U.S. ports and dredging contractors Thursday voiced concern that a House bill to expand liability for illegal ocean dumping could hamper legal harbor dredging activities.

The measure introduced by Rep. Gerry Studds, D-Mass., would allow illegal dumpers to be sued for removal costs and damages resulting directly from their activity."While it seems clear that the primary intent of (the bill) is to address the problem of illegal dumping of industrial and hazardous waste, the proposal is drafted so broadly that it may create uncertainty and potentially hinder legitimate dredging activities," Anne D. Aylward, maritime director of the Massachusetts Port Authority, told two House subcommittees Thursday.

She is also chairman of the American Association of Port Authorities.

"The potential to cause unintended harm is real," added Mark D. Sickles, executive director of the National Association of Dredging Contractors.

He explained that soon his industry will be the only one legally dumping anything in the ocean. But if strict liability applies to permit violations, ''it would unnecessarily increase the risk of dredging operations," he said.

"Should our customers give us erroneous information about the scope of the approved project or the exact location of the dump site, we are fully liable for this mistake," he continued.

Ms. Aylward and Mr. Sickles commented on the bill during a hearing before the subcommittees on Fisheries and Wildlife Conservation and the Environment and on Oceanography, Great Lakes, and the Outer Continental Shelf. Both are units of the House Merchant Marine and Fisheries Committee.

Rep. Studds chairs the fisheries and wildlife subcommittee.

Ocean dumping laws impose civil penalties on those who dump material into U.S. ocean waters without a permit, or who violate permit provisions. Rep. Studds' bill would make dumpers liable for harm caused to natural resources, losses of personal property or income directly caused by illegal ocean dumping.

Most ocean dumping permits involve dredged material, excavation debris or fish waste. While the bill also applies to vessels, municipalities are the largest ocean dumpers and would likely be most directly affected. Fuel spilled as a result of vessel propulsion is not defined as dumping.

According to a committee memo, the extent of illegal ocean dumping is unknown, because it is almost impossible to witness and difficult to track to its source.

Bush administration officials took no position on the bill.

Robert H. Wayland III, director of the Environmental Protection Agency's office of wetlands, oceans and watersheds, said "identifying, assessing and remediating illegal dumping in the marine environment, from a practical point of view, can be difficult."

While most ocean dumping is done by local governments, he continued, the bill "is silent as to whether private individuals, local governments and federal facilities are to be subject to the same liability rules." He said ''clear and workable" rules are needed, but drafting a liability regime envisioned by the bill "can raise complex problems."

"We are concerned that as a practical matter it may be extremely difficult and time-consuming for the courts to sort out which claimants have legitimate claims in this regard, (and) the extent of the damages may also be difficult to quantify," said Thomas A. Campbell, general counsel of the National Oceanic and Atmospheric Administration.