Parliament Hill's oldest building, an architectural gem known as the East Block, is vulnerable to the frequent earthquakes of the Ottawa area and needs at least $66 million in upgrades to make it more tremor-resistant.

Even with that minimum hardening of the walls and towers, the East Block will still be only 60 per cent as resistant to quakes as Canada's national building code requires for all modern buildings.

Those are the findings of a series of reports commissioned by Public Works in the wake of three major earthquakes that rattled the capital in 2010 and 2012 and set the Peace Tower and a main tower on the East Block swaying back and forth. CBC News obtained copies of the internal reports under the Access to Information Act.

"The advanced deterioration of the exterior masonry walls has been a concern for many years," says one report.

"The East Block building is unlikely to meet 60 per cent of the seismic design requirement of the (National Building Code of Canada) and will need to be upgraded."

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Map showing reports from more than 1,000 residents about the intensity of a strong June 23, 2010, earthquake north of Ottawa in Val-des-Bois, Que., that registered 5.0 in magnitude. ((Earthquakes Canada))

"The review of the building envelop investigation and screening reports has revealed significant and serious deterioration of the exterior masonry walls. Low strength lime mortar or totally degraded lime mortar was observed in numerous locations …"

Public Works is in the midst of a multibillion-dollar refurbishment of the three main structures on Parliament Hill, with the West Block well under way and the East Block next in line before workers begin a massive renovation of the Centre Block, home to the House of Commons and Senate.

Seismographs placed in the towers of these three buildings recorded the impact of relatively large earthquakes in recent years; that is, the magnitude 5.0 "Val-des-Bois" earthquake of June 23, 2010, the 4.5 magnitude "Saint-Hyacinthe" quake on Oct.10, 2012; and the 4.2 magnitude "Buckingham" quake of Nov. 6 that same year.

Towers swayed during recent earthquakes

The Peace Tower showed "strong motion" for all the events, while the southwest tower of the East Block swayed in an east-west direction during two of the quakes.

Other reports for Public Works between 2011 and 2013 investigated the crumbling masonry of the East Block walls, some of which date back to 1859 when construction began.

'Low strength lime mortar or totally degraded lime mortar was observed in numerous locations ...' - internal 2012 engineering report on East Block for Public Works

Public Works’ policy on heritage buildings such as the East Block is to bring them up to between 60 per cent and 100 per cent of the national building code’s standards for seismic resistance, while preserving their character. Experts have recommended the 60 per cent mark for the Gothic Revival structure, which appears to be the most vulnerable of the Parliament Hill buildings to earthquakes because of its much greater age.

Steel cable held tower together

Public Works has already undertaken a $14.1-million pilot project on one of the East Block's towers, at the northwest, which included seismic upgrading to develop possible solutions for the rest of the building. The two-year upgrade was finished in the fall of 2013. Until then, the tower had been held together with steel-cable strapping to prevent collapse.

A 2012 estimate provided by the consultant firm Hanscomb Ltd. says upgrading the rest of the East Block to at least 60 per cent of the national building code requirements for quake-resistance will cost $65.8 million.

Hanscomb also estimated the cost for making the East Block resistant to a blast, such as produced by a bomb, but all references are blacked out in the document under security exemptions in the Access to Information Act.

Public Works, meanwhile, hired the Montreal firm Arcop Architecture Inc. in July to make its own determination of the seismic upgrades needed, as well as other improvements.

"The prime consultant is reviewing the preliminary findings contained in the (Hanscomb) report, and must then conduct further analysis and on-site investigations to finalize the seismic rehabilitation of the building," said Public Works spokeswoman Annie Joannette.

The exterior of the oldest part of the East Block is scheduled for $167 million in upgrades between 2016 and 2022, but interior seismic hardening is still in the planning stages, as are upgrades to a 1910 addition to the building.

Seismic standards in Canada's building code are intended to allow the safe evacuation of people inside older buildings in the event of a major earthquake.

Buildings safe: Public Works

Joannette said that "all reports to date have determined that the buildings are safe to be occupied. The East Block is safe and was not damaged during recent earthquakes."

Barry Padolsky, an architect who recently worked on upgrading Ottawa's historic Museum of Nature to modern seismic standards, said similar challenges await the team that will upgrade the East Block.

"They will face a similar challenge, as do all heritage buildings, and the challenge not just technically how to do it but to make sure that you don't harm the building while you are installing it," he said in an interview.

"There is no question that these things have to be done because the Museum of Nature, Parliament Hill and other historic buildings in the capital are part of our heritage and we would never be forgiven if we didn't protect them."

The Centre Block's seismic upgrades, including to the Peace Tower, are scheduled as part of the major rehabilitation set to begin in 2018, after the Commons and Senate chambers have been temporarily moved to new locations.

Canada has two major earthquake zones, southwestern British Columbia and the Ottawa and St. Lawrence River valleys, including Ottawa, Montreal and Quebec City.

An October 2013 study commissioned by the Insurance Bureau of Canada estimated there is at least a five-to-15 per cent chance that an earthquake capable of significant damage will strike the southern Quebec and southeastern Ontario area in the next 50 years.

The study said unreinforced masonry buildings, such as that of the East Block and many historic buildings in Quebec City, are particularly at risk. A large quake could cost $60 billion in damage, mostly to shattered buildings.

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With files from Julie Van Dusen