U.S. District Judge Norma H. Johnson refused yesterday to block construction of a suicide prevention fence on the Duke Ellington Memorial Bridge that carries Calvert Street NW over Rock Creek Park.

A suit filed Tuesday by the National Trust for Historic Preservation and seven local groups claimed the eight-foot high wrought iron picket fence would mar the "architectural integrity" of the bridge and accused the District government of not following federal historic preservation and environmental protection laws in approving the $160,000 project.

Johnson, ruling on a request for a temporary restraining order, cited evidence presented by the District that proper planning procedures had been followed. She said the plaintiffs had not shown a "substantial likelihood" that they would win after a full hearing on the case.

Work on the bridge began a week ago. A similar fence is to be built next summer on the William Howard Taft Bridge that carries Connecticut Avenue over the park.

Since 1978, 33 people have jumped to their deaths from the bridges, which are about 125 above Rock Creek.

Edward Lee Rogers, attorney for the plaintiffs, said they would appeal the ruling or seek a preliminary injunction that would also block the Taft Bridge fence.