NNERS 2019 Grand Conceptor Award Alaskan Way Viaduct Replacement Seattle, Washington WSP USA Seattle, Washington One of Seattle's most seismically vulnerable highways has been replaced with a 1.7-mile underground tunnel containing a state-ofthe-art double-deck highway. Situated 200 feet beneath downtown, the new tunnel has a revolutionary flexible concrete core that combines with its underground location to make it withstand a 9.0 magnitude earthquake. Pioneering ventilation and fire control systems also make the tunnel one of the safest structures of its type in the world. The project eliminates a half-century-old barrier separating downtown from its waterfront, while paving the way for 9 new acres of publicfriendly space. MAY / JUNE 2019 ENGINEERING INC. 19