Fire-sparked power outage in downtown Calgary spotlights risk to city's key infrastructure

After enduring the devastating flood of 2013, Calgarians hardly needed another lesson on coping with disaster. They got one just the same on Thanksgiving weekend.

An electrical transformer in an underground utility vault caught fire, wrecking power and communications equipment and crippling a major chunk of downtown Calgary.

ENMAX Power Corp. said electricity won’t be restored until Thursday, meaning thousands of downtown residents remain displaced and thousands more who work in the Canada’s oil and gas hub will be shut out of their offices.

"However, this is if all goes according to plan," the company said on its website, referring to the planned power restoration. “There may be damaged equipment we can’t see and we will not know this until we energize the system.”

The outage, covering about 16 blocks on the west side of downtown, affected customers in 112 residential and commercial buildings.

Calgary Mayor Naheed Nenshi told Yahoo Canada News about 5,000 residents and 2,100 businesses with perhaps tens of thousands of employees were hit.

"Some buildings are going with backup generator power but it’s certainly not business as usual," Nenshi said in a telephone interview as he visited a downtown emergency relief centre.

"Right now our primary concerns are, as always, keeping people safe, looking after the vulnerable populations and making sure we get people back home and back to their offices quickly," the mayor said.

"The folks at ENMAX are working hard at fixing it while at the same time we are working on figuring out what it is that happened."

[ Related: Prairie province flood response: How ready is ready enough? ]

The vast majority of displaced residents are staying with family and friends, said Nenshi, who’s been promoting temporary couch surfing on his busy Twitter feed. Others have decided to remain in their apartments and survive without power (except for emergency lighting) or hot water, he said.

As of Sunday night about 270 people were being accommodated at a city shelter.

"But as some other buildings are having some ventilation problems I expect that number will increase quite significantly today," Nenshi said Monday.

The accident highlights just how vulnerable the infrastructure of a densely populated city can be to a single adverse event.

The June 2013 flood forced 75,000 Calgarians from their homes and inundated the utility floors of commercial buildings on the east side of downtown, damaging power, communications and climate-control systems.

In the wake of the $6-billion disaster, the city got the word out to reinforce backup systems, Nenshi said.

"Certainly we’ve been working hard on the message of having to have continuity plans in case of disaster for businesses," he said. "Most businesses have responded very well with having these plans in place."

The flood revealed the city’s life-support systems already had a fair bit of redundancy built in, the mayor said, allowing power to be rerouted and bringing some people back online fairly quickly.

"In this case, however, this kind of fire in an underground vault is very rare," Nenshi said. "We have not seen anything like it before."

[ Related: 2-alarm fire knocks out power at Toronto City Hall ]

While some local redundancy allowed the outage to be confined to a relatively small geographical area around the utility vault, Nenshi said the destruction of an estimated 3.5 kilometres of power and fibre optic cables was unexpected and hard to plan for.

"We still do’’t know the cause and once we know the cause we’ll be able to identify if there are other weak links in the network," he said.

The transformer that caught fire stayed dry during the flood last year, he said, but there is always the possibility it could have been affected in some other way by the massive power outages elsewhere in the system.

There’s no practical way to build in 100 per cent redundancy that foresees every possible trouble, he said.

"In all infrastructure you just have to make decisions between what’s affordable, what are you willing to do, what are you capable of doing," said Nenshi.

Calgary’s existing power and communications infrastructure has worked well for decades, was recently updated and is regularly inspected, the mayor said.

"So we really do need to figure out what caused this and to see if was just a freak accident or if there are other weaknesses in the network," said Nenshi.