"Where will Fairfax County draw the line on the creeping commercialism of Tyson's Corner?" a citizen asked last week at a public hearing to discuss the future of one of the nation's largest shopping centers.

The issue before the county Planning Commission was the southwestern edge of Tyson's Corner, where the proposed expansion of the commercial area has sent speculators scrambling and has worried residents in dozens of quiet neighborhoods nearby. The proposal goes to the Board of Supervisors for a final hearing Monday.

After the hearing last week, the planning commission unanimously approved changes in the area's Wolf Trap master plan that would allow some garden apartments, townhouses and commercial development south of Old Court House Road -- 770 acres of largely undeveloped land between Vienna and Tyson's Corner. The existing master plan now calls primarily for single-family houses on one-acre lots.

The latest plan is similar to one recommended last spring, except that the height of the townhouse-offices would be limited to two stories instead of three.

The planning commission reversed its position on a small area south of Freedom Hill Elementary School, along the west side of Lord Fairfax Road. Originally, the commission had recommended that five to eight townhouses per acre be permitted; the current proposal is to have a maximum of three to four single-family homes per acre.

William Lockwood, the commission member who proposed the changes, said that townhouse-offices along Old Court House Road would act as a sufficient "transition," or buffer, zone between residential areas and the five-to-nine story office buildings already being built across the street. Old Court House Road has been considered the "boundary" of Tyson's Corner expansion in all county plans since 1962.

While most civic groups and the county planning staff have endorsed some townhouse development in the area, the major issue has been whether the townhouses should be homes or offices -- or whether commercial development should be given a foothold "south of the border," as one resident said.

A task force, including civic groups and residents of Vienna, was created by the Board of Supervisors last summer because of the controversy over proposed changes to the Wolf Trap master plan. The task force has not ended the controversy although it appears to have clarified many of the issues. e

A majority of the task force issued a report recommending that no future commercial buildings be permitted south of Old Court House Road. A minority report from four civic groups called that "unrealistic" and urged that some commercial development be allowed.

Task force Chairman Paul W. Hammack Jr. told the commission that a majority of the members recommended no changes in zoning in the area. He said they opposed any commercial offices south of Old Court House Road because "we need the strongest possible barrier or line of demarcation" to prevent further commercial expansion of Tyson's Corner.

However, a member of the minority, Clyde Clark, said he favored a larger transition area that also taps the "potential that lies within the Wolf Trap area."

Sheila Todd, representing the YWCA at Wolftrap and Gallows Roads, said YWCA officials agree with the minority report that higher-density zoning is needed to develop much of the land to its "potential." The YWCA owns 6.5 acres of vacant land it has been unable to sell under present residential zoning, Todd said.

Lynn Beyer, of the Woodford Citizens Association, told the commission "some people want 500 acres of transition to defend the 200 acres below it . . . but if the area is to remain residential, you don't begin by allowing commercial buildings in it. At some point you have to drop from commercial to residential. There is no in between."

"I'd have to disagree, planning commission member Lockwood replied, "and my motion is something in between.This is not black and white but shades of gray."