H&H was selected to perform an in-depth electrical and mechanical inspection in conformance with Federal Requirements for the Nation Tunnel Inspection Standards (NTIS) the initial inspection of the new tunnel which replaced the Alaskan Way Viaduct. The new tunnel has a lower section utilidor for the pumping equipment along with north and south operations building each with four 500HP extraction ventilation fans and two maintenance air fans. Each tunnel is equipped with multiple 75HP jet fans and roadway dampers evenly spaced through the tunnel for the extraction fans.
The tunnel has a fire pipe deluge system and pumping system to remover the water. The tunnel has a communication system based control with PLC controllers, hundreds of cameras with DVR controllers, a fire detection system, an air monitoring system, and a complete security system. Each piece of equipment is remotely accessible and operable from the control system, with centers in each operations building. The majority of the electrical and mechanical equipment was visually inspected and operationally tested during the inspection.
The tunnel is a 2.5-mile long tube with two southbound lanes in the upper roadway, two northbound lanes in the lower roadway which provides a direct route in downtown Seattle on SR 99 between the stadiums and the Space Needle. It is the largest double-deck highway tunnel of its kind in the country.