Mowat Construction Company: Projects: Seatac South 160th St. Loop

Mowat Construction Company: Projects: Seatac South 160th St. Loop

Seatac South 160th St. Loop

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The focus of this project is to re-align the Seatac airport's north and southbound expressways and construct the final light rail section coming into the airport station. Six major structures were included:

• Airfield Access Tunnel - 120 LF cut and cover tunnel under the northbound expressway is cast-in-place concrete 55 ft wide
• 160th Loop bridge - 264 LF two-span, horseshoe shaped, reinforced box girder structure over the north and southbound expressways with a 223 ft radius and a 4 percent cross slope
• 170th Street bridge - 400 LF two-span, post tensioned box girder structure is part of the new northbound expressway alignment
• North Main Substation Overcrossing - 113 LF single span precast tub girder structure was constructed over an active substation. The deck was of composite construction consisting of half precast plank and half reinforced cast-in-place concrete
• LRT Aerial structures and At-Grade - 2,500 LF of multi-span single cell cast-in-place, post tensioned box girder structure and 2,900 LF of At-Grade trackwork framed in on both sides by cast-in-place retaining walls

Demolition required on the project included a water tower, the Radisson Hotel, a Bank of America, three bridges, and numerous smaller structures. New roadway construction included 103,000 SF of structural earth wall, 35,000 SF of cast-in-place wall, 90,000 CY of roadway excavation, 295,000 CY of gravel borrow, 57,000 tons of permanent asphalt paving, drainage improvements, signing, landscaping electrical improvements, and all of the associated traffic control necessary to maintain access to the active airport.