The National Park Service plans to repair and resurface the George Washington Memorial Parkway between Alexandria and Mount Vernon, a three-year project expected to begin in 1980 and cost $6.5 million.

The project has been proposed for several years, as the parkway's original concrete surface built in 1932 is broken and askew in many places. But only recently has the plan had a high priority among construction projects that Congress will be asked to fund.

A $500,000, year-long study of the parkway's construction needs will be started next year, said parkway Superintendent Donald W. Castleberry.

Secretary of Interior Cecil D. Andrus said last week in a letter to the Mount Vernon Council of Citizens Associations that a recently completed Federal Highway Administration engineering study of the parkway found "faulted and broken concrete slabs, as well as deficiencies in the timber guardials and in a number of drainage structures."

The Mount Vernon group, which represents 40 area civic associations, had asked the Park Service this summer to repair the parkway as soon as possible and at the latest by 1982, the 250th anniversary of the first President B. Norton Jr. That year also will be the 50th anniversary of the parkway, which was built to celebrate Washington's bicentennial.

No major charges will be made in the parkway and no additional lanes will be built, although a number of road intersections may be changed slightly, Castleberry said this week. Over the past few years groups have called for widening the parkway to speed weekday commuter traffic, but the Park Service ruled out such changes.