Initial geochemical characteristics of fluid fine tailings in an oil sands end pit lake

Dompierre, Kathryn A.; Lindsay, Matthew B.J.; Cruz-Hernández, Pablo; Halferdahl, Geoffrey M.

doi:10.1016/j.scitotenv.2016.03.002

Cited by 51 publications

(28 citation statements)

References 38 publications

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“…At this time, the maximum FFT depth in BML was 45 m, corresponding to a total FFT volume of approximately 1.9 × 10 9 m 3 . The average FFT temperature is approximately 13°C [ Dompierre et al ., ]. After commissioning, freshwater was pumped into BML from Beaver Creek Reservoir (Figure ) during ice‐free months.…”

Section: Methodsmentioning

confidence: 99%

“…Fluid fine tailings pore water chemistry is dominated by oil sands process‐affected water, which contains significant concentrations of dissolved ions (e.g., sodium, chloride, bicarbonate), naphthenic acids, petroleum hydrocarbons, and unrecovered bitumen [ Allen , ; Kavanagh et al ., ]. The initial FFT solids content is 25–35% (w/w), and is predominantly comprised of quartz and clay minerals including kaolinite, illite, chlorite, and illite‐smectite [ Dompierre et al ., ; Osacky et al ., ]. The residual bitumen content typically ranges from 1% to 6% (w/w) (G. Halferdahl, Syncrude Canada Ltd., personal communication, 2014).…”

Section: Methodsmentioning

confidence: 99%

“…Compressed nitrogen gas (275 kPa) was used to maintain the pistons in the closed position while the sampler was slowly lowered to the FFT‐water interface. Five cylinders were positioned above and fifteen below the FFT‐water interface, which was first determined by active sonar [ Dompierre et al ., ]. After a 10 min settlement period, the compressed nitrogen was evacuated from the cylinders into the sampler lines, and the pistons retracted to the open position using a vacuum pump.…”

Section: Methodsmentioning

confidence: 99%

“…The release of chemical constituents from the FFT will influence the long‐term geochemical and biological evolution of an EPL [ Dompierre et al ., ]. Mass transport between the FFT and overlying water cover can occur via two key processes: (1) advection and hydrodynamic dispersion driven by FFT dewatering and elevated solute concentrations in FFT pore water [ Dompierre et al ., ]; and (2) FFT disturbance due to fluid movement in the water cover (e.g., internal waves) causing a rapid, but intermittent, mass release to the water cover [ Dompierre and Barbour , ].…”

Section: Introductionmentioning

confidence: 98%

“…Management and reclamation of FFT pose substantial geotechnical and environmental challenges. Associated pore waters exhibit elevated concentrations of dissolved inorganic chemical constituents, and organic compounds such as naphthenic acids, petroleum hydrocarbons, and unrecovered bitumen [ Allen , ; Dompierre et al ., ; Kavanagh et al ., ]. Fluid fine tailings also exhibit high water content that persists for decades due to low settlement rates [ Kasperski and Mikula , ].…”

Section: Introductionmentioning

confidence: 99%

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Chemical mass transport between fluid fine tailings and the overlying water cover of an oil sands end pit lake

Dompierre

Barbour

North

et al. 2017

Water Resources Research

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Fluid fine tailings (FFT) are a principal by-product of the bitumen extraction process at oil sands mines. Base Mine Lake (BML)-the first full-scale demonstration oil sands end pit lake (EPL)-contains approximately 1.9 3 10 8 m 3 of FFT stored under a water cover within a decommissioned mine pit. Chemical mass transfer from the FFT to the water cover can occur via two key processes: (1) advection-dispersion driven by tailings settlement; and (2) FFT disturbance due to fluid movement in the water cover. Dissolved chloride (Cl) was used to evaluate the water cover mass balance and to track mass transport within the underlying FFT based on field sampling and numerical modeling. Results indicated that FFT was the dominant Cl source to the water cover and that the FFT is exhibiting a transient advection-dispersion mass transport regime with intermittent disturbance near the FFT-water interface. The advective pore water flux was estimated by the mass balance to be 0.002 m 3 m 22 d 21 , which represents 0.73 m of FFT settlement per year. However, the FFT pore water Cl concentrations and corresponding mass transport simulations indicated that advection rates and disturbance depths vary between sample locations. The disturbance depth was estimated to vary with location between 0.75 and 0.95 m. This investigation provides valuable insight for assessing the geochemical evolution of the water cover and performance of EPLs as an oil sands reclamation strategy. End pit lakes (EPLs) offer long-term FFT containment with relatively low initial costs [Cumulative Environmental Management Association (CEMA), 2012]. These mine closure landscapes contain FFT deposits under a water cover within decommissioned mine pits. In the future, EPLs will be incorporated into the larger mine Key Points: First study of solute release from fluid fine tailings (FFT) stored under water cover in first oil sands end pit lake Mass balance confirmed constituents in FFT pore water largest mass input to water cover Numerical models show advectiondispersion during FFT settlement controls mass transport

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Section: Methodsmentioning

confidence: 99%