• Project

SR 411 Cowlitz River Bridge – Replace Bridge Deck

Attention travelers! Two nighttime closures are scheduled for Monday, April 29, and Tuesday, April 30, to remove the temporary sidewalk from the south side of the SR 411 Cowlitz River Bridge, at milepost 12.4 in Castle Rock. The bridge will be fully closed from 8 p.m. to 6 a.m. each night. During the closures, travelers will need to use an alternate route.

Project overview

Starting in early 2023, contractor crews will kick off the much-anticipated project to enhance the SR 411 Cowlitz River Bridge, also known as the A Street Bridge or the PH-10 Bridge. This vital bridge connects the City of Castle Rock to the west side of the Cowlitz River.

The primary goal of this project is to extend the useful life of this nearly 60-year-old bridge. The planned improvements include replacing and widening the bridge deck, creating a new, wider sidewalk on the north side, and installing pedestrian and bicycle-friendly traffic barriers. Additionally, a new waterline will be constructed as part of the project.

These upgrades will not only boost safety and functionality for vehicle drivers but they also pave the way for smoother travels and enhanced connectivity for pedestrians, cyclists and all other modes of mobility.

Feb. 2023 - Spring 2024
Project status
Project hotline

What to expect

As we begin the crucial bridge deck replacement work, we want to keep you informed about the anticipated traffic impacts. Throughout the year-long project, there will be intermittent, alternating single lane closures and occasional full bridge closures. The majority of closures will occur during the daytime, with some nighttime and weekend closures scheduled between 10 p.m. to 7 a.m.

To ensure a smooth flow of traffic, we'll install temporary traffic signals on both sides of the bridge, operating similar to stop lights, allowing vehicles to pass through the construction zone one at a time. These signals will be active around-the-clock during the project. Additionally, flaggers will be present as needed to manage traffic through different phases of construction, with expected delays of 15-20 minutes.

During full bridge closures, you'll need to take an alternate route to access either side of the river, connecting the City of Castle Rock and surrounding areas. For northbound SR 411 (West Side Highway) travelers, use SR 506 to reach I-5, while southbound SR 411 (West Side Highway) travelers can use Lexington Bridge Drive for access to I-5. We'll notify you seven days in advance of each full closure through travel advisories, news updates, and reader boards near the project area.

Full bridge closures are necessary during concrete deck pouring to allow sufficient time for the concrete to set and cure. We'll make efforts to schedule this work overnight whenever possible to minimize traffic impacts.

Residents who live near the construction zone may experience construction noise and minor disruptions to their regular travel routes. We're collaborating with the school district and the city to minimize delays during peak school travel times.

Thank you in advance for your understanding and patience as we work to improve this important bridge for everyone's benefit. 

Beginning in Feb. 2023, the existing bridge deck along the SR 411-Cowlitz River Bridge, between mileposts 12.37 and 12.46, in Castle Rock, WA, will be removed in stages and replaced with a new, widened bridge deck that meets current bridge standards for safety and accommodates all modes of travel.