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SR 509 Completion Project Reaches a Major Milestone with $264M Apparent Best Value Proposal

OLYMPIA, WA — After years of planning, the Puget Sound Gateway Program took a major step toward completing the State Route 509 corridor with the Washington State Department of Transportation’s (WSDOT) selection of Guy F. Atkinson Construction as the apparent best value winner for the contract to build the next large phase of the project.

The work, under the Puget Sound Gateway Program’s State Route 509 Completion Project includes:  

  • Building the first of three new miles of SR 509 Expressway
  • Constructing new freight connections from the Kent Valley to Interstate 5 and Sea-Tac International Airport
  • Creating additional access south of the airport to business centers in SeaTac and Des Moines

WSDOT announced that the $263,975,895 price proposal resulted in the apparent best value for this design-build project. A design-build contract combines final project design and construction into a single contract. The apparent best value determination is based on a combined score for the design proposal and project price.

“We’re building a large and complex project that includes a new highway and new connections to I-5, which is rare in an urban environment,” said John White, Administrator of the Puget Sound Gateway Program. “Guy F. Atkinson Construction stood out for its creative ideas, accelerated construction schedule, and commitment to minimizing disruption to the traveling public. We look forward to working with them.”

Key Features of this Stage of Construction
The contractor will complete design work in 2021. Construction will start by early 2022 and is scheduled to wrap up by the end of 2025. The work includes:
  • The first mile of a new SR 509 Expressway between I-5 and 24th Avenue South in SeaTac 
  • A new interchange at 24th Avenue South in SeaTac that connects to the new SR 509 Expressway
  • A new, wider South 216th Street bridge with improved access over I-5 for people who drive, bike, and walk
  • New ramps along I-5 that connect to the new SR 509 Expressway
  • A new I-5 underpass at Veterans Drive in Kent, which provides a direct connection to the manufacturing and warehousing area in the Kent Valley
  • A reconfigured I-5/SR 516 interchange that improves mobility for people who drive, walk, bike, and use transit
Other Construction Stages of the SR 509 Completion Project
The first phase of the SR 509 Completion Project is underway and partners with Sound Transit to build a new SR 99 bridge as part of Sound Transit’s Federal Way Link Extension work. Combining these projects helps reduce the construction impact to nearby communities.

The final two miles of the new SR 509 Expressway between 24th Avenue South and 188th Street in SeaTac will be built under a separate contract, scheduled to be advertised in 2023 and completed in late 2028.

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