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A hydraulic fracturing operation in the greater Fort St. John area in northeastern British Columbia is shown in this undated handout photo.Jeremy Sean Williams

BC Hydro officials have worried that earthquakes triggered by fracking could damage or destroy some of the utility's dams in the province's north, an issue that has been a point of discussion among staff over recent years, documents show.

The concern about hydraulic fracturing – in which fluids are injected deep underground to shatter rock and release trapped oil and gas – is outlined in the documents, obtained through freedom of information legislation by the Canadian Centre for Policy Alternatives and provided to The Globe and Mail. According to the documents, Hydro officials have worried for several years that fracking too close to the Peace Canyon Dam in northern British Columbia might cause the dam to fail.

The issue is raised in a 2009 letter from Hydro's then-dam safety director, Ray Stewart, to a water rights comptroller in the provincial Environment Ministry. Referring to coal-methane fracturing in the area, Mr. Stewart wrote, "BC Hydro believes there are immediate and future potential risks to BC Hydro's reservoir, dam and power-generation infrastructure as a result of this coal-bed methane project."

Mr. Stewart wrote that possible consequences from coal-bed methane extraction include the "re-activation of existing geological faults in proximity of the BC Hydro facility," and the earthquakes caused by human activity "may be greater than the original design criteria for the dam."

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BC Hydro's deputy CEO, Chris O'Riley, responded on Monday by noting that the utility's dams are built to withstand much larger ground motions associated with higher-magnitude earthquakes than those linked to fracking.

"Fracking by itself cannot generate large magnitude earthquakes," he said in a statement issued in response to questions about the CCPA's concerns.

Additional documents suggest earthquakes in the Peace River region linked to fracking for shale gas caused further debate at BC Hydro, with dam-safety engineering scientist Des Hartford responding in March, 2013, to a colleague's concerns: "Fundamentally, hydraulic fracturing is one of these 'new and emergent' threats that require examination in the context of scientific and policy considerations in order that any meaningful management actions can be initiated if required."

Scott Gillis, Hydro's dam safety engineer in the Peace region, to whom Mr. Hartford was writing, said his concern was triggered by the 1963 failure of the Los Angeles-area Baldwin Hills Dam that killed five people and destroyed 277 homes. Oil and gas production has been linked to the dam's failure.

While Mr. Gillis acknowledged that the Baldwin Hills disaster occurred after "very intense exploration and development" unlike anything in British Columbia, he added that there is a "similarity" in small faults in the vicinity of the dam.

"Reactivation of these small faults could be problematic."

He wrote that the province should add buffer zones around extreme and high-consequence dams where hydraulic fracturing could not take place without a "prior full investigation" of risks and a risk-management plan.

Mr. O'Riley of BC Hydro said all earth-fill dams are designed to have some seepage, and fracking could increase natural seepage, "which only poses an issue of increased costs due to maintenance and operational requirements – not a dam safety issue."

Graham Currie, a spokesman for the BC Oil and Gas Commission, which regulates the oil and gas industry, said in a statement the province has established five-kilometre buffer zones around the W.A.C. Bennett, Peace Canyon and proposed Site C dams in which hydraulic fracking is not allowed.

While some subsurface rights were issued in the five-kilometre zone around Site C, the commission is talking about "additional permit conditions" in these areas, Mr. Currie wrote.

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John Clague, an earth sciences professor at Simon Fraser University, said he was skeptical about an "induced earthquake" damaging one of the Peace River dams because the quakes have tended to be too small.

"Interestingly, the location of the proposed Site C dam is much closer to the area where fracking is being conducted.

"I suspect that BC Hydro is taking this into account in the engineering design of the dam," Dr. Clague wrote in an e-mail.

Fracking has been linked to earthquakes in the oil and gas fields of Western Canada, with the journal Seismological Research Letters releasing research in March that examined 12,289 fracking wells and 1,236 wastewater wells in an area along the B.C.-Alberta border.

The research linked 39 fracking wells and 17 wastewater disposal wells directly to a number of earthquakes of magnitude 3 or higher.

The number of earthquakes in northeastern B.C. – small quakes detected by an increased array of government, industry and regulatory sensors – have increased from 20 a year in 2002 to about 200 a year in 2011, though many are quite small.

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