SR 18 Maple Valley to Issaquah Hobart Road
This project is the latest phase in WSDOT's plan to reduce congestion and enhance safety on SR 18 by widening the highway to a four-lane divided highway between Auburn and I-90. The widening is being done in segments, from west to east, and is complete all the way to Maple Valley.
The three-mile section extending to Issaquah Hobart Road is a two-lane undivided highway with the potential for high speed collisions. More than 23,000 vehicles use SR 18 through the construction zone on an average day.
This project will create a four-lane highway that will drastically reduce collisions, ease congestion, and result in smoother flow of traffic on SR 18.
Project benefits include the following, separates opposing traffic with a median, drastically reducing the potential for high-speed collisions; reduces the dip from the Cedar River to 236th Avenue SE; reduces risk of accidents by eliminating three intersections.
Increases highway capacity by two lanes and improves traffic flow by eliminating the traffic signal at 244th.
Builds 14 detention ponds to store and treat highway runoff; constructs 49 acres of wetland mitigation sites; improves Taylor Creek crossings by replacing culverts with seven bridges; realigns 1500-foot section of Taylor Creek.