PORTLAND – When the occasional charter boat runs aground in Casco Bay, it reflects badly on the city’s marine-related tourism industry.

That’s why the Portland Harbor Commission is offering to take owners and captains of small passenger vessels on a cruise of Casco Bay today.

Commission Chairman Thomas Dobbins said the two-hour voyage will highlight some of the bay’s navigational hazards and hopefully end a string of groundings in the bay.

“Over the last two years we have had four groundings,” Dobbins said. “We started to say, ‘Hey, is this Murphy’s Law or is something else going on?’ We are doing this to avoid a black eye for the city. That’s the last thing we want.”

Three commercial vessel groundings, which took place between August 2010 and September 2011, involved the same company — Portland Schooner Company. The Portland Fire Department’s fireboat hit an underwater object near Fort Gorges last October, causing $60,000 in damage.

Concern over the groundings started to heighten last fall, prompting the commission to host a meeting with vessel owners and others in October.

Dobbins said that meeting led to the idea of holding a voluntary training cruise before another boating season begins. Dobbins said there are several seasoned captains who are willing to share their knowledge of the harbor with their less experienced colleagues.

Nicole Clegg, spokeswoman for the city of Portland, said in a statement that “this training is not to single out or discuss particular incidents or vessels within past years the purpose for this training is to learn and move forward in protecting our bay’s well earned reputation as a professional and safe destination for local and visiting passengers.”

Clegg said participants should register at 9:30 a.m. today at 2 Portland Fish Pier, which is off Commercial Street at the Marine Trade Center complex. The cruise will depart at 10 a.m.

A large viewing screen with a global positioning system chart — donated by the Coast Guard — as well as a topographic picture of the ocean bottom will be displayed on the training vessel during the two-hour training session.

“There is plenty of open water in Portland Harbor, but the places where you can get in trouble may or may not be marked,” Dobbins said.

Bill Frappier III is captain and owner of Portland Discovery Land and Sea Tours. Frappier has agreed to donate his vessel, the Bay View Lady, for today’s tour. Frappier has been a captain on Casco Bay for 15 years.

He plans to take participants to some of the bay’s potentially dangerous navigation areas.

Frappier identified those areas as Bug Light; two shipwrecks on the inshore side of Fort Gorges; a ledge off House Island where a fishing boat sank a few years ago; a shallow, muddy area on the northwest side of Great and Little Diamond islands; and ledges on either side of Whitehead Passage between Peaks and Cushing islands.

Though only a dozen or so owners and captains had signed up to join the tour by Wednesday, Frappier said the cruise could go a long way in helping prevent another grounding.

“The worst thing that could happen is that the visitors who are planning to come to Portland get wind of a grounding and decide not to come,” he said. “This is our way of being proactive and making sure it doesn’t happen.”

Clegg said no members of the city’s fireboat crew would be attending the training.

“This is more intended for captains and pilots of small, passenger vessels,” she said.

Staff Writer Dennis Hoey can be contacted at 791-6365 or at:

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