Work to restore the Desimone-Briscoe School Levee continues this week as U.S. Army Corps of Engineers’ officials repair a 775-foot-long damaged segment on the right bank of the Green River in Tukwila.
The levee provides flood protection to more than 7.5 square miles of warehousing, light industrial, retail and residential structures with an estimated value of about $4.4 billion.
Bristol Construction Services, LCC was awarded the $3.3 million construction contract to repair the levee.
Under the PL 84-99 Levee Rehabilitation authority, the Corps pays for roughly 80 percent of the project and King County Flood Control District (KCFCD) picks up the remaining 20 percent. The project adjoins and complements the new floodwall built by the City of Kent as part of the KCFCD’s Briscoe-Desimone Levee Improvement project.
Damages to the levee were sustained during a March 2014 flood event, reducing the levee’s flood defense to a two-year level of protection, or a 50 percent chance of occurring in any given year. Once repaired, the levee will provide protection from an estimated 100-year event, or one percent annual chance of flooding.
Repairs include rebuilding the levee toe, re-grading the slope, adding a mid-slope bench and armoring the structure with a blanket of riprap to protect it from river flow.
In addition, the project includes an extensive planting plan including two willow lifts on the riverward face of the levee.
A total of 1,447 live willow and dogwood stakes will be planted along with 103 trees on these lower lifts. Trees will also be planted on the upper‐slope bench, the lower silt bench at the upstream end, and the wider crown on the downstream end. A total of 97 trees will be planted on these upper slope areas.
The portion of the Green River Trail System immediately above the project area will be closed during construction, expected to be complete by December 30, 2015.