|
at about 8 feet in height and 900 feet in length, developed underneath the steep rock walls of the west-facing slope. The avalanche started as a hard slab on the 35-45 degree slope. It began moving as a wet-snow avalanche near the lift terminal and continued into the canyon.
Comments: A key factor here was the decision on April 7 not to shoot the upper bowls. O'Leary and Conrad wanted to avoid a repeat of the April 12, 1969, avalanche wherein the base terminal of Chairlift 1 had been damaged. Avalanche and weather conditions in 1969 had been almost identical to those facing them in April of 1973. Their dilemma was whether to chance creating a large avalanche or to wait until the lower slopes had stabilized before shooting. They choose the latter course, and when they did implement control measures on April 10, shooting was ineffective. Then the area was hit by another large storm.
Following this accident, several changes were made at Alyeska Ski Area. When Chair 2 was rebuilt, the lift was shortened and the terminal moved uphill to the toe of the south-facing slope thus moving it away from the mouth of the canyon and out of range of the Sunspots avalanche. In addition, the canyon itself was slightly modified. By deepening, rechanneling, and constructing a diversion dam, ski area managers planned to slow down any avalanche headed for the base area. They also began more control work with a larger gun. The 75-mm howitzer was replaced with a 105-mm recoilless rifle. The more powerful weapon gave the area the capacity for continuous blind firing during prolonged periods of poor visibility. By preventing large accumulations of snow in the avalanche starting zones, the potential for large, destructive avalanches has been decreased. Since 1973, no avalanche has run the length of the canyon.
|
|
