Skagit River Hydroelectric Facilities Rockfall
Diablo and Ross Dams and their associated facilities, located in the North Cascades National Park, are surrounded by steep, rocky terrain susceptible to rockfall and rock slide events. Landslide Technology (LT) was retained by Seattle City Light to perform a geohazard investigation to design rockfall mitigation measures for the rock slope immediately behind the Diablo Dam Powerhouse.
To prevent scaled rocks from impacting the historic powerhouse, extensive protection measures were designed, including a series of rockfall fences and other temporary protection measures for use during thorough scaling operations. Rock bolting has occurred concurrently with construction of several attenuator fences.
Prior to the completion of this work, a significant rock slide, comprising of about 15,000 cubic yards of debris, occurred near Ross Powerhouse. The failure destroyed the Ross Dam barge landing and the Ross Lake Resort boat dock. LT was retained on an emergency basis to provide rock slope design services and full time construction support. Mitigation and construction included extensive scaling, blast excavation , and rock bolting.