Tacoma Trestle Track & Signal Project

CLIENT Sound Transit

LocationTacoma, WA

This commuter rail project involoved replacement of a 60-year-old, ¾-mile-long, single track timber trestle with a double track concrete pier trestle. 

Shannon & Wilson provided geotechnical and environmental services for this track and trestle replacement project. Commuter rail service along the corridor had to remain operational throughout construction.

Geotechnical engineering was challenged by up to 50 feet of very soft, highly compressible soil; the presence of multiple timber piles associated with the existing and prior trestles along the alignment; and very high head, high flow artesian groundwater conditions. The high artesian pressures, contaminated soil disposal costs, and archaeological finds ruled out drilled shaft foundations. A pile driving test program supported design and construction of the more than 200 24- to 42-inch diameter piles used on the project.


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