside your body does not leave,” said Jon Lipsky of Rocky Flats Technical Group. “And it’s known to cause cancer and birth defects.”

In 2016, Metropolitan State University of Denver and Rocky Flats Downwinders conducted a health study that found people living downwind of the nuclear weapons plant faced more health problems.

Lipsky is one of a large group of Coloradans to protest the site.

“If they opened up as a refuge for public access, it’s not safe,” he said.

RELATED: Colorado Department of Public Heath guide to issue

Rocky Flats underwent a massive cleanup beginning in 1994.

“Residual plutonium concentrations in surface soil average about 1.1 picocuries/gram,” according to a joint fact sheet from the Environmental Protection Agency, the Colorado Department of Public Health and U.S. Department of Energy.

“These concentrations are protective of human health for any exposure scenario.”

The tests led the EPA and other agencies to determine the refuge area of Rocky Flats is safe enough that unrestricted and unlimited use is acceptable.

“But we’re not talking about safe like falling off a bicycle or getting a bee sting,” Lipsky said. “We’re talking about plutonium and it’s not safe in any measure.”

“My message to [critics] then is don’t go. But don’t tell me I can’t go,” Golden resident Kim Griffiths said.

Griffiths lives in the Candelas development on the southern boarder of Rocky Flats.

“No one was hoodwinked into buying a property there. We all knew and we did our own research and found that it was a safe place,” she said.

She believes the open space will be a positive step forward for the area and will improve the lives of nearby residents.

“I understand the history. I’ve lived in the Colorado area for 40 years. But now we’re past that,” she said. “I think it’s fabulous for the Front Range to turn what was considered a major liability into an asset.”