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Seattle-Tacoma International Airport Third Runway

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Project Details

Location: Seattle, WA
Owner: Port of Seattle
Contractor: Tri-State Construction, Gary Merlimo Construction Co., Scarcela Brothers, Inc. (JV)
Engineer: HNTB; Hart Crowser

Products Used

- Reinforced Earth®

Expansion of the SeaTac International Airport in the early 2000’s included construction of a third runway, which required installation of a series of single face and multi-tiered Mechanically Stabilized Earth (MSE) wall structures.  The tallest of these MSE walls consisted of a four-tier structure with a total exposed height of approximately 140 feet (148 with wall base embedment).

The tallest of these MSE walls consisted of a four-tier structure with a total exposed height of approximately 140 feet (148 with wall base embedment).

The significant height of the retaining walls for the project left few viable options from engineering and economic standpoints.  The design team made a preliminary evaluation of more than sixty retaining walls and slope geometric relationships before selecting steel-reinforced Mechanically Stabilized Earth (MSE) walls for the three main retaining walls.  It is notable that a comparison of wall technologies provided by FHWA (1995) indicates that steel-reinforced MSE walls are a stand alone selection for heights exceeding 66 feet (20 meters).  A qualifications-based selection process by the Port of Seattle and HNTB found that Reinforced Earth® MSE wall technology had a reliable international track record with regard to retaining walls exceeding 100 feet in height.

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