Calvert County and the U.S. Army Corps of Engineers have ordered construction work stopped on a major housing development in the Prince Frederick area after the discovery that builders cleared innumerable trees without permission and disturbed sensitive wetlands.

The county issued its stop-work order to developers of Prince Frederick Woods on Monday "because of noncompliance with the conditions of the subdivision approval" granted by the Calvert County Planning Commission, according to Greg Bowen, the county's deputy planning director.

The developers received permission to build townhouses and single-family homes totaling 185 dwelling units on about 76 acres near Routes 4 and 231, Bowen said. The land was to be cleared in phases instead of all at once, Bowen said, and "the subdivision plan shows an established forest retention area" delineating trees that were not to be removed.

The developers -- Built-Rite Home Developer Inc. of Capital Heights and Thomas Builders of Columbia -- have told the county that the disturbance to the wetlands was unintentional.

T. Kevin Carney, president of Thomas Builders, blamed the error on "a wetlands delineation that . . . became the basis for the entire designed plan."

"It appears that that delineation of the wetlands is wrong," he said. "We've disturbed the wetlands, and we stopped. And we will restore and replant and clean up and make it right."

The American Chestnut Land Trust, a citizens group instrumental in the effort to preserve land in the Parkers Creek watershed, which includes a 3,000-acre nature preserve, issued a statement Monday saying it was "calling for swift enforcement action and stiff penalties to be imposed by the county and state environmental officials."

The developer "seriously damaged" the headwaters of Parkers Creek, the trust said in its statement. The group maintained that "the outright destruction of wetlands coupled with inadequate erosion control measures" was causing sediment to pour into Sullivan Branch, one of two tributaries that ultimately join to form the main stem of Parkers Creek.

Peg Niland, the land trust's executive director, said she toured the site and found it "absolutely treeless."

"You can feel your heart beating 90 miles an hour because you knew there wasn't a thing you could do," Niland said.

"It doesn't look like anything you've ever seen -- totally void of vegetation."

Calvert County commissioners briefly discussed the matter at meeting Tuesday but were advised by the county attorney to refrain from further comment because of possible litigation.

The Corps of Engineers sent a letter to Built-Rite in late February saying a "field investigation by a representative of this office has disclosed that you are responsible for the unauthorized discharge of fill materials" into areas under the Corps' jurisdiction.

The letter specified that the materials "have been discharged into waters of the United States, including wetlands adjacent to Sullivan Branch."

Sandra A. Zelen, an enforcement programs manager, wrote, "No future work is to be performed at this or any other location in a waterway or in wetlands without compliance with the law."

It is unknown how long work will be stopped on the development. Carney said the developers had hoped to have model units ready by summer or fall.