Lafayette Square, the country's first designed park and the front lawn to the White House, once was enclosed by a six-foot-tall Victorian ornamental iron fence that was removed in 1889 and all but forgotten until this week, when workers unearthed a Seneca sandstone footing on the north side of the park.

To the amazement of everyone, workers soon found a second and then a third pier, as the footings are known. In all likelihood, the piers that held up the elegant 19th century fence still surround the historic park, spaced seven feet apart and buried two feet under the ground.

"This is very cool, very much of a surprise," said Robert Sonderman, senior staff archaeologist for the regional office of the National Park Service. "Everyone always assumes that historical materials like this have been destroyed, but it's still here."

The piers are now deemed so significant that they are eligible for listing on the National Register of Historic Places, said Gregory McCarthy, the District's State Historic Preservation Officer.

In a letter responding to a request from the National Park Service, McCarthy said the piers were in excellent condition and were representative of the early landscaping at the country's first designed public park. Their discovery documents the actual location of the original fence.

McCarthy's determination means the 4-foot-tall piers cannot simply be demolished.

The work of installing a new security fence--which will replace the concrete Jersey barriers at the north edge of the park erected to protect the White House--came to a halt the day it began.

The new fence, a series of metal bollards linked by a black metal chain, is both strong enough to prevent a car from breaking through and aesthetically suitable for the historic setting, said Ann Smith, assistant director for project development for the regional office of the Park Service. Because the park is in a historic district, the design needed--and received--the approval of the Commission on Fine Arts and the National Capital Planning Commission, Smith said.

The original fence was built in 1853 to protect the newly installed Andrew Jackson statue. Although the fence had numerous gates, neighbors objected to having the park closed off and it was removed in 1889. It is now at the national park in Gettysburg.

Smith said there was nothing in the White House or Park Service files to indicate the footings were still in place. As delighted as she and others are with the surprise discovery, their historic value creates a quandary.

Smith said the new fence must be built for security reasons, but the piers need protection as well. She said the plans required the protective fence to be built right where the old footings are, bordering the existing quarter-round concrete edging that separates the sidewalk from the grass lawn and has been a part of park for decades.

There are three possible solutions, Smith said. The Park Service could leave the piers in place and still build the new fence; the sensitive area could be avoided entirely and a new location for the security fence found; or the footings could be removed to another location for public display.

Yesterday, archaeologist Ben Fischler, working under contract with the Park Service, stood in the trench he and others had dug by hand. He was taking measurements and drawing detailed pictures of the dark red piers, made of the same stone used in the Smithsonian castle and the nearby Renwick Museum.

"It was a surprise for me," said Fischler, who was required to be at the site during the digging in case of such a discovery. "These surprises are always a possibility, but not the first day, not in the first hour."

Smith said she and others would try to work out a resolution to the fate of the piers in the next week. "The clock for the contractor is ticking," she said. "We have to pay him for this time when he can't work."

CAPTION: Archaeologist Ben Fischler stands in a trench where workers discovered a Seneca sandstone footing in Lafayette Square.

CAPTION: The piers found are part of a six-foot-tall iron fence that was built in 1853 to protect the statue of Andrew Jackson.

CAPTION: "These surprises are always a possibility, but not the first day, not in the first hour," said Ben Fischler, an archaeologist contracted by the Park Service.