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The W.A.C. Bennett Dam on the Peace River is pictured on April 19, 2010 in Hudson's Hope, B.C.Jonathan Hayward/The Canadian Press

More than three years after BC Hydro was warned by engineering experts that the W.A.C. Bennett Dam has a "serious deficiency" that should be fixed without delay, the Crown corporation has applied to begin work that will not be complete before 2019.

The expert panel, in a 2012 report obtained by The Globe and Mail and then released Tuesday by the utility, warned that the arrangement of large rocks at the foundation of the 47-year-old dam, known as riprap, is damaged. That has allowed waves to erode the material beneath the protective layer of rocks, undercutting the upstream slope of the massive dam.

"Continued wave action, floods and relatively minor earthquake loads may trigger deeper sliding that could endanger the integrity of the crest," the report warns, "and even cause over-topping and eventual breaching of the dam."

The panel expected BC Hydro would complete the repairs by 2015. "The panel considers this to be a serious deficiency that should be remedied as soon as possible. The panel is pleased to learn that a 'riprap upgrade project' is scheduled to start in 2012 and is planned to be completed within three years. It should not be delayed. If an earthquake were to happen before the upstream slope and the top of the dam are repaired, serious damage may occur."

Those details were among the small excerpts that BC Hydro provided at the request of its regulator, the B.C. Utilities Commission, to justify the cost of the riprap- upgrade project. A decision by the commission on the proposal is expected next spring, and the repairs will be completed in 2019 or 2020.

Until Tuesday, the 240-page report was not publicly available. A senior Hydro executive released the report in response to questions from The Globe, and said a copy should have been provided to the regulator.

"Frankly, I think that was a mistake. I think we should have given them the whole report," Chris O'Riley, deputy chief executive officer of BC Hydro, said in an interview Tuesday. "It conveyed an impression that we were not being transparent."

However, Mr. O'Riley maintained that the timeline is reasonable, and noted that consultation has taken place and a reliable source for new rock has been secured at a local quarry. He said the dam is constantly being monitored to ensure it is sound, and the riprap upgrade is just one of the maintenance projects that will be carried out at a cost of about $250-million.

The 2012 report says the W.A.C. Bennett dam was "well designed for the time it was constructed," but the upper part of the dam may be vulnerable to damage during an earthquake. Since 2012, concerns have been raised by the BC Oil and Gas Commission about small earthquakes in the same northeastern region of B.C. triggered by fracking for natural gas.

Adrian Dix, the New Democratic Party critic for BC Hydro, said the delay in responding to the expert panel's concerns shows a disregard for public safety.

"It's reckless," he said in an interview. "BC Hydro was presented with a call for urgent action in 2012. And they are not going to be finished until 2020."

Mr. Dix also criticized Hydro for keeping the report secret, saying it should have been disclosed when safety questions were raised during the review of the Site C dam project, which is now being built downstream from the Bennett dam.

At that time, Hydro told the review panel that "failure of one of the upstream dams is very unlikely." Mr. Dix said the joint review panel was left to make its findings on the construction of Site C based on incomplete evidence.

Mr. O'Riley said it "never occurred to us" to table the report at the review hearings. "The report is very, very technical. There are probably 20 people in the province who are really qualified to interpret it."

Bill Bennett, the minister responsible for BC Hydro, said he has not read the report but is confident the Crown corporation is acting appropriately. "I'm comfortable the public is not at risk," he said in an interview. "As much as the NDP would like to find a bogeyman that they can get into the newspapers, there is nothing untoward here. [BC Hydro] knows what needs to be done."

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