| Construction name | State Highway 99 Tunnel Construction |
| Construction site | Seattle, Washington, USA |
| Owner name | Washington State Department of Transportation / WSDOT |
| Contractor name | Seattle Tunnel Partners (Dragados USA, Tutor Perini JV) |
| Features of construction | - Tunnel length: 2,856m
- Minimum curve radius: 1,800m
- Gradient: -4% ～ + 4%
- Maximum overburden: 65.2m
- Design earth pressure: 4.3bar Tunnel center
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| Segment | - Type: Reinforced concrete segment
- Outer diameter: 17,069mm
- Inner diameter: 15,850mm
- Width:1,980mm
- Number of ring pieces: 10
- Maximum mass of 1 piece: Approx. 17ton
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| Machine design conditions | - Design pressure: Maximum 7bar (10bar in emergency)
- Excavation speed: 60mm / min
- Segment assembly time: 30min / ring
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