Bitumen exploitation in Alberta’s oil sand region generates considerable amounts of waste including tailings and process-affected water that needs reclamation. Water capped tailings technology (WCTT) is currently being assessed as a potential wet reclamation strategy in the oil sand by the commission of Base Mine Lake (BML), the first commercial scale Pit Lake. Pit Lakes consist of ~40m of fluid fine tailings (FFT) deposited in old mine pit covered with a ~10m water cap. In order to be successful, pit lakes much achieve the ecological roles of a natural lake, which includes colonization of the water by macrofauna therefore necessitating the water cap to be oxic. Due to the reductive nature of the tailings, oxygen consuming constituents (OCC) such as methane, sulfide and ammonia are released from the FFT into the water cap potentially posing a threat to the success of the reclamation. Additional seasonal effects such as stratification and ice cover may further affect oxygen consumption by isolating parts of the water cap therefore allowing accumulation of OCC. Results shows that BML thermally stratifies during the summer and winter and that oxygen persist throughout the water cap despite reaching low level at the FFT-water interface (FWI) during summer. Consistent with the FFT acting as an OCC source, aqueous CH 4 and NH 4+ concentrations were highest closer to the FWI, decreasing upwards into the water cap. Using linear regression CH 4 was shown to be an important OCC during the summer of 2015 while NH 4+ and CH 4 were both important for the summer of 2016 highlighting the emergence of nitrification in BML. Detailed analysis of seasonal data revealed that accumulation of OCC below the hypolimnion depletes oxygen and favors methanotrophic activity. Results from both studies suggest that methanotrophs have a competitive advantage at low oxygen levels against nitrifiers. / Thesis / Master of Science (MSc) / Bitumen extraction in Alberta’s oil sand region generates substantial amounts of waste including tailings that needs reclamation. Pit Lakes have been proposed as a reclamation strategy, where tailings are deposited into a mined-out pit and covered with a water cap. To achieve the reclamation goal, the lake must be able to sustain life and must therefore maintain an oxic water cap. The underlying tailings poses a threat to the oxygenation of the lake because of the constant release of compounds that have the potential to consume oxygen. Additional seasonal effects due to temperature change may further affect oxygen consumption by isolating parts of the water cap. In this thesis the results of two years of field sampling and analyses show that despite active oxygen consumption from tailings-released compounds, oxic status is achieved in the upper layer of the lake during summer and under ice.

This study presents the dewatering assessment of a marl quarry with the future pit lake level predictions. The objectives of the study were / (1) to determine the dewatering requirements that would allow for the continuation of the quarrying operations in the deeper parts of the quarry, (2) to design an optimum dewatering system compatible with the site hydrogeological conditions and quarrying plans, (3) to assess the environmental impacts of dewatering on the local water (surface and ground water) resources and users, and (4) to predict the future pit lake level and flooding period for different meteorological conditions. To these ends, previous investigation reports and maps have been compiled and reviewed and field investigations have been conducted. During the field investigations pumping and observation wells were drilled and installed. After installation, in situ tests were conducted to determine aquifer parameters. It was found that properties of the material is conducive to the dewatering activities that will be necessary for the deepening of the open pit of the marl quarry. A groundwater model was developed based on the field data gathered. According to this model dewatering trenches will be needed to dewater the pit. The model predicted that operating these dewatering trenches would create an elongated cone of depression that will sufficiently lower the groundwater table so that quarrying operations can proceed. Lowering of the water table may produce a negative impact on groundwater resources within the aerial extent of the cone of depression. This potentially negative impact was investigated with model simulations and has been found that the impact to the resources would be negligible. Three scenarios were evaluated as possible dewatering discharge disposal solutions. The preferred scenario included the discharge of this water to the stream, which is flowing on the western side of the quarry. The pit will start to fill with water immediately after the dewatering operations stopped. In order to predict the pit lake flooding period and final lake elevation, pit lake hydrologic model was developed. The simulations predict that the final pit lake elevation would be at 991 m. The pit lake will rise to this level at approximately 72 years after closure.

This Master’s degree study examined concentration and isotopic trends of dissolved methane, isotopic trends of phospholipid fatty acids (PLFA), and generated 1st order flux calculations to identify and assess biogeochemical cycling of dissolved methane in the first full-scale demonstration of EPL technology in the Alberta Oil Sands Region (AOSR). Base Mine Lake (BML) was commissioned by Syncrude Canada Ltd. in 2012 to facilitate the long-term storage and remediation of Fluid Fine Tailings (FFT) that are generated as a result of bitumen extraction via the Clark Hot Water Extraction (CHWE) processes. The results of this project provide evidence of methane oxidation by type I methanotrophs in BML, reducing dissolved oxygen concentrations in the hypolimnion layer. The FFT layer is identified as a source zone of fermentative methanogenesis, creating saturated conditions of dissolved gases. Dissolved methane is transferred to the water column primarily by advective processes related to FFT consolidation, while diffusion is a significant secondary transfer mechanism. Dissolved methane concentrations decrease significantly across the FFT-water interface where diffusive flux rates decrease by several orders of magnitude. Concentrations decreased linearly through the hypolimnion to trace concentrations by the metalimnion, resulting in a minor enrichment of δ13C of the residual dissolved methane pool. A minor enrichment of δ13C in C14:0, C16:0, and C16:1 PLFA coincided across the same interval, indicating utilization of a less depleted carbon source further away from the FFT-water interface where dissolved methane concentrations were lower. PLFA δ13C signatures were depleted relative to expected values of typical DOC substrates, further supporting the incorporation of a depleted signature by transfer of depleted carbon from dissolved methane. / Thesis / Master of Science (MSc)

Populations of largemouth bass, Micropterus salmoides, and bluegill, Lepomis macrochirus, were evaluated from five pit-lakes in Muhlenberg County, Kentucky, to determine if accurate proportional stock density (PSD) data can be obtained from a mandatory creel survey. It was hypothesized that the proportion of stock-to-quality (300-400mm) and quality (+400mm) largemouth bass from four years (2007-2010) of creel survey data would be statistically similar to those generated through on-site sampling in 2011. Fish were collected via a combination of gill netting, seining, hook-and-line fishing, and boat-mounted electro-fishing. In two of the pit-lakes, the sampling-generated length frequency data was not significantly different from the creel survey data (Pump Gadj[1]=0.03, P=0.8629, Goose Gadj[1]=0.76, P=0.3850). There were significant differences between creel and sampling data for the other pit-lakes (Big Reno Gadj[1]=5.74 P=0.0166, Airstrip Gadj[1]=14.3 P=0.0002, Lime Gadj[1]=9.81 P=0.0017). At least one of the lakes likely demonstrated significances because of low sample size (Airstrip and/or Lime). Changes in population structure due to modified harvest regulations may be responsible for the significant differences (Big Reno and Lime). Population structures were verified with relative weight, length-at-age, and an assessment of five years of largemouth bass and bluegill PSD data. It appears that creel survey data does accurately reflect that of simple sampling techniques and can help guide management decisions.