Water Stewardship Information Sources
| ID | 1653 |
|---|---|
| Citation | Stantec Consulting Ltd. 2013. Qualitative Ecological Risk Assessment of Pipeline Skills: Technical Report for the Trans Mountain Pipeline ULC, Trans Mountain Expansion Project. Prepared for Trans Mountain Pipeline ULC. |
| Organization | Trans Mountain Pipeline |
| URL | https://docs.neb-one.gc.ca/ll-eng/llisapi.dll/fetch/2000/90464/90552/548311/956726/2392873/2451003/2393783/B18-15_-_V7_TR_71_01_OF_02_ERA_PIPELINE_-_A3S4W9.pdf?nodeid=2393787&vernum=-2 |
| Abstract/Description or Keywords | The purpose of this Ecological Risk Assessment (ERA) report is to evaluate the potential for ecological receptors (e.g., fish, fish eggs, invertebrates, amphibians, reptiles, birds, mammals, and plants) to experience negative environmental effects as a result of exposure to crude oil released to the environment as a result of the Project. The following summary is based upon the assumption that an oil spill as a result of construction of the Trans Mountain Pipeline would be a low probability event. Because of the nature of spills to land (i.e., the limited spatial extent of environmental effects in the context of much larger habitat units) and the existence of legislated processes pertaining to environmental remediation following such spills, the ecological risk assessment does not directly consider effects to terrestrial environments. Conversely, crude oil entering aquatic environments has the potential to spread or be advected rapidly downstream, and as a result has the potential to affect much more of the available habitat. Aquatic ecosystems are known to be sensitive to spilled oil, and therefore this ERA report focuses on spills that enter aquatic environments. The proposed TMEP pipeline corridor crosses 474 defined watercourses between Edmonton, Alberta and Burnaby, British Columbia, and runs parallel to several large rivers for a considerable portion of the distance. Where the pipeline runs parallel to a river, the potential for that river to be affected by oil in the unlikely event of an oil spill increases in proportion to the length of the pipeline corridor within the watershed, and the proximity of the corridor to the river. Based upon these and other criteria, hypothetical oil spill locations were selected in proximity to the Athabasca River near Hinton, Alberta; the North Thompson River near Darfield, British Columbia; the Fraser River near Hope, British Columbia; and the Fraser River near the Port Mann Bridge in greater Vancouver. This last location was selected to be as close as possible to the Fraser River Delta, in order to evaluate potential environmental effects of spilled oil on ecological receptors unique to the Delta, a tidal estuary. Although the proposed TMEP pipeline will potentially carry a variety of crude oils, diluted bitumen is expected to comprise a large percentage of the oil shipped. For that reason, a sample of Cold Lake Winter Blend (CLWB) was procured and tested to provide information on the physical and chemical characteristics of a representative product. CLWB was selected because it is currently transported by Trans Mountain and is expected to remain a major product transported by the new pipeline. In addition, the diluent in CLWB is condensate (a light hydrocarbon mixture derived from natural gas liquids), which is volatile and relatively water-soluble. Due to the higher level of risk associated with inhalation of volatiles and/or exposure to dissolved hydrocarbons, CLWB was considered to be a conservative choice for the ERA, as opposed to heavy crude oil mixed with alternative diluents such as synthetic oil, which contain fewer volatile and less water soluble constituents. A literature review was conducted to identify and acquire information on actual and modelled spills of heavy crude oils in the freshwater environment, and case studies were selected to inform predictions about the potential fate and transport and ecological effects of a diluted bitumen spill resulting from the Project. Actual spill case studies included the Kalamazoo River spill, East Walker River spill, Pine River spill, Wabamun Lake spill, Yellowstone River spill, OSSA II Pipeline spill, and the DM 932 barge spill, with crude oil types ranging from light crude oil to diluted bitumen and bunker type products. TMEP studies involving the behaviour of diluted bitumen on water in meso-scale experimental trials carried out at Gainford, Alberta (Witt O?Brien?s et al. 2013) were also reviewed. Finally, modelling case studies included predictions of oil spill fate and ecological effects conducted for the Enbridge Northern Gateway Project, representing a diluted bitumen and a synthetic crude oil, with hypothetical spill locations on the Athabasca, Crooked, Morice and Kitimat rivers in Alberta and British Columbia, as well as a predictions of oil spill fate and ecological effects of Jet ﾓAﾔ fuel released to the lower Fraser River near Vancouver. When crude oil is spilled, volatile components quickly evaporate, and more water-soluble components can dissolve into the water. The amount of hydrocarbon that will dissolve into the water depends upon a number of factors, including the availability of relatively water soluble hydrocarbons, the amount of mixing energy in the water column, and the viscosity of the oil. If there is sufficient mixing energy to entrain droplets of oil into the water column, then the rate of dissolution is increased in comparison to the case when oil is simply floating on the water surface. High oil viscosity increases the amount of mixing energy required. The resulting concentration of dissolved hydrocarbon depends upon the amount of oil released, relative to the amount of water flowing in the river. Therefore, high potential for acute effects to aquatic organisms occurs when light oils containing a high percentage of mono-aromatic hydrocarbons (MAH) and other light hydrocarbons are released into streams or small rivers with high gradients leading to highenergy mixing. Lower potential for such effects is observed as oils become more viscous, with lower percentages of MAH present, and as the level of turbulence decreases as river size increases, or river gradient decreases. Once in the water column, oil droplets may be exposed to suspended sediments; if there is adequate contact, the particulate matter may adhere to the oil droplets and the resulting oil-mineral aggregate (OMA) may become neutrally to negatively buoyant and remain submerged or sink in the water column. Formation of substantial quantities of OMA requires high suspended sediment concentrations, and is enhanced by salinity, which is not normally present in freshwater ecosystems. Oil may also contact sand and gravel particles along shorelines, resulting in initial stranding of oil that may sink if it later re-enters the water column. In high flows, submerged oil is transported downstream and prevented from settling on the riverbed. In contrast, low flows have the potential to result in high levels of sedimentation of submerged oil, particularly in quiescent areas where silty sediments accumulate. For spills in winter, direct environmental effects of spilled oil may depend upon the amount of snow and ice cover, as snow can absorb spilled oil, and ice cover on watercourses can prevent or limit contact between the oil and running water. Many ecological receptors are absent or dormant during the winter, and would not be exposed to the spilled oil. For such spills, there is a high potential to recover most of the spilled oil so that oil spill effects on ecological receptors can be minimal. Spills to rivers that are not ice covered in winter, however, would have environmental effects similar to the environmental effects of spills at other times of the year. For the four locations considered in this study (the Athabasca River near Hinton, Alberta; the North Thompson River near Darfield, British Columbia; the Fraser River near Hope, British Columbia and the Fraser River as it enters the Delta, near Vancouver), seasonal flow regimes are such that high flows are observed during the summer, as snow and ice melt in the mountain headwater regions. Low flows are typically observed in winter, as water equivalents build up in snowpack. Spring and fall represent shoulder seasons when flows are intermediate. Using information from the actual spill events and modelling case studies, the likely behaviour of spilled heavy crude oil, and extent of oiling, was predicted for each river system. Stochastic modeling was used to predict the fate and transport of oil for the Fraser River Delta, due to the unique nature and complexity of this environment. For the other three spill examples, professional judgement was used, based upon the case studies. From the predicted distribution of crude oil in the environment in each of the rivers, for winter, summer, and spring and fall seasons, interactions between spilled oil and ecological receptor groups were evaluated. Ecological receptor groups included aquatic biota (vegetation, benthic invertebrates, fish including eggs and larvae, and amphibians), terrestrial plant and soil invertebrate communities in riparian areas, mammals (with grizzly bear, moose, muskrat and river otter selected as representative types), birds (with bald eagle, Canada goose, great blue heron, mallard, spotted sandpiper and tree swallow selected as representative types) and reptiles (with the Western painted turtle selected as a representative) for the Delta oil spill scenario, two additional ecological receptors (biofilm and Western sandpiper) were evaluated. For each river, season and ecological receptor type, the expected spatial extent, magnitude, duration and reversibility of negative environmental effects was evaluated, again with reference to case studies. The spatial extent of environmental effects was found to vary, depending upon the season and river characteristics, and both the spatial extent and magnitude of environmental effects was often rated as ﾓhighﾔ, at least locally. However, effect durations taking into consideration oil spill response and restoration activities were typically less than five years, and often 12 to 24 months, and all rated negative environmental effects were considered to be ﾓreversibleﾔ. Evidence from the case studies showed overwhelmingly that freshwater ecosystems can recover from oil spills, often within relatively short periods of time. Taking all of these factors into consideration, it is clear that a crude oil spill into a freshwater environment could have substantial negative environmental effects that could be long-lasting if prompt and effective measures are not taken to mitigate the immediate impacts by containment and recovery. However, as described in Volume 7, the probability of a crude oil spill reaching freshwater is very low. This confirms that spill prevention, preparedness, and effective response activities must always be a primary focus to reduce the probability of an oil spill to be as low as reasonably practical (ALARP), and to have adequate oil spill response plans and procedures in place that have proven capability to reduce the magnitude and extent of actual effects. water quality |
| Information Type | report |
| Regional Watershed | North Thompson, Nicola, Fraser |
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| Project status | complete |
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