ANCHORAGE, Alaska (Reuters Life!) - When nature called on North America's tallest peak, climbers answered for decades with an improvised sanitation system.
They dropped their feces into glacier crevasses, trusting the force of moving ice to grind the waste material away.
Now that practice is being phased out. Climbers on 20,320-foot Mount McKinley and other snowy peaks in Denali National Park are required to haul out their wastes from at least portions of the mountains.
At the same time, the National Park Service has commissioned a multiyear study to determine the environmental impact of waste thrown over successive summers into the crevasses of the Kahiltna Glacier, the vast river of snow and ice that flows along much of the main McKinley climbing route.
"Theoretically, it gets ground carried 30 miles down the glacier. It should break down. Theoretically," said veteran Denali mountaineering ranger Roger Robinson, who has for years led a charge to clean up McKinley and other park mountains.
Robinson's efforts have resulted in widespread use of metal containers known as "Clean Mountain Cans," which serve as ultra-portable, snap-shut toilets, strapped to climbers' packs and toted around the mountain.
The cans, issued to each climbing team in Denali National Park, were introduced on a test basis in 2000. They are now mandatory, under rules enacted in 2006.
Once brought off the mountain after expeditions, which usually last three weeks, they are returned to authorities, cleaned by a contractor in Wasilla and put back into service.
The system has been successful enough that park managers have removed almost all the latrines that once served the 1,200 to 1,300 climbers who ascend McKinley each summer.
Even though climbers are still permitted to dump the contents of their cans into glacial crevasses between the 7,000-foot and 15,000-foot level, the mountain is far cleaner than it was in past times, experts say.
Younger climbers "have not been without the Clean Mountain Cans, so they don't know any other way," Robinson said. "They've seen the mountain quite clean compared to what some of us old farts saw."
Robinson will be presenting lessons from Denali later this week at a conference in Colorado he has organized. The "Exit Strategies" conference will examine methods of managing human waste in parks, recreation sites and wild lands and even underdeveloped villages that lack sewage systems.
Also presenting will be researchers from Alaska Pacific University, glaciologist Michael Loso and graduate student Katelyn Goodwin, who are trying to find out what happened to all the waste dumped into crevasses over the years.
The team already has some preliminary estimates: "It'll take anywhere between 30 and 400 years to melt out, depending on where it's deposited," Loso said.
Since McKinley climbing began in earnest in the 1960s, that means it is time to search the glacier terminus to see what may be dropping into the Kahiltna River, Loso said.
"Some of the waste should be already melted out now, or should be darned close to melting out," he said.
When it does, it may not be a pretty sight, Loso said.
"I think what you're going to have is big, messy, poopy plastic bags falling out," he said.
The waste is expected to appear in an extremely remote and little-visited site. But once they locate it, he and Goodwin hope to determine whether the glacially transported feces pose a health or environmental hazard, in the form of excessive E-coli or fecal coliform, in the river.
Such problems were detected in a somewhat similar study conducted in the Alps at the end of a much shorter glacier upon which sat a heavily used mountain house, Loso said.
But the freeze-thaw cycles, the grinding and ultraviolet rays to which Denali climbers' feces have been exposed might be enough to render the material biologically benign, he said.
Robinson, meanwhile, hopes the feces flow will come to an end altogether.
The fact climbers have successfully carried their cans up and down the mountain's highest and harshest elevations -- "the toughest part of the whole climb" -- makes it reasonable to expect future expeditions will pack out all waste without leaving a speck in crevasses, he said.
So far, the obstacles are logistical. "We've invented the system to bring it off, but we don't have enough cans to make it happen right now," Robinson said.
Editing by Jerry Norton