WSDOT SR-99 Alaskan Way Viaduct Demolition

With opening of the new, SR 99 Tunnel, demolition of the SR 99 Alaskan Way Viaduct moved forward on February 12, 2019. Phased removal of the 66-year old, double-deck, elevated highway involved an extensive combination of heavy equipment including cranes with huge hydraulic jaws, excavators, and fleets of large trucks to haul away the 255 million tons of rubble.

Amongst the multitude of demolition issues, noise was a concern. Greenbusch provided Environmental Noise Services for the project, as part of the project’s Environmental Compliance Plan (ECP), including:

- Construction Noise & Mitigation Plan
- Construction Noise Monitoring
- Vibration Propagation Testing
- Data Analysis & Reporting

APPROACH: Secured noise monitoring stations were set up along the 2.2 mile corridor for 24/7 monitoring throughout the nine-month demolition. Noise data was uploaded continuously and instantly available to the contractor through a web portal. If noise was close to exceeding established, predetermined levels, the contractor was notified via text message. The scale, aggressive schedule, visibility, and location of this project required a unique, real-time monitoring approach enabling the contractor to adjust field activities to stay within agreed-upon noise levels.