I-5 - JBLM Area Improvements - Congestion Relief Study

On May 23, 2017, the U.S. Department of Transportation Federal Highway Administration issued a Finding Of No Significant Impact (FONSI) for the Interstate 5 JBLM Congestion Relief Project.

On October 4, 2016, WSDOT published an Environmental Assessment (EA) for the I-5 - JBLM Vicinity Congestion Relief Project. The EA contains the results of our studies on how this project may affect the environment. The comment period for the environmental assessment was October 17 - November 22, 2016.

The $495 Million I-5 Mounts Road to Thorne Ln I/C - Corridor Improvements project was included in the Connecting Washington transportation-revenue package, approved by the Washington State Legislature in July 2015.

Why is there so much congestion?

Traffic on Interstate 5 in LakewoodInterstate 5 is a national highway of strategic importance. It moves goods and people between two borders and links major cities. It is a critical corridor for military use. Over the past several years, traffic has increased along the entire I-5 corridor, and nowhere has that increase been more noticeable than in south Pierce County through the Joint Base Lewis-McChord (JBLM) vicinity.

A combination of factors have contributed to the traffic growth through the area. Large businesses have moved in. JBLM and Camp Murray have expanded, and the communities of Lakewood, DuPont and Steilacoom have continued to develop. Each change has added demand on the already-crowded I-5 corridor. Motorists now see traffic congestion on a daily basis, especially during peak commute hours. Because secured military bases are located on both sides of I-5, alternate routes involve using perimeter roads around the bases. Those routes are neither convenient nor able to manage high volumes of traffic.

What is WSDOT doing about it?

In 2013, a joint I-5 corridor planning study was initiated involving WSDOT, JBLM, FHWA and local jurisdictions. The study evaluated the best way to improve transportation through the JBLM vicinity. The task of the planning study is to define improvements that could relieve congestion on I-5 from Center Drive to Gravelly Lake Drive, with a focus on the interchanges at the Steilacoom-DuPont exit (#119), 41st Division Drive/Main Gate exit (#120), Berkeley Street exit (#122) and the Thorne Lane exit (#123).

Specifically, the study addressed options to:

  • relieve congestion on I-5
  • improve system efficiency
  • enhance mobility
  • improve safety and operations
  • increase transit and alternative commute opportunities

This work was performed in three phases. Phase 1 conducted a Corridor Feasibility Study. You can read the full report and the summary report linked below:

During Phase 2, conducted in 2014, WSDOT conducted a comprehensive multi-modal corridor alternative analysis. In this effort, WSDOT evaluated alternatives other than adding lanes to I-5 that could improve mobility along the corridor. Public involvement was an important element of Phase 2.
In January 2014, WSDOT conducted an origin-destination study. The origin-destination study better identified the nature of local trips and regional traffic on and near Interstate 5 between Mounts Road and State Route 512. This study was documented in a report on Travel Patterns and Characteristics along the I-5 corridor in the JBLM vicinity.

The report describing the development and screening of multimodal options for the corridor can be accessed at the following link:

Between July and November 2014, alternatives advanced from Phase 1 were further evaluated along with those developed during the multi-modal Alternatives Analysis. Alternative "packages" including combinations of transit services, local road improvements and I-5 mainline and interchange improvements were defined and evaluated. Thirteen alternative "packages" were modeled for performance and evaluated for potential environmental impacts as well as implementation characteristics.

Performance criteria during the weekday p.m. peak travel period that were modeled and scored include:

  • Traffic speed.
  • Hours of congestion.
  • Travel time between Mounts Road and Bridgeport Way.
  • Number of people that could move through the corridor.
  • Percent of total person demand that could move through the corridor.
  • Potential person trips using HOV's (including vanpools and transit).

Implementation characteristics that were evaluated and scored include:

  • Relative cost to implement the alternative.
  • Amount of new Right-of-Way needed.
  • Ability to build the alternative in stages.

The result was proposed alternatives (pdf 485 kb) that were advanced into the NEPA environmental study process. Phased implementation of improvements is proposed with an initial or "opening year" alternative and a "future" alternative.

The proposed Initial Phase of improvements include:

  • Rebuilding the Thorne Lane interchange.
  • Rebuilding the Berkeley Street interchange.
  • Add one lane to each direction of I-5 from Thorne Lane to Steilacoom-DuPont Road.
  • Rebuilding the Steilacoom-DuPont Road interchange.
  • Possible local connection from Gravelly Lake Drive to Thorne Lane.
  • Bike/Pedestrian path along the I-5 corridor.

The proposed future phase would include:

  • Add one additional lane to each direction of I-5. Two lanes each direction would be Express Lanes restricted to through traffic only. Traffic entering or exiting I-5 in the JBLM area would use the outer three lanes.
  • Revisions to Main Gate interchange.

The report describing the Phase 2 Multi-Modal Alternative Analysis for the corridor can be accessed by clicking on the following links. The report has been broken up into three sections for user ease.

Final Phase 2 Report - I-5 JBLM Vic. - Congestion Relief Study Sections I-V (pdf 3250 kb)
Final Phase 2 Report - I-5 JBLM Vic. - Congestion Relief Study Section VI (pdf 6087 kb)
Final Phase 2 Report - I-5 JBLM Vic. Congestion Relief Study Sections VII-X (pdf 6106 kb)

Build Alternative & Environmental Studies

In Phase 3 of the study, NEPA environmental studies and documentation will be conducted for the proposed alternatives. WSDOT and other stakeholders will also evaluate proposed revisions to interchanges and document them in an Interchange Justification Report (IJR).
Click for larger view of map.


Why are studies needed?

The planning study will result in a NEPA environmental document and an IJR, which is a study required by federal law used to justify revisions to highway interchanges. The IJR documents the design of the preferred alternative, the planning process, the evaluation of considered alternatives, and the support and justification for requesting an access revision. With the results from the report, project stakeholders can take action to implement the preferred solutions.

What will the completed study include?

  • National Environmental Policy Act (NEPA) environmental documentation for proposed corridor improvements and preliminary engineering for the highest priority improvements.
  • A completed Interchange Justification Report for revisions to the four focus-area interchanges. 

Cost Estimate

In July 2015, the Washington State Legislature included $495 Million for the I-5 Mounts Road to Thorne Lane Interchange - Corridor Improvements project, as part of the Connecting Washington transportation-revenue package.   

What is happening in the mean time?

While the planning study is underway, some construction has already taken place in the corridor.  The construction projects will provide short-term improvements to help relieve congestion.  

  • Install ramp meters
  • Widen ramp lanes
  • Add a ramp lane and auxiliary lane
  • Install data collection stations
  • Install Intelligent Transportation System improvements

View a map of these preliminary project features. 

Financial Information

The financial information presented below is for the planning study.

  • 2003 Gas Tax (Nickel Funding): $0
  • 2005 Gas Tax (TPA): $0
  • Pre-Existing Funds (PEF): $6,502,000
  • Total: $6,502,000


How can I get more information?

Bill Elliott
Olympic Region Plans Engineer

Claudia Bingham Baker
WSDOT Communications Manager