Looking ahead to the mid-1980s, the Falls Church City Council has started overhauling the city's five-year comprehensive plan.

It's clear from a council resolution passed last week that city leaders are worried about the impact of I-66 and future Metrorail stops on Falls Church neighborhoods and the city's future housing supply.

In preparation for consideration of the plan next year, the council last week ordered the planning commission and planning staff to study three areas:

* The adequacy of multifamily housing in Falls Church "with a view toward revising housing policies and designating new sites for development." In the past two years, no new multifamily rental units have been constructed without government assistance in the entire Washington area, planners say.

Falls Church has 4,490 dwelling units, including 1,235 mid-rise apartments and 531 garden apartments. The most recent construction of multifamily units in Falls Church was in 1972, when a 576-unit apartment complex was built.

* The future development of neighborhoods near I-66 and Metro stations. Two Metro stops, just east and west of the city, are to open in 1986 and general traffic will be allowed on an I-66 interchange near Falls Church by the beginning of next year.

"The current master plan does not consider the impact of either the Metrorail stops or I-66 on residential and commercial development," said city Planning Director Henry Bibber. "We will certainly be looking to see what can be done to redevelop commercial, industrial and transitional residential land in these areas."

* The acquisition of land designated for open space (parks and recreation areas). City planners will determine priorities, specifying which privately owned sites should be purchased first, planners say.

"Even now the parcels marked for open space could disappear to private development if some set of distinct priorities isn't made," Bibber said. "We also want to explore how the open space can be preserved by private ownership or less than full ownership by the city."

The state-mandated master plan, last adopted by Falls Church in 1978, is revised every five years. The next revision must be completed by June.