Falls Church voters face an Election Day referendum on whether a supermajority of six votes on the seven-member City Council should be required to approve any construction or alteration of facilities in Cherry Hill Park.

The park is a favorite place for picnics, basketball games and evening strolls and provides a leafy green center for a city without many other open spaces. It is flanked by City Hall, the city community center and a popular landmark, Cherry Hill Farm, and has been the subject of frequent debate over more development in the area.

Mayor David F. Snyder said he and other supporters of the referendum, which will only be advisory, "are concerned that in the future the expediency of the day may overwhelm the long-term value of preserving the largest park in the city."

City Council member Merni Fitzgerald, chair of the Cherry Hill Park Coalition opposing the referendum, said the measure would allow any two council members "to hold the park hostage until the majority accedes to their demands. . . . They could say, 'Before you do anything in the park, you have to do my project first: Get me an office, get me a bus stop, fire a certain city employee.' "

Passing the referendum is only a first step. The General Assembly holds the power to change city charters, and the state delegate representing the city, Robert D. Hull (D), has indicated he does not like the supermajority idea.

"I guess he could refuse to propose it to the General Assembly," Snyder said, "but it would be more difficult to do that after the voters have approved the referendum."

So far, the City Council has resisted plans for a restroom and an underground library at the park, and voters have rejected a $4.8 million expansion of the community center.

The city charter requires a simple majority of four votes to purchase property and five votes to overturn Planning Commission decisions on land use.

The referendum would exempt from the six-vote requirement park-related projects for "routine maintenance" or "health and safety reasons." Fitzgerald said this could be a huge loophole.

"Who decides what is health and safety, or routine maintenance? You can imagine the horse trading over that," she said. "And doesn't that say a supermajority would be kind of clunky and unnecessary if the really important things are exempt from it?"

Vice Mayor Samuel A. Mabry, who supports the referendum, said he is concerned "that we have seen in the last 20 years an ongoing effort to build more stuff that would affect the park." The community center expansion plan the voters rejected would have made the building twice its current size. The referendum will not change a more modest renovation of the center that was approved April 26.

"Falls Church is getting very compressed," Mabry said. "We have got to reserve parkland."