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Transcript of Eagle Mountain – Woodfibre Gas Pipeline Project Geotechnical and geophysical tests James Lota,...
Eagle Mountain – Woodfibre Gas Pipeline Project
Geotechnical and geophysical tests
James Lota, FortisBC
September 25, 2014
Welcome
Why are geotechnical & geophysical tests needed?
• Common engineering practice when planning underground construction method such as horizontal directional drilling (HDD).
• Minimize environmental impacts and construction risk:
• Squamish Estuary
• Highway 99 at Industrial Way
Where are the tests being proposed?
3 boreholes in the Estuary
2 boreholes in the dike
1 borehole outside the
Estuary
4 boreholes along
Finch/Industrial
What is a borehole?
• Commonly used in engineering site assessments around the province.
• Used to collect soil samples to determine subsurface conditions of the area.
• Narrow vertical shaft bored into the ground to a depth of 20 to 70 metres (~ 10” diameter).
What is a borehole?
Heli-portable drill eliminates
need for clearing of
access trails
10” diameter20m – 70m deep
Core Sample
Non-Reactive Bentonite “Plug”
Approx. 30m x 30m safe workspace is required
Example of core samples
Typical borehole testing equipment
Heli-portable drill rig
Typical borehole testing equipment
Track mounted drill rig
Minimizing environmental impacts
• Boreholes in estuary were handpicked to minimize clearing requirements.
• No clearing – Dike or Finch Drive – Industrial Way.
• FortisBC will replant any disturbed areas with native vegetation.
What is geophysical testing?
• Three types of testing are proposed:
• Ground penetrating radar (GPR)• Electric Resistance Tomography (ERT)• Multi-channel analysis of surface waves (MASW)
• All the above technologies consist of portable equipment that workers can easily carry in the field.
Ground Penetrating Radar (GPR) environmental impacts
• Transmits radio waves into the ground to detect subsurface features.
• Non-invasive and relatively quick
Electric Resistance Tomography (ERT)
• Images sub-surface areas by measuring resistivity with low-levels of either AC or DC current.
• Helps determine the geometry, lithology, hydrology and/or petrology of subsurface geologic formations.
Multi-channel Analysis of Surface Waves (MASW)
• Exploration method used widely since the 1990s.
• Measures seismic surface waves generated from a seismic sources (such as sledge hammer).
• Results characterize or estimate stiffness/hardness of materials at depth.
Minimal environmental impact
• Hand clearing of brush and
deadfall, as necessary for
worker safety.
• Required by Worksafe BC to
avoid injuries.
• Animal walking trail width is
sufficient.
• Doesn’t require cutting down
large timber (e.g. > 3” – 4”)
Environmental Management Plan (EMP)
• Although geotechnical / geophysical tests have minimal environment impact, FortisBC has prepared extensive EMP that includes:• Environmental monitoring
• Archeological monitoring
• Environmental controls such as:• Schedule – access
• Tree and vegetation
• Fire
• Drilling waste
• Hazardous materials
• Waste management and disposal
• Air
• Noise
• Environmental incidents and spills
• Restoration
Proprietary and Confidential 19
Thank you