A few feet of dirt may have jeopardized Alexandria's long struggle to end the conflict over control of the city's waterfront.

Last week, city officials began filling in a small horseshoe-shaped area of the riverfront known as Oronoco Bay, at the foot of Pendleton Street. City officials say they were acting under a 1977 permit issued by the federal Government, but federal officials angrily respond that the city went too far and deliberately filled in land it did not have permission to touch.

"Frankly, I feel I've been had," said Jack Benjamin, a high-ranking official with the National Park Service who has worked closely with the city in attempting to resolve a 1973 federal title claim to the historic waterfront.

City Attorney Cyril D. Calley responded that the city had acted properly, and at all times within the scope of the permit issued by the Army Corps of Engineers three years ago.

But that is not the way Benjamin sees it.

"I'm certainly going to look very closely at every element of their plan (for the future of the waterfront)," Benjamin said last week, "especially those parts that promise to preserve the waterfront as it is forever. It's a little discouraging."

In 1973, the federal government filed a lawsuit claiming possession of the waterfront because of a much-disputed, 1791 high-tide line. The suit was viewed as an attempt by federal officials to keep high-rise development from coming to Alexandria, as had been the case up-river in Arlington.

For the past year, city and federal officials have conducted an elaborate dance of reconciliation, proposing alternative plans for the riverfront, holding public hearings and private meetings on the issue, and presenting a public posture of good will. Local and federal officials currently are trying to work out a joint plan for the area, which is expected to merge features of both federal and city proposals, including some open space and a mix of commercial and residential development along the mile-long waterfront.

The key to resolution of the dispute has been harmony between both sides, officials have said. But the current dispute over Oronoco Bay seems, at least in the view of federal officials, to have shaken the tenuous harmony.

"The city clearly violated the terms of their permit," Benjamin said. "They were permitted to fill in a small section of the eroding shoreline, but what they've been doing is widening Pendleton Street.

Pendleton includes an area where new townhouses have been built, and more new housing is on the drawing board.

"They went 200 feet north of the permit line and 100 feet east of it, into the river," Benjamin added. "That's not what the permit called for. This could have a very serious impact on our discussions."

Calley maintained, however, that the city filled in only a legally approved area in order to reinforce the eroding shoreline.

"We were having severe erosion problems in that area," he said. "The edge of Pendleton Street could have collapsed. The area involved is only about 40 feet long and 12 feet wide."

A spokesman for the Corps of Engineers said a letter had been sent city officials, "reminding" them of the permit's parameters. Calley said the letter had not yet been received.

Despite the city's protestations that it had acted within the limits of the permit, a clearly angry Benjamin said, "From now on, I'm going to examine everything they submit. I thought we had been dealing in good faith."