In the late 1700s, Captain George Vancouver called the channel at British Columbia's Seymour Narrows, "one of the vilest stretches of water in the world." Its deadliest feature: the twin peaks of Ripple Rock, lurking just below the surface of the swirling water. "Old Rip" had menaced shipping for centuries, sinking or damaging 119 vessels and claiming almost as many lives. But on April 5, 1958, the world's largest non-nuclear peacetime explosion pulled Ripple Rock's teeth forever.

• Ripple Rock lay between Vancouver Island and Quadra Island, 16 kilometres north of the village of Campbell River, about 200 kilometres northwest of Vancouver. The channel at Seymour Narrows is about 120 metres deep, but the south peak of Ripple Rock came within three metres of the surface at low tide. The rocks, and the waves and whirlpools they caused, damaged or sank 20 large vessels and over 100 small ones, killing at least 114 people.

• For fifty years various groups lobbied the government to do something about Ripple Rock. But other groups opposed its removal, hoping it could be used as part of a railway bridge from the mainland.
• In 1943 an effort was made to remove the rock using a floating drilling platform anchored over top of the rock. The current was so strong that the steel cables snapped and the plan had to be abandoned.

• In 1945 another unsuccessful attempt was made, this time using a barge attached to two massive overhead steel cables that stretched across the narrows. Turbulence was again a problem, and the project was cancelled after less than one-tenth of the required holes had been drilled.
• Nine men drowned during the operation when a boat capsized.

• In 1953 the National Research Council studied the possibility of tunnelling down from Maud Island, across under Seymour Narrows, and up into the rock. The project was described as "the world's biggest root canal."
• Work on the gigantic project began in November 1955 and lasted for 27 months.

• When the tunnelling was complete, workers drilled a series of "coyote tunnels" in the tops of the north and south peaks of the rock, and packed them with 1,375 tons of Nitramex 2H explosive. (This was ten times as much explosive as would be needed for a similar blast above water.)
• The blast was scheduled for April, a time when there would be few salmon in the area.

• On April 5, 1958, ships and planes were diverted, and the area within five kilometres of the site was evacuated. At 9:31 a.m., the plunger was pushed and Ripple Rock exploded with a "cataclysmic crash." The blast blew some 700,000 tons of rock and water 300 metres into the air, and caused waves several metres high, but there was little or no environmental damage.

• The blast was a complete success, lowering the rock to 14 metres below the water level at low tide at the south pinnacle (21 metres at the north.) Ripple Rock would never again threaten ships. The project is still considered a marvellous feat of engineering.
• The Ripple Rock explosion was one of CBC Television's first nationwide live broadcasts.

Medium: Television
Program: CBC Television News Special
Episode: The Explosion at Ripple Rock
Broadcast Date: April 5, 1958
Reporters: Bill Herbert, Ted Reynolds
Duration: 3:57