Construction of a controversial new, two-mile section of the bike trail along the George Washington Memorial Parkway began this week in a grassy meadow south of Alexandria, quickly following last week's approval of the new route by the National Capital Planning Commission.

It will remove the endless stream of bicyclists from county roads in the Collingwood area, where they had been "temporarily" routed in 1973 when the popular 14-mile bike trail from Washington to Mount Vernon was opened by the National Park Service.

But, despite four years of study, hearings and meetings, and a $525,000 appropriation from Congress to build it, the new route - also on the west side of the parkway - which has been selected by the Park Service, is as vehemently opposed by hundreds of residents in nearby subdivisions as was the "temporary" route.

The subdivisions west of the parkway, built after the scenic road to Mount Vernon was opened in 1934, use the parkway as a major auto route into Washington. Residents there have objected to the heavy bicycle and jogging traffic which - even on the new trail - crosses four of the small parkway feeder roads.

The dispute over where to put the two-mile section of the bike trail has pitted the huge subdivisions west of the parkway against the 100 families who live on the east side in a small enclave surrounded by parkland. Both groups jammed the federal planning commission hearing room last week, as they did a Park Service public hearing last spring.

The bike trail is a paved or compacted gravel path on parkland near the river except where it passes through the streets of downtown Alexandria and around Collingwood, where it crosses over to the west side of the parkway and follows local roads for almost two miles before crossing back in the tunnel entrance to Fort Hunt.

The new bike trail, even though it will be on parkland instead of running along residential streets, still will cross several local streets and thus "is inherently dangerous," Col. Donald Swygert, president of the Collingwood Citizens Association (west of the parkway), told the planning commission.

Fairfax County Supervisor Warren Cikins also spoke against the new route, charging that "the Park Service's study has been incomplete and its decision premature," and that it was disregarding the opinions of its own consultants and the vast majority of area residents, who live west of the parkway.

John F. Herrity, chairman of the county's Board of Supervisors, appearing "as an individual," endorsed a tunnel or bridge across the parkway - one of more than a dozen proposals considered but rejected by the Park Service.

The bridge and tunnel ideas as well as possible east-of-the-parkway routes, were rejected for environmental and safety reasons, said commission alternate member John Parsons, who represents the Department of Interior on the federal planning agency. He added that the consultant's traffic study done last summer, which recommended the bike trail be located on the east side, possibly in an extra lane directly on the parkway, was not a comprehensive study and its east-side suggestion was rejected for safety reasons.

Park Service land on the east side of the parkway is sometimes only 18-20 feet wide, compared to a minimum 150-foot right of way on the west side. The Park Service felt the narrow east side right-of-way virtually eliminated the possibility of an east-side bike trail in the area unless it were routed along narrow roads - a solution which Parsons said, would merely transfer the present safety problems on the small west-side roads across the parkway to the east side.

The idea of a tunnel or bridge across the parkway between Wellington and Collingwood Roads, backed by many west-side residents, would not only be expensive and visually damaging to the scenic parkway, Parsons said, but bicyclists wouldn't use it. Instead of crossing the parkway on the existing Alexandria Avenue bridge and then crossing back several hundred yards later by a tunnel or bridge, they would just stay on the narrow east-side roads, Parsons pointed out.

The main consideration in selecting the route was to get the bike trail entirely on Park Service land and as much as possible off all roads, however, the bike trail will still follow Northdown Road, a Park Service road, for about 100 yards and is routed through Alexandria city streets for about two miles.

Commission chairman, David M. Childs, said while he found himself being persuaded by both east and west-side residents he too felt it must be remembered that the parkland "no more belongs to local residents than it does to bicyclists or visitors from Wyoming." He urged approval of the Park Service route for safety reasons.

Two alternate commission members apparently were persuaded by objections raised by west-side residents. Jacqueline Wells, representing the chairman of the House District Committee cast the sole vote against the Park Service because she said she was concerned about "safety" and Thomas W. Kerley, representing the Secretary of Defense on the planning agency, abstained after saying he felt a more complete environmental review of the project should be done.