Ripple Rock

Ripple Rock, within Seymour Narrows near Campbell River B.C., was a marine hazard responsible for more than 20 large vessels and at least 100 smaller vessels being damaged or sunk. Before its destruction in 1958, Ripple Rock had claimed at least 114 lives.

photographer R. E Olsen

In 1931 a Marine Commission's findings brought a recommendation to remove Ripple Rock, but it was 1942 before an attempt was finally authorized. Despite the extreme hazard the rock created, its removal was bitterly opposed by some, who saw it as a bridge support for a railroad connecting Vancouver Island to the mainland.

In 1943 a drilling barge 150 feet (46 m.) long was floated over the rock, held in place by one and half inch (3.8 cm) steel cables attached to six concrete anhors totaling 1,100 tons (998 tonnes).The plan was to drill holes into the top of the rock, fill with explosives and blast Ripple Rock away bit by bit. The enormous drilling barge quivered and tossed in the violent water, the anchor lines vibrating continually. The attempt failed as anchor lines broke at an average of one every 48 hours.

A second attempt was made in 1945 with a plan to hold the drill barge in position by attaching it to two enormous steel overhead lines, each weighing 11 tons (10 tonnes). The 3,500 foot (1067 m.) cables were stretched across Seymour Narrows 135 feet (41 m.) above high water. Again, water turbulence severely hindered the operation; of the estimated 1,500 drill holes needed only 139 were drilled, 93 blasted, before the contract was terminated.

Eight more years passed, then the National Research Council directed a feasibility study on tunnelling to the rock by sinking a shaft from Maud Island under Seymour Narrows and up into the peaks of Ripple Rock. When this underground approach was recommended, Dolmage and Mason Consulting Engineers were retained to plan the project.

Contracts for the job went to Northern Construction Company, J.W. Stewart Limited, and Boyles Brothers Drilling Company. Work began in November 1955. A camp established on Quadra Island was connected by causeway to Maud Island. An average of 75 men lived at the base camp; three shifts of hard rock miners working around the clock advanced six feet per day on a 570-foot (174 m.) shaft sunk from Maud Island.

From the shaft, a 2,500-foot (762 m.) tunnel was driven to the base of Ripple Rock, where it divided into branches for the two pinnacles. From vertical tunnels 300 feet (91 m.) high there extended a series of “coyote” tunnels into which the explosives were placed.1,400 tons (1,270 tonnes) of Nitramex 2H explosives (10 times the amount needed for a similar explosion above water) were packed into the drilled rock.

Every possible effect of the world's largest non-atomic blast to date was carefully considered and precautions made.

When Ripple Rock blew at 9:31:02 am. April 5, 1958 the sight was awesome. 700,000 tons (635,028 tonnes) of rock and water erupted in a blast that reached a height of 1,000 feet (305 m.). The spectacle lasted less than 10 seconds before the debris was engulfed in a cloud of gas.

Live television coverage, very new at the time, broadcast the event across the country. People in Campbell River saw the blast on the screen, but felt and heard nothing of the explosion only a few miles away. Cushioned by the water, the sound was heard only within a small area, and the tidal effect was slight.

No damage was sustained. 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, although understandably somewhat perturbed.

As a result of the project, 45 feet (14 metres) of water instead of 9 (3 m.) now clear the south pinnacle at low tide, and 70 feet (21 m.) flow over the north. This mammoth undertaking is still considered a marvel of engineering.