The Explosive History of Ripple Rock

The Explosive History of Ripple Rock

Ripple Rock, Campbell River's Biggest Explosion

In 1958, the largest non-atomic explosion blew up 635, 000 tons of water and rock over Seymour Narrows. This ENOURMOUS explosion reached heights of 305 metres (1000 feet)! This massive feat of engineering and ingenuity refers to the demolition of the underwater mountain known as Ripple Rock.

Crossing Seymour Narrows with DIVESAFE

Ripple Rock, located in the bottleneck passage known as Seymour Narrows, is a notorious marine obstacle that claimed the lives of many before its destruction. All boat traffic heading north of Campbell  River must cross this treacherous passage, including commercial divers. DiveSafe students have the opportunity to to cross Seymour Narrows during their studies and view the awesome power of the Discovery Passage. 

Ripple Rock's History

Ripple Rock was a twin-peaked, underwater rock located in Seymour Narrows, a treacherous, bottleneck portion of the Discovery Passage. Currents ran as fast a swift-moving river in this passage, and combined with the underwater monster that is Ripple Rock, all kinds of marine hazards lurked under the surface.  Whirlpools, eddies, vertical currents, crosscurrents, and rapids threatened all kinds of ships moving cargo and goods through this busy passage. At low tide, some sections of this narrow passage only cleared 3 metres (9 feet). Seymour Narrows was a perilous passage, sinking many boats and claiming the lives of at least 114 people before Ripple Rock’s recommended removal.

ripple rock

The First Attempt

The first attempt to blow Ripple Rock occurred in 1943. The plan was to drill into Ripple Rock at slack tide and plant explosives into the rock. A drilling barge would be anchored by six thick cables attached to concrete anchors. Once detonated, dredges and scows would remove the rubble from the explosion. The heavy, concrete anchors (weighing between 150 and 235 tons) were dropped into the ocean, but the turbulent waters snapped them easily numerous times over. 

The Second Attempt

A second attempt was made in 1945. The idea was to attach two heavy, massive steel cables high above, running across Seymour Narrows, that would attach to the drilling barge. This barge was set to drill 1500 holes for blasting, however, only 93 holes were made before tumultuous waters hindered the project again.

12739 drilling barge watermarked 1024x668 1

The Final Attempt

In 1954, a new plan was made to tunnel from Maud Island to Ripple Rock, planting explosives in small coyote tunnels running up into the rock. In November, 1955, a 174 (150 feet) metre shaft was sunk from Maude Island. From this shaft, an underwater 762 metre tunnel was built to the base of Ripple Rock, splitting off into smaller tunnels that drove up 91 metres (300 feet) vertically into the underwater mountain. 1,400 tons of explosives were packed into these smaller tunnels. For reference, 10 x more explosives would be needed for a similar detonation on the surface. On April 5, 1958, this final attempt to blow Ripple Rock was ultimately successful and is regarded today as an engineering achievement. It is one of the world’s largest man-made non-nuclear explosions to date. On April 5, 1958, seven hundred thousand tons of water and rock exploded 305 metres (100 ft) in the air. This giant explosion only lasted about 10 seconds before a cloud of gas covered the site.

ripple rock tunnels
ripple rock explosion

Today, Ripple Rock now clears 14 metres (45 ft) of water at low tide on the southside, and 21 metres (70 ft) at low tide in the north. While strong currents still run throughout Seymour Narrows, it is a considerably safer passage for commercial fishing boats, commercial diving boats, cruise ships, tugboats and supply barges carrying cargo and lumber. These vessels need to time their passage based on the tides, even with the destruction of Ripple Rock. The bottleneck passage contains whirlpools and fast moving currents. DiveSafe Students have the opportunity to travel these dangerous waters and cross Seymour Narrows. See for yourself, and sign up for one of our Commercial Dive classes today!

For more information, please visit the Campbell River Museum’s website, or check this article from the Macleans archive.

Dive Safe International Commercial Diving
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