Stretching 1.5 miles across Lake Washington from Seattle the new SR 520 bridge the world's longest floating bridge is an engineering marvel the old bridge was built in 1963 we've taken a beating over the decades with wind and wave action washed out in retrofitted in the 90s to extended structural life and as a result we've done all the work that we could to extend it and it needed to be replaced the 1.5 billion dollar superstructure replaces its 53 year old predecessor the new bridge features greatly enhanced seismic and sustainability advances including the ability to withstand 98 mile-per-hour winds and a 1,000 year earthquake with Western Washington located inside the seismically volatile Ring of Fire combined with Lake Washington soft silk bed a traditional bridge design would have been problematic instead the eight member team maintained the floating bridge concept but this time making it a lot bigger better and safer Lake Washington at this location is over a mile wide and for most of that with the water is over 200 feet deep in addition the bed of the lake is very soft soil and that soft soil extends another 200 feet so if we tried to do a more typical bridge with columns or piers they would have to be over 400 feet tall to get to the foundation material the state has used floating bridges to frost Lake Washington for over 60 years and they've all proven to be the most efficient type structure for this location the new SR 520 bridge features 21 of the largest and heaviest pontoons ever built these massive hollow concrete supports each tipping the scale at a staggering 11,000 tons our cable anchored to the lake floor for bridge stability they also contain intricate sensors that allow non-stop monitoring for water and structural integrity to cross pontoons and 50 for supplemental stability pontoons make up the rest of the support structure the new bridge also features an innovative stormwater protection system that utilizes specially designed catch basins located.

In the pontoons to collect runoff pollutants while the old bridge merely discharged untreated stormwater directly into the lake you know at the end of the my career when I look back what I'm going to remember most fondly about this is how our team really positively impacted the community we added reliability we added increased mobility and we really improve the lives of the community here when I was 12 when this bridge opened in 1963 I remember telling my father how much I wanted to work on a project like the floating bridge and so to see it open so successfully is really a dream come true for me because it's almost twice as wide more than three times as high 10 decibels quieter and so much safer resilient and easier on the environment the new SR 520 bridge is a buoyant triumph of engineering excellence.