Clean-up and repair work of a series of rockslides blocking both lanes on State Highway 20/North Cascades Highway was scheduled to begin Monday (June 29), the Washington State Department of Transportation (WSDOT) said in a press release, and will require the existing detour to remain in place until further notice. There are exceptions for emergency vehicles.
The work will clean up the highway east of State Highway 530, with travelers detouring around the slide area via Highway 530, Rockport Cascade Road, and Cascade River Road between Rockport and Marblemount. Emergency vehicles will be escorted onto Highway 20 and allowed to use a bypass lane.
Interwest Construction contractor crews expect the work to take at least a month, WSDOT said, depending on the weather. Initial evaluations by geotechnical engineers show the slope above Highway 20 is unstable and will require removing overhanging trees and rocks before reinforcing the slope with dowels to hold the rock in place.
Funding for this project comes from Washington state’s preservation funds and is expected to cost around $700,000.
The slide occurred the night of June 10, dumping about 150 cubic yards of debris onto both lanes of the highway. Since then, more rocks have fallen, and now crews estimate 1,000 cubic yards of debris — about 70 dump truck loads — will need to be removed, WSDOT said.