What caused the massive rockslide on Highway 20?
WSDOT engineering geologists and Federal Highways Association (FHWA) both attribute the massive rockslide to the record amounts of rainfall we received in October, 2003. Shortly after the soggy weather in October, November brought freezing temperatures. The rockslide happened early in the morning November 9, which is the coldest part of the night. The freeze and thaw conditions that were occurring at that time, are what is believed to have brought down the hillside. The second rockslide Within four days of crews removing the rock and debris from Highway 20 to create an emergency access lane for Diablo, a second slide came down Falls Creek, covering the road and blocking the emergency lane. Weekend rain, November 16 and 17, washed smaller rock and debris out of Falls Creek. Maintenance crews were able to clear the rock and debris and reopen the emergency access lane to Diablo by Thursday, November 20. December 17 rockslide On December 17, 2003, a small rockslide occurred above Afternoon
