Offshore LNG terminal near

Construction of the first of two planned offshore liquefied natural gas terminals in the state could begin as early as May when a 300-foot-long barge is floated into waters 3 miles off the coast of Marblehead.

Excelerate Energy LLC's $300 million pipeline and terminal would be built by a 150-person crew that would work 24 hours a day on rotating shifts until November. The carbon-steel, 24-inch, 40-foot -long pipes are to be welded and X-rayed on board the barge. Also aboard the barge, workers would control a mechanical plowing device that would unearth 3 feet of ocean bed. After the pipe is lowered into the trench, it would be covered mechanically from the barge with the same sediment. The terminal is scheduled to be operating by December.

Both companies still need state and federal permits.

New construction details are emerging as the work is set to begin after two years of acrimonious debate that pitted local fishermen and politicians against Excelerate and Neptune LNG LLC, the companies that are to build the LNG terminals. Fishermen and politicians objected to the terminals, saying they would be placed in key fishing grounds. The LNG companies argued that the region needs more natural gas.

The planned terminals were approved late last year by then-governor Mitt Romney and endorsed this year by the US Maritime Administration . The terminals, which would be about 5 miles away from each other, would allow 950-foot ships to dock at sea and pump natural gas to the HubLine, an existing underwater pipeline that delivers gas throughout New England. Ships are to arrive at the terminals every week and take about a week to unload. Each ship would carry enough liquefied natural gas to heat 30,000 homes a year.

The terminals would be just the second and third offshore LNG docking stations in the world. The only existing one is 116 miles off the coast of Louisiana, and that was completed in 2005.

Excelerate's new terminal would connect with the existing HubLine pipeline off Marblehead.

Neptune is waiting for two ships to be constructed to open its terminal. That terminal could be completed by the beginning of 2010, said Neptune spokeswoman Julie Vitek.

While there are several proposals to build LNG terminals in New England, Vitek said the addition of an offshore port would meet New England's increased demand for natural gas. She said the region's demand is expected to increase by 1 to 2 percent a year over the next two decades, with Massachusetts consuming half of the gas.

John Sheridan, spokesman for Algonquin Gas Transmission, which would build and maintain Excelerate's new pipeline, said the line would be monitored by computer. " If there were any type of fluctuations of pressure," Sheridan said, "we would notice that on the system, and we would take any type of precautionary steps."

Sheridan said there have been no leaks or problems with the HubLine, which Algonquin built in 2000. The 30-mile underwater pipeline runs from Salem to Weymouth and connects with a pipeline that receives natural gas from Nova Scotia.

The Coast Guard has not established a security zone for the Excelerate terminal, to be 13 miles southeast of Gloucester.

Doug Pizzi, an Excelerate spokesman, said the company would use up to five ships at the terminal, with the LNG load leaving regularly from Trinidad. He said the vessels are registered in Belgium and staffed with Belgian officers. Excelerate must provide a list of names, nationalities, and passport numbers of the 25 crewmates to the Coast Guard before docking, Pizzi said. In the future, one-quarter of the crewmates would be American citizens, Pizzi said. Besides Belgians, the crews consist of citizens of France and the Philippines.

While Neptune isn't expected to begin constructing its new offshore terminal until 2009, it is already planning its security operations for the terminal. Vitek, the Neptune spokeswoman, said she expected that the security zone around the terminal would encompass 5 square miles. That area would prohibit commercial and recreational vessels.

Neptune is a subsidiary of Suez LNG NA LLC, which owns Distrigas of Massachusetts LLC. Everett's Distrigas, the only onshore LNG facility in the state, employs strict security each time an LNG ship arrives.

The ships are met near Deer Island by the Coast Guard and escorted into Boston Harbor by tugboats, Boston police, and State Police.

Neptune has not decided who would build its 13-mile pipeline and terminal.