Montgomery County is challenging efforts by four North Bethesda homeowners to block plans to build a $6.5 million state-of-the-art swim and dive center in their neighborhood.

The center, already funded and approved by the county, is scheduled to open in 1988. It is to be built on 3 1/2 acres in Wall Local Park, on Nicholson Lane between Rockville Pike and Old Georgetown Road.

The pool is intended to serve the southwestern part of the county, said Barbara Modine, aquatics coordinator for the county Department of Recreation.

The county's only indoor pool, White Oak, serves the eastern part of the county. The department is proposing that a pool be built for the Olney area, Modine said. The independent communities of Rockville and Gaithersburg already have indoor pools, she said.

The North Bethesda homeowners, who live on Nicholson Lane across from Wall Park, filed suit against the county in June 1984, saying the park was for local, not regional, use.

"A regional center would be serving many communities," said Beatrice Chester, one of the plaintiffs and a homeowner in the 680-unit Old Georgetown Village subdivision of town houses, condominiums and apartments. The subdivision's developer donated the parkland to the Maryland-National Capital Park and Planning Commission (MNCPPC) as a condition for approval of his rezoning request.

"Basically we feel we should have gotten a local park, as expected," Chester said. "We have some concern about the additional traffic and security in the area."

MNCPPC's North Bethesda master plan, a guideline for development, designates the 13-acre site as a local park, said Myron Goldberg, chief of park planning, acquisition, engineering and design with MNCPPC.

But, Goldberg said, other local parks in the county have regional facilities -- such as the Long Branch Public Swimming Pool at Long Branch Local Park in Silver Spring. Also, ball fields used by all county residents are located in local parks, he said.

In December 1984, the Montgomery County Circuit Court ruled against the North Bethesda homeowners. They appealed to Maryland's Court of Special Appeals and on Oct. 3 the court reversed the judgment and sent it back to the Circuit Court to determine whether the regional center use was consistent with the definition of a local park.

On Tuesday, the county asked for a review of the Court of Special Appeals' decision. The Court of Appeals will now decide whether to hear the case.

Meanwhile, the county is beginning to draw up a detailed design of the facility, which is to accommodate 500 people. Construction is scheduled to begin in a year.

"We have been proceeding with the project all along," said Bill Bullough, an aquatic supervisor with the Department of Recreation. "There is no reason not to proceed. We haven't been told by the courts not to."

Preliminary plans for the indoor pool, presently called the Regional Indoor Swim Center, include an Olympic size (50 meters long, eight lanes) main pool with a 176-foot-long water slide and a diving well.

The plans also call for a 75-foot diving extension with four diving boards and three diving platforms.

A second, smaller pool would be only 3 1/2 feet deep at its deepest point and have a slide and an entry ramp for handicapped swimmers. According to the plans, the two locker rooms would have saunas and the facility would be equipped with two Jacuzzis for up to eight people each, a weight and exercise room and a room for meetings and swimming and safety instruction. Lessons in scuba diving and synchronized swimming are planned.

On a daily basis, the center is expected to charge $1.75 for adults and $1 for children and seniors, Modine said. Anticipated costs for annual passes are $115 for individuals and $225 for families with up to four children.