LIKE THE WILSON Bridge that would be its link to Virginia, National Harbor -- a family resort complex proposed for the Prince George's Potomac waterfront -- is threatened by litigants citing environmental concerns. Just as regional backers of the bridge-design proposal seek to speed the federal approval process, advocates of National Harbor must overcome legal hurdles that may be raised by the Environmental Protection Agency.

In April, plans for National Harbor seemed to be passing what most local and regional officials believed was a final environmental review. The National Capital Planning Commission, the central planning agency for the federal government in this region, had commissioned the study. It concluded that economically the project could be a plus for the county and surrounding area -- and that the project met federal environmental requirements.

Opponents promptly vowed to use "any means necessary" to block plans for the resort. Some have argued for a smaller project, not on the waterfront; others want no project and are urging that the waterfront site be preserved as a park. Were no other parkland there, they might have a case. But protected parkland is plentiful along these shores.

Now an EPA regional official has written a letter to the planning commission review officer that criticizes aspects of the study. The letter says the study "inappropriately" limited the range of alternatives considered in determining use of the property and failed to address possible damage to air quality, aquatic life and nearby communities.

Some project opponents have said they view the EPA concerns as fodder for a possible delaying lawsuit. Unlike the bridge proposal, the harbor project does not involve replacement of an essential deteriorating transportation link. But National Harbor is a widely supported waterfront attraction designed to bring new life, new jobs and welcome prestige to the county and region. As with the Wilson Bridge, regulatory requirements for National Harbor should not be overridden in a dash to completion. But federal officials and, if it comes to that, the courts need to be careful as well that these requirements not be idly invoked for no purpose other than to subject projects to fatal delays.