Defenders Magazine

From Bombs to Birds

How a former nuclear weapons site in Colorado became a wildlife haven

by Jennifer Weeks

Courtesy Department of Energy

Bruce Hastings drives a van down a dirt track across the grassy, rolling foothills of the Rocky Mountains in Jefferson County, Colorado. The high-rises of downtown Denver are visible 16 miles to the southeast, with a spider web of roads and suburban houses filling much of the space in between. But up here the land is green, broken only by scattered trees.

Hastings, deputy manager of the Rocky Flats National Wildlife Refuge, eases the vehicle down tracks that plunge into deep green draws, cut by creeks that run from west to east. On the north-facing slopes of these crevasses, mule deer and elk graze among hawthorn, chokecherry and wild plum shrubs. In one thicketed creek bottom a long-eared owl lurks in a cottonwood tree. As we crest the other side of the draw a big jackrabbit bursts out of the grass, flattening his spoon-shaped ears back as he runs. "Now he thinks we can't see him," says Hastings, chuckling.

This 3,953-acre refuge—one of the most recent additions to the country's national wildlife refuge system—is home to a wealth of plants and animals, including imperiled species such as Preble's meadow jumping mouse, bald eagles, several colonies of black-tailed prairie dogs, burrowing owls, sandhill cranes and northern leopard frogs. Common mammals found here include coyotes, muskrats, porcupines, gray and red foxes, badgers and minks. "Eastern and western flora and fauna mix here where the prairies meet the Rockies, so it's a very biologically diverse area," says Erin Robertson, a biologist with the Center for Native Ecosystems in Denver.  

But it isn't just this diversity, nor the refuge's proximity to one of the country's largest cities, that makes Rocky Flats interesting and important. It's the refuge's troubled past: For nearly four decades, the federal government ran a top-secret nuclear weapons facility in the center of this sprawling property. Here workers wearing respirators and protective suits processed radioactive materials into components for bombs. They left behind tons of plutonium and uranium, and acres of contaminated land and water. After years of wrangling about its future and a decade-long cleanup, Rocky Flats is finally emerging from its shadowy, Cold War past and entering a more visible, greener future.   

The dark start of Rocky Flats' history came in 1951, when the U.S. Atomic Energy Commission (predecessor of today's Department of Energy, or DOE) annexed several thousand acres of grasslands for what was billed as an urgent national mission: making triggers for atomic bombs. A 400-acre zone in the middle of the site quickly developed into a small city of buildings, trailers, tanks and storage pads bustling with human activity. Outside the barbed-wire fences, the rest of the site was left as grassland to provide a security border against spies and saboteurs.

For much of the Cold War, Rocky Flats and other atomic-bomb plants like it operated under tight secrecy, designed to keep Soviet leaders from learning details about the U.S. nuclear arsenal. These restrictions also concealed lax environmental policies, such as burying or improperly storing radioactive and toxic wastes. 

Nuclear operations at the Flats received little press coverage or public scrutiny until 1969, when a large fire at one of DOE's buildings nearly caused a catastrophic radiation release across the Denver area. State health officials started testing air, water and soil around the plant for contamination. In 1973 they found radioactive tritium in a creek flowing out of the site. Peace activists campaigned to close Rocky Flats down, organizing demonstrations outside the fence in the 1970s and 1980s that drew thousands of protestors. 

In 1989 the FBI and Environmental Protection Agency (EPA) raided Rocky Flats after a secret investigation into rumored illegal burning and dumping of radioactive wastes. Soon afterward the Cold War sputtered out. Without a military purpose, Rocky Flats' mission shifted to cleanup—a job at least as daunting as building bombs. The FBI raid had frozen operations in full swing, leaving tons of plutonium and uranium onsite in various stages of processing. Rocky Flats was one of the most polluted properties in the nation.

After several years of debate over how to clean up Rocky Flats' heavily contaminated core sector and what to do with the site, clean-up operations began in 1995. Federal government plans (formalized by Congress in 2001) to turn the bulk of the property into a national wildlife refuge required less-stringent soil radiation standards than residential or commercial development, since no people would live or excavate there. (For similar reasons, more than three dozen other refuges in the United States, the Pacific and the Caribbean have also acquired land from closed military facilities, including bases in Maine and Alabama and the former Rocky Mountain Arsenal east of Denver.)

A former weapons production site might seem like an unlikely place to establish a wildlife refuge, but in fact many military sites retain large swaths of high-quality wildlife habitat. As at Rocky Flats, operations at many of these facilities were clustered in core areas, and following extensive clean-up and testing, were shown to have had little effect on land and wildlife around the periphery. According to the Nature Conservancy, almost 330 endangered and threatened species are currently found on Defense Department lands—more imperiled species than are found on any other category of federal land.

Cleanup contractor Kaiser-Hill removed enough waste from Rocky Flats to fill a 65-story building the size of a football field, plus hundreds of buildings and tons of plutonium and uranium—a job that took a decade and cost $10 billion. In 2007 EPA certified that cleanup at Rocky Flats was complete except for long-term monitoring in the core industrial zone, which will remain under DOE control. Nearly 4,000 acres of intact buffer lands around this core were officially christened as a national wildlife refuge on July 12, 2007.  

"Rocky Flats has remained a native and natural environment around the cleanup area," says Tom Ryon, a wildlife biologist who did surveys at the site during cleanup. "It has rare tallgrass prairie plants, healthy wetlands, and lots of native plains species, and it hasn't been grazed or disturbed."

For proof of this, biologists point to a small, shy mouse that escapes predators by leaping into the air and using its six-inch tail to steer itself in flight. A federally threatened species, Preble's meadow jumping mouse is one of the smallest hibernating animals on the Great Plains. It lives near streams and waterways along the eastern slopes of the Rocky Mountains in Colorado and Wyoming. All three major creeks crossing Rocky Flats have been designated as critical Preble's habitat. 

"The Preble's mouse is important because it's an indicator species for the health of riparian areas," says Erin Robertson, "The fact that Preble's are still living at Rocky Flats shows that those streams and wetlands have remained pretty intact since the area was settled." The situation is very different in the sprawling Rock Creek subdivision east of Rocky Flats, she notes. "There aren't any Preble's down in there."

The refuge also has many different plant communities, including rare tallgrass prairie, a mix of species like big and little bluestem, switchgrass and upland sedges. "Those areas are relics of tallgrass prairie communities that date back to the Pleistocene era, and Rocky Flats is one of the largest remaining pieces in the West," says Ryon. 

All told, more than 190 species of birds use the refuge, from locally common red-winged blackbirds and lark buntings (Colorado's state bird) to rarer species like blue grosbeaks, long-billed curlews, Wilson's snipes and blue-gray gnatcatchers. Marshes in the creek draws attract herons, cormorants and ducks. "Wetlands are being destroyed all around us, but here's a place where they're thriving, and species like boreal frogs and tiger salamanders are using them," says Ryon. "On warm nights you can hear frogs calling."

A few critics argue that the cleanup was rushed and the site isn't safe for use as a wildlife refuge, but most local conservationists and officials see it as a success—although they want to make sure regulators enforce long-term controls to keep visitors safe. Many studies have been done at the site since the 1970s to assess whether contamination threatens wildlife. Most recently, tissue samples taken from deer in 2002 did not detect radioactivity. For humans, the added risks of developing cancer at Rocky Flats are minute—1 in 6.7 million for refuge workers, and 1 in 11.1 million for visitors.

"We know there's virtually no risk today, and we're ensuring through monitoring that it stays that way," says Shirley Garcia, environmental coordinator for Broomfield County, which lies east and downwind from the refuge. Garcia worked at Rocky Flats for 15 years and has supervised cleanup operations there and at other nuclear sites. "We also want our community to be able to use and enjoy the refuge and help maintain it."

Ironically, however, the refuge is still closed to the public—not because of security concerns or health hazards, but because the U.S. Fish and Wildlife Service (FWS) doesn't have funds to staff it. The service is currently managing Rocky Flats as a satellite of the Rocky Mountain Arsenal refuge, located on the prairie east of Denver. (This 17,000-acre wildlife refuge, which was a chemical-weapons manufacturing site before it became part of the national wildlife refuge system in 1992, is the new home of a herd of bison, introduced there from Montana in 2007 with help from Defenders of Wildlife). 

Rocky Flats' limbo status is just one illustration of how seriously budget cuts are eroding our national wildlife refuge system. Recent studies by the Government Accountability Office and Management Systems International, a private consulting firm, have confirmed that consistent underfunding and declining staff levels are making it difficult for refuges to accomplish their central mission—conserving wildlife and its habitat. "The problems facing Rocky Flats are emblematic of the problems facing wildlife refuges across the country," says Noah Matson, Defenders' Vice President for Land Conservation. "Each year, America's wildlife refuges fall further behind as budgets typically fail to keep pace with inflation, which means just to keep the office lights on and fuel in the trucks, some refuges are laying off staff, literally closing their doors to visitors, and being forced to let invasive plant species spread virtually unchecked. How much longer until we collectively decide that America's land, waterways and wildlife deserve better?" 

Whenever the budget picture improves, one priority at Rocky Flats will be removing invasive plants—like mullein, toadflax and knapweed that have colonized parts of the refuge—and reseeding those sections with native grasses. Historically, grazing and wildfire kept plant species in balance on prairie grasslands. FWS might allow limited cattle grazing at Rocky Flats to control invasives, says refuge manager Steve Berendzen, but wild deer and elk could suffice. Berendzen is also interested in creating a wildlife corridor, possibly with an overpass or underpass, to help elk cross state route 93 at the western edge of Rocky Flats when they roam down from the Front Range. "They cause a lot of traffic problems in winter when they come down looking for grass, so we may be able to get state transportation money to keep animals away from cars," he says.

FWS also plans to remove 28 miles of unused roads and 13 stream crossings at Rocky Flats and make the refuge into a hub for existing and planned recreational trails that crisscross the area. Although development starts close to the site's eastern border, Rocky Flats remains one of the largest undeveloped tracts along Colorado's Front Range, and neighboring towns have bought land north, west and south of the refuge to conserve open space. 

Rocky Flats' worth is obvious to anyone who stands on this windy mesa and looks east to the housing subdivisions that fill the Denver basin—developments with names that reflect their past association with nature, such as "Wildgrass" and "Silvertrees." Up here, humans have ceded most of the land back to wildlife, and our imprints are now buried under prairie grasslands that toss ceaselessly in the wind.

Freelance writer Jennifer Weeks covers energy and environmental stories from her home near Boston, Massachusetts.