PROJECT: SKAGIT RIVER HYDROELECTRIC FACILITIES ROCKFALL, Diablo, Washington

Ross Dam Rockfall
Large Rockfall Blocking Access Road to Ross Dam

Diablo and Ross Dams and their associated facilities, located in the North Cascades National Park, are surrounded by steep, rocky terrain susceptible to rockfall events. Beginning in 2008, Landslide Technology (LT) was retained by Seattle City Light to perform an investigation and design rockfall mitigation measures for the rock slope immediately adjacent to 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 rockfall, comprising about 15,000 cubic yards of material, occurred near the Ross Powerhouse. The failure blocked access to the Ross Dam boat dock and the Ross Lake Resort. LT was retained on an emergency basis to provide rock slope design services and full time construction support. Mitigation and construction is currently underway.