FALL RIVER — As a politician, Edward Lambert has thrown lots of hats into lots of rings.

But yesterday, at a news conference discussing the Coast Guard decision that appears to deal a death blow to the Weaver’s Cove LNG terminal proposal, the outgoing mayor, who departs tomorrow, showed off a special hat he plans to toss somewhere else.

The tan baseball cap, labeled “Hess LNG,” was presented to him a few years ago by Hess Corp. CEO John B. Hess.

It wasn’t really a gift, Lambert said. It was more of an arrogant assertion that Hess and Weaver’s Cove Energy were going to build the terminal despite nearly universal opposition.

“I told Mr. Hess at the time that I had a very special place for this hat and it would not be joining my hat collection,” Lambert said. “It is my hope that before the end of business on Friday, I get to toss this off the Brightman Street Bridge into the Taunton River,” he said.

“This decision, I think, now gives me the rationale for doing that.”

Whether Lambert may be able to get past the MassHighway barricades to get on the bridge tomorrow — the state has closed it for repair work — remains an open question.

But what isn’t an open question is that the Coast Guard ruling, which declared that LNG tankers would pose an unacceptable navigational hazard, was a devastating blow to the six-year-old terminal proposal.

Coast Guard Capt. Roy A. Nash didn’t even consider other key issues, such as security or environmental concerns in making his ruling.

He rejected the Weaver’s Cove plan after simply considering the hazards posed to navigation along the path that LNG tankers would have to take from Narragansett Bay to the Taunton River.

“As a practical matter, this project is now dead,” declared Thomas McGuire, the city’s corporation counsel, saying one strength of the ruling is that “It’s not just one reason. [Nash] has many reasons this project cannot go forward.”

There may be an appeal and Hess and Weaver’s Cove may continue to offer legal challenges, he said. However, “The Coast Guard has written a decision that is not going to get overturned.”

Not only would a court have to dismiss Nash’s experience and his detailed arguments, said McGuire, “Even in the extremely unlikely event that an appeal reversed the decision . . . [Nash has said] the Coast Guard would use its discretionary authority to prohibit repeated LNG traffic.”

“This is an ending to something that never should have begun,” said state Rep. David N. Sullivan. “It’s a great victory for the people.”

Lambert said Fall River “was told six years ago by the industry and others that we could not fight this, that it would happen over our objections, that we ought to just take it, and the longer we disagreed, the more economic benefits would disappear.”

He said the comments showed “the arrogance of this company” and that they, along with some federal regulators, were wrong when they insisted that the city could not stop the project.

After approval appeared certain when federal regulators gave it the green light, the commonwealth’s congressional delegation put on the brakes by declaring that the Brightman Street Bridge was a historic structure and could not be demolished after a new version of the bridge was constructed.

That posed a huge problem for Hess and Weaver’s Cove because the drawbridge opening of the old bridge could not accommodate LNG supertankers.

Weaver’s Cove then suggested solving that problem by using smaller tankers, ones that haven’t even been built.

But the Coast Guard said the navigational issues were insurmountable.

If nothing else, the ships would have to come to a complete halt between the bridges and then be pushed sideways to make it up the river.

And Nash, in his ruling, said that if one of the tankers broke down in the narrow dredged channel leading to the Braga Bridge, the only way to extract it would be to tow it backward down the Bay, which would be unacceptable.

Lambert said, as he has with other victories, that it’s time for Hess and Weaver’s Cove to throw in the towel even as he tosses the Hess LNG cap into the Taunton. He is leaving to take a job at UMass Dartmouth’s Center for Policy Analysis.

The proponents may try to keep it alive, he said, but even with his departure from the mayor’s office at week’s end, the city “will not take our foot off the throat of the beast until that beast is deceased.”

gemery@projo.com