1. Background

2. Planning

3. Explosion

4. Cultural references

5. See also

6. References

7. External links

Ripple Rock is an underwater mountain that had two peaks (9 feet and 21 feet below the surface) in the Seymour Narrows of the Discovery Passage in British Columbia, Canada,^[1] a part of the marine trade route from Vancouver and coastal points north. The nearest town is Campbell River. Only 2.7 metres (9 feet) underwater at low tide, it was a marine hazard in what the explorer George Vancouver described as "one of the vilest stretches of water in the world."^[2][3] The hazard was not only hitting the rock but also big, dangerous eddies caused by tidal currents round the rock.^[4] Ships using the strait preferred to wait until slack tide.

Its top was removed by a planned explosion on 5 April 1958.^[5] This is a National Historic Event in Canada. The Ripple Rock explosion was seen throughout Canada, live on CBC Television. It was one of the first live coast-to-coast television broadcasts of an event in Canada.^[6]

It was so named in 1862 by Captain Richards, RN,^[7] because its summits were about at sea level and made a prominent standing wave in the fast tidal current of the strait.

Background

The first known large ship to fall prey to Ripple Rock was the sidewheel steamer Saranac in 1875, as it was heading north to Alaska.^[8] At least 20 large and 100 smaller vessels were badly damaged or sunk between then and 1958. At least 110 people drowned in these accidents.

Planning

In the 1860s a plan was started to link Vancouver Island to the mainland at Bute Inlet, using Ripple Rock as a mid-support for the bridge. This plan continued through the years, and caused political opposition to destroying Ripple Rock, until it was decided to destroy the rock to improve safety for mariners.^[9]

As early as 1931, a marine commission recommended removing Ripple Rock,^[10] but it was not until 1942 that the government authorized attempts to remove it and issued the first contract to do so.^[11]

The first attempts at planting explosive charges on Ripple Rock were made with floating drilling barges with the goal of blasting the rock into pieces. The first, in 1943, was secured with six 3.8 cm steel cables^[12] attached to anchors that altogether weighed 998 metric tons.^[13] This approach was abandoned when one cable broke on average every 48 hours.^[13] Another attempt in 1945, involving two large overhead steel lines was similarly abandoned after only 93 (out of 1,500 planned) controlled explosions were successful.{{dubious|date=January 2019}}

In 1953, the National Research Council of Canada commissioned a feasibility study on the idea of planting a large explosive charge underneath the peaks by drilling vertical and horizontal shafts from Maud Island in the sound. Based on the study, this approach was recommended. Dolmage and Mason Consulting Engineers were retained to plan the project, and three firms, Northern Construction Company, J.W. Stewart Limited and Boyles Brothers Drilling Company, were granted the contract, which cost in excess of 3 million Canadian dollars.

Although not planned as a test for nuclear weapons purposes, this large underground explosion at Ripple Rock was of interest to nuclear weapons scientists at the United Kingdom's Atomic Weapons Research Establishment at Aldermaston, which sent a delegation to Canada and set up various monitoring instruments to record data from the explosion. Little more is known of their objectives, although there are detailed accounts in two declassified documents in the National Archives in London.^[14][15][16]

Explosion

Between November 1955 and April 1958, a three-shift operation involving an average of 75 men worked to build {{convert|500|ft|m|-1}} of vertical shaft from Maud Island, {{convert|2370|ft|m|-1}} of horizontal shaft to the base of Ripple Rock, and two main vertical shafts up into the twin peaks, from which "coyote" shafts were drilled for the explosives. The contract was awarded to two firms for $2,639,000. At the time of the contract it was estimated the tunnels and shafts would not be completed until either 1957 or 1958.^[17] 1,270 metric tons of Nitramex 2H explosive was placed in these shafts, estimated at ten times the amount needed for a similar explosion above water.

The explosion took place at 9:31:02 am on 5 April 1958. 635,000 metric tons of rock and water were displaced by the explosion, spewing debris at least 300 metres in the air which fell on land on either side of the narrows. The blast increased the clearing at low tide to about 14 metres (45 feet).^[18] After this, its two peaks were 13.7 m (45 ft) and 15.2 m (50 ft) underwater.^[19]

The Royal Canadian Mounted Police had cleared the area of people within 3 miles of the explosion, and the engineers and TV crew that witnessed the explosion were housed in a bunker.

The explosion was noted as one of the largest non-nuclear planned explosions on record, though Soviet authorities reported a larger explosion in the Ural Mountains to carve a new channel for the Kolonga River and in China to open a copper mine.{{cn|date=January 2019}}

Cultural references

Vancouver based punk rock band the Evaporators' 2004 album was named after Ripple Rock and includes a song that details its history and destruction.

The first song recorded about the blasting of Ripple Rock was named "Ripple Rock" and was recorded by Canadian folk and country singer Stu Davis.

In 2008 Campbell River celebrated the 50th anniversary of the blast with a commemorative blast done by a Vancouver special effects company. It took place at 9:31:02 AM, on 5 April 2008.

See also

• List of the largest artificial non-nuclear explosions

References

External links

• Google Earth view (Seymour Narrows is at the center of the image)
• Museum at Campbell River history of Ripple Rock
• Stories in the News article on Ripple Rock
• The Taming of the Rock, by Jeremy Leet
• "B.C.'s deadly Ripple Rock blown up" CBC broadcast from April 5 1958
• Courtesy of the Hagley Museum & Library: The Maud Island Mine head for the Ripple Rock tunnel
• Courtesy of the Hagley Museum & Library: Loading explosives for placement in the Ripple Rock Tunnels.
• Ripple Rock 1958 (Canada) - One of Top 10 biggest non-nuclear explosions ever Film clip on Live Leak website

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