Many participants, including those that provided oral statements and oral evidence, expressed concerns about the behavior and fate of spilled dilbit (bitumen blended with condensate or synthetic crude oil). A primary concern was the potential for dilbit to sink when spilled into fresh or marine waters.
Northern Gateway said that oil spilled in water would behave in different ways depending on the physical and chemical characteristics of the oil and on the environmental conditions it is exposed to. The environmental, physical, and chemical processes acting upon spilled oil in a river or lake are illustrated in Figure 6.1, based on evidence submitted by Northern Gateway. Similar processes would occur in the ocean. These processes are collectively called weathering.
Northern Gateway said that none of the hydrocarbon products it was proposing to ship could be considered sinking oils, as they would initially be less dense than water, and would float. The company said that the products potentially carried on the pipeline, including dilbit, would weather like other floating oils, and could submerge or sink in some circumstances. Parties such as Haisla Nation and the Gitxaala Nation did not agree with Northern Gateway's position that dilbit would float like a typical crude oil, or that it is comparable with crude or refined oils shipped through pipelines or transported in marine tankers.
Many participants said that the diluent component of dilbit would separate, evaporate, and leave behind the heavier bitumen component. Northern Gateway said that dilbit is not a simple two-phase mixture of bitumen and condensate, but is instead a new, cohesive, blended product. The company said that, when spilled onto water, lighter hydrocarbon fractions of the entire blend would begin to evaporate. It said that, as lighter fractions evaporated, the viscosity of the weathered dilbit would increase, and evaporation of remaining lighter fractions would be progressively inhibited. Environment Canada and Natural Resources Canada agreed with that general characterization of dilbit evaporation.
Northern Gateway said that, as spilled oil weathers, it may disperse from large patches or slicks into smaller patches, or even small droplets. It said that large patches of thick oil are not likely to be submerged by waves and that smaller aggregations of oil are more susceptible to overwashing, temporary entrainment or submergence, and emulsification. Northern Gateway said that the dilbit products proposed to be shipped would not be likely to disperse significantly. It also said that dispersion potential depends on factors such as wave energy, water temperature, and the degree of oil weathering. The company said that even the most viscous oil could be dispersed over the longer term with sufficient wave energy. It said that condensate and synthetic crude oil were much more prone to evaporation and wave dispersion than diluted bitumen products.
Northern Gateway said that oil may become entrained in the water column by wave- or current-induced water turbulence in freshwater and marine environments. It said that the depth and duration of submergence depends on factors such as oil density and viscosity, wave energy, and size of the oil particles. It said that entrainment in the water column would typically be temporary, and that the oil would resurface in calm conditions.
Northern Gateway and Haisla Nation said that oil can form emulsions with water. Northern Gateway said that bitumen diluted with synthetic crude was likely to emulsify and, although unlikely to sink in marine water, could be overwashed by waves and temporarily submerged. Northern Gateway said that emulsification reduces the evaporation of lighter hydrocarbons from the oil.
Northern Gateway, Haisla Nation, and Environment Canada said that there are circumstances where oil can sink in water. Northern Gateway said that the portion of oil that could sink would depend on suspended sediment concentration, water turbulence, and the degree of oil weathering. Northern Gateway said that, while dilbit is not likely to sink due to initial weathering alone, if not recovered in a cleanup operation, dilbit weathered over a period of weeks could eventually sink.
Northern Gateway, Haisla Nation, and Environment Canada all said that oil may sink if it attaches to sediment or organic particles that sink. Northern Gateway and Environment Canada said that smaller droplets of oil are more prone to interact with suspended particulate matter.
Northern Gateway said that total suspended solids concentrations are generally low in the Confined Channel Assessment Area. It said that large aggregations of heavily-weathered dilbit or emulsions are not likely to sink as there would not be a sufficient quantity of sand or sediment, except in nearshore areas. Environment Canada recommended that additional suspended sediment and suspended particulate matter data be gathered within the project area to support further assessment of oil fate and behavior and to enhance marine spill fate and trajectory modelling. It said that this work would be appropriately conducted under the direction of a Scientific Advisory Committee.
Concerns regarding the potential behavior of dilbit spilled in water, and the potential for it to sink or submerge, were also raised by the Province of British Columbia, the Government of Canada, ForestEthics, Living Oceans Society, and Gitga'at First Nation.
Fisheries and Oceans Canada expressed uncertainty as to whether dilbit would float or sink. Environment Canada and Natural Resources Canada said that dilbit spilled in water would clearly initially float because its density is less than the density of water.
Environment Canada referred to its research indicating that the potential for oil to sink depends on many factors, such as evaporation, photo-oxidation, emulsion formation, water temperature, salinity, and oil particle size. It said that uptake of particulate matter is the most important contributor to increased density of spilled oil. It said that experience with previous spills shows that some of the oil could sink, some would float, and some would become neutrally buoyant and temporarily submerged or overwashed. It said that it did not have enough information to make quantitative predictions of dilbit behaviour, and was planning research on the topic.
Transport Canada said that the physical characteristics of the spilled product are the most important oil behavior indicators that a spill response organization needs to know when responding to an oil spill. It said that it had not heard anything new in evidence that led it to believe that a response organization would not treat a dilbit spill as a blended crude oil product. It said that the current response regime was set up to respond to such spills.
Northern Gateway said that spilled oil undergoes a number of changes as it weathers on the water surface, including a loss of the lighter hydrocarbon fractions with a resultant increase in density and viscosity. Northern Gateway said that, as the density and viscosity of the product increase, the evaporation of the lighter hydrocarbons decreases dramatically.
Parties said that the density of water can vary according to temperature and pressure. Northern Gateway said that the density of fresh water is approximately 1,000 kilograms per cubic metre and that of sea water is approximately 1,025 kilograms per cubic metre. Should the density of the hydrocarbon or emulsion exceed that of the water, the hydrocarbon is likely to sink. Northern Gateway said that there is a higher potential for oil to sink in fresh water than seawater due to the lower density of fresh water. The company said that the maximum initial density of any hydrocarbon to be carried on the proposed pipeline would be 940 kilograms per cubic metre, measured at 15 degrees Celsius, as this would be the maximum allowed under its proposed pipeline tariff specification.
Figure 6.1 Simulated oil fates processes in lakes and rivers
* MAH refers to monocyclic aromatic hydrocarbons (such as benzene, toluene, ethylbenzene, and xylene – combined, BTEX) and PAH refers to the lighter polycyclic aromatic hydrocarbons. These compounds are both volatile and relatively soluble in water.
Northern Gateway said that oil density and viscosity increase as weathering progresses and that density and viscosity decrease with increasing temperature. Northern Gateway said that viscosity is one of the most important properties influencing the behaviour of spilled oil and it affects the following processes:
Environment Canada said that viscosity is an important property influencing the behaviour of spilled oil. It recommended more research to measure the rate of density change due to evaporation as dilbit weathers. In response to questions from Northern Gateway, Environment Canada agreed that, even for the heaviest oil products, most evaporation would be expected in the first 48 hours.
Northern Gateway tested the physical properties and weathering behaviour of four representative hydrocarbons that may be transported by the project: synthetic crude oil, condensate, and two dilbit products (one diluted with condensate, and one diluted with synthetic crude oil). Northern Gateway said that a primary purpose of its laboratory testing was to generate input parameters for its spill modelling. The results of this work informed Northern Gateway's ecological and human health risk assessment work and oil spill fate and trajectory modelling discussed in Chapter 7.
The testing was conducted in a laboratory "bench-top" setting using recognized procedures. Changes in properties, such as evaporation rates, density, viscosity, the tendency and stability of potential emulsion formation, and oil adhesion, were measured. In turn, these results were used to predict the behaviour of the hydrocarbons in terms of characteristics such as evaporation, dispersion in the water column, emulsion water content, viscosity, and density. The behaviour was predicted for a variety of environmental scenarios, at various times after a spill. Northern Gateway conducted its testing at water temperatures of 1 degree Celsius and 15 degrees Celsius, to approximate possible seasonal water temperatures in the Confined Channel Assessment Area. Environment Canada said that evaporative weathering studies conducted by Northern Gateway for dilbit products and synthetic crude were in good agreement with its own similar studies.
Northern Gateway said that its laboratory testing weathered the oils in a wind tunnel and not on the water surface. The company said that the results of the wind tunnel testing did not account for potentially high viscosities that might be reached due to emulsion formation with water. Northern Gateway said that the wind tunnel data were then used to predict changes in density and viscosity, due to evaporative loss or weathering, by correlating the rate of evaporation of oil under the conditions in the wind tunnel to other environmental conditions of the scenarios modelled.
Northern Gateway conducted additional research using a wave tank to further assess the potential for dilbit to sink based on weathering alone. Northern Gateway said that the wave tank testing simulated more realistic environmental conditions than the laboratory bench-top testing. Wave tank testing had also been recommended by Haisla Nation. The work indicated that, although not likely to sink, oil could be temporarily submerged due to current or wave action.
Some participants expressed concern regarding Northern Gateway's measurements and conclusions for its wave tank testing. The Gitxaala Nation and Haisla Nation said that the density of the dilbit was not measured at water temperatures that may be present along the marine shipping routes. Northern Gateway said that the density of the dilbit tested would not be likely to reach the density of sea water even under colder water temperatures. It said that the increase in oil density at colder water temperatures would be offset by higher viscosity, which would reduce evaporation-based density increases. The company also said that the density of an emulsion would not exceed the density of the water in which it formed. Northern Gateway said that density, viscosity, and emulsion formation must all be examined together to consider the potential for an oil to sink.
The Gitxaala Nation filed reports indicating that heavy oils to be transported by the project may sink in the marine environment, under the right environmental conditions. This conclusion was partially based on weathering studies conducted by Environment Canada on two bitumen products. Northern Gateway did not agree with this conclusion and said that one of the products tested would not meet the proposed tariff specifications for the oil pipeline. It said that the density of the other product following weathering was still less than that of sea water, and that the products tested were already highly weathered prior to testing. Northern Gateway also said that the methodology used by Environment Canada did not approximate environmental conditions associated with an actual spill event. Northern Gateway said that it saw no evidence in Environment Canada's studies that would lead it to the conclusion that the oil tested would sink.
One of the Gitxaala reports was critical of the evaporation rates assumed by Northern Gateway in its studies, and concluded that additional research would be required to address the behavior of dilbit spilled in the marine environment. Environment Canada said that numerous factors in addition to evaporation rates must be considered in a spill scenario, and that additional research is required to support the conclusions noted in both Northern Gateway's and the Gitxaala Nation's studies. In response to questions from the Panel, the Gitxaala Nation said that dilbit could submerge, rather than sink, depending on environmental conditions.
In response to questions from the Panel, Northern Gateway's expert said that, based on his experience, he had confidence in Northern Gateway's descriptions and models of oil behavior. He said that his research with the dilbit products indicated that they behave similarly to other heavy fuel oils that he had worked with. In terms of transferring small-scale trials to progressively larger-scale work, he said that he did not expect there to be a significant difference in oil behavior. Another expert also said that he was of the view that the oils transported by the project are a type of oil that response organizations are familiar with.
In response to questions from the United Fishermen and Allied Workers Union, Northern Gateway said that its oil spill fate and trajectory modelling, conducted as part of its pipeline ecological and human health risk assessment work, considered the potential for oil to sink based on weathering alone and after interaction with suspended particles. Depending on the circumstances modelled, sinking was predicted for both dilbit and synthetic crude. Synthetic crude was sometimes predicted to be more prone to sinking due to its lower viscosity and higher potential for entrainment and interaction with suspended sediment. Northern Gateway said that, for the oils it modelled, it would take many days for them to sink based on evaporative losses only.
Northern Gateway said that dilbit is expected to behave similarly to an intermediate fuel oil or lighter heavy fuel oil, such as Bunker C, when spilled in marine waters. Haisla Nation agreed. Northern Gateway said that experience with previous spills indicated that products with a density less than or equal to water, similar to the dilbit products it tested, do not sink based on weathering alone. Rather, exposure to sand or other particulate matter is required for the products to sink. Haisla Nation said that the exact behaviour of spilled oil and associated cleanup efforts would depend on the circumstances and that every spill is different. Northern Gateway agreed.
Northern Gateway said that there have been no significant marine spills of the specific dilbit or synthetic crude oil products that may be carried by the Enbridge Northern Gateway Project. Northern Gateway said that approximately 70 cubic metres of a bitumen-based product diluted with condensate and synthetic crude oil had been spilled into Burrard Inlet in Burnaby, British Columbia, in 2007. The oil floated and was subsequently recovered by skimming and mechanical recovery techniques. Environment Canada said that sediment aggregation was not observed in this spill. In response to questions from Northern Gateway, Environment Canada agreed that dilbit would behave in a similar fashion to the product spilled into Burrard Inlet, but there could be subtle differences due to the presence of synthetic crude in the product.
Haisla Nation said that much of the oil from the Enbridge pipeline spill into Talmadge Creek and the Kalamazoo River near Marshall, Michigan, in July 2010 sank or submerged within 24 hours. Northern Gateway said that the majority of the spilled oil floated, and that 15 to 20 per cent of the oil submerged. It said that submergence was caused by increased density of the product due to evaporation of the lighter hydrocarbons, interaction with sediments, or emulsification. It said that the oil particles observed to have submerged or sunk were typically smaller particles or aggregations, ranging from 1 to 75 millimetres in size. Northern Gateway said that an underwater "slick" of oil was not observed, and that entrained oil-sediment mixtures settled in low-flow or still-water areas. Northern Gateway also said that, at the time of the spill, the river had high flow and a high concentration of suspended solids.
Fisheries and Oceans Canada, Environment Canada, and the Gitxaala Nation agreed that past spill examples of intermediate and heavy fuel oils, and research regarding these products, may provide useful information as to how products to be transported by the project might behave if spilled in the marine environment. They also said that additional research would be required regarding the behavior, fate, and environmental effects of the products to be shipped, as the actual behavior of spilled oil depends on the environmental conditions at the time and the physical and chemical characteristics of the product.
In a letter of comment, the Friends of Clayoquot Sound discussed the spill of 500 cubic metres of Bunker C oil from the Nestucca Barge in 1988 near Gray's Harbour, Washington. The Nestucca spill was also noted by Haisla Nation and the United Fishermen and Allied Workers Union. The spilled oil had a density of 986 kilograms per cubic metre and was overwashed by waves. Some was transported 175 kilometres north of the spill site and washed up on approximately 20 kilometres of shoreline on Vancouver Island 2 weeks later. Northern Gateway said that the oil had been submerged in the upper few metres of the water column.
Northern Gateway tested the physical properties of four representative oils that may be transported by the pipeline and provided additional information on physical and chemical properties of these representative products. In response to questions from the Gitxaala Nation and Environment Canada about how representative the tested oils were, Northern Gateway said that, in terms of behavior, they were good surrogates for the types of products that would be shipped on the pipeline. Northern Gateway said that the proposed tariff specification maximum density of 940 kilograms per cubic metre would constrain variation in physical properties and behavior.
The Gitxaala Nation said that there may be significant variability in the physical and chemical properties of the products potentially carried by the project. In response to questions from Northern Gateway, Natural Resources Canada and Environment Canada confirmed that variability within hydrocarbons is typical, and that blending of oil is commonplace within the oil industry. Environment Canada said that, dilbit has not been studied as much as other oils. Natural Resources Canada said that, while it is not likely that oil behavior differs radically among similar classes of hydrocarbons, more information about dilbit behaviour would inform spill response.
Environment Canada said that dilbit chemical composition is variable and needs to be considered as an important aspect of dilbit behavior. It recommended that Northern Gateway keep spill responders, regulators, and researchers informed regarding the physical and chemical properties of products which may be transported by the project. Environment Canada said that information about chemical characteristics is needed when developing forensic models to distinguish spilled oil from background hydrocarbons, and is also relevant to toxicological properties. Northern Gateway said that it would include, in its operational spill response plans, data on the physical properties of each product to be transported by the project.
Environment Canada recommended that Northern Gateway help regulators and other researchers obtain product samples to be used in studies about the environmental fate and behavior of products that would be shipped by the project. Northern Gateway said that it was willing to assist in the acquisition of samples from producers.
In response to questions from the Kitimat Valley Naturalists and others, Northern Gateway committed to further analysis of physical and chemical properties of the products moved on its system. Northern Gateway said that it would engage other industry partners to examine a potential system to meet the recommendations of Environment Canada. In response to questions from the Panel, Northern Gateway clarified that, in the event that other industry partners were not willing to participate, it would undertake such work on its own.
Northern Gateway and the United Fishermen and Allied Workers Union said that the most acutely-toxic components of oil are monocyclic aromatic hydrocarbons (such as benzene, toluene, ethylbenzene, and xylene – combined, BTEX) and lighter polycyclic aromatic hydrocarbons. These compounds are both volatile and relatively soluble in water.
Northern Gateway said that the dominant polycyclic aromatic hydrocarbons found in petroleum products are lighter two- and three-ringed polycyclic aromatic hydrocarbons. It said that, unlike chemicals such as polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons in petroleum products do not bioaccumulate up the food chain as they are metabolized and excreted in a water-soluble form by organisms such as fish and crustaceans. It said that the Canadian Council of Ministers of the Environment standards confirmed this position. The United Fishermen and Allied Workers Union noted research undertaken following the Exxon Valdez oil spill, which indicated that polycyclic aromatic hydrocarbons are generally neither bioaccumulative, nor persistent in biota.
Northern Gateway said that hydrocarbon exposure after a spill would be low-level and of short duration for many animals, including fish and crustaceans. It said that concentrations in tissues would be relatively low and would not persist. Northern Gateway said that the absence of appreciable hydrocarbon bioaccumulation was the reason it did not include top predators, such as killer whales, as receptor species in its ecological risk assessment. Northern Gateway said that, in contrast, molluscs are unable to readily metabolize aromatic hydrocarbons and may accumulate moderate amounts of hydrocarbons.
Northern Gateway said that bioavailability depends on a number of factors such as the characteristics of the chemical and its location in the environment. It said that a substance can be present in the environment, but be relatively unavailable to biota. For example, oil dispersed in the water column and tightly bound to fine particulate or organic matter may pass unabsorbed through the gut of fish and other invertebrates. Weathered oil can eventually be buried and isolated in sediments.
Northern Gateway said that the potential for acute toxicity is the result of a balance between bioavailability, toxicity once exposed, and duration of exposure. The toxicity of compounds that are relatively insoluble in water is generally limited, as they are less bioavailable to aquatic biota. Higher molecular weight polycyclic aromatic hydrocarbons may be taken up directly into fats or ingested after binding to organic particulate matter. Monocyclic aromatic hydrocarbons are the most soluble, but tend to evaporate or weather quickly and have a short period of exposure. Two-ringed polycyclic aromatic hydrocarbons are semi-soluble, and three-ringed polycyclic aromatic hydrocarbons are considered only slightly soluble.
Northern Gateway said that, following an oil spill, concentrations and mixtures of hydrocarbons in water or sediment vary over time as a result of the differential solubility of individual chemical constituents and weathering. As a result, there is no single answer to the question of how toxic a particular hydrocarbon product may be.
Northern Gateway noted the differences between toxicological effects exhibited in laboratory studies and the recovery of species and populations following spill events. It said that many studies have also demonstrated sublethal effects that may not lead to actual reduction in fitness or population level effects. Northern Gateway said that, while sublethal effects may not be fully understood, a good understanding of population-level effects has been attained.
Fisheries and Oceans Canada said that toxicity tests, such as the LC50 test, are often conducted in a closed system with direct exposure at high concentrations. It said that such tests may approximate initial exposure levels where water column concentrations are quite high. It said that, in a real spill event, spatial dilution through current and wave action would cause water concentrations to fall off over time.
The Gitxaala Nation said that weathering can produce toxic intermediate products, and that products such as bitumen are generally lower in alkanes (straight-chain hydrocarbons), which are the most readily biodegradable compounds in crude oil. It said that aromatic compounds (more complex, cyclic compounds) may degrade much more slowly, over years to decades. A Gitxaala Nation expert said that asphaltenes are another class of compounds present in bitumen products that are relatively slow to degrade. Northern Gateway said that asphaltenes are present in all petroleum products to varying degrees.
Northern Gateway analyzed polycyclic aromatic hydrocarbon concentrations within representative products that may be transported by the project. In response to questioning from Haisla Nation, Northern Gateway said that, although other hydrocarbon products with higher polycyclic aromatic hydrocarbon concentrations may also be transported, those concentrations would not be likely to change Northern Gateway's conclusions regarding potential acute and chronic effects of an oil spill. Northern Gateway said that, even if total polycyclic aromatic hydrocarbon concentrations were much higher than those modelled using the representative products, potential effects would still be in the lower end of the range of concentrations for which potential effects may occur. It said that a variety of factors must be considered when assessing acute and chronic effects. It also said that a large spill would have significant adverse effects that are generally reversible through mitigation and natural recovery.
Northern Gateway said that commercial vessels already carry substantial volumes of heavy fuel oil throughout coastal waters. It said that dilbit is currently being transported by pipeline throughout North America, and is shipped by tankers through British Columbia coastal waters. The Canadian Coast Guard and Environment Canada said that ship traffic is projected to grow, and that heavy oils are increasingly being transported by tankers around the world.
In response to questions from Douglas Channel Watch, Northern Gateway said that the issue of the potential submergence of diluted bitumen and other oils has been recognized by industry, regulators, and the public. Northern Gateway outlined a number of related research and development activities currently taking place in North America to enhance understanding of heavy oil behavior and to further develop response options. Northern Gateway committed to participate in some of these activities and noted the importance of additional information to assist in spill response planning.
Northern Gateway said that, although additional research is always helpful, it was of the view that the currently available research, including its own work, allowed a good understanding of how products potentially shipped by the project might behave in the environment.
Northern Gateway committed to participate in, and contribute funding to, a collaborative government-industry-university research effort to study the environmental behaviour and fate of diluted bitumen. Northern Gateway proposed the establishment of a Scientific Advisory Committee consisting of various technical experts to facilitate this research, as recommended by Environment Canada. The Scientific Advisory Committee would be guided by a management team and an advisory panel. Northern Gateway envisioned that the research would be a broader initiative led by a government agency such as Environment Canada, with Northern Gateway being a key participant. Northern Gateway said that its discussions with Environment Canada indicated that Environment Canada had already identified potential sources of funding for the initiative.
Living Oceans Society said that it supported future research initiatives, including laboratory studies related to dilbit spill behavior in the marine environment. It noted the need for larger-scale research in controlled outdoor facilities. In response to questions from the Panel, Northern Gateway confirmed that, in the event that a broader initiative was not established, it would undertake and fund, in consultation with Environment Canada, those elements of the initiative that would be directly applicable to the project.
Environment Canada, Fisheries and Oceans Canada, and Natural Resources Canada identified the need for additional research on the fate, behavior, and effects of heavy oil products to be transported by the project. Transport Canada said that such research would further inform spill response planning.
Environment Canada recommended that Northern Gateway consider research on environmental behavior and fate models, addressing topics such as weathering, dispersion potential, oil-particulate interactions, submergence, and remediation options for shorelines. The results of this research would be closely linked to Environment Canada's recommendation for additional spill modelling and risk assessment studies. Environment Canada recommended that this work be guided by an expert scientific committee.
In response to questions from the Panel, Haisla Nation, and the United Fishermen and Allied Workers Union, federal government departments outlined research that they were proposing to conduct on the behaviour, fate, and transport of dilbit products in a marine environment. This research would be conducted outside of the context of the Enbridge Northern Gateway Project and would occur over several years. The departments said that the work was being undertaken because there are many proposals to transport dilbit products throughout Canada and the United States. They said that the work would contribute to spill response associated with rail, pipeline, and ship incidents. The federal research would also examine response options and consider oil behavior in varying sea states and environmental conditions. In turn, this research could inform additional toxicological studies and environmental effects research. Fisheries and Oceans Canada and Environment Canada said that research on biological and toxicity effects associated with oil spills is typically undertaken in collaboration with academia.
Different terms may be used to describe the state of oil spilled in water. The Panel used the following definitions in its consideration of the evidence:
Dispersed oil: fine droplets of oil on the water surface or suspended in the water column through wave action or other turbulence.
Emulsion: an oil and water mixture or “mousse.”
Entrained oil: small globules of oil or an emulsion that has temporarily submerged due to wave action or other turbulence. The oil or emulsion may be neutrally buoyant, meaning that it is not floating, but simply submerged in the water column.
Floating oil: oil on the water surface.
Flocculation or oil-mineral aggregates: an electrostatic process in which very fine, clay-sized particles bind to very small oil particles.
Oil/suspended particulate matter, oil/sediment or oil/total suspended solids interactions, or oil bound to sediment: larger silt- and sand-sized particles, or other organic matter, that are bound to oil particles.
Overwashed oil: similar to entrained oil, but typically occurring as larger accumulations of oil referred to as pancakes or mats, where water turbulence is not energetic enough to move the oil deeper in the water column. Overwashed oil would typically remain close to the surface.
Submerged oil:* a variety of oil states that are below the water surface, such as entrained oil or overwashed oil, but is not sunken oil.
Sunken oil:* oil that has sunk to the bottom of the watercourse or to the ocean floor because it has become denser than water.
Tarballs: small, rubbery balls of oil weathered at sea.
* The Panel often heard that oil could sink. Depending on the context, the Panel understood this to refer to sunken or submerged oil.
The Panel acknowledges the variety of opinions from experts regarding the behavior and fate of oil spilled in aquatic environments. These experts generally agreed that the ultimate behavior and fate of the oil would depend on a number of factors, including the volume of oil spilled, the physical and chemical characteristics of the product, and the environmental conditions at the time.
The Panel finds that likely oil behaviour and potential response options can be predicted from knowledge of the type of oil spilled and its physical and chemical characteristics. Details of oil behaviour and response options cannot be specified until the actual circumstances of a spill are known.
The Panel is of the view that, if placed along a spectrum of: tendency to submerge; persistence; and recovery difficulty, dilbit would be on the higher end of the spectrum, similar to other heavy oil products.
The Panel accepts evidence from previous spills showing that, in response to circumstances at the time, the behaviour of heavier oils, including conventional oils and synthetic crudes, can be dynamic. Some oil floats, some sinks, and some is neutrally buoyant and subject to submergence and overwashing.
Although the project would transport different types of oil, the majority of the evidence presented during the hearing process focussed on whether dilbit is likely to sink when spilled in an aquatic environment. In light of this, the Panel has chosen to focus its views on dilbit. The Panel heard that the fate and behaviour of dilbit has not been studied as much as that of other oils.
Although there is some uncertainty regarding the behavior of dilbit spilled in water, the Panel finds that the weight of evidence indicates that dilbit is no more likely to sink to the bottom than other heavier oils with similar physical and chemical properties. The Panel finds that dilbit is unlikely to sink due to natural weathering processes alone, within the time frame in which initial, on-water response may occur, or in the absence of sediment or other particulate matter interactions. The Panel finds that a dilbit spill is not likely to sink as a continuous layer that coats the seabed or riverbed.
The Panel accepted the following facts in reaching its findings:
The Panel benefitted from the Gitxaala Nation's critique of Northern Gateway's bench-top and wave tank testing, which concluded, in part, that Northern Gateway's work "came closer than anybody else to mimicking environmental conditions" and stressed that more work needs to be undertaken under a wider range of environmental conditions. This critique did not appear to fully consider interactions between density and viscosity of the oil. The Panel also notes that the Gitxaala Nation's expert did not have access to the methodology used in the Environment Canada studies on which the critique was partly based. Such access could have further informed the critique. Environment Canada's experts did not conclude that dilbit is likely to sink in the marine environment.
If dilbit sinks due to weathering over the longer-term, or due to interactions with sediment or suspended particulate matter, the evidence indicates that such sinking would likely be patchy in distribution and not likely to result in widespread, thick mats of fresh, sunken oil on the bottom of the watercourse or ocean. In the marine environment, sinking is most likely in nearshore areas or as smaller particles of oil in deeper waters. Except in certain nearshore areas, suspended sediment concentrations throughout most of the Confined Channel Assessment Area and Open Water Area are not likely to be high enough to cause sinking of larger aggregations of oil or oil emulsions. In rivers and lakes, sinking of oil-sediment mixtures would be most likely in areas of low turbulence or slow current.
Although the evidence does not indicate that dilbit is prone to sink in the marine environment, it clearly indicates that dilbit would be subject to emulsion formation and temporary submergence. This would cause challenges in tracking and recovering spilled dilbit. All parties, including Northern Gateway, acknowledged this point. In response to questions from the Panel, the Gitxaala Nation's expert clarified that his work could be interpreted as indicating that dilbit may not necessarily sink, but that it could submerge. The Panel notes that other heavier conventional and synthetic crudes carried by the project may also be prone to submergence, depending on environmental circumstances.
The Panel finds that Enbridge's spill of dilbit into the Kalamazoo River near Marshall, Michigan, provides a case study of the behavior of dilbit in the freshwater environment. The Panel finds that the evidence presented on the Marshall, Michigan, spill demonstrates that dilbit can sink in some circumstances. The relatively small proportion of the spill that sank to the bottom of the river presented significant cleanup challenges. The Panel understands that cleanup is ongoing to this day.
The Panel acknowledges that dilbit may be prone to stranding on the shoreline in both freshwater and marine environments. This could occur on shorelines closer to the spill within a relatively short time frame or as a result of temporarily submerged oil being transported and washing up on the shoreline elsewhere. Oil spill response is discussed in Chapter 7.
The Panel considered how representative the products tested by Northern Gateway were of the products potentially transported by the project. Northern Gateway provided data on physical and chemical properties of representative examples of condensate, synthetic crude, and dilbit. These data represented a range of properties, all of which would meet the proposed tariff specifications.
The Panel finds that Northern Gateway has provided it with sufficient information to assess the general behavior and potential environmental effects of the types of products to be transported by the project. The information provided by Northern Gateway was also sufficient to inform the Panel's assessment of spill response planning.
The Panel accepts Northern Gateway's commitment to provide additional data on physical and chemical properties of products that would be shipped on the project to support detailed spill response planning and modelling. The data may also facilitate research conducted outside of the context of this project.
The Panel accepts the expert evidence that toxic components of the products likely to be shipped on the project generally do not bioaccumulate in the food chain in most species. Hydrocarbons are prone to natural biodegradation processes. This assists in the natural recovery of the environment.
The Panel finds that toxic effects from a major spill would be significant in the short term, and that longer-term chronic effects could also occur. The duration of chronic effects would depend on the volume and type of oil spilled; its persistence in the environment; species affected; and the extent of natural dispersion by wind, waves, and currents. Acute effects are likely in the event of a spill of any hydrocarbon. Chronic effects are more likely to be associated with spills of heavier hydrocarbons, such as dilbit.
The Panel recognizes the scientific uncertainty associated with sublethal, secondary, and synergistic effects. There is ongoing research and debate as to the extent to which these effects result in measurable effects on the environment. The Panel is not persuaded that the presence of residual hydrocarbons necessarily results in a measurable effect at the species or population level. Food safety would be protected through guidelines and standards for allowable residual hydrocarbon concentrations in seafood.
In the Panel's view, the weight of evidence indicates that disagreement among experts on the fate and behaviour of spilled oil is related to specific details that may not be significant from a spill response perspective. Additional research is required to answer outstanding questions related to the detailed behaviour and fate of dilbit. All parties with technical expertise on the topic were in agreement with this.
The Panel finds that research on the behaviour and cleanup of heavy oils is required to inform detailed spill response planning and heavy oil spill response in marine and freshwater environments. Northern Gateway has committed to be responsible for this research.