SR520 W Montlake to Evergreen Point Bridge Approach Bridge North

Project Overview

The old SR 520 west approach bridge, built in the early 1960s, served as a vital link between Seattle’s Montlake neighborhood and the SR 520 floating bridge. Built on hollow columns, the old bridge was aging and vulnerable to earthquakes. The new westbound bridge is designed to modern earthquake standards and includes a dedicated HOV/transit lane, providing a safer and more reliable connection. Pacific Pile and Marine was tasked with Design-build installation and removal of 1.3 miles long pile-supported work trestle, large-diameter drilled shaft installation, and marine heavy lift support.

Project Highlights

  • Installation and removal of a 1.2 mile, 262,000 SF, pile-supported work trestle to support construction activities.
  • Installation of (96) 10-ft diameter casing up to 100-ft in length and placed the cages necessary for the construction of the bridge pier substructure.
  • (16) shaft cages were installed and 4,000 CY of drill spoils removed from site.
  • PPM designed the method to support drilled shaft excavation.
  • Casing was installed through the water column and overburden soils and penetrated a minimum of 6.5-ft into glacial till soils.

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