Between November 1955 and April 1958, a three-shift operation involving an average of 75 men worked to build of vertical shaft from Maud Island, 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. 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.