The Westside Subway Extension project is about to embark on some more seismic testing in the Century City area. The testing is scheduled for Feb. 15 to 18 and possibly Feb. 27. The testing will be done in the 1600 and 1700 blocks of Selby Avenue and on parts of Century Park West.

As we explained in a post last month, the testing is being done as part of the subway planning process to determine to the exact location of a branch of the Santa Monica Fault in the Century City area. The location of the fault will likely determine exactly where the subway tunnels can be built.

More details on the tests are posted after the jump in a letter to residents in the area.

Dear Resident:

As you may know, Metro recently conducted a series of field seismic tests as a part of the ongoing work to prepare the Draft Environmental Impact Statement/Environmental Impact Report (Draft EIS/R) analyzing the proposed Westside Subway Extension.  Based on initial review of the data, we must conduct these same “Mini-Vib” tests in another area and conduct another type of test in certain areas.

The upcoming work will occur on portions of Selby Avenue north of Santa Monica Boulevard and on Century Park West.  No additional testing is anticipated at this time on Selby Avenue on the south side of Santa Monica Boulevard or on Warnall Avenue.

We will conduct the “Mini-Vib” testing during the daytime on portions of the 1600 and 1700 block of Selby Avenue.  Also, due to a malfunction that occurred during the initial “Mini-Vib” tests, we will need to repeat the tests along a portion of Century Park West during the evening.

While the first round of tests produced good data, more sensitive “Micro-Vib” tests are needed on the 1600 and 1700 block of Selby Avenue to produce additional data and confirm the accuracy of the data from the initial tests.  Similar to the “Mini-Vib” tests, sensors will be placed along the ground.  This time however, workers will hand place a small “Micro-Vib” vibration box that will produce ground vibrations.  These vibrations will be more gentle than the kind generated during the “Mini-Vib” tests.  The “Micro-Vib” tests will be conducted at night on portions of Selby Avenue north of Santa Monica Boulevard.

The information from the field seismic investigations will provide further electronic images of the soil with information on rock layers, near-surface faulting, and bedrock elevations and depths along specific areas.

Please note that we are still evaluating multiple route options for the subway tunnels to connect stations at Century City and Westwood.  No decisions or determinations about this have been made.  Data gathered from this seismic evaluation will be a part of making that determination.

When testing will take place:
Testing will take place during February 15th through 18th, and possibly on February 27, 2010.  Some of the testing needs to be completed at night (between 9 p.m. and 6 a.m.) to minimize interference from traffic vibrations and to minimize potential traffic disruptions. The daytime work will be completed between 8:30 a.m. and 5:00 p.m.

“Mini-Vib” Testing:
•    Monday, February 15 (8:30 a.m. to 5:00 p.m.):  Selby Avenue from 1745 Selby Avenue to 1629 Selby Avenue  (This work is scheduled for the holiday to avoid disrupting Emerson Middle School classes.)
•    Tuesday, February 16 (9:00 p.m. to 6:00 a.m.): Century Park West from 1930 Century Park West to Santa Monica Boulevard

“Micro-Vib” Testing:
•    Wednesday, February 17 (9:00 p.m. to 6:00 a.m.): Selby Avenue from Santa Monica Boulevard to 1715 Selby Avenue
•    Thursday, February 18 (9:00 p.m. to 6:00 a.m.) and/or Saturday, February 27 (8:30 a.m. to 5:00 p.m.): Selby Avenue from 1731 Selby Avenue to 1629 Selby Avenue

How testing will occur:
Sensors will be placed along the street and every two feet the crew will place the applicable vibration source (MiniVib truck or MicroVib box) on the surface of the street, then produce a vibration in order to take a reading of the vibrations along the street.  The crew will move through each testing location and remain in front of any given residence for no more than 20 – 30 minutes.  Residents may encounter some moderate noise as the crew performs the test. For “Mini-Vib” truck testing, the sound level should be no more than 70 decibels, or similar to that of truck traffic.  For “Micro-Vib” box testing, the sound level should be no more than 60 decibels, or similar to that of normal conversation. One northbound traffic lane will be blocked on Century Park West on the evening of February 16 and traffic along Santa Monica Boulevard will be reduced to one lane in each direction at Century Park West during the testing.  One parking lane on the east side of Selby Avenue will be blocked while work is underway on February 15, 17, 18, and possibly on February 27.

What to Expect During Testing:
•    A crew of up to 6 people.
•    A “MiniVib” truck or a “MicroVib” vibration source box (see photos above).  Any additional passenger vehicles associated with the work will be parked in legal parking spaces.
•    Parking lane and/or 1 lane of traffic will be blocked while work is under way (see above for details).
•    Traffic on Santa Monica Boulevard may be reduced to one lane in each direction overnight on February 16.
•    Lanes will be cleared at the end of the work period and re-opened for regular use.

It may be necessary to conduct additional field work during the daytime a few weeks following this testing.  If this is necessary, we will inform the area(s) where this work will take place.

For more information about this testing or about the Westside Subway Extension, please leave a message at 213-922-6934 or go to “Contact Us” online at metro.net/Westside.  For anything requiring immediate attention, please call 323-889-5311.