Monday, October 06, 2008

Seymour Narrows

Saturday, September 20:

We checked out of our motel in Courtenay and headed north along Highway 19 for Port Hardy.

Along the way we passed the lookout over Seymour Narrows.

This placid scene doesn't do justice to the treachery of this patch of water.


Here is what the signboard at the lookout said about the history of Seymour Narrows:

"Seymour Narrows, 14 km. north of Campbell River is a 3 kilometer (2 mile) long by 750 meters (barely 1/2 mile) wide stretch of hazardous waters separating Vancouver Island and Quadra Island. Tides rushing through the narrows reach velocities of 10 to 15 knots (12-18 mph), with cross currents and vertical current creating whirlpools 3 to 9 m. (20 to 30 ft) in diameter.

Prior to 1958, Seymour narrows was decreed the most dangerous area for nautical navigation in North America. Ripple Rock, consisted of two hump-like summits about 900 m. (3000 ft) long and 100 m. (350 ft.) wide between Vancouver Island and Maud Island.

The highest point was within 3 m. (9 ft) of the surface at low tide. The strong currents and dangerous whirlpools could swallow small boats and deflect large ships onto the rocks. The earliest recorded loss was the sinking of the side-wheeler steamer USS SARANAC in 1875. In total 119 vessels and 114 lives were recorded lost to the sea. Ripple Rock restricted trade and commerce, limiting the growth of British Columbia."


Various attempts were made to explode this ridge of rock, with no success.

Finally
"In 1955 contracts to tunnel underneath the seabed into the twin pinnacles were awarded ... A 75-man crew working in three shifts tunneled an average of about 2 m. (6 ft.) per day. Over 28 months 8,534 (28,000 ft.) of drilling was done at a cost esceeding $3.1 million, resulting in a 171-m. (570-ft.) vertical shaft at Maud Island and a 750-ft (2,500-ft.) main tunnel under the ocean floor. Two 90-m. (300-ft.) vertical raises into each peak of Ripple Rock were then packed with 1,400 tons of Nitramex 2H explosives.

"At 9:30 a.m. on 5 April 1958, Dr. Victor Dolmage, a Ministry of Public Works consulting engineer pushed the plunger that initiated the world's largest ever non-nuclear explosion. Over 700,000 tons of pulverized rock and water erupted in a blast which reached 305 m. (1,000 ft.), and then the rubble dispersed along the bottom.



The highest pinnacle went from 3 m. (9 ft.) below the surface to 14 m. (47 ft.)

"This event was one of the first live television broadcasts in Canada. People were glued to their TVs in anticipation of watching this historic engineering event. Tidal wave warnings were issued and access to the area restricted. It was expected that the massive explosion would generate a large wall of water threatening coastal areas. Luckily it never materialized. No damage was sustained and the effects on fish stocks were minor.

"Large and small vessels now travel safely through Seymour Narrows without danger of grounding on the twin peaks, but it can still be a difficult and sometimes treacherous place to navigate."

- British Columbia Ministry of Tourism, Sport and the Arts.

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