On almost any day, Spec. 4 Chris Harvill will leave his clerk's job in the Fort Belvoir finance office at about 4:30 p.m. By 4:40, he will have bought two six-packs of beer at the base's package store. By 4:50, he will be back in his 20-by-20 barracks room, out of his uniform and into his jeans. By 4:55, the stereo will be playing and a a game of backgammon will be in progress.

"And that," says Harvill, "is usually all there ever is. The only difference from that point on is what time I knock off and go to bed."

"Sometimes," he adds, "we go to the electronic game room at Springfield Mall and spend a lot of money. But most of the time we just hang out here in the barracks. I can barely remember the last time I spent an evening any differently."

By his own description, the 21-year-old Harvill is a Fort Belvoir "barracks rat" -- a soldier who takes home $550 a month, who is 2,000 miles from his Paradise Valley, Ariz., home and who is counting the eight months until he can leave Belvoir and the U.S Army permanently.

Harvill, and hundreds like him, are familiar figures around Fort Belvoir, the sprawling, 9,200-acre base just south of Mount Vernon on the Potomac River.

Belvoir, the largest Army base in the Washington area, is both a major local business and a sizeable Fairfx County neighborhood. The base employs 5,000 civilians in addition to its military complement. Some 6,000 solldiers are assigned to Belvoir and almost all of them live on the base. The 6,000 soliders have about 6,000 dependents.

Belvoir residents send their children to Fairfax schools, are active in local church and civic organizations and contribute mightly to the economy of the southern part of the county. Indeed, owners of businesses along U.S. 1 just north and south of Belvoir say they couldn't come close to surviving without trade from the base.

Belvoir's influence also spills into neighboring communities, where many mailboxes have "Lt. Col." or "Maj." before the residents' names. Nearly 10,000 Army retirees live in southern part of the county and use the Belvoir officers' clubs.

Most of the time, however, Fort Belvoir is a neighborhood totally into and unto itself.

"I've sometimes gone two, three weeks without even setting foot off the base," said Col. David O. Cooksey, the chief of staff. "I would say that Ft. Belvoir is extremely self-sufficient. . . . No, that isn't entirely good, but it is certainly more good than bad, from an Army point of view."

Because Belvoir is chiefly an engineers' and Engineer-training base, its soldiers tend to be older, and thus a little more mature, than those at a typical Army post.

"We have a lot of family men, and our men have professional pride," said Lt. Col. Gordon Fetkenhour, Belvoir's director of personnel and community activities. "You don't keep professional pride by running off to D.C. or the bars along Rte. 1 every chance you get." p

For another thing, Belvoir is a well-rounded community. "We have one of everything -- and it's a good one," jokes Cooksey. The base grapevine agrees. Bellvoir facilities and programs are said to be far above the Army average.

Belvoir is one of the few bases of its size in the U.S., for example, to offer interest-free emergency loans, a full-service marina, five branch libraries and a complete post exchange store. It has won Army awards for various services such as juvenile offender rehabilitation and the base newspaper.

Belvoir tends to encourage informality. Enlisted men often call their sergeants by their first names, and waves are as common as salutess. Also, the 30-month average tour of duty allow people to get aquainted and to get to know each other's problems.

"If I call the community health nurse here and say I have somebody who has to see a psychiatrist this morning, they know I mean this morning ," says Capt. Donna Weddle, Belvoir's protestant chaplain. "That could never happen at Ft. Hood, Texas."

A major problem for the Belvoir community is its location in one of the most expensive metropolitan areas in the country.

"It can cost three times as much as a guy has been paying somewhere else just to put a roof over your head off base here," says Capt. Barry Teel, director of Belvoir's welcoming program for new arrivalls.That means nearly everyone wants to live on base -- and that, in turn, has produced waiting periods as long as 30 months for base housing.

Even so, living on base can leave much to be desired. Of Belvoir's 1,600 units, nearly 500 are officially classified "inadequate," which means they lack dishwashers, laundry equipment, modern kitchens and air contitioning.

Sgt. Don Dolliver, his wife Sandy and their two young daughters were assigned such a place in Belvoir's Lewis Heights complex a little more than a year ago.

For months, Sandy Dolliver did the laundry in the kitchen sink because the family could not afford a washing machine, and the nearest laundromat was half a mile away. Then, despite her misgivings about city life ("I'm a country girl, I'm not used to this"), Sandy Dolliver took a job as a waitress. She had to work on the night shift so her husband could stay with the children.

Because their apartment is "inadequate," the Army charges the Dollivers only $188.73 of their $209-a-month housing allowance, and they may pocket the difference. "Still, coming here has been a big adjustment mostly because of the expense," said Dolliver, a 24-year-old supply sergeant. "I almost never go off base because I can't afford to."

Soon, however, the Dollivers and other Belvoir families may find it easier to leave the base. On Oct. 31, the Washington area was officially designated expensive enough for soldiers assigned here to receive a "variable housing allowance" of at least $120 per family per month.

That, combined with basic housing allowances that average about $200 a month for privates and slide upward according to rank, may be enough for soldiers to be able to afford off-base apartments, especially in the lower-cost Woodbridge area. "We're waiting to see what happens," said Cooksey. "We may have a lot of vacancies."

One man who's staying, however, is Sgt. Jim Worchester.

A 24-year-old clerk in the emergency loan office, Worcester is a divorced father. He says he "could never have made it in the outside world -- people are so cold. But here at Belvoir, people have been wonderful. I never have to hunt for babysitters, and Jenny (who is 6) can get a lot of mothering from the wives who live on my block because they know what she's been through as an Army child."

Worchester and others say however, that Belvoir is not the bargin center that Army bases are generally supposed to be. "I often find items cheaper at stores along Rte. 1 than here," Worchester said. For example, regular gasoline at the base filling station cost $1.17 a gallon last week. The price was the same at the Hess station just outside Belvoir's south gate -- and the Hess attendent did the pumping.

Officers and enlisted men agree that Belvoir's largest social problem is alcoholism. "It's Subtle, but it's there, and it causes big problems," said Cooksey. "However, give me the Fairfax County police blotter and the Fort Belvoir police blotter, and I'll find the same percentage of alcholo-related incidents."

Timothy Sullivan, 20, a Belvoir private from Massillon, Ohio, says he has never gotten into trouble because of drinking. "But I sure could if I keep on drinking a six-pack a day," he adds.

Six beers daily is about double what Sullivan used to drink as a civillian.

"The difference? The Army's the difference, man," said Sullivan. "Sometimes I dring and just go riding around with my buddies. It gets so lonely here sometimes."

"Come payday," said Pvt. Charles J. Nist," everybody here is zonked. For no reason. Just because it's payday." Nor is hell-raising far behind. "On a recent payday," said chief of staff Cooksey, "I had one of my tires slashed, right here in the Fort Belvoir cocoon." The culprit has not been identified, but Cooksey is willing to bet he wasn't sober at the time.

Should Belvoir intensify its links with Fairfax County? Should it invite schoolchildren to use its facilities? Should it open its halls to PTA and civic association meetings?

Community activities director Fetkenhour doubts such moves would be possible, in a practical sense. "We can't just say, 'We have six baseball fields and anyone who wants can come in and use them.' Our first priority has to be our own folks here. After they've used what they need, there usually isn't much left."

"We don't try to close Fairfax Countyunty out, and we don't try to push our people off the facility into Fairfax County," said Cooksey. "We like the camaraderie that can be built up by staying on base,, but we never insist on it. Soldiers are people. Some stay. Some don't"

Or, as Fetkenhour put it, "You don't have to go off the base, but you'd go a little ding-y if you didn't."