Cape Cod Bay dumping ban expected today

Federal and state officials are expected to announce today that boaters will no longer be able to discharge waste into Cape Cod Bay, part of an effort to make the state's coastline off limits to boat sewage.

The no-discharge zones, which are designed to make waters cleaner and safer for swimmers and beach enthusiasts, as well as improve shellfish stock, extend 3 miles from the coastline.

While federal and state rules already prohibit the discharge of untreated waste in navigable waters, many marine sanitation devices on boats can still release waste with bacteria counts 70 times higher than allowed under state law for shell-fishing and swimming waters. The release of waste introduces diseases such as hepatitis to people or make shellfish unsuitable for human consumption, according to the state Office of Coastal Zone Management.

The decision follows last week's announcement of a similar ban for Boston Harbor. Governor Deval Patrick wants the entire coastline free of boat discharge by 2010. About two-thirds of the state's coastline will now have bans.

"It's good news for boaters and clean water in general," Ian A. Bowles, the state's Energy and Environmental Affairs secretary, said in a telephone interview yesterday. "Cape Cod Bay is a signature piece of water for Massachusetts. It's important for it to be fully protected."

Enforcement will begin immediately. Violators can be fined $2,000.

Encompassing 600 square miles, Cape Cod Bay will be the largest no-discharge area in the state. It is used annually by more than 3,240 commercial and recreational boats, which will have to empty sewage at one of seven pump out facilities in the bay.

The bans have been generally supported by boaters, who want clean waters and have customarily avoided dumping their tanks near the shoreline, state officials said. Officials from the Massachusetts Marine Trades Association, which represents the state's boating community, could not be reached for comment, but the group has voiced its support.

Today's news conference will take place in Dennis and include appearances by US Representative William Delahunt; Robert Varney, the US Environmental Protection Agency's New England regional administrator; and Leslie-Ann McGee, the state's Coastal Zone Management director.

Material from the Associated Press was used in this report. James Vaznis can be reached at jvaznis@globe.com.