Regional park officials may decide tonight to scrap longstanding plans to double the size of the golf course at Sterling's Algonkian Regional Park.

A 200-acre tract that park officials had expected to use for the second 18-hole course has been declared wetlands by the Environmental Protection Agency and the U.S. Army Corps of Engineers.

Wetlands are protected by the EPA because they shelter important wildlife and plants that can't thrive elsewhere. The agency prohibits the filling in of wetlands, which would be necessary to build a golf course, said Fred Kelly, an engineer with Gordon Associates of Reston, a firm retained by the park authority.

A decision against building would likely disappoint many area golfers, who must either join a country club or wait in long lines at public courses to play a round in Northern Virginia. And it would disappoint the Northern Virginia Regional Park Authority board, which has wanted to build another public course.

Adding 18 holes to the course at Algonkian Park, located off Route 637 on the Potomac River, was originally estimated to cost about $2 million, according to architects, but now may cost as much as $3 million because of the expensive adjustments that would be required in a newly designed course.

Gordon Associates and the project architect, Ault, Clark of Bethesda, tonight will present to the park authority board a golf course design that would not affect the wetlands. It would locate about six holes on Lowes Island, a piece of park authority-owned land across Sugarland Run from the park.

Lowes Island, located directly along the Potomac River, is subject to flooding. Fairway and green areas would have to be elevated, accounting for some extra expense, and a bridge would have to be constructed across Sugarland Run to connect the area with the rest of the course.

Besides that, the park authority might eventually have to spend extra money on maintenance, Kelly said. Heavy rains could leave silt and debris on the course, which would have to be cleaned up before play.

Charles A. Bos, a Loudoun supervisor and representative to the park authority board, said the park board had already rejected an earlier plan to build 27 instead of 18 new holes because of expense. Now the board may have to forget the entire project. "We'll have to have a good discussion about whether it's worth proceeding or not," Bos said. "The bottom line comes down to cost."

Bos said expanding the course had been a pet project for the park authority board because the course is so popular (about 45,000 rounds of golf are played there yearly), because Northern Virginia needs more golf courses and because a developer had donated 200 acres of land south and west of the present course.

The developer, Kettler & Scott of Vienna, gave the land as one of many donations, mainly to Loudoun County, offered in exchange for permission to build Cascades, a huge community surrounding the park.

Richard Hausler, an executive vice-president for Kettler & Scott, said the developer gave the land to Loudoun County, which then turned it over to the park authority. Hausler said his company knew the land was not suitable for residential and office development, although the company did not know the land was wetlands. He said the company assumed the land would be used for open space or a wildlife preserve.

"The point was to take land of environmental quality and put it into the right hands," Hausler said.

Kettler & Scott is not required to give additional proffers.

The EPA and the U.S. Army Corps of Engineers told park officials about six months ago that new federal statutes prohibited them from building on about 95 percent of the 200 acres donated by the developer.

Darrell G. Winslow, executive director of the regional park authority, said his staff would look for another site if Algonkian is rejected.

"We'll keep searching and looking, but it's very difficult to find suitable places," Winslow said.

Winslow said his staff has estimated that eight golf courses would have to be built today to meet the current demand for public golfing in Northern Virginia.

Almost all Northern Virginia courses are crowded, said James O. Wiley, a Loudoun representative to the park board and an avid golfer.