Due to an editing error, a story in yesterday's editions on security preparations for Pope John Paul II's visit here Oct. 6 and 7 suggested incorrectly that vacations and days off for National Park Service employes will be canceled on Oct. 7. Vacations and days off will be canceled only for the 750-member U.S. Park Police force and for about 2,700 officers of the 4,100-member D.C. Police Department.

Deputy Chief Hugh A. Groves, field commander of the 705-member U.S. Park Police force here, stood in his headquarters conference room in Southwest Washington, scrutinizing a hugh strategy map of the Mall studied with arrows, X's and hatch marks where Pope John Paul II will hold his historic outdoor mass on Oct. 7.

"We'll have officers standing at 20-foot intervals along the south side of this chain link fence," Groves said, pointed with a swagger stick. "The crowds will be to the north, here."

The police will be wearing "soft hats, not helmets," Groves said. His luminous green eyes narrowed for a moment. "This is a religious service," he said. "We don't want to go too heavy on police presence."

Across town at 23d and L Streets NW, Deputy Chief Robert K. Klotz, commander of the D.C. Police Department's riot-trained special operations division, chewed thoughtfully on the end of a pencil in his office cluttered with street maps, photographs and other memorabilia of past demonstrations.

"The basic problem," he said is getting the people in, keeping them in control at the mass and then getting them out of here when it's over."

"This is a people problem [but] we don't want a policeman every two feet. We don't want an armed camp out there," he added.

Groves and Klotz, both veterans of Washington's many street battles and now the two top strategists for crowd and traffic control during the unprecendented papal visit here, rushed through a hectic schedule this week of staff sessions, telephone conference calls and meetings with church, city and federal officials as they tried to firm up final plans and sought that delicate balance between adequate security for the pope and avoidance of a garrison-state atmosphere.

Both stressed in separate interviews that their concern is not so much hostility or planned disruption within the crowd but the sheer magnitude of the throngs -- officially estimated at anywhere from 500,000 to 1 million -- and possible spontaneous over-enthusiasm of those surging toward the pope when he arrived on the Mall.

"This is going to be a religious service -- not a 'pro-anti' demonstration," said Klotz. "I see little potential for violence . . . We're depending on [volunteer] ushers and marshals provided by the [Roman Catholic] Archdiocese [of Washington] to do a lot in the personal handling of things on the Mall."

The law enforcement presence throughout the pope's two-day visit to Washington will nevertheless be extensive.

In addition to the fully mobilized 50-member park police force and approximately 2,700 officers of the 4,100-member D.C. Police Department, a large Secret Service detail is assigned to provide 24-hour personal protection of the pope.

Vacations and days off have been canceled for both U.S. Park Service and D.C. Police on Oct. 7.

Klotz said there is no plan at this time to mobilize the D.C. National Guard.

Other police jurisdictions, including those in the surrounding suburban counties, also have been called on to help, especially with traffic as the crowds descend on the city.

Traffic control and the movement of people to and from the Mall is expected to be the biggest headache. General plans call for parking out-of-town charter buses and other vehicles outside downtown Washington -- the Pentagon, West and East Potomac parks and RFK stadium -- and ferrying the crowds in by shuttle buses and Metro subway trains.

A vast area from the Lincoln Memorial to the Capitol will be closed to traffic on Oct. 7 except for the shuttle buses. Thousands of worshipers are expected to walk to the Mall. Regardless of the most meticulous planning, officials acknowledge that the bus and train systems probably will not be able to smoothly cope with the hoards of people expected, and extensive congestion of both vehicular and pedestrian traffic is likely.

In addition to police, the archdiocese plans to provide 4,000 to 5,000 volunteers -- mostly marshals wearing distinctive armbands or badges -- to assist the crowds, give information and direct those in need to first aid stations, lost person centers, public telephones, food concessions and hundreds of portable restrooms that will dot the Mall area.

The 10,000-square foot, three-tiered stage and altar from which Pope John Paul II will say the mass on the Mall will be surrounded by a 42-inch-high chain link fence. The fence also will extend several hundred yards from the altar at the Smithsonian Castle along Jefferson Drive on the southern side of the Mall to 14th Street on the west and 3rd Street on the east.

Police officials explained that the pope will enter and leave the Mall by Jefferson Drive, necessitating greater security in that area.

"I recommended the fence," Groves said. "I felt we needed something a little more sturdy" than the customary snow fencing used by Park Police for large public gathering on the Mall and Washington Monument grounds.

National Park Service officials estimated that more than a mile of fencing will be needed and will cost about $25,000. The archdiocese has agreed to pay for the portion of the fence surrounding the stage and altar, the officials said.

Groves, Klotz and other senior police officials have studied video tapes of the pope's visit last June to Poland, noting with some conern his tendency to break from the scheduled itinerary to mingle with the zealous crowds around him.

"We're not looking for any trouble," said Groves. "The only thing is those crowds. Sometimes they become a little over-enthusiastic."

As for the size of the crowd expected here Oct. 7, both police and archdiocese officials acknowledge they have no concrete basis for their rough estimate of 500,000 to 1 million.

The Msgr. Raymond J. Boland, co-chairman of the papal visit here, indicated $500,000-plus" on the official Park Service application for use of the Mall.

Park Service representatives said that in informal talks with church officials, they have discussed the possibility of 1 million as a maximum number. With three weeks to go, they said it is still too early to attempt estimates based on numbers of chartered buses, hotel bookings and other specific information.