A Refuge from Chemical Weapons

Just 10 miles northeast of downtown Denver, the Rocky Mountain Arsenal National Wildlife Refuge is a world away, a sanctuary for the furred, feathered, and scaled, as well as people looking to connect to nature without driving into the mountains.

But in its previous incarnation as the Rocky Mountain Arsenal, the site was one of the country’s most notorious brownfields — abandoned land where contaminants in the soil complicate any redevelopment efforts. 

Before the U.S. Army decommissioned it in the 1980s, it had served as a manufacturing and disposal site for chemical weapons for decades, uses that left a witch’s brew of hazardous waste in their wake. The Army produced mustard gas, napalm, sarin, and other toxic chemicals at the arsenal from World War II until 1969, when the U.S. government shut down chemical weapons manufacturing. In the ensuing years, the site was used for pesticide manufacturing, fuel storage, and chemical weapons disposal.

In 1985, the government declared the property a Superfund site and launched a massive cleanup effort. One aspect of restoration, however, had already begun naturally: Due to the general absence of people, bald eagles and many other animals had started to return to the site by 1986. In 1992, Congress passed legislation making the site an official wildlife refuge.

Since then, more than 330 animal species have been spotted in the 15,000-acre refuge, including deer, snapping turtles, burrowing owls, and a host of migratory birds. One longtime denizen of the high plains, bison, returned to the refuge in 2007 when 50 of the animals were reintroduced to the land. These days, the herd usually numbers about 250.

More recently, the refuge reintroduced black-footed ferrets to the site. Once thought to be extinct, the ferrets have been on the rebound since a pocket of holdouts were discovered in Wyoming in 1981. They eat prairie dogs, which are plentiful at the Rocky Mountain Arsenal, and take over their burrows once mealtime is over.

The refuge has likewise become more hospitable to human visitors. Wildlife watching is the main draw: The bison roam freely in a 10,300-acre fenced area that is accessible via an 11-mile driving loop. There are also 20 miles of easy hiking and biking trails and a pair of lakes for fishing. Many of the trails are paved and wheelchair-accessible, including the 0.6-mile Lake Mary Loop Trail. “It offers a little something for everybody,” says Sarah Metzer, the refuge’s visitor services manager.

Although the cleanup was officially completed in 2010, restoration work is ongoing, Metzer says. Homesteaders worked the land here from the late 1800s until the army’s arrival, planting trees, digging irrigation canals, and otherwise reshaping the land for agriculture. The refuge aims to undo that work and return the land to mixed and short-grass prairie.

“There’s still quite a bit of restoration work needed to account for those disturbances to the land during that homestead period,” Metzer says.

The bison are a big part of that work, she adds. They provide all kinds of “different ecosystem services,” she says, “whether it’s creating paths in the soil for other species, or trampling seeds down, or carrying and distributing seeds on that thick fur of theirs, or just fertilizing the soil, which they do every day.” 

“The benefit for us in conserving [the bison] that we nearly eradicated from the North American landscape is that they can do some of the things that we would only be able to accomplish with heavy machinery,” Metzer says. “They’re doing all of that naturally, just by existing out on the prairie.”