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Eagle Mountain – Woodfibre Gas Pipeline Project Geotechnical and geophysical tests James Lota, FortisBC September 25, 2014
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Welcome
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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
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Where are the tests being proposed?
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3 boreholes in the Estuary 2 boreholes in the dike 1 borehole outside the Estuary
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4 boreholes along Finch/Industrial
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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).
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What is a borehole? Heli-portable drill eliminates need for clearing of access trails 10” diameter 20m – 70m deep Core Sample Non-Reactive Bentonite “Plug” Approx. 30m x 30m safe workspace is required
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Example of core samples
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Typical borehole testing equipment Heli-portable drill rig
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Typical borehole testing equipment Track mounted drill rig
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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.
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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.
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Ground Penetrating Radar (GPR) environmental impacts Transmits radio waves into the ground to detect subsurface features. Non-invasive and relatively quick
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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.
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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.
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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”)
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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
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Thank you Proprietary and Confidential 19
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