WSDOT begins in-water test pile and noise study for SR 520 bridge project

SEATTLE –WSDOT begins work in Lake Washington and Portage Bay on Oct. 23 to study potential noise reduction measures during in-water pile driving. A pile is a circular steel column that is driven into the ground to provide support for bridge structures. This study will help determine the best pile installation methods that minimize effects on the surrounding communities, as well as fish and wildlife in this area.

Dave Becher, SR 520 Program Construction Manager, noted that “This study will cost less than a million dollars of the $4.65 billion program budget, yet will allow us to test innovative technologies to help us reduce noise during pile driving. This up-front expenditure should allow us to minimize impacts during pile driving as well as more accurately estimate the cost for in-water steel in Portage Bay and Union Bay.”


Working from a large barge, crews will install nine steel test piles north of SR 520 between Portage Bay and the western high rise in Lake Washington. The study will allow crews to test soil conditions on the lake bottom, monitor underwater and airborne noise, and evaluate potential noise reduction methods that could benefit people, fish, and wildlife during construction. Each of the piles is between 40 and 120 feet long, and will be installed using a combination of vibratory and impact hammers. The test piles will be removed after all monitoring work is complete.