The new light rail line across the floating bridge had to be constructed while keeping the bridge itself – which connects the cities of Seattle and Bellevue – open to traffic.
Oldcastle Infrastructure had to ensure the weight that would be added to the bridge was kept to a minimum, and address the additional loads and stresses applied to the bridge during construction.
Our Oldcastle Infrastructure business developed a new mass production process for the manufacture of a highly specialized lightweight precast rail block, created specifically for this project. This “Dual Block” railroad tie system provided the right solution for this unique situation.
A team of consultants and engineers, in collaboration with the University of Washington, developed and lab tested the product over several years in advance of the project. Field testing for proof of concept was conducted using an initial production run of blocks produced by Oldcastle Infrastructure using the materials, methods and procedures that would be later be used for full-scale production.
Over 8,800 Dual Blocks of five types and 57 total variations were needed to complete the rail line. The lightweight concrete of the Dual Blocks minimized the weight of the installation and all conductive components for each block were grounded back to shore, to prevent stray current penetration.
This ambitious project took three years to complete – from 2017 to 2020. Rail service from Seattle to Bellevue is due to commence in 2023.