Montgomery County is proposing to create a landfill site in a quarry and to build a waste treatment plant in Dickerson to begin operation when the county runs out of permitted disposal capacity in 1990.

However, county planners said last week that Montgomery also should choose several more landfill sites for the distant future beyond 1990 because open land in the county is becoming scarcer every year.

A task force is proposing that the county dump solid waste in the Travilah Quarry between Rockville and Gaithersburg as well as build a plant to derive fuel from trash at a Potomac Electric Power Co. electricity station near Dickerson. In addition, the task force said that the county could expand the Oaks landfill in Laytonsville, the county's current waste-disposal site, as a backup should the other two options not be feasible, according to a report from County Executive Charles W. Gilchrist.

Gilchrist said that the proposed fuel-processing plant is part of the county's long-range goal to recycle resources whenever possible and that disposing of solid waste at the Travilah Quarry will have little enviromental impact and could be continued for 40 years.

However, if either option is not feasible, the county simply could expand the Oaks landfill as a backup by piling trash higher, he said in his report to the County Council.

The task force considered -- and then disregarded -- a plan to select new landfill sites throughout the county because none of the sites available could be used for more than 15 years and because estimated start-up costs would be about $25 million each. But it is an option that the planning board thinks should be reconsidered.

At a meeting last week, the planning board voted to support Gilchrist's proposal, but with the further recommendation that the county choose sites for future landfills now, before rampant development makes it impossible to find space. A staff report to the board noted that only nine of 22 potential landfill sites identified in a 1978 study remain available.

"Since a new landfill site is compatible with most of the disposal technologies and is a necessary long-term element, consideration should be given to reserving land at a selected site for future landfilling needs," the board stated in its report to the council.

Planners also argued that, while the county has no legal obligation to close the Oaks landfill when it reaches capacity in 1990, it should do so because of promises made to the Laytonsville residents. New landfill sites could be an alternative to expanding the Oaks landfill, according to Carl Mitchell of the planning staff.

Mitchell said the county would have to buy the sites now to keep them from development, something that the County Council may or may not think it has the funds for.

"We feel, however, that there should be a backup landfill so that Oaks will not have to be expanded," he said. "Many feel that a promise was made to the residents near Oaks. The landfill was only supposed to be temporary."

Gilchrist said in his report that the Oaks landfill could be expanded and used for another 20 years at minimum cost, although he noted that it would be visually unattractive to the community.

Gilchrist also is proposing that the county expand its recycling program, although it already has "one of the largest source separation, or recycling, programs in the nation." He said he would like to see Montgomery recycle up to 15 percent of its trash compared with the 3.5 percent that now is reused.

The waste study was begun last summer after the County Council decided that it would be too expensive and politically risky to haul trash from Montgomery residents across its borders into neighboring counties.

The county, with the help of the state, Pepco and a private company, has been testing burning refuse at the Dickerson power station and conducting a study of its health effects. The facility to burn the trash would be similar to one being operated in Baltimore, according to the report.

Mitchell said the owners of the Travilah Quarry are enthusiastic about the plan to dump solid waste there while they continue quarrying and may offer to run the landfill themselves and bill the county. Either way, the county will pay the company for the use of the quarry, he said.

The major problem with the Travilah Quarry is that the county may not be able to pump the ground water effectively from underneath the waste in the 250-foot-deep pit, he said.

The County Council will review the proposal and make a decision sometime this year.