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TIB Project Information

Snohomish County's Larch Way Roundabout


Larch Way Roundabout

Locust Wy and Logan Rd

FY 2024 Urban Arterial Program
Current Phase : Bid Authorization
Total TIB Funding : $2,500,000

County: Snohomish   |   Legislative District: 32   |   Project Length: 0.14   |   TIB Engineer: Greg Armstrong   |   Last Payment Date:

Project Information

Funding Year 2024
Program UAP
Current Phase Bid Authorization
Legislative District 32, 1
Congressional District 2
Federal Route Number 2530
Project Length 0.14 mi.
ADT 12,141
Functional Class Minor
Type of Work Safety
Project Contact Sheela George
Contact Email
TIB Engineer Greg Armstrong
Last Payment Date
Cultural Resource Assessment CRA & BER

Project Schedule

  Target Date Actual Date
Project Selection Date   12/02/2022
Delayed Project Date 01/01/2024  
DAHP Assessment Date   10/27/2022
Predesign Approval
Design Approval 02/01/2023 12/22/2022
Bid Auth. Approval 01/01/2024 10/16/2023
Construction Approval 01/30/2024
Project Closeout 06/30/2025
Audit Date  
Withdrawn Date  

Project Funding

TIB Funds Project Costs
Environmental Study 0 0
Design Study 0 0
Total Predesign 0 0
Special Study 0 0
Design 0 0
Right of Way 0 0
Total Design 0 0
Construction Engineering 326,226 435,000
Construction Contract 2,173,774 2,898,579
Other Construction 0 0
Total Construction 2,500,000 3,333,579
Total TIB Funding 2,500,000 3,333,579

Local Funding Partners

Funding Amount Percent
SNOHOMISH COUNTY 833,579 25.0%
WSDOT Funding 0 0.0%
Total Local Funding 833,579 25.0%

Project Description

This project constructs a single lane urban roundabout with a northbound slip lane at the Larch Way/Logan Road and Locust Way intersection, providing intersection operations of LOS C in 2035 (rather than no-build operations of LOS F) and avoids Swamp Creek environmental buffers. The projects roadway improvements include curbs, gutters, and a shared-use path. In 2006 and in 2016, engineers completed a traffic signal warrants analysis, turn lane warrants, queue lengths analysis, and LOS analysis. At the time of both analyses the intersections conditions warranted a traffic signal with an eastbound left turn and right turn lane as well as a westbound left turn lane. The intersection met the 4-hour vehicle volume, peak hour delay, and peak hour volume warrants resulting in the recommendation for a traffic signal or a roundabout. Synchro and SimTraffic modeling software were used to evaluate the operations of the stop-controlled and signalized intersection. Using 2035 volume forecasts, the analysis recommended left and right turn lanes at each leg of the intersection with the signal alternative. Due to Swamp Creeks environmental buffers, these turn lanes were not feasible. The final decision based on the Traffic Analysis was to construct a single lane roundabout with a northbound slip lane. This will prevent the corridor from falling into arrears.

Project Pictures

Project Delays

Delay Type Resolution Date Comments

No delayed project history.

Project Payments