The National Park Service plans to spend about $450,000 to build an alternate route for a 1.5-mile section of the popular George Washington Memorial bicycle trail near Fort Hunt - if it can only decide where to put it.

Congress appropriated the money in 1974, more than double what it cost to build the entire 14-mile bike trail in 1973, after residents in the Collingwood and Fort Hunt area complained of being overrun and occasionally run over by bicyclists. More than 200,000 bicyclists a year now pedal along the scenic path from Washington to Mount Vernon.

The only places it does not follow a separate gravel or paved path is in Alexandria, where it winds through the streets of Old Town, and near Collingwood, where it follows small Park Service and Fairfax County roads and croses briefly over to the west side of the parkway.

After more than a year of study, the Park Service will hold a public meeting Wednesday (8 p.m. at Mount Vernon Inn) to unveil half of dozen new route possibilities through the Collingwood area. Some are on the west and some on the east side of the parkway, some involve huge concrete and steel bicyle bridges as long as 600 and 800 feet over the parkway and feeder roads. Some of the plans cost as much as $839,000.

Collingwood residents themselves are divided, with some wanting the bike trail to remain on the west side (sast side residents), some wanting it on the east side (west side residents) and others wanting various combinations of the two or no bike trail at all.

The major complaints of area residents have been that the bicyclists clog the narrow roads, impeding automobile traffic and endangering themselves. Families living along the roads claim that there has been as increase in crime, accidents and littering and that cyclists sit on people's lawns and occasionally even come to the door and ask for water or to use the bathroom or telephone.

U.S. Park Police and Parkway Superintendent Charles A. Veitl say there have been almost no crimes reported in the Collingwood area attributed to bicyclists and no major accidents in the three years the bike route has been established. The Park Service apparently is sensitive to these complaints, however, and is spending much time and money to reroute this small segment of the bike trail.

One major possibility not mentioned in the environmental impact assessment prepared by the Park Service and distributed to virtually all residents along the bike route is that it will keep the existing trail on the west side of the parkway. It has already spent thousands of dollars constructing boardwalks and bridges through the woods on the west side. The Park Service could then construct a new riverside trail as well, providing some measure of relief for west side residents. Bicyclists and hikers would thus have two routes to choose between and many might go to Mount Vernon on one side and return on the other.

Superintendent Veitl said this week the Park Service has no plans to eliminate any existing section of the bike trail through the woods and bicyclists are as free as motorists to use Park Service and Fairfax County roads.

The seven official alternatives proposed by the Park Service for sections of the bike route between Wellington, Collingwood and Fort Hunt - except for Alternative 1 - need to be combined to carry the bike route the entire 1.5-mile distance.

Alternative 1 is to create no new bike route but to spend $38,000 improving the existing route over the old Alexandria Avenue bridge and along West Boulevard Drive, with additional traffic signs and minor road and curve improvements.

Alternative 2 is to continue routing bicyclist over the Alexandria Avenue bridge but then to construct a relatively short bike trail in the narrow median between West Boulevard Drive and the parkway. After traveling only about one-half mile on the west side the trail would cross back over the parkway on an 800-foot long concrete and steel bridge by Collingwood Road. Addiitonal concrete and wood bridges could also be built to take bicycle and pedestrian traffic over the several small roads that feed into the parkway along that stretch. This could cost up to $543,000.

The 3d alternative would pick up where alternative 2 (and 5) end, and build a new bicycle and hiking path from Collingwood to Fort Hunt on a reconstructed river's edge. This would provide a panoramic view of Fort Washington across the Potomac and restore the badly eroded riverbank near Fort Hunt. This would cost an estimated $839,000, with much of the cost for riprapping and restoring the shoreline.

An alternate to the Park Sercice's Alternative 3 would follow roughly the same route but would put the bike trail closer to ther parkway instead of along the river's edge. It would cost just over $400,000.

Alternative 4 would keep the bike route on West Boulevard Drive, west of the Parkway, but would remove the route from the county-owned sections of the road by building a new bike trail through woods beside the parkway from Collingwood Road to Waynewood Boulevard. This would cost $448,000.

Alternative 5 is to use the existing county and Park Service roads on the east side of the parkway, which was the route orginally planned for the bike trail, but making $2,100 in road and sign improvements.

Alternative 6 again assumes retention of the bike route on West Boulevard Drive for just about one-half mile and then bridging back over the parkway at Lee Avenue in another large concrete and steel bridge, this one 580-feet long. It would cost an estimated $240,000.

The separate bicycle-hiking bridges over the parkway and small feeder roads were among major suggestions made by area residents at a public meeting on the bike trail in 1974. All the bridges would have a major visual impact and detract from the scenic parkway, according to the environmental assessment.