The October rainstorms
The week of October 16 through 21 is on record as one of the wettest weeks ever in Western Washington history. Monday, October 20, alone shattered nearly every record. The Diablo Dam, just off State Route 20, received 16.25 inches of rain in five days. This large amount of water overwhelmed the roads, creek beds, culverts, drainage systems, and ultimately proved to be more water than the Cascade Mountains could absorb. The record rain led to the record-breaking rockslides.
The damage
As WSDOT crews got to the scene, it was clear the damage was extensive. At Pyramid Creek, 200 feet of roadway was washed away and guardrail was left hanging in the air. All along the highway culverts were broken or plugged, incapable of controlling the raging water. Drains were overwhelmed. Damnation Creek and Thornton Creek left their channels and flowed across the highway, destroying sections of the highway. Small rock and mudslides also littered the road off and on between Marblemount and Diablo, causing extensive damage.
What did WSDOT do to repair the highway?
Within a month, WSDOT crews and contractors had repaired nearly all the damage. Working days, nights and weekends, they put creeks back in their beds, replaced culverts and drainage systems, shored up and repaved roads and replaced critical guardrail that protects drivers from the steep hillsides. This quick response prevented more damage during the next round of storms in November. It also helped us clear the road of snow more quickly and easily the next spring.