About the I-5 Chamber Way - Stage 2 - Project Design Concepts 

In June 2020, WSDOT held an online open house to share project improvement concepts with the community. During the online open house, a survey was presented which provided an opportunity for people to share their thoughts and ideas about the project improvement concepts. If you missed the opportuntiy to participate in the online open house, please continue reading to learn about each of the projects improvement concepts.  

Criteria and screening methodology to narrow between options

Strategies (project alternatives) are being developed, analyzed and advanced for further consideration based on their measurable benefit in addressing safety, reliability and mobility issues. The following set of criteria will be used for alternatives screening:

• Improves Congestion
• Improves Safety
• Cost
• Local Acceptance
• Minimizes Impacts to Critical Areas
• Minimizes Impacts to Right of Way
• Chehalis Flood Compatibility
• Emergency Services Connectivity
• Constructability
• Strategies are being evaluated for different elements of the highway system

 
Project Need Map 

Safety and congestions trends 

Congestion backups and delays are affecting all users on I-5 in Chehalis during peak travel times due to high traffic volumes in an area where I-5 reduces down from three to two travel-lanes in each direction. Continued growth in the region will contribute to increased traffic backups, travel delays and collisions if no improvements are made.

Traffic modeling shows congestion on the mainline freeway and interchanges

As more people use I-5 in the future, congestion will begin earlier and last longer. Traffic models estimate that congested freeway durations on I-5 through Chehalis will increase as follows, if no improvements are made to I-5:

• Northbound travel: durations will increase from 1 hour in current conditions to almost 4 hours by the year 2045
• Southbound travel: durations will increase from 2 hours in current conditions to over 4 hours by the year 2045

View the maps to understand more about the current and future forecasted traffic conditions and speeds along I-5 mainline in the project area.

I-5 Congestion and Speeds - Existing Conditions (2019)

Congestion also affects the delays (included in measuring “level of service”or “LOS”) for interchanges and intersections leading to the highway. View the following maps to understand current and forecasted future traffic at interchanges and intersections in the project area.

Existing Conditions (2019) and Future Conditions (2045) with no improvements 

WSDOT worked with project partners to evaluate and screen a range of strategy options. The Strategies will be prioritized as a “Primary Need” or ”Secondary Need”, as defined by the state funding description:

• Primary Need strategies: Improve I-5 mainline between the Chamber Way and SR6 interchanges, including operations of the Chamber Way interchange
• Secondary Need strategies: Improve I-5 mainline between the Chamber Way interchange and the Mellen Street Couplet overpass
• Supplemental strategies: Improvements that are not defined within the state funding description but contribute to solving the Primary and Secondary needs

An initial screening of the strategies was performed and several were not advanced for further evaluation due to their poor ratings on performance and cost:

Primary Need Strategies

Primary Need – Chamber Way Interchange: Widen Bridge & Modify Signal Timing Strategy
Features:

• Widens north side of bridge to add new westbound lane between State Avenue and southbound ramp terminal
• Modifies traffic signal at northbound and southbound ramp terminal intersections
• Reduces congestion at northbound and southbound ramp terminal intersections

 
I-5 - Chamber Way Interchange - Widen Bridge & Modify Signal Timing strategy 

Primary Need – Chamber Way Interchange: Roundabouts Strategy

Features:

• Signalized intersections are replaced with roundabouts at Louisiana Avenue, the southbound and northbound ramp terminals, and State Avenue
• Existing bridge remains and is utilized by adding a shared use path on the north, expanding the existing sidewalk on the south to a shared use path, installing a center median and allowing for one travel lane in each direction
• Reduces congestion at Louisiana Avenue, southbound and northbound ramp terminals, and State Avenue intersections
• Improves vehicle safety by reducing the number of intersection conflict points

 
I-5 - Chamber Way Interchange - Roundabouts Strategy 
(NOTE: This design graphic is a conceptual layout and final configurations and number of roundabouts will be further refined if this strategy moves forward). 

Primary Need – I-5 Widening Between the SR 6 and Chamber Way Interchanges and West Street Overpass Replacement

Features:

• Widening in the northbound and southbound directions are independent of one another
• Widening requires rebuilding the West Street overcrossing
• Improves I-5 mainline capacity
• Provides opportunity to improve safety at curve north of SR 6

 
I-5 Mainline Widening Strategy - South Segment 

Any proposed widening improvements to I-5 mainline, between the SR 6 and Chamber Way interchanges, will require the replacement of the existing West Street overcrossing. Features of the bridge replacement include:

• Provides access for pedestrians and cyclists
• Replaces functionally obsolete bridge

West Street Strategies

Three strategies have been developed for the connection of West Street with the existing roadways on the west side of I-5:

West Street with Roundabout

Features:

• Constructs a new roundabout at the intersection of West Street/Airport Road/Louisiana Avenue
• Yielded movements reduce delays caused by stopping

 
West Street Strategy - Roundabout

West Street At-Grade T-intersection

Features:

• Constructs a new At-Grade T-intersection at West Street/Louisiana Avenue and at-grade intersection at Louisiana Avenue/Airport Road
• Vehicular movement on Louisiana Avenue is given priority at intersections

  
West Street Strategy - At-Grade T-intersection 

West Street Elevated T-intersections

Features:

• Constructs new Elevated T-intersections at West Street/Airport Road and Louisiana Avenue/Airport Road
• Prioritizes vehicular movement on Louisiana Avenue

West Street Strategy - Elevated T-Intersection

Secondary Need Strategy

Secondary Need – I-5 Widening Between the Chamber Way Interchange and Mellen Street Couplet

Features:

• Widening in the northbound and southbound directions are independent of one another
• Widening requires rebuilding the structure at Salzer Creek
• Improves I-5 mainline capacity
• Provides opportunity to improve safety with wider shoulders and increased sight distance

 
I-5 Mainline Widening Strategy - North Segment

Supplemental Strategies

The project is also considering a number of supplemental strategies, which may be included in the package of solutions depending on their benefits to I-5 in the project area and available project budget:

Features: 

• Ramp metering for on-ramps between 13th Street and Harrison Avenue
  • Used during peak hours or during heavy traffic on I-5
  • Relatively low cost improvement to help smooth flows on I-5
• Roundabouts on SR6 at the I-5 Southbound ramp terminal and SW Riverside Drive intersections
  • Replaces existing signalized intersections with roundabouts
  • Improves vehicle safety by reducing the number of intersection conflict points
  • May encourage drivers making local trips to remain on the local system

 
Supplimental Strategy - SR 6 Interchange Ramp Terminal Improvements 

Next Steps

We are at an early point in the design process. Once a preferred strategy is chosen, this project will begin the Environmental Review and Design Development phases with a goal of starting construction in 2023.