Unlike New York, there will be no blasting to build subway in Los Angeles

Earlier today, something went wrong with construction of New York City’s Second Avenue Subway when a planned underground blast broke through the surface sending dirt and debris into the air and causing other property damage. Here’s coverage by the New York Times and the New York Daily News — the Daily News actually has photos of the blast.

This is certainly unfortunate and we will be watching as our colleagues in New York work to figure out what caused this accident. It’s worth noting that no blasting at all is planned here in Los Angeles as part of the construction of either the Regional Connector or the Westside Subway Extension, both of which require tunnels to be built.

In its cover story on this project earlier this month, the New York Times Magazine noted that geology is a critical factor in determining how tunnels and stations get built. The geology is quite different in Los Angeles than it is in New York.

We understand that there have been hundreds and hundreds of planned blasts for the Second Avenue Subway over the last year that have gone off without a hitch. This is the first time anything like this has happened. On the positive side, it appears that there weren’t any injuries from this accident and that the scene was cleaned up with streets reopened within an hour. We’ll keep monitoring this and pass along any relevant information.

3 replies

    • Hi Joe;

      Yes, there is methane gas under many parts of our region. Here’s some more information from a FAQ on the Westside Subway Extension’s web page:

      30. I’ve heard that there is subsurface gas and tar in the study area. How can I be sure that the system can be constructed and operate safely?

      Subsurface gas is present throughout much of the greater Los Angeles area and is prevalent throughout the entire Westside Subway Extension alignment area. The highest concentrations of underground gasses are found in the area immediately surrounding the Fairfax District in the area near to the La Brea Tar Pits. Lower levels of gas concentrations are found in other parts of the corridor. While tunneling for transportation projects calls for special considerations, other projects have been successfully and safely constructed in subsurface gas zones within the project area including buildings with deep parking garages and basements, storm drains, sewer projects and other utility projects. Similar protocols for safety and testing apply to these projects as they do for any transportation project.

      Safety, both during construction and eventual operations, is one of Metro’s highest priorities. It was also one of the key evaluation criteria during the Draft EIS/EIR, and has been further evaluated as a part of the Final EIS/EIR. Information on this topic in the Final EIS/EIR can be found in Chapter 4.

      We have safely operated the current Metro Red/Purple Line subway for over 15 years and have successfully constructed subway tunnels where subsurface gas has been present. In 2005, an American Public Transit Association Peer Review Panel determined that “It is possible to tunnel and operate a subway along the Wilshire Corridor safely.”

      During construction, the pressure face TBMs isolate gas from workers and the public, while gassy soil and tar sands are separated and treated appropriately. Enhanced ventilation systems will be used where necessary to ensure tunnel and station safety and, if necessary, double gaskets for the tunnel lining or other measures may also be installed.

      Where needed, tunnels and stations will be designed and built to provide a redundant protection system against gas intrusion. This might include:

      Physical barriers to keep gas out of the tunnels
      High volume ventilation systems

      Gas detection systems with alarms
      Emergency ventilation triggered by the gas detection systems.

      During operations, safety codes require rigorous and continuous gas monitoring, alarms, automatic equipment shut-off and additional personnel training.

      Please see our Construction Fact Sheet for more information. You may also wish to view the presentation from our meetings in August 2009 and January 2011 for more information about subway construction, as well as the video “A Subway Story: Metro’s Westside Subway Extension.”