Growth in the 5,200 acres surrounding Fair Oaks Mall and the I-66, Rte. 50 interchange apparently is running nearly 50 percent higher than the rate projected by Fairfax County planners four years ago.

Fairfax planners said in a report released this week that rezonings in recent years will produce considerably more development than was anticipated in what is known officially as the Fairfax Center Plan, which was adopted in 1982 by the Fairfax Board of Supervisors to guide growth in the west-central part of the county.

"The major impact of this projected increase in the level of development will be its effect on the transportation system within the area," the study said.

Although numerous road improvements to be paid for by developers are planned, the study said projected traffic levels could produce a gridlock.

The review of the plan started nearly a year ago, after more than two dozen proposed changes to the 1982 plan for the area were submitted to county planners by residents, developers and zoning lawyers. County officials named a citizens task force to work with planners to study those changes and the existing plan.

Because developers recently won approval for several major mixed-use projects or have started construction, some Fair Oaks residential areas that wanted in 1982 to be protected from commercial development have asked for the right to allow their neighborhoods to be redeveloped for commercial or high-density residential use. Homeowners in Fairfax Farms, Pendercrest, Cedar Lake Estates and Random Hills said traffic in the area has increased dramatically, prompting them to seek developers who might want to redevelop their neighborhoods.

According to the new study, Fairfax officials predicted growth on available Fair Oaks sites would be at 75 percent of the maximum allowed in the land use plan. That rate would have "yielded 12.4 million square feet of non-residential development," the study said.

Now, "It seems likely that development based on the existing plan could approach 18 million square feet," the report said.

As it has turned out, developers have won the right to build bigger complexes than predicted four years ago by agreeing to provide a variety of amenities, including road improvements, open spaces, housing and improved pedestrian access.

In one instance, Hazel-Peterson Cos. built a segment of the Springfield Bypass and a new interchange on I-66 as part of the deal it struck with Fairfax officials when the Fair Lakes mixed-use project was approved. The interchange and the road are to open this summer.

The Fairfax County Planning Commission will hold public hearings Wednesday on 15 proposed changes to the area land-use plan. Of the 15 items, the planning staff and members of the task force have agreed on recommendations for 11. There are also minority reports from task force members.

Here is a sampling of the agenda and staff and task force recommendations:

*Fairfax Farms -- Staff and task force members are recommending denial of a proposal by homeowners in the 338-acre subdivision along Route 50. Residents there had asked to redevelop their land for high-density residential use and some retail and commercial space. The land, across Route 50 from Fair Oaks Mall, is under contract to a Northern Virginia developer.

The minority report urges support for a mixed-use development on the Fairfax Farms site.

*Random Hills -- Staff members and the task force differ sharply about the future of this area. The staff is supporting redeveloping the 60 acres west of Ridge Top Road for high-density residential use, with 12 units on each acre.

In contrast, the task force said those 60 acres should be used for office buildings. Russell Mosher, speaking for the minority on the task force, said high-rise residential units should be built on that site. Random Hills was one of the first neighborhoods in Fairfax County to organize and sell to a developer.

*Pendercrest -- Both staff and task force members are calling for office development on the 26-acre site near the core of the Fairfax Center study area.

*Super 29 Drive-In -- Staff is recommending deferring action on the tract until the Board of Supervisors adopts new criteria for sites for neighborhood shopping centers. The task force said any redevelopment should be preceded by a developer assembling nearby parcels that are now owned by several parties. Stringfellow Road -- Staff and task force members are recommending denial of a plan to change 203 acres at the northeast corner of

*Stringfellow Road and Route 29 from low-density residential to possible town house development with five to eight units on each acre.

*Cedar Lakes Estates -- The staff is recommending approval of a dramatic change for the 53-acre parcel west of West Ox Road and I-66, from one house per acre to a potential 20 housing units per acre. The task force is calling for a mix of new residential and office complexes on the Cedar Lakes acreage.