New Brunswick's largest generating station at Mactaquac may have to be closed 55 years ahead of schedule, according to a study prepared for NB Power and obtained by CBC Television News.

The Mactaquac Dam and hydro electric generating station was built in the mid 1960's and was scheduled to operate for a century. But according to a report delivered to NB Power last fall by a panel of international engineering experts, the structure has deteriorated rapidly and may not last even half of its expected life.

"A total lifetime of 45 to maximum 60 years for the concrete structures and therefore the entire project is to be considered realistic," concluded the report.

Mactaquac has been plagued by problems almost since its completion. Concrete in the structure has been growing steadily, causing the dam to expand and crack.

Jim Brogan, an NBPower General Manager, says it's caused by a chemical reaction.

"This reaction causes the concrete to grow or swell to expand. That expansion, is putting pressure on the mechanical embedded equipment in the station."

Concrete expert Webb Langley, who has worked on Hibernia and the Confederation Bridge, says the problem is significant.

"The history of this dam is that the expansions have not slowed down with time and normally we do see a lessening of expansions but in this case it hasn't happened. "

N.B Power has had to face facts. The problem can't be overcome so the generating station will have to be shut down as early as 2013, according to the experts, 55 years ahead of schedule.

It's a huge operational decision and news to N.B Power critics such as lawyer Rod Gillis.

" I don't know where the citizens of this province are going to come up with the money to pay for it," he says.

What it will cost and when it will show up on the utility's accounts, no one is saying.