Geotechnical Fieldwork: Los Angeles Country Club
Metro contractors are preparing to conduct a series of geotechnical field tests on the grounds of the Los Angeles Country Club 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.
Where: City of Los Angeles (Los Angeles Country Club)
- April 18, 2011 6:00am - midnight
- April 19, 2011 9:00 pm - April 20, 2011 6:00 am (if necessary)
Note: Should any work need to be cancelled and rescheduled, Metro will inform you of new work date(s)/time(s).
Precautions for Existing Utilities:
For any location where the type of work will involve intrusive subsurface exploration (rotary-wash borings, CPT, and hollow-stem-auger borings), the work area will be cleared of existing underground utilities prior to starting the work. Underground Service Alert (USA) will be notified at least 48 hours in advance of the work. The work sites will also be scanned for utilities using geophysical methods. A drilling location will be selected within the given work site to avoid conflicting with existing utilities. The upper portions of the soils will be drilled using hand auger equipment, to further reduce the risk of damaging utilities. However, there will still be a risk for damage to some types of utilities such as PVC sprinkler lines.
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.
- Moderate noise.
Continuous Core Drilling
Continuous core drilling will consist of two methods: hollow-stem coring and rotary coring. Hollow-stem core borings will be drilled using a truck-mounted drilling rig advancing a core barrel into the ground by spinning a 6- to 8-inch diameter casing with a drill bit into the ground to collect samples of the various soil layers. No drilling fluid will be used for hollow-stem coring. Rotary core boring operations will consist of a truck-mounted drilling rig advancing a core barrel into the ground while circulating drilling fluid through the hole, similar to rotary-wash drilling. After the exploration is completed, the soil cuttings generated and slurry used during drilling will be placed in drums, tested for adverse chemicals, and disposed of off-site on a daily basis. As for all borings, the work areas will be scanned for utilities prior to drilling, and the upper soils will be hand augered. At the conclusion of drilling, the hole will be filled with grout and its top patched with asphalt to match the surrounding grade. There will be two to three support trucks for the drilling process. Parking lanes and traffic lanes will need to be coned off during work.
What to Expect During Continuous Core Drilling:
- A drilling crew consisting of up to 4 personnel per rig.
- A truck-mounted drill rig and support trucks (see photo).
- For rotary core drilling, a 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.
- For hollow stem drilling, drums to collect soil cuttings for sampling and disposal at conclusion of drilling.
- Moderate noise and moderate vibration.
" Mini-Vib " Truck Seismic Surveys: Equipment to be used will consist of a "Mini-Vib" truck, seismograph recording truck, cable sensors, electric generator and a geophysical survey crew of up to 6 people. Sensors will be placed along the street. Approximately every five feet, the truck will place a "plate" on the surface of the street, then, vibrate the plate in order to take a reading of the vibrations along the street (see photo). The "Mini-Vib" truck will move through each testing location and remain in front of any given location for about 15 to 20 minutes. Residents may encounter some moderate noise as the truck performs the test. The sound level at a distance of about 50 feet from the truck should be no more 70 decibels, or similar to that of average daytime traffic.
" Micro-Vib " Seismic Surveys: Equipment to be used will consist of a portable "Micro-Vib" vibration source box, seismograph recording truck, electrical generator, cable sensors, and a geophysical survey crew of up to 6 people. Sensors will be placed along the street. Approximately every two feet, the portable "Micro-Vib" box will be vibrated by the electrical generator source (see photo). The "Micro-Vib" box will be moved manually through each testing location and remain in front of any given location for about 20 to 30 minutes. For "Micro-Vib" box testing, the sound level should be no more than 60 decibels, or similar to light daytime traffic.
What to Expect During Field Seismic Testing:
- A geophysical survey crew of up to 6 people.
- A "Mini-Vib" truck or "Micro-vib" vibration source box, seismograph recording truck, and support vehicles. 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.
- Traffic on street where work is conducted will be reduced to one lane in each direction on each day of testing.
- Moderate to loud noise and moderate to strong vibration.
- Lanes will be cleared at the end of the work period and re-opened for regular use.
Other Important Information:
- All work has received necessary approvals.
- It may be necessary to conduct additional fieldwork following this testing. If this is necessary, we will inform the area(s) where this work will take place.
- For more information about the Westside Subway Extension, please leave a message at 213.922.6934 or online at www.metro.net/westside.
- For day-to-day testing location updates, please follow us at twitter.com/westsidesubway
- For emergencies or issues needing immediate attention, please call 323.236.2117.