Snohomish County Public Works Department completed environmental mitigation work near the Waldheim Slide, at milepost 20 on the Mountain Loop Highway. Environmental mitigation is construction work intended to offset known impacts to natural resources such as streams, wetlands or endangered species. Crews completed emergency repairs to the highway in 2010 and 2011. Federal funding and other regulations require Snohomish County to complete mitigation work to address the impacts of the emergency repairs.
The Waldheim Slide project environmental mitigation work included installing woody debris in the river downstream of the slide to improve in-stream fish habit and creating a wetland located near Little Beaver Creek.
The Waldheim Slide repair work began in July 2015 and was completed in November 2015.