WSDOT SR 99 Bored Tunnel Design-Build

Greenbusch provided Construction Noise monitoring for the duration of the building of the SR 99 Tunnel that replaced the Alaskan Way Viaduct. Scope elements included permitting and design-related support for the construction noise aspects of the project that opened February 2019. The firm played a vital role as the noise expert in negotiating variance details such as noise wall heights, variance sound level limits, and prescriptive mitigation requirements. Greenbusch performed 3-D computer noise analysis for the Project’s Noise Control Plan which served as the framework for construction noise mitigation standards on the project and for any supplemental plans prepared during construction.

Greenbusch also organized field crews to collect ambient vibration data along the tunnel alignment during the design phase of the project. During construction, vibration monitoring was conducted while a southern section of the Alaskan Way Viaduct was demolished to make way for the South Portal construction area to support the mining operation. Monitoring locations included nearby commercial facilities, sensitive public infrastructure, and the viaduct structure itself.