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. The project would widen seven miles of Interstate 5 in Pierce County, from DuPont to Lakewood, adding an HOV lane in each direction. The proposed changes would reduce chronic traffic congestion through the JBLM corridor. To widen I-5, new interchanges are being reconstructed using roundabouts instead of signals to improve traffic flow and reduce the potential for collisions. The new interchanges are grade-separated from the existing rail line, reducing conflicts with trains.
The funding for the project spans over a 10 year period. The funding schedule and right-of-way acquisition play a big part in determining when construction occurs.
Based on the funding schedule, the I-5 Mounts Road to Thorne Ln I/C Corridor Improvements project is broken up into 4 separate construction projects:
During construction, travelers will see:
- Reduced speed limit in work zone
- Overnight ramp and lane closures
- Shifted lanes
- Long-term ramp closures and detours
Originally built in the 1950s, Interstate 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.
In 2013, a joint I-5 corridor planning study (PDF 1.34MB) 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:
Next, in 2014, we conducted a comprehensive multi-modal corridor alternative analysis. This effort evaluated alternatives other than adding lanes to I-5 that could improve mobility along the corridor. Public involvement was an important element of this analysis.
We also conducted an origin-destination study to help identify 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 (PDF 3.8MB) along the I-5 corridor in the JBLM vicinity.
The report describing the 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 3250KB)
Final Phase 2 Report - I-5 JBLM Vic. - Congestion Relief Study Section VI (PDF 3087KB)
Final Phase 2 Report - I-5 JBLM Vic. Congestion Relief Study Sections VII-X (PDF 6106KB)
Last but not least, National Environmental Policy Act (NEPA) environmental studies and documentation were conducted for the proposed alternatives. WSDOT and other stakeholders evaluated proposed revisions to interchanges and document them in an Interchange Justification Report (IJR). This information can be found under the Environmental tab.
In 2010, WSDOT and JBLM joined forces to create the Traffic Circulation Committee – an operations planning team comprised of leaders from JBLM, WSDOT, Washington State Patrol and local municipalities. The team met weekly to identify issues, brainstorm solutions, assign actions and communicate progress. Since then stakeholders and community engagement has been a top priority for addressing transportation issues in this corridor.
- City of Lakewood
- City of DuPont
- Town of Steilacoom
- City of Lacey
- City of Yelm
- Joint Base Lewis-McChord
- Nisqually Indian Tribe
- Intercity Transit
- Pierce Transit
- Sound Transit
- Pierce County
- Puget Sound Regional Council
- Thurston Regional Planning Council
- Washington National Guard
- Washington State Patrol
- Federal Highway Administration
An online open house was held November 16 to December 16, 2020, giving the public the opportunity to comment on the South Study Area Supplemental Environmental Assessment. Due to the Governor’s Stay Home – Stay Healthy Order issued on March 23, 2020, no in-person open house was available. Instead, the project information was made available to view online.
A combined environmental hearing and informational open house was held on Monday, November 7, 2016 at the McGavick Conference Center, Clover Park Technical College, in Lakewood, WA. The public comment period for the I-5 - JBLM Vicinity Congestion Relief Environmental Assessment (EA) was October 17 through November 22, 2016.
Numerous public presentations have been held for the project since 2013 at regional council meetings, local community groups and open house events.
- April 11, 2018 DuPont Open House held at Pioneer Middle School.
- May 23, 2016 DuPont Open House held at Pioneer Middle School.
- May 4, 2016 Tillicum and Woodbrook Community Update Meeting held at Tillicum Elementary.
- Sept. 1, 2015 Tillicum and Woodbrook Community Meeting held at the Tillicum Community Center.
- May 5, 2015 Open House held at the McGavick Conference Center, Clover Park Technical College in Lakewood.
- June 11, 2014 Public Open House held at Eagles Pride Golf Course.
Open House Library
May 23, 2016 Open House display boards - DUPONT
May 4, 2016 Community Update Meeting - TILLICUM
September 1, 2015 Community Meeting - TILLICUM
May 5, 2015 Open House display boards - LAKEWOOD
I-5 - Mounts Rd. to Center Dr. - Auxiliary Lane Extension - Completed September 2018
In 2017, contractor crews working for WSDOT began construction to extend the auxiliary lane on northbound Interstate 5 between Center Drive and Steilacoom-DuPont Road one and a half miles south to Mounts Road.
By extending the auxiliary lane south about 1.5 miles to start at the Mounts Rd. bridge, trucks approaching the weigh station and entering and exiting traffic will use this lane while the majority of traffic uses the adjacent three through lanes.
To accommodate the auxiliary lane, northbound I-5 was widened into the center median. The final lane configurations will include three 11-foot-wide lanes, one 12-foot-wide lane and 8 feet on the inside shoulder.
Construction finished in 2018. Eventually, the extended auxiliary lane will ultimately become part of the HOV lane that is being built in the I-5 Mounts Road to Thorne Lane I/C Corridor Improvements project.
I-5 - Steilacoom-DuPont Rd. to Thorne Lane - Corridor Improvements - Complete December 2021
In 2018, construction crews began working on the I-5 - Steilacoom-DuPont Rd. to Thorne Lane - Corridor Improvements project. To relieve chronic traffic congestion and improve mobility along I-5 in the vicinity of Joint Base Lewis-McChord, WSDOT is rebuilding the interchanges at Thorne Lane and Berkeley Street and adding lanes to I-5. Once construction is finished, the new lane in each direction on I-5 will open as an HOV lane.
The changes would reduce chronic traffic congestion through the JBLM corridor. New interchanges that incorporate roundabouts and grade separation from the rail line improves traffic flow and reduces the potential for collisions.
Construction reached substantial completion in December 2021. The contractor will finish minor punch list items in early 2022.
I-5 - Mounts Road to Steilacoom-DuPont Road - Corridor Improvements
To relieve chronic traffic congestion and improve mobility along I-5 in the vicinity of Joint Base Lewis-McChord, WSDOT is proposing to rebuild the interchange of Steilacoom-DuPont Road (Exit 119) and adding HOV lanes to I-5. This will support congestion relief on I-5 during peak traffic periods while maintaining access to neighboring communities and JBLM. The proposed build alternative also includes grade separation of the roadway over the railroad. The project is currently undergoing environmental reviews. Construction is scheduled to begin in 2023.
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I-5 Mounts Road to Thorne Lane I/C Corridor Improvements - Proposed Gravelly Thorne Connector
The new Gravelly-Thorne Connector proposed design consists of a non-motorized shared use path. The shared use path will provide a much needed pedestrian and bicycle connection to and from Tillicum without having users trespass on to Sound Transit railroad right-of-way or use the shoulder of I-5. The shared use path will be built so emergency vehicles can use the path as an alternative to I-5 if conditions warrant.
Also included in this phase of construction is a proposed bicycle and pedestrian path between Lakewood and DuPont, providing a multi-modal option for travel. A stakeholder engagement process evaluated options and determined that a Shared-Use Path alignment through Lewis North (parallel to roads open to the public) would best meet this need.
Next steps for this phase of construction include right-of-way acquisition, final design and a competitive bidding process. These activities will proceed based on availability of funding.
The vicinity map shows the four stages of construction of the I-5 - Mounts Road to Thorne Lane I/C Corridor Improvements project.
- Stage 1: I-5 - Mounts Road to Center Drive - Auxiliary Lane Extension - Construction began in spring of 2017, and was complete in 2018. Northbound I-5 was widened between Mounts Road and Center Drive for an auxiliary lane.
- Stage 2: I-5 – Steilacoom –DuPont Rd. to Thorne Lane – The design-build contract will began mid-2018, and will finish in summer 2021. This project rebuilds the Thorne Lane and Berkeley Street interchanges, adds auxiliary lanes, and adds a fourth lane to I-5 in each direction from Thorne Lane to just past JBLM's main gate. The fourth lanes will operate as HOV lanes once construction is complete.
- Stage 3: I-5 – Mounts Road to Steilacoom-DuPont Road project - Scheduled to begin in 2022. This project will build improvements between Mounts Road (Exit 116) and Steilacoom-DuPont Road (Exit 119). Improvements to the Steilacoom-DuPont Road interchange are being finalized.
- Stage 4: Gravelly-Thorne Connector and Shared-Use path. Next steps for this project include right-of-way acquisition, final design and a competitive bidding process. Project construction will begin in 2023.
2020 Environmental Supplemental Environmental Assessment
On June 30, 2021, 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 Revised Environmental Assessment (PDF 31MB).
WSDOT has published the I-5 JBLM Vicinity Congestion Relief - South Study Area Supplemental Environmental Assessment (PDF 61.84MB).
This document was prepared as a supplement to the 2017 Environmental Assessment (EA) for the project's North Study Area. The Supplemental Environmental Assessment (SEA) describes the South Study Area and cover the potential environmental effects related to transportation, noise, natural resources, parks and recreation, community resources, and other resources.
- The South Study area is located between the vicinity of the Mounts Road (116) and Main Gate (120) exits.
- The North Study Area is located between the Steilacoom-DuPont Road (119) and Thorne Lane (123) exits.
- The North Study Area and South Study area overlap between Exits 119 and 120.
This SEA analyzes project-specific impacts in the South Study Area and operation of a High Occupancy Vehicle (HOV) lane in each direction through the complete study area (North and South).
An online open house was held November 16 to December 16, 2020, giving the public the opportunity to comment on the SEA.
2017 Environmental Assessment
On May 23, 2017, WSDOT published a Revised Environmental Assessment (REA) and Finding of No Significant Impact (FONSI) for the I-5 JBLM Vicinity Congestion Relief Project. The REA contains the results of our studies on how this project may affect the environment. Comments received on the previously published Environmental Assessment (EA) from agencies and the public were considered in preparing this Revised EA.
The final documents are listed below.
Finding of No Significant Impact, Table of Contents, Acronyms & Glossary (PDF 364KB)
Executive Summary (PDF 97KB)
Chapter 1 Introduction (PDF 931KB)
Chapter 2 Setting, Planning and Outreach (PDF 115KB)
Chapter 3 Description of Alternatives (PDF 1.4MB)
Chapter 4 North Study Area Analysis
Chapter 5 South Study Area Analysis (PDF 459KB)
A. Environmental Commitments (PDF 41KB)
B. Discipline Studies and List of Preparers (PDF 58KB)
C. References (PDF 59KB)
D. Distribution List (PDF 47KB)
E. Agency and Tribal Correspondence (see below)
F. Public Involvement (PDF 770KB)
G. Public Comments and Responses (PDF 3MB)
H. Project Exhibits and Plans (PDF 6.6MB)
I. Section 106 Programmatic Agreement (PDF 921KB)
Interchange Justification Report
Interchange Justification Report (PDF 5MB)
IJR Appendix A (PDF 2.8 MB)
IJR Appendix B (PDF 232 KB)
IJR Appendix C (PDF 780 KB)
IJR Appendix D (PDF 589 KB)
IJR Appendix E (PDF 440 KB)
IJR Appendix F (PDF 412 KB)
IJR Appendix G (PDF 702 KB)
IJR Appendix H (PDF 804 KB)
IJR Appendix I
IJR Appendix J
IJR Appendix K (PDF 10 MB)