YELLOWSTONE, Wyo. -- It was 30 degrees below zero and 30 miles from the nearest plowed road. But in the snowbound visitors center at Old Faithful, cash registers rang merrily with sales of geyser postcards, and the restaurant had a 10-minute wait for a lunchtime table.
"I'm amazed to see people in the park at 30 degrees below," said Jeanne Keffeler, a Minnesotan who had expected on a recent midweek visit to be largely alone as she explored Yellowstone off season on cross-country skis. "I've been stunned by the amount of snowmobiles."
Over the past 20 years, the number of summer visitors to Yellowstone has increased by a third, while winter visitors have doubled. Now, 25 years after park officials first encouraged the use of snowmobiles, about 80 percent of the park's winter zTC visitors use them. The rest are largely cross-country skiers who often complain that snowmobiles shatter the silence and foul the air.
"When you wake up at the lodge at Old Faithful, you hear that hornet's nest sound," said Michael Scott, program director of the Greater Yellowstone Coalition, a regional environmental group. "If it's a chill morning, you get inversion and air pollution."
At nearby Grand Teton National Park, where the number of winter visitors is increasing by almost 10 percent a year, officials have started to charge a winter entrance fee of $10 for a weeklong vehicle pass. In Yellowstone, a fee of $4 a week has been charged for several years.
In the winter of 1992-1993, Yellowstone had 140,000 visitors -- the level forecast for the year 2000. Snowbound for five months of the year, one gasoline station in the park that winter ran out of fuel.
In West Yellowstone, Mont., the main outfitting town for snowmobilers, a thick blue haze over the entrance to the park has left rangers coughing and suffering from nausea.
Winter in Yellowstone, a serene and often magical wilderness experience, is increasingly tainted with urban problems.
During the three-month winter season, park rangers record an average of one snowmobile accident a day and one drunken driving arrest a week. Patrolling with radar guns on the park's 185 miles of snowmobile trails, rangers issue an average of five tickets daily to snowmobilers who violate the park's 45-mile-per-hour speed limit.
"With 1,500 to 2,000 snowmobiles a day, if only 5 percent break the rules, they can wreak havoc," said Dan Sholly, Yellowstone's chief ranger. "It's 35 below, a guy's drunk, and you have to get him to jail."
Although Yellowstone's summer visitors still outnumber winter visitors by about 20-to-1, there is growing off-season pressure on the park.
With 1.4 million snowmobiles registered in the United States, snowmobiling has become a $2-billion-a-year business. According to Snowgoer magazine, the nation's "top gorgeous trailside sight" is Old Faithful.
Auguring more use, last year snowmobilers inaugurated the Continental Divide Snowmobile Trail. It starts in west-central Wyoming, in Lander, traverses a chain of national forests and national parks, and ends 340 miles west, in West Yellowstone.
"Ten years ago there were six rental companies in West Yellowstone; today there are 18," said Ken Takata, a manager for Yellowstone Adventures, an outfitter.
"For snowmobilers, Yellowstone has become an experience they don't want to miss," said Bill Butts, general manager of Flagg Ranch, a hotel at the park's southern entrance that is promoting snowmobile tours. "The snow makes the wildlife stand out."
Taking a middle road, park officials are quietly putting the brakes on the unthrottled growth of snowmobiling. Over the past two years, the park has stopped issuing commercial permits to new snowmobile outfitters. It cut the maximum size of snowmobile groups to 10, from 15. And it banned snowmobilers who do not have a license to drive a car.
To cut pollution, park officials inaugurated an express entrance lane this winter in West Yellowstone. Instead of idling their machines in long lines, half of the visitors now speed through that entrance waving prepaid tickets.
Pollution monitors have been mounted at the gate. And in West Yellowstone this winter, Conoco started marketing a synthetic, biodegradable oil that has cut in half the amount of oil-based pollution from the average snowmobile's two-stroke engine.
Fearing that Yellowstone will put a cap on snowmobile tourism, the governors of Wyoming and Montana recently joined the call for "a clean machine."
In a gradual improvement over the last 25 years, the average amount of noise produced by a snowmobile running at 35 mph has dropped to 74 decibels from 88 decibels in 1972.