This is the second part in The Source’s new series called “Subway Facts & History” to address some of the issues generating discussion involving the Westside Subway Extension project. The facts below are based on information from Metro staff and consultants planning the project. The information, in various forms, has already been publicly released.
One of the complications of planning any major project in greater Los Angeles is dealing with the fact that we live in earthquake country — as the above map shows. It’s one thing to build something so that it will be safe when the ground shakes in an earthquake. It’s quite another thing to build for earthquake safety when you are sitting directly atop an active fault.
The issue for the Westside Subway Extension is the presence of the active Santa Monica Fault in the Century City area where it runs beneath Santa Monica Boulevard. The location of the fault has two potential impacts: It could affect where the Century City station is built, as well as the location and orientation of the tunnels in that area.
Two basic routes for the subway between western Beverly Hills and Century City are being studied as part of the project’s Final Environmental Impact Statement/Report. One route would run under Santa Monica Boulevard to reach a station under that street. The other would run south of there and go under parts of the Beverly Hills High School campus to reach a station beneath Constellation Boulevard.
Here are some facts:
•As part of the environmental impact studies for the Westside Subway Extension, Metro is conducting geotechnical field tests to learn more about seismic characteristics in the Beverly Hills, Century City & Westwood areas
•A strand of the Santa Monica Fault appears to extend under the Los Angeles Country Club and beneath Santa Monica Boulevard from somewhere between Century Park East and Avenue of the Stars and extending west until it begins to turn away from Santa Monica Boulevard somewhere near Westwood Boulevard.
•In addition to the Santa Monica Fault, Metro is also trying to better understand another possible seismic feature, the West Beverly Hills Lineament, which runs north-south through the western part of Beverly Hills near the Beverly Hills High School.
•One way of reducing the risk from an earthquake is for the tunnels to cross the fault in a perpendicular manner rather than run parallel to it, thereby limiting the tunnel’s exposure to the fault.
•Subways can and have been built in earthquake zones around the world and in Los Angeles, although it often requires special engineering and special construction techniques. Special designs have been developed for subway tunnels to facilitate short, perpendicular crossings.
•No transit agencies in North America have built subway stations within known active fault zones.
•Another project being planned by Metro, the Crenshaw/LAX light rail line moved the location of the La Brea station planned for that line to avoid having it sit directly atop the Newport-Inglewood Fault.
•Subways have a solid history of surviving strong earthquakes. While there was significant damage throughout Santiago, Chile following the 8.8 magnitude quake in February 2010, their subway system was running within 2 days.
•Besides Santiago, some other earthquake-prone cities with subways are Tokyo, San Francisco, Mexico City and Istanbul.
•Metro’s Red Line tunnels withstood the 1994 Northridge earthquake without any damage.
•The Metro Red Line tunnels cross the Hollywood Fault, considered to be active, north of the Hollywood/Highland station. Special designs were employed where the tunnels cross that fault that allow it to better withstand an earthquake and, if needed, be more easily repaired.
•Last fall’s draft environmental impact statement/report for the subway included geotechnical information gathered up to that point.
•Further geotechnical analysis is being done along the entire nine-mile alignment that is currently being studied. That information will be released later this year.
•Once the Final EIS/EIR is released, and there is a period for public review, it will be considered by the Metro Board of Directors. They will decide whether to proceed and make decisions about the project, including the location of the Century City station.
•Assuming the project moves forward, additional geotechnical tests will be performed, including in the Century City area, as a part of further engineering for the project.
Related: Subway Facts & History, Part 1: Building atop subway tunnels
I thank you for your response. Your statement (rather unscientifically) makes me wonder how reliable your facts are.
What are your credentials?
Are you an engineer or? Do you work for Metro or a subsidiary? I look forward to your response.
As you may have read in other articles on this site, the Gold Line Eastside tunnel was built without any surface settlement by utilizing what are call Earth Pressure Balance (EPB) tunneling machines. Settlement issues are typically a matter that can arise and is dealt with during the excavation of the tunnel, not once it is completed. The use of EPB machines is a significant difference between current tunneling methods and those used during the construction of the present Metro tunnels. I am sure the Metro Construction Staff and Contractors will be working very hard to continue the record begun by the Goldline Eastside team.
As far as sound and vibration issues, you should go to Hollywood Blvd or Vermont Blvd and stand above the subway lines there. You will experience more vibrations and sounds from the vehicles on the street than you ever will from the trains traveling below you. 45-75 feet of compacted soils is just too dense a barrier.
This brings me to a final point, I am aware from conversations I have had with workerswho were there at the time that when the Northridge event hit, the workers in the yet to be completed Vermont/Hollywood Segment of the Redline tunnels did not even feel the event. I have always (rather unscientifically, I would add) used the following simile to explain this:
Imagine you are in a violent hurricane in the middle of the ocean. Would you rather ride out the storm on an aircraft carrier or submarine? The submarine is able to stay below the surface where the energy from the storm is unable to significantly move the water that surrounds the sub. The Carrier, even as large as it is, has to deal with the full effect of the energy and movement of the ocean surface.
The same is true for the tunnels – althought the seismic energy moves through the ground, it can not accelerate (move) the tunnels because of the soil pressure surrounding them. Of course a tunnel crossing a fault that ruptures will certainly move, but that is why the special section of the Hollywood Hills Metro tunnel was designed and build.
LOVE that chart. Can it be updated to show the 9.0 Sendai Earthquake info? Hate it when uneducated idiots talk as if we’re the only earthquake-prone city on Earth with a subway.
Thank you for this added information. I will repeat my question from part one – Carol Spencer 8/3/11 11:20 am
Does Metro offer a document or means/method/way that offers recourse to the property owner who signed and settled the property acquisition for a Metro tunnel before construction begins beneath their property in the event that vibration and/or sound and/or settlement or other problems arise once the subway is operating?
There are hundreds of homes in the Westwood area as well as residential and High School property in Beverly Hills that might be affected per my question above.
What is our future recourse?
I have heard that we must SUE Metro – there should be a means other than legal action – after all Metro warns their might be future subsidence, vibration etc. Is it included in the contract the property owner signs?
Please publish this information.