A proposal to put a new Giant Food store in Montgomery County's prestigious Potomac Village has spawned expansion moves by an existing Safeway store and polarized residents of the community that is known for its resistance to commercial development.

Giant said that if its project receives the necessary commercial zoning, it will form a "roads club" to solicit money from other property owners in the area to widen and improve the intersection of Falls and River roads -- two clogged commuter routes. The road improvement project is not otherwise scheduled for state-financed construction until 1989.

Fernando Bren, president of the West Montgomery County Citizens Association, said that "many people favor the addition of another grocery store in the area, but object to the 45,000-square-foot scale which Giant's proposing. . . . The community is getting unnecessarily polarized by the issue."

Bren said that more than 300 residents from the neighborhoods bordering Falls and River roads, where the development is proposed in southwestern Montgomery, attended a special town meeting on the issue in July. "The turnout was dramatic," he said. "Most people who verbalized concerns worry that we could have another Rockville Pike out here if the rezoning goes through."

Representatives of the Giant chain said they have been urged "for years" by customers who shop at other Giant stores in Rockville and Bethesda to build in the exclusive residential area.

"We've been at this for about 10 months, and judging from what we're hearing, the community wants us to come in with our prototype store, which is 53,330 square feet," said David W. Rustein, a Giant senior vice president and general counsel. "With this smaller model, we'll be cutting out services and products in Potomac to accommodate more of a neighborhood-store concept."

But even the scaled-down Giant proposal is not compatible with either the county's zoning law or the Potomac Master Plan, which would have to be amended to permit additional commercial facilities in the area.

Current county zoning law states that no designated commercial area can be larger than 15 acres. Potomac Village's four quadrants at Falls and River roads are considered one commercial area and now have 16.9 commercial acres -- two acres above the limit -- because they were zoned before the county created the 15-acre cap.

Giant said it would like an additional six or seven acres of commercially zoned land so it can build its store on the southwest corner of the Falls and River roads intersection.

The Montgomery County Council currently is considering a zoning amendment that would allow more commercial zoning throughout the county, provided that master plans for individual regions also recommend going above the 15-acre commercial zone limit. As a result, in the case of Giant's planned Potomac development, there is also a pending proposal that would amend the Potomac Master Plan to allow the increased zoning.

"It's sort of a hand-and-glove approach. If both don't pass, then neither will apply," said Tom Robertson, the community planner working on revision of the Potomac Village Master Plan for the Montgomery County Planning Board.

A County Council committee has scheduled an Oct. 24 work session on the zoning amendment, and the full council will consider it at a later date. The planning board also has set an Oct. 24 work session on the Potomac Master Plan amendment to consider testimony it heard last month.

Representatives from Safeway Stores Inc. told county planners at the September meeting that it wants to enlarge its existing 20,000-square-foot store on the southeast corner of the Falls and River roads intersection by at least 60 percent, and requested that the master plan not limit future commercial zoning on their side of the street.

"We objected to the statement in the master plan that said no additional commercial zoning was needed on our side of the road, and decided to get involved in the process," said Tom Castleberry, Safeway regional real estate developer.

Castleberry said the Potomac Village Safeway has "wanted to expand almost from the time we came in there in 1968. But we were always told by residents that they liked things 'just the way they are'. . . . It has always been a low-key village concept."

"We felt if Giant was the only one to get additional commercial zoning, the door would effectively be shut in our faces," he said. "The message we got from park and planning was if you want to expand, 'do it now,' " while the whole issue of commercial zoning is under discussion.

Castleberry said that even without a zoning change, Safeway's Potomac store could be expanded by 12,000 square feet by relocating retailers in the adjacent shopping center, by moving its parking lot and by adding a second-floor stock room served by an escalator. The larger store would be able to increase its imported items, enlarge its delicatessen and bakery and offer a full-service seafood market. But it would not have a pharmacy like the one proposed by Giant because the existence of a nearby Drug Fair prohibits another drugstore in the same quadrant.

"There are no height restrictions under present zoning, so we can expand right now. But we want to be involved in the process because we don't like some of the road improvements or the bike path route proposed by the master plan," he said.

The Potomac Chamber of Commerce generally supports increased commercial zoning in the area and the Giant proposal in particular.

"Our population out here has almost doubled in the past two or three years, and we just feel it would be good to have another food store to anchor the Falls Road area," said Stephen C. Blakeslee Jr., president of the Potomac Chamber.

Blakeslee said he and other businessmen in the area were especially pleased when Giant said it would take the lead in forming a "roads club" to improve traffic flow in the area. Giant has "agreed to pay for a major portion of necessary road improvements, turning lanes, et cetera, so their store on Falls Road won't open to the same clogged two-lane road we have now," Blakeslee said.

A Giant spokesman declined to say how much money the company was willing to commit to the roads project.

Blakeslee said the housing boom in the area has outstripped road improvements and left many commuters, who are too far from a Metro subway station or connecting buses, facing hour-long car trips into Washington and traffic jams at the end of the day when they go to the grocers.

Safeway's Casteleberry agreed that some road improvements are necessary, but said he is not sure additional lanes on River and Falls roads will solve the problems. "A lot of residents out here feel wider roads create their own obsolescence. And they're not sure they want to make it easier for more people to move in."

Mary Anne Thane, zoning chairman for West Montgomery Citizens Association, said, "It's really the domino effect that we're concerned about. Rezonings will be applied for all around the village's quadrant. We've already got a medical building coming in for rezoning. We don't want it to explode from a neighborhood shopping center into a regional one. That's what we're afraid of."

Thane and others note there already are signs that developers are waiting for the commercial zoning cap to be lifted. Two town-house developments have been proposed, as well as a plan by Chevy Chase Savings & Loan to move and restore the historic 1880s Perry General Store by adding retail and office space there and a bank branch.

"I don't see how the planning board can legally turn down other people if Giant gets what it wants," Thane said.