Freshwater Fisheries in Canada: Historical and Contemporary Perspectives on the Resources and Their Management

Chapter 18: Assessing the Potential Risks of Tailing Ponds Failures to Aquatic Ecosystems in Canada

Mark S. Poesch


Canada is a country rich in natural resources such as forests, minerals, and oil and gas. In particular, Canada’s oils sands region remains one of the most important global sources of bitumen (Mossop 1980). The oil sands region, near Fort McMurray, Alberta, occupies an area of approximately 142,000 km2. In this area, there is an estimated 27 billion m3 (170 billion barrels) of recoverable oil, representing the second largest oil reserve globally after Saudi Arabia (Dillon et al. 2011). Although these oil reserves were first discovered in 1778 by Peter Pond, a Hudson Bay Company fur trader, industrial exploitation did not begin until nearly 200 years later (Berkowitz and Speight 1975). Since that time, the oil sands region has expanded drastically.

The ability to monitor and assess the impacts of resource extraction activities to aquatic ecosystems remains controversial. Since the early 1960s, the areas in and around Fort McMurray are among the most altered landscapes anywhere in Canada (Chu et al. 2015). The majority of oil sands is extracted from surface mining. Oil is extracted by use of hot water (79–93°C) to separate bitumen from other constituents such as clay, sand, dissolved metals, and organic compounds (Giesy et al. 2010). Primary (coking) and secondary (catalytic hydrotreating) processes are used to upgrade the bitumen to synthetic crude oil (Chalaturnyk et al. 2002). The remaining by-products, including water, are referred to as “oil sands processed water” (OSPW) and are stored on site in tailings ponds. It is estimated that 4 m3 of OSPW are produced for each cubic meter of oil sands processed (Holowenko et al. 2002). There is a zero discharge policy for OSPW; thus, all OSPW must remain on site (Giesy et al. 2010), although some releases have been approved in the past (Regional Aquatics Monitoring Program [RAMP] 2016; Culp et al. 2021). This has resulted in over 1 billion m3 of tailings held in containment systems (Del Rio et al. 2006), and there is growing concern regarding leaks and spills (Dillon et al. 2011).

Tailings ponds have grown substantially in the oil sands region over the past decade. Estimates by the Government of Alberta show that total tailings pond area has increased from approximately 77 km2 in 2010 to 110 km2 by 2020, an increase of over 40% in a decade. During the same time, total active area of oil sands operations increased from 178 km2 to 270 km2, a 50% increase (Alberta Environment and Parks 2020). A report by the Commission for Environmental Cooperation, an international organization created by the North American Free Trade Agreement, showed “consistent evidence of seepage of OSPW from tailing ponds into groundwater at certain monitoring wells that are close in proximity to surface water, including tributaries of to the Athabasca River” (CEC 2020). The report further notes that, in 2017, Syncrude estimated that 785,000 m3 of OSPW migrated beyond interception systems build to contain this spillage. Oil sands processed water has been shown to be present in McLean Creek and the lower Beaver River (Fennell and Arciszewski 2019) as well as in groundwater samples <1 m beneath the Athabasca River (Frank et al. 2014).

The levels of toxicity from the OSPW in these areas is sufficient to cause impacts to aquatic biota. Naphthenic acids are one of the main concerns in OSPW, as it both persistent and toxic to aquatic organisms. Naphthenic acids can be as high as 110–120 mg/L in OSPW, which is toxic to a range of aquatic organisms (Giesy et al. 2010). Toxicological impacts of OSPW has been shown on a wide variety of fishes, including Yellow Perch Perca flavescens (Nero et al. 2006a), Goldfish Carassisus auratus (Lister et al. 2008; Nero et al. 2006b), Fathead Minnow Pimephales promelas (Colavecchia et al. 2004; Kavanagh et al. 2011), and White Sucker Catostomus commersonii (Colavecchia et al. 2006).