Each year, the South Dakota National Guard places troops throughout the Black Hills as part of the Golden Coyote training exercise.
But the Adjutant General of the Guard has postponed training in one location: the Buffalo Gap National Grassland.
Areas in the National Grassland while beautiful in looks might possibly contain a high level of radiation.
"So I think it's something we should know more about and take very seriously," said Gary Heckenliable, with Action for the Environment.
The same area is where the South Dakota National Guard wanted to train as part of Golden Coyote this summer.
"We've been working on getting this cleared for about three years," said Adjutant Major General of the South Dakota National Guard Tim Reisch .
But those plans are on hold after a study was brought forward conducted by Charmaine White Face, Coordinator of the Defenders of the Black Hills.
"There are some places where there is a greater occurrence of it and I think that's where Charmaine is talking about, that is a specific area down there where that is very, very close to the ground," said Heckenliable.
And if radiation is close to the ground, Heckenliable says it poses more of a threat.
"I think what you set yourself up for is not any tragedy tomorrow but it's an accumulative kind of thing that over the years can produce things like cancer," said Heckenliable.
Adjutant Major General Tim Reisch says the National Guard tested the area and the results showed no safety concerns - but he's decided to play it safe.
"The safety of our soldiers and airmen is paramount and there's always a chance that the first testing would be wrong so we'd rather take another test and do further testing then take a risk," said General Reisch.
But he says the cancellation won't prevent the soldiers from training.
"We've been training in the black hills for almost 30 years with this exercise so we do have other places to choose from. So that's good," adds Reisch.
General Reisch says soldiers would have occupied the area for at least ten days during training.
The location was central to training on the Pine Ridge Reservation and in northern Nebraska.