Incidents like Cape Ray blasting mishap deemed rare

A close call for a Cape Ray family on Newfoundland and Labrador's southwest coastearlier this week, during blasting operations, is a very rare occurrence in the construction industry.

Rock-breaking expert Ben Hammoudsaid incidents like the one in Cape Ray typically only occur when heavy recycled tire mats areincorrectly placedover the blast siteor when too manyexplosivesare used.

• Emera shuts down Cape Ray site as it investigates rock striking home

"You wantthe rock to move because that's the point of the blasting to fragment and heave the rockbut you want that body of rock to remain on site and not go on adjacent properties," Hammoud said. Heworkswith an Ontario firm called DST Consulting Engineers, whichprovides advice to construction companies that carry out blasting operations.

He said it's actually safer to break rock with explosives than by mechanical means.

"When controlled and done properly, blasting is very safe," Hammoud said during an interview with the Corner Brook Morning Show.

Blasting operationssuspended

Such reassurance is cold comfort to the Wallfamily in Cape Ray.

Their home was damaged andAiden Wall,18, barely escaped injury lateMonday afternoon when a seven-kilogram rock crashed through theroof and landed on the floor, not far from their dining-room table.

It's believed the rock came from a blast that occurred about a quarter-of-a-kilometre away.

The work is related to the construction of the Maritime link, which will carryelectricity from Newfoundland and Labrador to Nova Scotia.

Blasting operations have now been suspended while an investigation is completed.

Mammoud said so-called "fly rock"incidents are not unheard of, but are very rare.

Blasting mats key to controlled explosion

So what makes for a safe blast?

Mammoud said it's essential to determine the correct amount of explosives, and this islinked to the type of rock being broken.

And in order for it to be a controlled explosion, blasting mats weighing about a tonne each are required.

He said a backhoetypically places the mats in a pre-determinedpattern, depending on how the workers want the rock to move.

He said the mats also minimize the noise of the blast,which is important inpopulated areas.

He said the direction of the blast is also controlled by the angle of the blast holes, and the timedelay between each charge.

He said there are rareoccasions when a blast will "backfire," with the energy from the blast moving in the opposite direction.

If this is not anticipated and the matcoverage is inadequate, fly rock incidents can occur.

"It's not a very good experience," he explained.