Army Corps of Engineers repairing Union Slough Levee near Everett

Published Sept. 17, 2015

Repairs to the Union Slough Levee start in earnest today as U.S. Army Corps of Engineers officials commence construction on a 100-foot-long damaged segment on the southwest corner of Smith Island, just south of Everett’s Water Pollution Control Facility.

Located on the Snohomish River’s right bank, the $86,000 project will address sloughing, slope scour, and the loss of embankment material caused during high river flows in November 2014.  Damages reduced the levee’s flood defense to a five-year level of protection, or a 20 percent chance of occurring in any given year. 

Once repaired, the levee will be restored to a 20-year level of protection, or a five percent chance of occurrence.  Under a cost-share agreement, the Corps pays for 80 percent of construction costs and Snohomish County Diking District #5 picks up the remaining 20 percent.

Repairs to the segment include rebuilding erosion protection along the 100-foot damaged section with an additional 25 feet on both sides for tie-in purposes, regrading the levee slope to make it more gradual on the riverward side, and adding a blanket of rock armor to protect against erosive river flows.  The construction plan calls for the reuse of existing spall rock and riprap for the repair, meaning a minimal need for new materials.

Construction is expected to be complete by the end of September, restoring the levee to its designed 20-year level of flood protection.

Throughout the planning process, the Corps coordinated with a number of interested agencies and stakeholders to develop a plan to restore reliable flood protection to the community behind the levee.

Release no. 15-038