Southern Maryland governments will place scores of officials and police officers on duty Friday--a day when authorities expect nothing unusual to happen.

Friday, of course, brings New Year's Eve, and with it the long-anticipated change to the year 2000, or Y2K. Whether computer clocks can digest a date that does not begin with the digits "19" will determine whether the stroke of midnight brings a cascade of computer shutdowns.

Such failures could cause chaos, because computers help run electricity grids, water systems, telephone networks and other crucial services.

But Southern Maryland officials say they have conducted extensive repairs and tests of critical systems. They say they expect the new year to bring nothing more than the usual revelry.

But just in case, officials in each of the region's three counties plan to set up a multi-agency command post. In addition, the region's nuclear power plant and its large military bases will have extra staff on hand.

Those working will hope the extra effort is all for nothing.

"It will be a good exercise, we think--that's all," said Donald P. McGuire, Charles County's director of emergency services.

McGuire will lead about 50 people who will gather in the County Government Building in La Plata on Friday and stay through Saturday.

Those summoned include a double-shift of 911 operators and representatives from the Red Cross and Department of Social Services, in case shelters must be opened.

If communication by telephone and computer fail, an amateur radio operator will be on hand to maintain contact with the state's emergency operations center in Reistertown, north of Baltimore.

To reduce the potential for massive crashes at midnight, Charles County will shut down its computers at midday Friday and bring them back up the next day, Jan. 1.

Similar precautions are to be taken in Calvert and St. Mary's counties, officials said.

The Calvert Emergency Operations Center will be activated at 7 p.m. Friday and remain open until 4 a.m. New Year's Day, said Robert Short, director of public safety for Calvert County.

The center will be staffed by more than a dozen state and county officials, and key county staffers and law-enforcement officers will be on call, Short said.

Despite the preparation, Short said, officials expect that "things should roll over with no problem whatsoever."

He said the county has been undergoing Y2K preparations for more than a year, including successful tests of emergency communication systems.

"We're just covering ourselves is what we're doing," Short said. "We just want to be ready if something happens."

Police agencies are scheduling extra working hours.

Charles County Sheriff Fred Davis said he has canceled all leave between Dec. 29 and Jan. 3 and has doubled the number of officers normally working New Year's Eve.

In Calvert County, leave also was canceled, according to Capt. Robert R. Hampshire. He said the office will deploy 36 deputies, more than triple the number of officers usually on duty on New Year's Eve.

In St. Mary's County, sheriff's officers plan to set up a special New Year's Eve command post at headquarters in Leonardtown. The center will have an extra bank of phones, cellular phones and maps of the night's special patrol assignments.

In addition to the regular 3 to 11 p.m. and 11 p.m. to 7 a.m. shifts--that each will field 11 officers--St. Mary's officers will field a special 10 p.m. to 4 a.m. "power shift" to be staffed with the sheriff's SWAT team, among with 18 additional deputies and an additional K-9 officer.

Part of that preparation is for the normal New Year's Eve incidents associated with too much partying. Sheriff's staffers have assembled more than 200 "mass arrest" kits that include the paperwork needed for on-scene crowd arrests at a rowdy party or other disturbance.

"We're preparing for the worst and expecting nothing to happen," said St. Mary's Sheriff Richard J. Voorhaar (R). "We feel we will have ample personnel to do everything from directing traffic to arresting disorderlies, should the need arise."

Major installations in the region are getting special attention.

At the Calvert Cliffs nuclear power plant, backup equipment including radio telephones will be available to supervisors, said spokesman Karl Neddenien.

Officials at the plant have spent several years preparing for the Y2K changeover and are not expecting any problems, he said. "We're certified Y2K-compliant," said Neddenien. "Our system is ready. It's been thoroughly examined."

The Indian Head Naval Surface Warfare Center, a testing and research facility for explosive materials, will add personnel and security patrols on New Year's Eve at a coal-burning utility plant on the base, said Chris Adams, a spokeswoman for the Charles County facility.

Equipment at the base has met Navy standards for Y2K compliance, Adams added.

"We have been required to do testing on every piece of Y2K-related equipment," Adams said. "We've tested everything and are Y2K compliant."

At the Patuxent River Naval Air Station in St. Mary's County, Capt. Paul Roberts said the base has made arrangements for emergency generators and a special operations center will be running in case the Navy needs assistance with equipment on aircraft in the fleet.

Roberts said schedules for testing aircraft and equipment, which are typically light over a holiday period, have not been disrupted because of Y2K concerns.

"It's nothing exceptional to us," said Roberts. "We feel very well prepared for Y2K."

Staff writers Annie Gowen, Raymond McCaffrey and Steve Vogel contributed to this report.