SOMERSET, Mass. — For the first time in more than a half century, coal is no longer king on Mount Hope Bay.

The Brayton Point Power Station, the last major coal-fired power plant in New England, opened for business for the final time Wednesday and was expected to cease electric generation for good at midnight.

The end has been coming.

Under pressure from environmentalists and regional policymakers promoting cleaner forms of energy, Brayton Point was first marked for closure three years ago and Texas-based owner Dynegy has given no signal it intends to change course.

The slow march toward closure doesn't soften the blow for the roughly 100 workers left at the plant this week, survivors of a workforce that numbered 170 people last year and more than 250 people in the plant's heyday.

"It's devastating to the whole area," said Robert Clark, president of the Utility Workers Union of America Local 464, which represents Brayton Point employees. "You can look at it as its own economic engine since the 1960s. So many people derived income from Brayton Point. So many people have put their kids through college."

Clark said the last day of work for around half of the workers left at Brayton Point will be Friday. The remainder will stay on to decommission the plant through June and July.

They have applied for federal help under a program to compensate for the effects of the North American Free Trade Agreement, citing imports of Canadian hydropower.

"We have many people between the ages of 50 and 60 who, statistically, have the most difficulty finding a new job," said Clark, who retired in 2011. "There is no safety net."

After the plant, which can power 1.5 million homes, is effectively discommissioned this summer, Brayton Point's future is a mystery.

For decades the plant was the town's largest taxpayer, but efforts from local officials to persuade plant owners to convert it to burn natural gas went nowhere. The smaller coal-powered Montaup plant, also in Somerset, closed in 2010.

"Dynegy is listening to interested parties and would be open to selling the Brayton Point site," company spokesman David Onufer wrote in an email response to questions about the property's future.

Coal was once a dominant power source in New England, but the combination of cheap natural gas and stricter environmental regulations made the fuel uneconomical even with President Donald Trump's pledge to restore the industry.

Coal accounted for only 2 percent of New England electricity generation last year, according to figures from electrical grid operator ISO-New England. Three smaller coal-fired power plants are now left in New England, two in New Hampshire and one in Connecticut.

Most surprising to many, the 2014 announcement that Brayton Point would close came just one year after ownership finished building, at a cost of $1.1 billion, the 500-foot twin cooling towers visible from much of Rhode Island's East Bay. The towers were meant to protect fish from hot water being dumped into the Mount Hope Bay.

State Rep. Patricia Haddad, D-Somerset, Brayton Point's chief political supporter in Boston over the years, wants to position the property to take advantage of offshore wind power development, but she said there isn't a fallback plan right now.

Even as they celebrated Brayton Point's closing Wednesday, environmentalists lamented the fact that coal's demise is a result of the natural gas "fracking" boom.

"This certainly is a victory, but just the beginning," said Jonathan "Jay" O'Hara, who along with fellow activist Ken Ward used a lobster boat to block a 689-foot coal barge from landing at Brayton Point in 2013.

— panderson@providencejournal.com

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On Twitter: @PatrickAnderso_