One of the landfills at Rocky Mountain Arsenal National Wildlife Refuge. The layers of soil and vegetation on top act as a pump to keep water from infiltrating into the contaminated materials deep below. (Photo by Ariana Brocious, NET News)
The United States has a long history of making and storing military weapons around the country. Some of those sites became contaminated, requiring lengthy and expensive environmental cleanups. In recent years a few have been converted into wildlife refuges, becoming a kind of oasis for animals -- and people.
David Lucas pointed out a bald eagle nest -- about the size of a Volkswagen Bug -- tucked into a tree within a sprawling swath of prairie and wetlands. He manages the 15,000-acre Rocky Mountain Arsenal National Wildlife Refuge, just a few miles northeast of downtown Denver. It’s one of the largest in the country.
“Seeing 80 bald eagles here in the winter is a pretty exciting sight,” Lucas said.
It’s unusual to find such a large tract of open land in the urban sprawl of Colorado’s Front Range. And it’s not by chance. Since World War II and through the Cold War, the U.S. Army used the expansive site to make bombs and chemical weapons, like mustard gas. Shell Chemical Company used the site to make agricultural pesticides until the early 1980s.
“More than 600 chemicals were used or manufactured at the Arsenal, and they included all sorts of things, such as volatile organic compounds, pesticides, heavy metals, as well as some byproducts that are unique to manufacturing chemical weapons. They’re nasty chemicals,” said Warren Smith, spokesman for the Colorado Department of Public Health and Environment.
Those chemicals -- some toxic -- contaminated the land and groundwater. Charlie Scharmann, the Army’s program manager at the Arsenal, said they became aware of some contamination issues back in the 1970s, and started working with the state health department to monitor groundwater and soil contamination. In 1987, the site was put on a national list of hazardous waste sites -- more commonly called Superfund sites -- that require serious cleanup.
“The main strategy with our cleanup was to contain the contamination on site, largely. We did do some limited treatment of soil, but by and large we wanted to contain it and intercept the pathways where people and animals could no longer be exposed to contamination,” Scharmann said.
The cleanup project cost $2.2 billion. The contaminated soil, buildings, and other debris were isolated into two huge on-site landfills, with two or three layers of leak-proof clay and plastic liners underneath. Scharmann said that was actually safer than moving all the materials somewhere else. These landfills have specially designed caps on top—layers of several feet of clean soil, crushed concrete, and gravel, planted with vegetation. Now, they look almost like small hills among the prairie. Scharmann said the vegetation helps prevent rain or snow from infiltrating and spreading more contamination.
“The soil acts as a sponge and the vegetation acts as a pump to move the water out,” Scharmann said.
The layers also keep burrowing animals, like prairie dogs, from digging into the contaminated materials below. Discovery of then-endangered bald eagles helped spur Congress to designate the site as a national wildlife refuge in 1992. Scharmann said that’s not as counterintuitive as it may sound.
“The interesting thing about this site is that most of the contamination occurred in the center of the site. But much of the site was a buffer zone from operations in the center. Much of property on the perimeter of the site was not used for active military use or used by Shell Oil Company,” Scharmann said.
Wildlife occupied the perimeter of the site even when it was being used by the military. Although closed to the public, that open space provided birds and other animals an oasis from encroaching development.
Once the Environmental Protection Agency determined they were sufficiently clean, Refuge Manager David Lucas took over managing the Arsenal lands for the U.S. Fish and Wildlife Service.
On our tour, Lucas pointed out one of the formerly most contaminated spots. Native grasses now cover the landscape. Aside from the fence and sign, it looks just like any other spot on the prairie. Lucas said that’s exactly the point. “That’s the goal. The goal is that this mixes in, and wildlife uses this exactly the same as all the other lands out here.”
Lucas said Fish and Wildlife employees monitor various animal species to see if they’re picking up any of the chemicals. So far, they haven’t found any significant contamination among wildlife.
U.S. Fish and Wildlife has restored almost 10,000 acres of land into native short and mixed-grass prairie, said Lucas. “We have 86 bison currently grazing on about 2,500 acres, but they will be grazing 12,000 acres of grasslands eventually.”
Five groundwater treatment plants were also built as part of the cleanup, walling off underground water supplies to make sure no contaminated groundwater leaves the site. Water is pumped up, cleaned, and sent back down to the aquifer. The Army has paid to provide uncontaminated drinking water to nearby residents. The expansive views of restored wetlands, including lakes from the Homesteading era, woodlands, and grassland, can quickly make you forget how close you are to Denver.
“As a national wildlife refuge, we have a purpose to manage for wildlife, that’s our main goal. But here in Denver our other primary purpose -- what we can do a lot of in an urban location -- is educating millions of people on conservation,” Lucas said.
Lucas said those two purposes guide the refuge, which sees more than 300,000 visitors a year.
The total cleanup took a couple decades and was mostly finished in 2011. But there will always be a portion of the site, like the landfills, closed to the public. The Army, state health department, and EPA continue to test and review their cleanup effort to make sure it’s working.
“We feel really good about what we’ve accomplished out there, turning property into something that will be an asset for the community to use long term,” Scharmann said.
Rocky Mountain Arsenal isn’t the only Superfund site that’s been cleaned up and reused. Just 20 miles away, near Boulder, sits the Rocky Flats National Wildlife Refuge, home to a nuclear weapons plant for decades. While the radioactive material made the cleanup there more controversial, the EPA declared it finished in 2005. Plant and wildlife diversity abound on Rocky Flats dry tallgrass prairie, but the Fish and Wildlife Service still needs funding before the area can be opened to the public.