Designed to Withstand Seismic Activity
Over the past 170 years, the Coos Bay Area has experienced relatively low seismic activity. However, it is now well understood that the Oregon coast may be susceptible to a large magnitude earthquake associated with the Cascadia Subduction Zone (CSZ).
All critical project foundations and structures have been designed to withstand a 9.3 magnitude CSZ earthquake. Plans will also be put in place to ensure any potential hazards created by an earthquake, including soil liquefaction, are mitigated.
All critical LNG facilities are designed to meet Safe Shutdown Earthquake standards, whereby certain structures, systems and components that are critical to safety would remain functional in the event of an earthquake.
Tsunami Specific Design Safety Features
To address tsunami hazards at the LNG terminal and South Dunes site, all buildings designated as “shelter in place” sites or “vertical tsunami refuges” will be built to the same elevations designated in evacuation protocols for North Bend and Coos Bay. Vertical tsunami refuges shall be at or above an elevation of 52 ft. at the South Dunes site, and at or above 60 ft. at the LNG terminal site.
Every element of the Terminal and South Dunes facilities deemed critical for operations and safety has been designed to exceed the 2475-year tsunami event and meet code requirements. The LNG processing areas will be built to an elevation of 46 ft. or above.
Planned safety features include a 46-ft. high impervious berm to protect the LNG tanks and provide on-site containment of a single 160,000 m3 LNG tank in the highly unlikely event of a breach.
Hydrodynamic modelling results:
The project areas are in white with their planned finished grade elevations as required for Design Level Tsunami from the table below.
|Critical Minimum Elevation (FT.)||Design Elevation|
|Marine Terminal (Typical)||34.5||34.5|
|LNG Tank Protection||34.5||46.0|
|Corridor and Roseburg Forest Products||21.5||46.0 – 62.0|
|South Dunes (Typical)||31.8||51.0 – 56.0|