This is the longest bridge in Sound Transit’s system, and it represents the most difficult part of the $3.2 billion light rail, 8-mile extension from Angle Lake to downtown Federal Way.

Voters were promised light rail service by this year until Sound Transit learned the soil was weaker than early route designers realized. It took three tries for the agency and contractor Kiewit Infrastructure West to produce a shape whose 500-foot-long central span passes over wetlands instead of through them, while withstanding a massive future earthquake. Kiewit expects to complete it by September.

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