Base de données de recherche des TNO

Régions: Sahtu Settlement Area

étiquettes: physical sciences, permafrost, hydrology, bathymetry, environmental baseline, habitat, topography, geophysics, site reconnaissance, biophysics

Objectif(s): The proposed biophysical and reconnaissance studies are aimed at collecting data to assess the feasibility of constructing a potential oil and gas pipeline for the Mackenzie Gas Project. Data gathered from these studies will be used, in combination with existing technical/scientific information and local knowledge, to develop a knowledge base for: planning, assessing and producing environmental plans; progressing engineering design, and supporting regulatory processes. The 2006 work programme includes: route and site reconnaissance; aquatic and terrestrial studies; and engineering, geological and geophysical studies.

Description du projet: The proposed biophysical and reconnaissance studies are aimed at collecting data to assess the feasibility of constructing a potential oil and gas pipeline for the Mackenzie Gas Project. The 2006 work programme includes: route and site reconnaissance; aquatic and terrestrial studies; and engineering, geological and geophysical studies. Route and site reconnaissance comprise: verification of the location for pipeline routes through the Sahtu Settlement Area; verification of locations for proposed gas compression facilities; determination of optimal locations for infrastructure sites such as camps, equipment storage sites, access roads, granular and borrow resource sites, and re-vegetation test sites; visual inspection and confirmation of landform features; identification of land features that may be important to the location or construction of the proposed pipeline routes. Work will include assessments of both temporary and permanent access routes, which will be conducted by helicopter as well as through ground observation. Reconnaissance surveys will consist of a three to five-person team, including a local community assistant. Helicopters will land at sites determined by the local community assistant to be non-sensitive areas, and will likely include lands close to proposed pipeline crossing of major watersheds, locations of unique land features and locations where difficulty may be encountered during pipeline construction. Land surveys and soil sampling may be required at some locations. The time on the ground at landing sites will generally be less than one hour. Aquatic studies in relation to potential barge landing sites, water supply and disposal sites, access road watercourse crossing locations, water bodies adjacent to borrow sites, pipeline watercourse crossing locations and spring break-up comprise the following activities: documentation of bathymetric, hydrologic, channel and shoreline features; examination of water quality, and fish and fish habitat; and assessment of ice conditions along proposed pipeline centre lines, effects of ice on banks and channels, winter flow volumes and rates within channels, amount of snow cover in the immediate vicinity of pipeline crossings and ground temperature. At most locations where aquatic studies are planned to be conducted, the presence of groundwater discharge will be evaluated. In areas where significant groundwater discharge is identified, the following qualities likely to be documented include geological and hydrogeological setting, groundwater flow rate and groundwater quality (both field and laboratory analyses). The aquatic studies will be conducted by three or four-person teams (including a local community assistant), primarily by helicopter with the slight possibility of access by boat or ATV. Terrestrial studies will comprise vegetation mapping, timber cruising, rare plant surveys, rare plant mitigation planning, and investigations related to landforms, soil and permafrost. Wildlife investigations are also planned under this category of work, details of which are described in a Wildlife Research Permit issued by the Government of the Northwest Territories Department of Environment and Natural Resources. Vegetation mapping and rare plant surveys will be conducted concurrently by helicopter at potential infrastructure sites, roads, borrow sites, the anchor field and at select locations along the pipeline routes. Sampling equipment will include handheld items such as GPS units and cameras. Rare plant specialists will survey areas identified (during vegetation studies carried out from 2002-2004) as having high potential to support rare plant species using a random meander technique. Rare plants that can be confidently identified in the field will be documented on site. The plant and its habitat will be photographed and the location, habitat information and population size recorded. If plants cannot be identified, a sample of the plant will be collected to be identified at a later time; however, sampling will only take place if the population found is large enough to allow sampling (i.e., at least twenty plants). Where rare plant species have been observed in areas that may be affected by development, a mitigation planning survey will be conducted. A thorough search of the area will be undertaken to determine the extent and characteristics of the population. Terrestrial studies will also involve soil sampling, typically at sites where rare plant surveys will be conducted. A soil pit (approx.15 cm x 15 cm) will be excavated with a spade or auger to a depth of approximately 0.5 m or to the top of the permafrost. The exposed soil profile will be document, and following assessment, the soil pit will be backfilled with the excavated material and the sod replaced. At some locations, soil samples (approx. 500-1,000 g) will be collected for laboratory analysis. Active layer thickness may also be measured using hand probes at some locations along the proposed study corridor. This information will be used to assess the potential for ground disturbance to the active layer and underlying permafrost. Engineering studies will comprise the following activities: thermistor data recovery to obtain readings from previously installed instrumentation for information on thermal conditions that affect frost heave and thaw settlement; assessment of stream temperatures to support stream-crossing design and frost bulb development; river channel and thalweg surveys to validate hydraulic assumptions at watercourse crossings; assessment of slope stability design; examination of soil resistivity to support cathodic protection design and grounding requirements and locate field test sites for identifying potential sites for thermosiphon trials; verification of methodology of airborne and surface geophysical investigation techniques used to determine unfrozen and frozen intervals along the pipeline corridors; aerial photography for pipeline route changes that are outside the area of original air photo coverage along the original pipeline corridors; and fault line surveys to identify the locations of potential near-surface faults that could affect pipeline design. Most of these field investigations will be carried out by helicopter with watercraft possibly also employed for barge landing and camp water intake studies. Study teams will consist of up to six persons, including a local community assistant. Helicopter landings will take place in existing clearings or in areas with low vegetation. In some instances, sites will be cleared with chainsaws to create a safe landing site and to undertake a land survey. Non-sensitive areas will be selected as landing sites based on recommendations from the local community assistant. The length of time on the ground will depend on the proximity of the landing sites to investigation sites as well as the time required to properly evaluate sites. Results of the biophysical and reconnaissance studies will be shared with community organizations through reports, and in community meetings where the proponent is invited to participate.