After weeks of effort, I finally get permission to tour the Rocky Flats National Wildlife Refuge, although the wildlife agency asks that I not bring McKinley along, because of what spokesman Matt Kales called his penchant for "media sensationalism." I go instead with wildlife managers Steve Berendzen and Bruce Hastings. Berendzen is thin and clean-cut; Hastings has a graying beard and softer edges. They drive me past a churning gravel plant and onto the refuge. We first head north, winding into a drainage that hides a decaying ranch house and a historic barn purchased and abandoned by the Atomic Energy Commission when Rocky Flats was originally built. A pond is iced over with the morning's frost. As we approach, a coyote sprints between two mule deer bucks stalking a beleaguered doe, then darts past a gnarled cottonwood and up a steep slope.

Berendzen and Hastings are biologists, far more adept at identifying wildlife than assessing nuclear cleanups. As we wind up and down the steep gullies flanking the site, they point out purplish clumps of big bluestem grass, a busy swirl of ravens. Finally, we arrive at a barbed wire fence with yellow DOE "No Trespassing" signs attached at regular intervals. A few boxy monitoring devices dot a riprap-lined holding pond. We climb along the fence until we can see the pancake-flat plateau where Rocky Flats' 800 structures used to be. There are a couple of bulldozers and a line of conifers, and then there is nothing, just acres and acres of level, tawny earth. In the distance, we see the subdivisions of suburban Denver. "The EPA and the Colorado department of health have determined the site is clean," says Berendzen, "and we accept that." Due to funding shortages, no work has been done to develop facilities for visitors. Should the money materialize, the Fish and Wildlife Service plans to build six to eight miles of hiking trails on the land and open them to the public.

To discourage potential visitors, Wes McKinley has introduced legislation requiring that the refuge post signs stating that Rocky Flats was a "nuclear weapons" plant where "radioactive and other hazardous materials" were "used and released," and distribute pamphlets informing visitors that during the plant's operation, the DOE and its contractors "buried, burned, and sprayed plutonium and other radioactive and hazardous materials onsite." The first two times McKinley introduced his bill, officials from nearby cities, afraid of the possible impacts on local real estate prices and on the refuge, helped derail the legislation. This winter, it was killed in committee again.

Like much of Rocky Flats' buried history, the record of McKinley's grand jury panel will not soon be unearthed. The grand jury voted to indict a number of individuals who worked at the Department of Energy and Rockwell International, the contractor that operated Rocky Flats at the time, for environmental crimes. But Rockwell was permitted to plead guilty to lesser violations, and no action was taken against the DOE employees. "The Justice Department wanted to indict the workers, the valve-turners; we wanted to indict the people responsible, in the office with their fancy golf clubs and high-dollar whiskey," McKinley says. Outraged, the grand jury wrote a report outlining the indictments they recommended, but the report and all the documents on which it was based were sealed by a judge. Though the grand jury's report was eventually leaked in full, the documents remain sealed today, despite nearly 20 years of effort to make them public.

The museum that took on the task of keeping those buried memories alive, meanwhile, is struggling. Cleanup contractor Kaiser-Hill gave the museum's board $150,000 to get started, but additional money from the Department of Energy, which helped to fund a number of other museums across the DOE complex, was slow to materialize. In late 2007, after six years of effort, the museum received a $492,000 appropriation; the board will need around $5 million, however, to buy land, design exhibits and construct a permanent building. Private efforts have proven equally disappointing -- some opponents of the plant have said that they are not interested in memorializing a place whose existence they fought for so long. The splitting of the atom had many insidious side-effects; one frequently overlooked byproduct was the way that the secrecy of the Cold War split the community and its memories. It scared those on the outside, isolated those on the inside, and created a situation where transparency and accountability were entirely absent. Between the intense secrecy and the confusing, contradictory swirl of stories surrounding Rocky Flats, we may never know "what really happened" there, and what hazards still remain.

In the summer of 2007, for the first time since Rocky Flats ceased production, a plutonium trigger manufactured at Los Alamos received "diamond stamp" approval, signaling that it was ready for use in a warhead. As the nation embarked on another nuclear buildup, it remained an open question how we would remember the previous one: an underfunded wildlife refuge, a modest museum, a cautionary sign, a placard on the highway? "Everyone looks at the museum for different reasons," said Shirley Garcia, who worked at Rocky Flats for 15 years and now serves as president of the Rocky Flats museum board as well as environmental coordinator for nearby Broomfield County. "They want to keep the history because it's important and it's a story that needs to be told. … That's all well and good. But my primary purpose is to retain the institutional knowledge of what's out there so that people don't forget about it, so that people don't start saying, 'Let's develop it, it's beautiful out there, we can build million-dollar homes.' " 

Plutonium has a half-life of 24,000 years. The half-life of memory, by contrast, is a much briefer thing. The contamination at Rocky Flats will long outlive our efforts to control or even remember it. Like the radiation Jerry San Pietro used to chase, like his elusive burial map, like the documents Wes McKinley fought to release, like the waste trenches and the rumors and the memories, Rocky Flats' contested history is now invisible to the naked eye.