Seattle, WA: Workers Inside the SR 99 Tunneling Machine

Posted by Infra on Tuesday, July 5th, 2016

This video was provided by Ballard Marine Construction, the firm in charge of managing and performing hyperbaric work on the SR 99 Tunnel Project in Seattle. It shows crews at work behind the SR 99 tunneling machine’s cutterhead during a planned maintenance stop in spring 2016. To stabilize soil and water that would otherwise flow through openings in the cutterhead, crews must pump compressed air into their work space at the front end of the machine. This creates hyperbaric conditions, which are similar to those found in an underwater dive. Learn more about this work and the tunnel project at

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