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April 26th, 2017 ~ Vol. 87 No. 17
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Looking Back - John Kinnear
How to Blow Up an Underwater Mountain
Looking Back
USS Saranac sunk in 1875 at Ripple
Last Wednesday was the anniversary of one of the most spectacular man-made explosions ever to occur in its time. It was referred to back then as one of the largest non-nuclear explosions on record. This mammoth blast occurred at exactly 9:31:02 am on April 5th, 1958 and once and for all got rid of a problem that had plagued the Seymour Narrows for over a century.

The Seymour Narrows is a five kilometer stretch of the Discovery Passage which was named by Captain Vancouver after his ship H.M.S. Discovery in 1792. The Passage starts around Campbell River on Vancouver Island, where the Georgia Strait narrows, and eventually widens out further north around Telegraph Cove. This inland passageway is the favoured route of cruise ships that wend their way north between Vancouver Island and the mainland. It eventually becomes the Johnston Strait that leads northward towards the Queen Charlotte Islands and Alaska. Captain Vancouver described Seymour Narrows as: “one of the vilest stretches of water in the world.”

It was a nasty piece of business for mariners for sure because right in the middle of its narrowest spot lay two rock pinnacles just below the surface of the water. Throw a 15 knot current into this dicey situation and things could and did go very wrong. It wasn’t just those subsurface hull rippers that could be an issue. There was also the big, dangerous eddies caused by tidal currents around the rocks. Navigating through this swirling 750 meter wide stretch with those two hidden headaches beneath led to a horrific loss of shipping and lives. It is reported that 20 large and over 100 smaller vessels were badly damaged or sunk and that 114 people lost their lives in the narrows.

The very first large ship recorded to have been caught in its trap was the USS Saranac, a side-wheel steam sloop on its way to Alaska. Saranac was a United States Navy ship that had seen action in the Atlantic and the Pacific and also saw service during the American Civil War. She was on a mission in 1875 to collect natural curiosities for the Philadelphia Centennial Exposition when she wrecked on the Ripple rocks, and sank in an hour, despite being run ashore and made fast. The captain and her 13 crew then made their way on foot to Victoria. That’s some walk!
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Probably one of the most interesting ship casualty stories is that of a vessel named for the famous Canadian hydrographer William J. Stewart. The Stewart, built in 1932, spent many years mapping the West Coast for the Dominion Government. But in 1944 she struck Ripple, floundered and then was beached to avoid sinking. In 1979 she was purchased by the Oak Bay Marine Group, renamed the Canadian Princess, refurbished as a hotel ship and towed to Ucluelet harbor. There she was permanently moored as a floating fish lodge. She was a fine looking vessel, painted white, but I guess I will never get to walk over the gangways to her from shore as she was sold and is being cut up for scrap this year.

So getting back to double trouble we find that a marine commission in 1931 recommended its removal but it wasn’t until 1942 that this controversial move was approved. There were some that were bitterly opposed to it and had visions of it being used as a bridge support for a railroad connecting Vancouver Island to the mainland. Now doesn’t that sound interesting? Wouldn’t that have made a great train trip!

There was a removal attempt in 1943 involving a 150 foot long drilling barge secured by cables over the rock with six concrete anchors weighing 1,100 tons. The violent water at Seymour kept breaking the 1 ½ inch steel cables so two years later they tried again with two overhead cables, each weighing 11 tons, stretched across the narrows 135 feet above the water to secure the barge. The water turbulence was still just too much for them and they gave up.
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Finally in 1953 the National Research Council directed that a feasibility study be done to tunnel into the rock and use explosives from below. The concept , which was eventually approved, was to sink a vertical shaft from Maud Island nearby, tunnel under Seymour Narrows and then up into the twin peaks. A camp was built on Quadra Island and a causeway built over to connect to Maud in 1955 and then began three years of round-the-clock shifts of 75 hard rock miners digging at about six feet per day. That vertical shaft went down 570 feet before it headed horizontally for 2,500 feet until it was under the pinnacles. It then split into two branches that each went up vertically about 300 feet into the peaks. Man, the surveyors really had to know what they were doing on this effort. “Coyote” tunnels were then driven horizontally so that the 1,400 tons of Nitramex 2H explosives could be placed. Nitramex is mostly ammonium nitrate with trinitrotoluene (TNT) added. The SS Mont-Blanc that blew up in Halifax harbour in 1917 was loaded with TNT and picric acid (TNP) and we all know what happened there. Dangerous stuff when not handled right.

So on April 5th, 1958, with every precaution taken, that deadly mix was set off and promptly threw 635,000 metric tons of rock and water about 1,000 feet in the air. CBC covered the blast with one of its first ever live broadcasts. Observers from the United Kingdom, studying nuclear explosions, came to observe the effects of this muffled blast. And muffled it was. They had to use ten times the amount that would have been used in a surface blast to counter the smothering effect all that Seymour Narrows water would have.
continued below ...
So on April 5th, 1958, with every precaution taken, that deadly mix was set off and promptly threw 635,000 metric tons of rock and water about 1,000 feet in the air. CBC covered the blast with one of its first ever live broadcasts. Observers from the United Kingdom, studying nuclear explosions, came to observe the effects of this muffled blast. And muffled it was. They had to use ten times the amount that would have been used in a surface blast to counter the smothering effect all that Seymour Narrows water would have.

Live television coverage was broadcast of the event all across the country so people in Campbell River, only a few kilometers away, saw the blast on the screen. Most felt or heard nothing of the explosion as the sound, cushioned by the water was heard only within a small area. There wasn’t even much of a tidal effect. No damage was sustained. According to the Campbell River Museum write-up: “Careful monitoring by the Fisheries Department found that five orca, a school of porpoises, two sea lions and one fur seal seen near the area before the explosion were all seen again afterward.” Bet they were moving south. Fast! I would have been!

The blast increased the clearance over those two pesky pinnacles by about 45 feet at low tide for the south one and about 70 feet for the north one. And so it was that Ripple Rock, that navigators nightmare, was gone forever. But the treacherous currents, swirling eddies and turbulent tide-rips still remain.

You can check out this spectacular explosion on YouTube, the National Film Board footage at https://www.nfb.ca/film/ripple_rock/ or the special CBC archives footage. It’s pretty dam neat. As John Candy from Second City Television’s (SCTV) Farm Report used to say: “Yup blow’d up good, blow’d up real good!
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April 26th, 2017 ~ Vol. 87 No. 17
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