Coordinates: Ripple Rock was an underwater, twin-peaked mountain in the Seymour Narrows of the Discovery Passage in British Columbia, Canada, a part of the marine trade route from Vancouver and coastal points north. The nearest town was Campbell River. Only 2.7 metres (9 feet) underwater at low tide, it was a marine hazard, described by the explorer George Vancouver as "one of vilest stretches of water in the world." It was destroyed by a planned explosion on April 5, 1958. 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 coverages of an event in Canada.
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. 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.
As early as 1931, a Marine Commission recommended removing Ripple Rock, but it was not until 1942 that the government authorized attempts to remove it. There was political opposition to the destruction of Ripple Rock, as some felt it would serve well as a bridge support to connect Vancouver Island to the mainland.
The first attempts at planting explosive charges on Ripple Rock were made with floating drilling barges with the goal of blasting away the rock in pieces. The first, in 1943, was secured with six 3.8 cm steel cables attached to anchors that altogether weighed 998 metric tons. This approach was abandoned when one cable broke on average every 48 hours. Another attempt in 1945, involving two large overhead steel lines was similarly abandoned after only 93 (out of 1500 planned) controlled explosions were successful.
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 ended up costing 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, London   
Between November 1955, and April 1958, a three-shift operation involving an average of 75 men worked to build a 174 metre vertical shaft from Maud Island, a 762 metre horizontal shaft to the base of Ripple Rock, and two main 91 meter vertical shafts 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  1,270 metric tons of Nitramex 2H explosives were 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 April 5, 1958. 635,000 metric tons of rock and water was displaced by the explosion, resulting in debris at least 300 metres in the air, falling on land on either side of the narrows. The blast increased the clearing at low tide to about 14 metres (45 feet). 
The Royal Canadian Mounted Police cleared the area of 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.
The first song recorded about the taming of Ripple Rock was named "Ripple Rock" and recorded by Canadian folk/country singer Stu Davis.
In 2008 Campbell River celebrated the 50th anniversary of the blast with another commemorative blast done by a Vancouver special effects company. It took place at 9:31:02 AM, April 5, 2008.
- "Ripple Rock". BC Geographical Names. http://apps.gov.bc.ca/pub/bcgnws/names/19876.html.
- "Canadians Destroy Rock Periling Ships In 1,375-Ton Blast". New York Times (CAMPBELL RIVER, B. C.). April 6, 1958. p. 1. Retrieved 9 August 2010.
- B.C.'s deadly Ripple Rock blown up, CBC Broadcast Date: April 5, 1958
- ES 4/310 Measurements of ground shock and air blast from the Ripple Rock explosion. The National Archives, London, 1959.
- FO 371/135561 Technical Conference on detection of nuclear tests. The National Archives, London, 1958.
- FO 371/135561 Request for information on Ripple Rock explosion. The National Archives, London, 1958.
- "Blast to end Peril at Ripple Rock Popular Mechanics, June 1956, pp. 120-121.
- A YouTube video of the Ripple Rock explosion.
- 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