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Notice of Field Work - March 7 - 11

Geotechnical Fieldwork: Westwood/Comstock Hills Area

Metro contractors are preparing to conduct a series of geotechnical field tests in the Westwood/Comstock Hills area as a part of the Final Environmental Impact Statement/Environmental Impact Report (Final EIS/EIR) for the Westside Subway Extension.  This work will build on the data gathered during the Draft EIS/EIR for the project and provide further soil and seismic information along the route of the Locally Preferred Alternative (LPA).  In certain areas, noise and vibration tests will also be conducted.  Following the tests, the data will be analyzed and used to make further informed decisions about subway construction.

Work to be work performed will consist of three (3) different types of testing and, weather permitting, will be performed Monday, March 7 - Friday, March 11; 9am - 3:30pm at the following locations:

  • Warnall Ave between Santa Monica and Eastborne Ave
  • Santa Monica Blvd and Comstock Ave

Note:  Should any work need to be cancelled and rescheduled, Metro will inform you of new work date(s)/time(s).

Rotary-Wash Drilling

The rotary-wash borings will be drilled to obtain soil samples for testing and evaluation, and at some locations to install soil gas monitoring wells. The borings will be drilled using truck-mounted rigs operated by crews consisting of up to four personnel. The drill bit will be advanced to depths of 80 feet or greater. Drilling fluid consisting of bentonite slurry will be pumped into the borehole and circulated into a washtub at the ground surface, where cuttings will be removed prior to re-circulating the fluid through the hole. Soil sampling will be performed at 2½ to 5-foot vertical intervals by advancing a sampler using an automatic hammer. At the conclusion of drilling, the slurry will be placed in drums, tested for adverse chemicals, and disposed of off-site. The drums will be removed from the work site on a daily basis, prior to the end of each work period. The borehole will be filled with grout and its top patched with asphalt to match the surrounding grade.

What to Expect During Rotary-Wash Drilling:

  • A drilling crew consisting of up to 4 personnel per rig.
  • A truck-mounted drill rig (see photo) and truck equipped with additional drilling supplies.
  • Wash tub to collect and circulate drilling fluid at ground surface during drilling operations, and drums to contain drilling fluid for sampling and disposal at conclusion of drilling.
  • Parking lane and/or one lane of traffic will be blocked while work is under way on residential streets, and up to two lanes on business/arterial streets.
  • Moderate noise and moderate vibration.
  • Lanes will be cleared at the end of the work period and re-opened for regular use.

Cone Penetrometer Testing (CPT)

Cone Penetrometer Testing (CPT) will consist of a truck, which advances a steel cone tip into the ground by pushing approximately one-inch diameter steel rods attached to the cone tip. As for all borings, the work area will be scanned for utilities prior to drilling, and the upper soils will be hand augered. At the conclusion of testing, the hole will be filled with grout and its top patched with asphalt to match the surrounding grade. Parking lanes and traffic lanes will need to be coned off during work hours.

What to Expect During CPT Soundings:

  • A CPT truck (see photo).
  • Parking lane and/or one lane of traffic will be blocked while work is under way on residential streets and up to two lanes on business/arterial streets.
  • Moderate noise.
  • Lanes will be cleared at the end of the work period and re-opened for regular use.
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