Graham v. Public Employees Mutual Insurance

This appeal arises from a dispute which erupted between two insurance companies and their insureds following the May 18, 1980, explosion of Mount St. Helens. The early pyroclastic flows from the eruption, along with hot ash and debris, began melting the snow and ice flanking the mountain and the broken glacial ice blocks within the Toutle River valley. This water, combined with torrential rains from the eruption cloud, existing groundwater, water displaced from Spirit Lake, and ash and debris, created mudflows which began moving down the valley shortly after the eruption began. This process…