The U.S. Army Corps of Engineers has suspended its development permit for the controversial Courtland Farm subdivision beside historic Oatlands Plantation, a decision that could delay construction.

The move was part of a settlement reached this week with the National Trust for Historic Preservation and other groups, which sued the Army Corps in March to block construction of a 277-home development on 200 acres south of Leesburg. The Army is responsible under the Clean Water Act for protecting waterways and wetlands from development.

The lawsuit, filed in U.S. District Court in Alexandria, alleged that the Corps illegally issued a permit allowing construction on less than an acre of wetlands because it wrongly concluded that its actions would have "no effect" on the 1804 plantation.

At issue was whether the Corps should have considered the impact of the entire development on Oatlands or just the impact of disturbing the wetlands.

As part of the settlement, the Corps called for "re-opening the consultative process" to determine the subdivision's impact on Oatlands, according to a letter from Maj. David L. Pedersen, the Corps' acting district engineer. The letter, addressed to Loudoun-Kline LLC, instructed the project developer "not to conduct any further activities" in the wetlands. In exchange, the national trust and other groups dropped their lawsuit.

"The Corps has basically agreed to do everything we asked for in the lawsuit, which is to stop and look at the impacts of the housing development as a whole on Oatlands," said Elizabeth Merritt, the trust's deputy general counsel. "The question will be whether there are ways the development can be modified to make it less harmful to Oatlands, less visually intrusive."

The long-term ramifications for one of Loudoun County's most disputed developments remain uncertain and will depend on a series of government and private actions. Swaths of trees have been cleared from the property in recent months, and it is unclear whether, or for how long, similar activities may be delayed.

Another attorney for the preservation groups, former Loudoun supervisor Mark R. Herring, called on the county's building and development department to suspend or revoke building permits that were granted based on the Corps' now-suspended permit.

"Because the underlying Army Corps permit has been suspended, Courtland Farm-Loudoun LLC is no longer in compliance" with county rules or approved plans, according to a letter from Herring to Terrance Wharton, director of building and development. He called on the county to issue a "stop-work order directing that no further grading or other land-disturbing activities occur."

Herring said continued work would "unnecessarily harm resources that may be identified for protection" by the Corps as part of the process it is launching to reexamine the project's effects.

County attorney Jack Roberts said the county would look into the matter.

A Corps spokeswoman, Diana Bailey, said the Corps would do additional analysis, and she cited Pedersen's letter for specifics. Pedersen said the Corps would follow the strictures of the National Historic Preservation Act. "Once I have completed my review . . . I will decide whether to reinstate, modify or revoke" the permit, he said.

Merritt said the Corps process can take months or years, though she expects it will move swiftly in this case.

"We'll certainly put pressure on the developer to stop" construction while that process is ongoing, she said. Of particular concern is the area that can be seen from the Oatlands site, she said, adding that she hopes to prevent the foreclosure of future "mitigation options" the Corps could require to reduce the development's impact.

The trust owns Oatlands. The other groups that filed suit were the Piedmont Environmental Council and the Audubon Naturalist Society.