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The Big Bang
by Charles K. Hurst

Where were you at 9:00 A.M. April 5, 1958?

If you were watching television, no doubt you were watching the first live coast-to-coast broadcast of the Canadian Broadcasting Corporation. The occasion was the demolition of Ripple Rock—the biggest nonnuclear explosion ever deliberately set off and the focus of worldwide interest.

Those of you who have the pleasure of taking a cruise on the Love Boat or other excursion craft to Alaska, have no doubt, traversed the Seymour Narrows along the inner passage up the Pacific Coast north from Vancouver. Since 9:31 A.M. on April 5, 1958, it has been no big deal, and even such big boats as the Island Princess have no difficulty transiting the narrows at all stages of the tide. I took the trip to Alaska several years ago and had the pleasure of being on the bridge when we went over the remains of Ripple Rock. I was disappointed that the captain had never heard of the big bang.

Up until 1958 this navigation hazard just north of Campbell River had been the nemesis of many ships. No one knows precisely how many ships or people have been lost, but since 1875 five large ships were sunk and nineteen more have been damaged. In addition to the large vessels, more than one hundred fishing boats, tugs, and yachts have gone to the bottom, and 114 lives lost. The first recorded casualty was the Saranac, a 2,150-ton United States naval vessel. One of the last victims was the William J. Stewart, which was severely damaged in 1944.

Between 1921 and 1941 many demands were made for removing the hazard of Ripple Rock, twin peaks of rock that jut from the floor of Seymour Narrows, and a number of studies were made to determine the feasibility. With the entry of the United States into World War II and the possibility of submarine attacks on American supply routes to Alaska, pressure increased to improve the inner navigation route.

In 1942 and 1945, attempts were made to remove Ripple Rock by drilling from stationary floating scows and loading the holes with explosives—the traditional method of removing solid material from channels. But the strong currents and turbulent water in Seymour Narrows made the task near impossible. In 1953, a new study suggested attacking the problem from below the surface of the water rather than from above: construct a 760-metre tunnel from adjacent Maude Island under the narrows, then two ninety-metre shafts up into the pinnacles of the submerged mountain; load the shafts with explosives, and blow the lid off. That was the effective answer. The project—the largest ever undertaken by the Department of Public Works, of which I was a part—started in October 1955 with no fanfare and was completed with a big bang on April 5, 1958.

It sounds very simple, although many innovative mining techniques were used. However, the successful conclusion of the project had some other interesting aspects. For instance, the blast occurred during the International Geophysical Year and the large explosion offered scientists an opportunity to investigate various physical characteristics of the Earth. By measuring the seismic waves, geophysicists were able to determine, among other things, that the Earth's crust under the Rocky Mountains and the Selkirk range is twenty kilometres thicker than under the Canadian Shield.

American, English, as well as Canadian agencies studying nuclear explosions were also observers, and carried out close-in, seismic, and air-blast measurements. Their instruments placed in the tunnels and peaks were still operating an hour after the explosion. Elsewhere, the Department of Fisheries and the Fisheries Research Board of Canada surveyed the area for surface kills immediately after the blast and studied the effects on fish placed in cages at various distances from the centre of the blast site.

The size of the explosion created some administrative headaches. The explosive manufacturers didn't want to be held responsible for any unwelcome results, the contractors refused to set off the blast, and so the federal government had to authorize the removal of Ripple Rock's pinnacle and assume responsibility through a special order-in-council. This raised the question of who would press the button. Since the button was to be located in an bunker on Quadra Island inaccessible to press or TV, a distinguished public personage was ruled out; the consulting engineer to the ministry of public works was given the job.

I said that the blast was set off at 9:31 A.M. on April 5, 1958. Why not, for instance, at noon on May 1? Because timing was very important. We wanted to avoid periods when there were no major fish runs through the area. We needed extreme high tide so the water would lessen the rock fragments entering the air space above. And we needed to ensure the best time for a live, coast-to-coast television broadcast. The weather conditions were also crucial—a heavy cloud cover could have led to the air compression wave being reflected downward with unforeseen results and explosion-related gases being concentrated.

If any of you have lived in a neighborhood where sewer, waterline, or road construction requiring blasting, you will be aware of the effect that the explosion has on your house. With 1.25 million kilograms of explosives needed for Ripple Rock, the potential risk of damage was considerable. Twenty-eight adults, twenty-two children, and their pets living within a five-kilometre radius of the blast were evacuated by the RCMP the day before the event. Signs were posted warning people to stay out of the area. Roadblocks were set up on all roads. Marine patrol kept all craft away. Air service controllers in Vancouver were told to keep aircraft clear. To forestall speculative insurance claims, the Underwriters Adjustment Bureau surveyed all buildings within a wide area of Seymour Narrows both before and after the explosion. Only one claim was received.

Before the event, rumours predicted a tidal wave three to eighteen metres high and travelling as much as 160 kilometres an hour. National Research Council measurements showed, however, that nothing spectacular happened. Whatever tidal wave there was petered out within a few kilometres.

By 9:32 A.M. on April 5, the tremor from the epicentre had subsided and the beautiful blossom of the explosion had withered away. The three-million-dollar firecracker had proven to be no misfire. It was indeed the best bang for the bucks.

Charles K Hurst, who retired as chief engineer of Public Works of Canada in 1975, was concerned with the demolition of Ripple Rock. He lives in Ottawa.

This article originally appeared in the Beaver, December 2003/January 2004.

Maggie of Malagash
Ione Paton recounts her mother's childhood growing up in turn-of-the-last-century Nova Scotia.