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The Hazard Beneath Seymour Narrows
Ripple Rock was a submerged twin-peak mountain of solid granite located in the Seymour Narrows, a treacherous stretch of water between Vancouver Island and mainland British Columbia. For decades, it posed a deadly threat to marine navigation. The peaks of Ripple Rock sat just below the surface, creating violent eddies and whirlpools that claimed over 100 ships and more than 110 lives by the mid-20th century. The currents in the narrows could reach speeds of up to 15 knots, making it one of the most dangerous marine passages on the Pacific coast.
Engineering the Impossible
In the early 1950s, the Canadian government approved a plan to eliminate Ripple Rock by detonating it from within. Rather than attempting a surface demolition, engineers decided to tunnel beneath the seabed from Maud Island, a nearby landmass. The project required:
The Detonation and Its Impact
On April 5, 1958, at precisely 9:31 a.m., the explosives were detonated in a controlled blast. The explosion displaced over 635,000 tons of rock and water, sending a plume 1,000 feet into the air. It was the largest non-nuclear explosion in North America at the time and remains one of the largest man-made blasts ever conducted for navigational purposes.
The blast was broadcast live on Canadian national television and radio, with thousands of spectators watching from nearby hills and boats. The shockwave was felt miles away, and the resulting underwater crater permanently altered the seafloor, making the narrows safer for shipping.
Legacy and Cultural Significance
The Ripple Rock explosion became a symbol of Canadian engineering prowess and environmental transformation. It was featured in documentaries by the National Film Board of Canada and is still studied in civil engineering and geology courses. The site is now a popular location for divers and marine researchers, who explore the altered currents and marine life that have since returned.
Locals recall the event vividly. One resident, just six years old at the time, remembered being taken by his father to witness the blast from a safe distance. The sound, he said, was like thunder rolling through the mountains. Fishermen were quick to take advantage of the stunned fish that surfaced after the explosion, jokingly calling it the biggest "DuPont fishing trip" in history.
Lessons from Ripple Rock
The Ripple Rock project demonstrated the power of coordinated engineering, geology, and explosives work. It also highlighted the importance of:
Ripple Rock was a submerged twin-peak mountain of solid granite located in the Seymour Narrows, a treacherous stretch of water between Vancouver Island and mainland British Columbia. For decades, it posed a deadly threat to marine navigation. The peaks of Ripple Rock sat just below the surface, creating violent eddies and whirlpools that claimed over 100 ships and more than 110 lives by the mid-20th century. The currents in the narrows could reach speeds of up to 15 knots, making it one of the most dangerous marine passages on the Pacific coast.
Engineering the Impossible
In the early 1950s, the Canadian government approved a plan to eliminate Ripple Rock by detonating it from within. Rather than attempting a surface demolition, engineers decided to tunnel beneath the seabed from Maud Island, a nearby landmass. The project required:
- A vertical shaft 500 feet deep
- A horizontal tunnel 2,370 feet long under the seabed
- Two vertical shafts drilled upward into the twin peaks of Ripple Rock
- Placement of 1,270 metric tons of Nitramex 2H explosive
The Detonation and Its Impact
On April 5, 1958, at precisely 9:31 a.m., the explosives were detonated in a controlled blast. The explosion displaced over 635,000 tons of rock and water, sending a plume 1,000 feet into the air. It was the largest non-nuclear explosion in North America at the time and remains one of the largest man-made blasts ever conducted for navigational purposes.
The blast was broadcast live on Canadian national television and radio, with thousands of spectators watching from nearby hills and boats. The shockwave was felt miles away, and the resulting underwater crater permanently altered the seafloor, making the narrows safer for shipping.
Legacy and Cultural Significance
The Ripple Rock explosion became a symbol of Canadian engineering prowess and environmental transformation. It was featured in documentaries by the National Film Board of Canada and is still studied in civil engineering and geology courses. The site is now a popular location for divers and marine researchers, who explore the altered currents and marine life that have since returned.
Locals recall the event vividly. One resident, just six years old at the time, remembered being taken by his father to witness the blast from a safe distance. The sound, he said, was like thunder rolling through the mountains. Fishermen were quick to take advantage of the stunned fish that surfaced after the explosion, jokingly calling it the biggest "DuPont fishing trip" in history.
Lessons from Ripple Rock
The Ripple Rock project demonstrated the power of coordinated engineering, geology, and explosives work. It also highlighted the importance of:
- Subsurface mapping before marine construction
- Controlled blasting techniques in sensitive environments
- Public communication and safety planning during large-scale demolitions
