For the off-road warriors of Northern and Central California, few wild landscapes are as enticing as the Clear Creek Management Area, with its deep canyons, scampering feral pigs, rainbow-hued flowers and giant rock formations.
But on Thursday, a 48-square-mile swath of the Diablo Mountains in San Benito and Fresno counties was labeled a virtual death zone where five visits a year over three decades could lead to lung cancer and other crippling diseases.
The recreation area was abruptly closed for the foreseeable future by the federal Bureau of Land Management, after a three-year by the Environmental Protection Agency found that dangerous levels of asbestos dust were being stirred up by motorcycles and other off-road vehicles.
Any human use -- even camping and hiking -- was deemed potentially dangerous, especially to children, and outlawed until the BLM develops a new plan for the area.
Clear Creek, which registers 35,000 visits a year, has long been known as the largest U.S. deposit of asbestos, a natural mineral and known human carcinogen. It harbors an EPA-designated toxic Superfund site, the former Atlas asbestos mine. Previous studies over several decades found high levels of asbestos in the area, but the results were not as conclusive as in the new 160-page assessment, EPA officials said Thursday.
For the last three years, the BLM has closed the area from June to October, the dustiest months. Closing the site year-round was "an extremely tough decision," said bureau Field Manager Rick Cooper. "But my first priority must be protecting the health of visitors and employees."
The bureau, which first studied Clear Creek asbestos in 1992, has warned visitors in parts of the area to avoid breathing dust and drinking water from the creek. BLM employees are required to wear respirators on dusty days and to decontaminate after each visit.
But off-roaders have largely ignored the warnings. Don Amador, the western representative of the BlueRibbon Coalition, a national off-road group, said his group was raising funds to challenge the closure in court.
The type of short-fiber asbestos in the region, known as Coalinga chrysotile, he contended, is "not a health risk." Noting that the management area, which has 800 miles of trails, has been named one of the top 10 off-road areas in the nation by motorcycle magazines, he added, "We are in for a long, hard battle."
The EPA and other federal agencies, however, have found that chrysotile asbestos is toxic.
Moreover, officials said, they found other types of asbestos -- including tremolite and actinolite -- all known carcinogens. To collect samples, EPA technicians rode the area's rugged trails on dirt bikes and in SUVs with the windows down, taking 300 samples in February, September and November. They wore backpacks with small air pumps and filter intakes at shoulder height, close to the torso to simulate effects on children.
The asbestos fight is not the first to roil the recreation area. In 1985, the U.S. Fish and Wildlife Service listed the San Benito Evening Primrose, a wildflower found only in the Clear Creek area, as a threatened species, touching off a 20-year battle between environmentalists and off-roaders over how to protect it.
After a lawsuit by the Tucson-based Center for Biological Diversity and the California Native Plant Society, off-road use was officially restricted to 242 miles of trails to protect the primrose and other fragile species, although enforcement reportedly has been spotty.
Thursday's complete closure seems likely to divide environmentalists, many of whom are attached to the area's hiking, rock climbing and bird-watching pleasures. "I'm not sure the decision is wrong," said Brian LeNeve, a native plant society activist who led the battle for the primrose.
But, he added, "I am also not a fan of the government protecting us from ourselves. . . . Even with the EPA final report, I would go to Clear Creek again with no worry."
Emily Roberson, an ecologist with the Center for Biological Diversity, praised the EPA effort as "meticulous in data collection and analysis. It is a much greater health hazard than previously thought. And the BLM is going to have to be very careful if they open it up."