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Oil sand mine tailings are primarily contained by dykes constructed of permeable sand tailings. The environmental impacts of process waters released from these tailings facilities are controlled by groundwater flow within the impoundment structures. Transient groundwater flow characteristics were assessed within the Tar Island Dyke structure at the Suncor Inc. site near Fort McMurray, Alberta, to assist in quantifying potential long-term environmental impacts. A sequence of low-permeability fine tailings underlying the tailings water pond is supported by coarse sand tailings that are connected to and form the containment dyke structure. A clay unit separates the foundation from the underlying limestone that is hydraulically connected to the Athabasca River. The primary groundwater flow pathways are through the toe of the dyke and through the foundation. Field data and numerical simulations indicate that drainage of process water within the structure remains transient yet decreases over time. The fine tailings and pond become perched atop unsaturated coarse tailings, significantly restricting seepage and producing an environmental legacy with reclamation implications. The release of potentially contaminated process water continues to decrease, resulting in diminishing environmental risk. The lowering of pore-water pressures within the main dyke has increased its strength and long-term stability. Key words: tailings, oil sand, seepage, process water, modeling. Les rejets miniers des operations de sables bitumineux sont principalement contenus par des digues construites a partir de rejets de sable permeable. Les impacts environnementaux des eaux de procede provenant de ces parcs a rejets sont controles par l'ecoulement souterrain a l'interieur meme des parcs a rejets. Les caracteristiques de l'ecoulement souterrain transitoire ont ete evaluees pour le parc Tar Island Dyke au site de Suncor Inc. pres de Fort McMurray, Alberta, afin de quantifier les impacts environnementaux potentiels a long terme. Une serie de rejets fins a faible permeabilite sous l'etang du parc a rejets est supporte par des rejets de sable grossiers qui sont relies aux digues, et ainsi forment la structure du parc. Une unite d'argile separe la fondation du calcaire sous-jacent; cette fondation est connectee a la riviere Athabasca. L'ecoulement se fait principalement par le pied de la digue et a travers la fondation. Des donnees recueillies sur le terrain et des simulations numeriques indiquent que le drainage de l'eau de procede demeure en regime transitoire mais diminue avec le temps. Les rejets fins et l'etang sont maintenant perches au-dessus des rejets grossiers non satures, ce qui restreint de facon significative la percolation et entraine un heritage environnemental ayant des implications au niveau de la restauration. L'ecoulement d'eau de procede potentiellement contaminee continue de diminuer et par le fait meme diminue le risque environnemental. La baisse des pressions interstitielles a l'interieur de la digue principale a contribue a augmenter sa resistance et sa stabilite a long terme. Mots-cles : rejets, sables bitumineux, percolation, eau de procede, modelisation. [Traduit par la Redaction], Introduction The oil sand deposits of Northern Alberta provide approximately one-third of Canada's crude oil supply (Alberta Energy 2006). These deposits contain bitumen, an extremely viscous form of petroleum, which [...]

The potential of compound-specific isotope analysis to assess in situ biodegradation of methyl tert-butyl ether (MTBE) in groundwater is examined in laboratory studies at the University of Waterloo, Waterloo, Ontario, Canada. The research suggests that carbon isotope analysis could possibly be used to trace in situ biodegradation of MTBE and tert-butyl ether.

A flexible, passive method of bioremediation in an aquifer involves the introduction of dissolved substances through a permeable wall. The wall filled with pumping and injection wells is placed across the contaminant plume path. Longitudinal dispersion of injected substances ensures maximum mixing with the contaminated ground water. A pulsing cycle is followed to ensure a stable microbial population and effective biodegradation system.