If Congress and the Obama administration fail to avert a budget impasse next week, the National Park Service will move to furlough more than 21,000 employees in a two-day process of closing down the National Park System.

The shutdown, coming as many eastern parks are heading into the traditionally tourist-heavy fall leaf-peeping season, could cost gateway communities upwards of $30 million a day in lost revenues, according to the National Parks Conservation Association. Too, the economic impact would be something of a double-whammy for those gateway communities that lost revenues when the budget sequestration imposed early this year led some parks to delay their openings, while others shuttered campgrounds.

Across the 401 units of the park system, closures will be conducted quickly, with "day visitors ... instructed to leave the park immediately" and overnight visitors given two days to leave the parks.

"Wherever possible, park roads will be closed and access will be denied," states the Park Service's contingency plan (attached below) drafted in the event Congress fails to pass a Continuing Budget Resolution to keep the government operating. "National and regional offices and support centers will be closed and secured, except where they are needed to support excepted personnel. These steps will be enacted as quickly as possible while still ensuring visitor and employee safety as well as the integrity of park resources."

According to the plan, posted on the Interior Department's website Friday, each of the Park Service's seven regional offices will be whittled down to about three full-time employees.

At individual parks, "Due to the dramatic differences in operations, size, visitation, location, and infrastructure represented in national park sites, the number of employees required to carry out the essential activities defined above will vary greatly from site to site. As a rule, staffing will be held to the very minimum for the protection of life, property, and public health and safety. Only personnel absolutely required to support these activities will remain on duty. Wildland fire personnel required for active fires or for monitoring areas currently under a fire watch will remain on duty.

"All other personnel, including law enforcement, EMS, and Fire Management not deemed excepted will be furloughed, but will be subject to being called back in the case of an emergency."

Of the agency's 24,645 employees, all but 3,266 will be furloughed if the closure comes about, according to the plan.

At the NPCA, officials decried the possible closure of the park system, saying it could impact as many as 750,000 visitors a day and cost gateway communities as much as $30 million in lost revenues every day the parks are closed.

“A government shutdown would make a bad situation even worse for our national parks,” said Theresa Pierno, the NPCA's acting president. “Families, school groups, and tourists from around the world have made plans expecting our parks to be open. Instead, they face the possibility of disruption and disappointment, while local businesses and park concessioners that serve them face the prospect of lost revenue and further economic hardship.”

While the threat of government shutdown occurred in 2011, the government actually shut down in late 1995 and early 1996 for a total of 27 days. According to NPCA’s 1996 report, this shutdown cost park-dependent communities an estimated $14 million daily.

"Mariposa County, adjacent to Yosemite National Park in California, saw 25 percent of their adult population temporarily out of a job due to the park closure," NPCA said in a release. "The communities around Everglades National Park were hit with an estimated decrease in direct sales of up to $1.4 million. In today’s dollars, a government shutdown next week could be even more devastating to these communities."

“When our national parks closed in 1995-96, I received an outpouring of calls from gateway communities alarmed by the situation,” said Phil Francis, recently retired superintendent of the Blue Ridge Parkway, typically the most visited National Park Service unit in October, with nearly 60,000 visitors spending $1.4 million each day.

“The potential shutdown adds insult to injury because these communities are already concerned about the recent cutbacks in funding for national parks that have harmed the Park Service’s ability to serve visitors. No one expected these cuts to happen again. Now we’re looking at not only a potential shutdown, but the likelihood of another round of cuts. If that happens, there’s a good chance it’s going to be even harder than last year,” added Mr. Francis.

Chris Fogg, executive director of the Bar Harbor Chamber of Commerce in Maine, said the potential shutdown could be devastating to the Bar Harbor community.

“Acadia National Park is an economic driver for our community and we could see a potential loss of $684,000 per day. The beautiful fall foliage in October attracts nearly 10,000 visitors daily and the loss could be shattering to our community," he said in comments distributed by NPCA. "Because of the sequester and the late opening of Acadia’s roads, business was already down about 30 percent in April and May of this year in comparison to the average of the previous five years. We just can’t believe that Congress is letting this happen."

Grand Canyon National Park averages more than 11,000 visitors per day during the month of October. Kevin Striet, business director of Grand Canyon Tour & Travel, is also concerned about a possible shutdown.

“Grand Canyon Tour & Travel operates several buses daily to the South Rim filled with anxious passengers, both domestic and foreign, and some of whom, have planned their whole trip around the chance to visit the Grand Canyon," he said in the NPCA release. "The thought of having to re-direct hundreds of passengers at a moment's notice is not one that we like to think about but as the day comes with no resolution to an approved budget, the actuality of having to re-route passengers to other tours, or to perhaps cancel their excursion altogether, is daunting. We are hoping that at least a temporary budget is approved until a more permanent solution can be found."