PORTLAND, Maine — Millions of gallons of crude oil from the nation’s heartland are crossing Maine in railroad tank cars bound for a Canadian oil refinery, raising concern among environmentalists and state officials about the threat of an accident and spill.
The oil is primarily coming from the Bakken shale-oil field in North Dakota, with lesser amounts from neighboring Canada. Trains carried nearly 5.3 million barrels of the light crude — more than 220 million gallons — across the state and into New Brunswick last year, and the volume is growing.
Railroads that operate in Maine say the increased business has resulted in more jobs and investment in the state. Moving oil by train is safe, railroad officials say, with upgraded tracks and tank cars.
‘‘The statistics tell you how much has been transported [in Maine], but to the best of my knowledge, there hasn’t been any spilled or released,’’ said Robert Grindrod, chief executive of the Montreal, Maine and Atlantic Railway Ltd., which carried nearly 3 million barrels of oil across Maine last year.
The more oil that’s shipped, the greater the likelihood of a spill, said Glen Brand of the Sierra Club. It was fortunate that oil didn’t spill into the Penobscot River when a Pan Am Railways oil train derailed March 7 in Mattawamkeag about 100 yards from the river, he said.
What’s happening in Maine is happening across the country as US oil production has increased, much of it in areas with limited pipeline capacity. North Dakota production doubled between 2010 and 2012.
Five years ago, US trains transported 9,500 carloads of oil, according to the Association of American Railroads. The number grew to 233,811 carloads last year.