Public Works

6300 Southcenter Blvd.,
Tukwila, WA 98188

Phone: 206 433-0179
Fax: 206 431-3665

Email the Public Works Dept.

Riverton Flapgate Removal Project

Project Overview

Remove two culverts and flap gates that confluence with the Duwamish River; daylight creek, install trail bridge over creek, habitat improvements and planting for 1,200 lineal feet of creek, inc 1/4 acre backwater wetland habitat and 400 ft of river; associated structural improvements for TIB roadway and adjacent commercial property. The objective is to increase available salmonid rearing habitat and increase flood refuge in lower Duwamish River and improve fish access to Riverton Creek and enhance salmon rearing and resting area.

Project Status Update


At present, the focus of the project has been on pilings and anchors. The steel pilings that support the future trail bridge have been installed; three of the soldier piles for the retaining wall on the Gateway North property have been installed; two sacrificial test anchors at the SR 599 off ramp sheet pile wall have been driven and will be tested this week; large wood debris anchors are being installed and thus far the two tests have passed.  


Contractor completed installation of the Large Wood Debris (LWD) in the backwater wetland. The roadway sheet pile wall tie-back anchoring resumed on 9/14/20 and is expected to be completed by 9/25/20. The project will continue through 10/30/20 and then will be suspended until the summer of 2021, when the in-water work window reopens. The Green River Trail will reopen during the suspension.


Contractor completed the installation of the poured-in-place bridge abutments this week. The bridge is being fabricated off-site and will be placed in Summer 2021. Contractor is working on finishing up the project for the year. They are placing temporary erosion controls to last through the shut-down period and will be paving the Green River Trail so that it may reopen during the shutdown period.

Contact Information

For specific questions, contact Mike Perfetti at 206-433-7192 or email at