Tetra Tech INCA was the structural designer for the South 160th Loop ramp. The project consisted of a new roadway that includes a 264-foot long, two span, cast-in-place concrete box girder bridge near the South 160th Street area.

Existing ramps north of the Sea-Tac International Airport parking garage will be at least partially demolished and removed. The bridge has a complex geometry with tight curves and skewed abutments and pier. The bridge is supported by spread footings.

The project included design, environmental review, site and hazardous material surveys, and relocations to support the development of a multi-lane return-to-terminal ramp on the Northern Airport Expressway in the vicinity of the South 160th Street overcrossing.