DENVER -- On Tuesday, a federal judge will hear from both sides of a controversial plan to put hiking and biking trails on the Rocky Flats National Wildlife Refuge.
The U.S. Fish and Wildlife Service plans to open 20 miles of the trails in September.
Many environmental groups and others are suing the federal government to stop them from opening.
In Tuesday's hearing, they'll try to convince a federal judge to prevent the trails from opening while the case makes its way through the system.
For 47 years, a plant -- on the land adjacent to the refuge -- made triggers for nuclear weapons.
In 1989, the federal government shut it down, spent $7 billion to clean it up and in 2005 deemed the land safe.
"This is one of the most well studied pieced of land on the planet," said Lindsay Masters, an environmental protection specialist with the Colorado Department of Public Health and Environment.
Masters has been a part of some of the thousands of tests on the refuge's and plant's land.
"Those soil samples showed it was suitable for unlimited use and unrestricted exposure, meaning you could put homes on it," Masters said.
But not everyone believes the government studies behind those soil samples, including Mark Johnson, the Jefferson County Public Health executive director.
"We have had a long history of the government agencies out there not being totally honest with us...and now they’re telling us everything is fine. And I just am skeptical," Johnson said.
He would like to see more third-party groups review and study the land. He would also like the government to open up all records from a sealed grand jury proceeding.
When asked if he would use the trails if they open, Johnson said, "Colorado has lots of beautiful trails and beautiful places to go and I would probably go to those instead of Rocky Flats."
However, Masters, the CDPHE scientist, has been to the plant and refuge many times and has no concerns about plutonium levels there.
"I think the biggest concerns are rattlesnakes and sun exposure," Masters said. "Realistically those are your greatest threats."