The U.S. Army Corps of Engineers unveiled new rules for preventing some but not all development on sensitive wetlands, sparking praise from environmentalists, denunciations from builders and surprise criticism from a leading public safety official in the Clinton administration.

The Corps said it would no longer allow contractors to rely on a national permit system to launch projects degrading small wetland parcels of three acres or less. Environmental groups deemed the existing program a rubber stamp for builders.

Starting June 7, the Corps of Engineers will require builders to file an individual application for any development affecting half an acre of wetlands, lowering the threshold for a thorough federal review of the construction and increasing the likelihood of delays.

The new rules aim to prevent residential or commercial development in flood-prone regions near streams and creeks, where people may be killed or property damaged in times of severe weather.

It is unclear how bad the new delays will be for contractors seeking federal approval for their subdivisions.

The Corps of Engineers estimates that is workload for individualized permits, under its new rules, will rise 20 percent. Most wetlands permits, about four-fifths, are granted within 120 days.

In 1992, the Bush administration vowed to ensure there would be no net loss of wetlands. President Clinton has moved the goalposts, proposing that the Corps seek a net gain of 1 million acres of wetlands by fiscal 2005.