The inquiry delving into the collapse of the Algo Centre Mall in Elliot Lake resumed Tuesday following a short break to allow lawyers time to read a vital report that outlines what likely caused the roof to collapse.

The Norr report — a forensic study commissioned by the OPP as part of its continuing investigation into the mall collapse — cited severe rusting in the structure's steel supports from years of exposure to water and road salt.

The report was used by inquiry lawyers as they questioned Rod Caughill, a former supervisor for the original owners of the mall. Caughill did maintenance work on the roof-top parking lot, a portion of which collapsed last June, killing two women and injuring dozens of others.

'Surprising failure did not happen earlier'

Steel supports were so rusted at the time of last year's deadly Algo Centre Mall collapse that it looked as if they had spent decades in sea water, the Norr report said.

Justice Paul Belanger is head of the inquiry probing the collapse of the Algo Centre Mall last June that killed two women and injured several others. (Yvon Theriault/CBC)

"The rates [of corrosion] observed in the Algo Centre Mall are comparable to those found in a 'marine environment'," the report states. "It is in fact somewhat surprising that failure did not happen earlier."

Ontario Provincial Police investigators asked Norr — an architectural and engineering company — to do the forensic engineering report.

The 142 pages of findings, made public on Tuesday, amount to an account of a tragedy long in the making that could have been averted.

According to the report, the collapse occurred when a weld between a support column and beam failed in two stages because of corrosion caused by years of water and road-salt penetration.

The collapse may have been unprecedented in the developed world, the report says.

'The rates [of corrosion] observed in the Algo Centre Mall are comparable to those found in a 'marine environment.' It is in fact somewhat surprising that failure did not happen earlier.'—Norr report

"One is hard-pressed to find a similar example where a carbon steel-framed building in North America or Europe continued to corrode to the point of failure, when no extreme loading is present," the report states.

As the judicial inquiry into the collapse has already heard, leaking occurred because an "intrinsically flawed" waterproofing system installed in 1980 failed from the start, prompting years of complaints.

Inquiry documents show some residents dubbed the shopping centre the "Algo Falls." Others jokingly advised taking an umbrella when shopping there.

Looming catastrophe

Still, despite some efforts — one of which saw workers fill cracks and joints in the cement with colourful pool noodles — the leaks continued.

Severe rusting like that seen in a marine environment is seen on the steel support structure following the collapse last June of the Algo Centre Mall in Elliot Lake, Ont. (Norr report/Canadian Press)

"The fact that the roof was allowed to leak for 32 years is perplexing," the report states. "A number of actions could have been taken to avoid collapse had the critical condition been identified in time."

Even more perplexing, perhaps, is that none of the engineers and others who inspected the mall over the years foresaw the looming catastrophe.

Two companies, Pinchin and MRW, issued "unequivocal" reports attesting to the soundness of the structure, while an MRW report released just two months before the collapse deemed the corrosion "not of structural significance."

"The clean bill of health given to the structure by a number of consultants in the past few years before collapse is quite alarming," the report states.

Norr also makes the new allegation that Coreslab, the company that supplied the precast concrete for the roof deck, and John Kadlec, the structural engineer, misled the mall's original owner about the capabilities of the product, likely in an "aggressive effort" to win a competitive tender.

Didn't complete all repairs

During his testimony on Tuesday, Caughill confirmed he was aware of the problems identified in a 1991 inspection report conducted by Trow Engineering.

He said some work was done to repair the roof, but didn't complete all the repairs Trow recommended in its report, which included waterproofing, re-bonding cement, and fixing surface rust on beams.

The report — which noted a deteriorating roof-top parking lot, wide-spread corrosion, rust staining and several beams that weren't fireproofed — said the structure could be compromised if repairs weren't made immediately.

Caughill is expected to testify the rest of the week.

Commission stops contempt action

In another development, the inquiry has stopped its contempt action against the shopping centre’s owner.

In a statement Tuesday morning during the proceedings, Commissioner Paul Belanger said Bob Nazarian had turned over 85,000 emails to the commission. Those emails will now be screened for relevance before being admitted at the inquiry.

Rod Caughill worked for the original owners of the Algo Centre Mall in Elliot Lake and did maintenance work on the roof-top parking lot. He's testifying at the Elliot Lake Inquiry this week. (Supplied)

"They'll be reviewed electronically to produce potentially relevant emails," Belanger said. "Those e-mails so identified will be screened for relevance by a law firm retained for that purpose by the commission."

Nazarian was expected to be in court in Toronto on Wednesday to be cited for contempt over his previous failure to turn over the emails.

Given the compliance, Belanger said he is discontinuing the action.

The inquiry is probing the collapse of the Algo Centre Mall last June that killed two women and injured several others.

With files from The Canadian Press