Hazel Beall fondly remembers the winters of nearly 50 years ago when she and her friends would sleigh ride down a challenging hill that was on the property of a large dairy farm in Fairfax County.

Today, when Beall drives by the scene of many of her childhood memories, she no longer sees the hill or farm. Both have been replaced by the Fair Oaks Shopping Center alongside Rte. 50 and Interstate 66, which has become the centerpiece of an area filled with commercial and residential construction that many developers say will soon make it a major Fairfax business hub.

"You always feel like you'd like to go back to your roots," Beall said. "Now my roots are under the cement. We know the feeling when you say you can't go home again."

To many others, however, the development can't come quite fast enough.

"Most of Northern Virginia is going to be interested in the area," said Stephen Beck, vice president for development of Centennial Development Corp., which has plans to construct more than 2 million square feet of office, retail, hotel and residential complexes on 81 acres adjacent to the shopping center.

Echoing other developers and planners, Beck said factors including the mall, nearby I-66, the planned Springfield Bypass that is planned for just west of the mall, lease rates that are lower than those elsewhere and strategic county planning all make the Fair Oaks area prime for future development.

A Holiday Inn and three office buildings already have opened. Construction on one of the Centennial office buildings could begin this spring, Beck said. Other Centennial plans call for a 300-room hotel, seven office and retail buildings ranging from five to 10 stories in height and 630,000 square feet of mid- to high-rise apartment buildings.

Large-scale development of the area began about six years ago with the opening of the shopping mall, which has 188 retail outlets, including six department stores.

Gil Brooker, the center's general manager, said business has been so strong since its opening that he expects the mall to be "No. 1 in Northern Virginia this year," as measured by the volume of sales per square foot. He said he believes the Tysons Corner shopping mall ranks first.

The mall also will become a part of the current building boom when construction begins next month on a 90,000-square-foot wing that will add another 35 to 40 stores to the mall.

"For the foreseeable future, we're going to see amazing growth in the mall's business," Brooker said.

Since the mall's opening, businesses as well as county planners have realized the area's potential for growth. The mall area "is one of the premier sites of Northern Virginia," said William Keefe, Fairfax County chief of long-range planning.

He added that the mall is in one of the central cores of a 5,300-acre area that was identified by the county in a 1982 plan for future development. Included in that area is a 180-acre site about a mile south of the mall that someday will be the location of the county's government facilities as well as commercial buildings.

The three office buildings that have sprung up around the mall all are enjoying one unique aspect: They're 100 percent filled with workers. The immediate mall area has attracted a wide range of tenants, including government contractors, architectural and law firms, life insurance companies, mortgage firms and such medical services as the Group Health Association, which is housed in a five-story building overlooking Rte. 50.

John R. Bogardus, general manager of the Holiday Inn located at the center, said business has been better than expected since the facility opened in December 1984.

He said use of the hotel's meeting space exceeded first-year projections by 20 percent and an average of 75 percent of the facility's 252 rooms are filled on a typical night, mostly with business people. That room occupancy rate is better than those of many hotels in Washington, where the occupancy rate averages 69 percent, according to the Hotel Association of Washington.

One of the major employers at the shopping center locale is Contel, a telecommunications firm that houses more than 500 employes in two buildings. The firm first moved to the area in 1982 from Vienna, and last May expanded into a new eight-story facility at one end of the mall.

William Kamachaitis, Contel's executive vice president, said the Fair Oaks location is an important tool for recruiting employes.

"We're in a competitive marketplace for high-technology people," said Kamachaitis, whose company has major contracts with U.S. and foreign governments. "The mall provides for an unusual convenience for employes."

He added that commuting in the opposite direction during rush hours is an added attraction for the firm's employes, most of whom live in Northern Virginia.

What helps speak for the success of the Fair Oaks area is the fact that most developers are constructing buildings prior to obtaining any tenants to fill their projects.

"We don't think we're going to have any problem" renting space, said James Evans, vice president for development and construction of The Evans Co., which recently began work on a 12-story office building next to the mall. Occupancy is planned for March 1987.

Evans said the amenities of the Fair Oaks area will make projects like his competitive with other Northern Virginia commercial concentrations, such as at Tysons Corner, the Dulles Access Road area and the Vienna Metro site.

Other developers agreed. Thomas Knoll, vice president of Richmarr Construction Corp., said that because of better planning at Fair Oaks, "the end product here will be substantially better than what you have at Tysons Corner . . . . You won't have the same gridlock as the Tysons area."

Knoll's company is planning a 14-acre site next to the mall that will house two 10-story office buildings and a 180-unit apartment complex. Groundbreaking is scheduled for this fall.

Other major projects are under construction near the shopping center. Hazel-Peterson Cos. is developing the massive Fair Lakes site, 620 acres about a mile west of the mall that will contain 35 commercial buildings and 1,300 residential units. Other projects under construction just west of the mall include 590 residential units called Fair Ridge, by The Milton Co., and an office complex developed by The Washington Corp. in an area that the county has approved for up to five buildings.

Most developers praised the long-range planning efforts by the various parties to shape the area into a mix of residential and commercial properties that is transforming what was once grazing land into "the ideal site for the downtown area of Fairfax County," said planning official Keefe.

"It's been a rare example of politicians, business people and citizens working together," said Robert Kelly, a spokesman for Hazel-Peterson Cos.

Still, for someone like Beall, the Fair Oaks development brings only laments. Beall, whose 81-year-old father is one of the last remaining homeowners immediately adjacent to the shopping center, said numerous developers have been trying to buy his property at 4226 Legato Rd. for the last five years. But she said her father has no intention of selling the home she grew up in.

While Beall acknowledged that development of the area was inevitable, she said, "I'd like to have seen it develop more slowly."