Lake Wabamun Research Articles

Critical Analysis of Train Derailments in Canada through Process Safety Techniques and Insights into Enhanced Safety Management Systems

Canada’s rail transportation network is a critical part of Canada’s integrated supply chain which connects industries, consumers, and resource sectors to ports on the Atlantic and Pacific coasts. One transportation activity that is essential to most industries, especially oil and manufacturing, is the rail transport of dangerous goods (DG). Although rail transportation of DG is beneficial to Canada’s economy, not paying attention to the safe transportation of these types of goods can have irreparable effects on the economy, human lives, and the environment. Recent rail accidents, such as Lake Wabamun in 2005 and Lac-Mégantic in 2013, have shown that there is still room to increase the safety of transportation of DG by rail through improving railways’ safety management systems (SMS). As a result, investigations to increase the safety of rail transportation of DG have been started. This work is part of these initiatives focusing on enhancing railways’ SMS, particularly DG main-track train derailments. The current study applied detailed root cause analysis (RCA), the bow tie analysis (BTA), and incident databases to identify the main causes and consequences of these types of accidents (2007–2017). Then, the relationship between these factors and gaps in SMS elements were identified and the frequency of each factor was investigated. The results showed that the main gaps are related to process and equipment integrity, incident investigation, and company standards, codes, and regulations. Furthermore, some useful recommendations are presented to improve the management of each SMS element and reduce these gaps.

The effect of site characterization data on injection capacity and cap rock integrity modeling during carbon dioxide storage in the Nisku saline aquifer at the Wabamun Lake area, Canada

Geological storage of CO2 is an option for mitigating global climate change resulting from greenhouse gas emissions. Effective selection, design, and operation of storage sites require reliable models for predicting the response to CO2 injection. This paper revisits preliminary studies of CO2 storage in the Nisku saline aquifer in Alberta, Canada, which were conducted to assess CO2 injectivity, plume migration, and geomechanical response during 50 yr of injection, using model input parameters estimated from data available at the time. The new work presented here involved modeling of CO2 injection using the same tools but with input parameters obtained from data acquired in an evaluation well. The first series of new simulations modeled fluid flow using a commercial black-oil simulator and predicted a lower maximum injection rate (0.80 million t [Mt]/yr [0.88 million tons (Mtons)/yr] compared to 1.0 Mt/yr [1.1 Mtons/yr]) but a CO2 plume width nearly identical with the preliminary prediction (as a consequence of increases in some parameters that offset decreases in other parameters). The second series of new simulations was undertaken using a coupled thermo–hydro–mechanical simulator and predicted ground surface uplift approximately four times less than the preliminary study and (when injecting above the fracture pressure) fracture dimensions several times greater. As before, thermal effects resulting from cool CO2 injection were observed to promote lateral fracture growth in the aquifer and reduce (but not prevent) vertical growth into the cap rock. Use of the evaluation well data in this study enabled a more confident conclusion that injection above the fracturing pressure is not feasible for this site.

Using Debitage Analysis to Investigate an Alberta Archaeological Site

Ahai Mneh (FiPp-33) is a significant pre-contact archaeological site in Alberta. Located west of Edmonton on Lake Wabamun, this site contains material from the Early Prehistoric right up until Late Prehistoric pre-contact times. Ninety-five percent of the lithic artifacts collected are pieces of debitage. Aggregate analysis is a method of examining the whole of the debitage collection, rather than analysing singular pieces. This method is more time efficient, less subject to bias, replicable, and is used often, and successfully, at archaeological sites with immense quantities of debitage. Here I use aggregate analysis to examine the debitage assemblage from two field schools at Ahai Mneh. I investigate various characteristics such as size, raw material type, cortex amount, and number of dorsal scars. I argue that this method is successful, as it provided new information on where people were acquiring raw materials, as well as what types of flintknapping occurred at this site. These analyses resulted in the determination of a focus on local raw material, yet this material was being brought to the site as prepared cores or blanks, rather than complete unaltered cores. Tool production was the focus at this site, and this trend continued throughout time.

Inland Oiled Wildlife Response: It’s a Different Animal

ABSTRACT 2017-311 The Oiled Wildlife Care Network (OWCN) was established in 1994 to address the need for timely, consistent, and professional science-based preparedness and response for wildlife at risk from oil spills occurring in the marine waters of California. Its mission focused on providing a high level of professional care based on the best available technology and science combined with the experience of many organizations that were pioneers in the field of wildlife rehabilitation. Since that time, the OWCN and its now more than 35 members have responded to over 100 spills while caring for more than 8,200 impacted animals. In 2014, in response to the increased risk due to changing sources and transport patterns in oil coming to refineries in California, the State legislature expanded the OWCN’s responsibility to include responding to oiled wildlife impacted during oil spills in all surface waters of California. Since then, the OWCN has worked to expand its plan and resources to ensure readiness to provide best achievable capture and care to a host of new species in the myriad of habitats and locations found in a large and ecologically diverse state. The biggest challenges to this expansion are the increased diversity of species and their habitats (California has 233 species and subspecies of reptiles and amphibians), and the increase in geographical scope. Working with the California Department of Fish and Wildlife (specifically the Office of Spill Prevention and Response, or OSPR), the OWCN staff have identified species at risk and response challenges unique to an inland environment and terrestrial species and the appropriate resources meet those challenges and fill current gaps. We have incorporated lessons learned by colleagues during wildlife responses to inland spills including CNR Lake Wabamun (2005), Enbridge Kalamazoo River (2010), Silvertip Pipeline Yellowstone River (2011), and CNRL Cold Lake (2013). We have repurposed and redesigned existing equipment as well as acquiring additional mobile equipment to increase capacity and decrease response time. We have identified and trained first responders over a wide geographical area focusing on regions with increased risk of incident and impacts while leveraging our current primary care facilities with field stabilization and wildlife transportation plans to achieve maximum flexibility and cost effectiveness. We detail both the process that was used to develop this expansion and the resulting additions to the wildlife plan aimed to provide best achievable care to all wildlife species impacted by an inland oil spill in California.

Reservoir modeling for Wabamun lake sequestration project

AbstractA study, entitled “Wabamun Lake Sequestration Project” or “WASP,” was performed to evaluate large‐scale CO2 storage opportunities in the Wabamun area including potential risks. The project examined the feasibility of storing 20 megatons (Mt) of CO2 per year over 50 years. This scale is one order of magnitude larger than the typical benchmark (1 Mt/year) used in academic research and commercial projects that are currently in place or under review. The study was conducted by a group of researchers from several universities as well as industry consultants. This study presents an overview of the reservoir modeling part of this study, which the authors were responsible for. The main objectives of the reservoir modeling for WASP project were as follows: (1) estimation of storage capacity (traditionally, this value is projected based on the available pore space, but we have an additional practical consideration: the maximum amount one can inject within short period of time [~50 years] and within a localized injection area [~30 km × 90 km]); (2) investigation of CO2 plume movement and pressure distribution during and after injection including the effect of formation dip angle on the plume shape and its migration; (3) investigation of the long‐term fate of injection associated with free phase CO2 (risks of leakage) and aquifer pressurization (possible geomechanical changes and related phenomena); (4) investigation of the phase behavior of H2S initially available and dissolved in brine during CO2 sequestration process. The WASP reservoir modeling study mentioned above led to a few important findings. The most important one is that, when CO2 is being injected into a sour aquifer, initially dissolved H2S will release into the expanding CO2 plume and accumulate at the leading edge of the plume. Also, the large‐scale injection scheme (20 Mt/year), which requires multi well injectors, provides very different pressure response compared to a one well (1 Mt/year) scenario.

Effect of Dynamic Loading on Wellbore Leakage for the Wabamun Area CO2-Sequestration Project

Summary The most viable options for permanent removal of carbon dioxide (CO2) from the atmosphere include large-scale injection of CO2 from stationary sources, such as coal-fired power plants and heavy-oil production, into brine-filled formations. One of the main risks identified with storing CO2 in the subsurface is the potential for leakage through existing wells penetrating the caprock. The wellbore system has several components that can fail and create leakage pathways, including type and placement of wellbore casing and cements, completion method, abandonment, and wellbore expansion or contraction by changes in temperature and pressure. Of the 1,000 wells in the study area near Wabamun Lake, Alberta, 95 wells penetrated the immediate caprock above the proposed Nisku injection formation and were identified as potential leakage pathways. The leakage risk of these wells was evaluated on the basis of knowledge of the well design, current well status, and historical regulations in the area. Only four wells, for the subset of 27 wells studied, were identified as requiring workover, which was less of a problem than anticipated. To evaluate the risk of creating leakage pathways by thermal and pressure changes caused by CO2 injection, a 3D finite-element model was built by use of poroelastoplastic material models for cement and formation. Multistage simulations for casing/cement and cement/ formation interactions with temperature-enabled elements were conducted. A parametric study of cement properties was conducted to investigate cement design and its mechanical properties for injection wells. The simulation results indicated that thermal cooling might reduce near-wellbore stresses, which would increase the risk of integrity loss in casing/cement and cement/formation. The parametric study revealed that the risk of debonding and tensile failure would increase with increasing Young’s modulus and Poisson’s ratio of the cement under dynamic-loading conditions. In addition, low mechanical cement strength would increase the risk of shear failure in the cement.

2-D reactive transport modeling of the fate of CO2 injected into a saline aquifer in the Wabamun Lake Area, Alberta, Canada

Carbon capture and storage (CCS) is a viable option to reduce emissions of anthropogenic CO2 into the atmosphere. One important component during the storage site selection process is the prediction of the movement and the fate of the injected CO2 in the chosen reservoir. The fate of CO2 injected into a saline aquifer of the Devonian Nisku Formation in Alberta (Canada) was simulated using the reactive transport code TOUGHREACT. A 2D radially symmetric model was developed for a 50-year CO2 injection phase followed by a 1000-year storage period. CO2 was injected into the bottom 10m of the Nisku Formation at a rate of 1Mton/year for 50years. The injected supercritical CO2 spread out radially up to 3.5km after 50years of injection and 6.0km after 1000years of post-injection. After 1000years, the injected CO2 was trapped in the Nisku Formation underneath the excellent seal of the Calmar shale predominantly as free CO2 via hydrodynamic trapping (76%) and to a lesser extent by solubility trapping (23%) in aqueous phase (HCO3-(aq)). Mineral trapping of injected CO2 in the Nisku aquifer was negligible. This study predicted the interactions of the fluids and rock minerals with injected CO2 in the storage Nisku aquifer, the Calmar caprock and the bottom rock Ireton shale. This information will be highly beneficial for potential future CO2 injection projects targeting the saline aquifer of the Nisku Formation in Western Canada.

2-D Numerical Modeling of CO2 Storage in the Devonian H2S Containing Nisku Aquifer in the Wabamun Lake Area (Alberta, Canada)

The Devonian Nisku aquifer has been identified as a suitable CO2 storage site in the Alberta Basin, but this aquifer contains significant amounts of H2S. Numerical simulations were performed to investigate the impact of dissolved H2S in the brine on the behavior of the injected CO2. No major differences in geochemical reactions were observed between model runs with and without H2S. Extensive dolomite dissolution was observed in both model runs, which caused a minor increase in porosity and permeability of the aquifer. The majority of the injected CO2 was trapped in the Middle Nisku as a free supercritical phase and the rest was dissolved in the brine.

Geomechanical modeling for CO2 storage in Nisku aquifer in Wabamun Lake area in Canada

During CO2 injection, increasing pore pressure and temperature reduction create geomechanical deformation of both the reservoir and surrounding rocks. One of the most important concerns with respect to the long term CO2 storage is that stress changes caused by injection could lead to formation fracturing or reactivation of fracture networks and fault movements which could potentially provide pathways for CO2 leakage through previously impermeable rocks.Nisku geological formation located in Wabamun lake area was chosen as storage target based on storage capacity, expected ease of injectivity, low leakage risks and lack of interference with current petroleum production in the area. In order to determine whether the injection-induced stress changes affect the viability of this target formation to act as an effective storage unit, the geomechanical assessment model of the injection process has been developed, which couples the thermal flow model and geomechanical model covering all layers from the basement to the surface, and incorporates the modeling of dynamic injection-induced fracture. This work established the methodology for investigating the increase of well injectivity by allowing fracturing, and assessing the effect of the injection temperature.The pressure and stress variations were modeled during and after CO2 injection utilizing a coupled flow and geomechanical software. Since injected CO2's temperature may be considerably lower than the formation temperature, thermal effects were incorporated into the models. In order to increase the well injectivity, the case of allowing fracture initiation and propagation in Nisku was considered. The modeling shows that total minimum in situ stress is not constant and can be dramatically reduced by injection of cold CO2, thus leading to spontaneous fracturing. The cases of isothermal and thermal injection (without containment) show that operating above the fracture pressure in Nisku will increase the well injectivity (from 1Mt/year to at least 2Mt/year) but creates potentially long fractures and also the possibility of fracturing the caprock.Decreasing temperature due to CO2 injection will result in stress reduction and smaller surface deformations compared to the isothermal model. Thermal effects of cold CO2 injection will also reduce the fracture (injection) pressure and enhance the horizontal fracture propagation through Nisku. However, to make recommendations on a design that does not jeopardize isolation capacity of the containment requires site specific geomechanical and in situ stress data for all overlaying strata, in order to assess the risk of vertical propagation more accurately.This study predicts that CO2 injection in the Nisku zone is not likely to cause any significant surface heave and is not likely to have any environmental impact associated with surface deformations.In summary, the geomechanical factors put significant constraints on CO2 storage in Nisku in terms of injection pressures that may be limited by fracture propagation, injection rates that can be achieved without compromising the seal and excessive fracture propagation, and the CO2 placement affected by a fracture. The demonstration of the importance of thermal effects on CO2 storage is the most important contribution of this work.

Trophic relationships of two species of grebe on a prairie lake based on stable isotope analysis

We used stable isotope analysis of carbon and nitrogen to investigate the trophic relationships of Western (Aechmophorus occidentalis (Lawrence)) and Red-necked (Podiceps grisegena (Boddaert)) Grebes from Lake Wabamun, a large prairie lake in north-central Alberta, Canada. We collected tissue samples (i.e., pectoralis muscles and primary feathers) from 42 Western and 22 Red-necked Grebes (adults and juveniles) that had died in captivity after an oil spill on Lake Wabamun on 3 August, 2005. We also collected fish and invertebrates, focusing on taxa known to serve as prey for grebes. Based on comparisons of 15N enrichment in muscle tissue, Western Grebes, northern pike (Esox lucius Linnaeus), yellow perch (Perca flavescens (Mitchill)), and lake whitefish (Coregonus clupeaformis (Mitchill)) were top consumers in Lake Wabamun, as were Red-necked Grebes. Adult Western Grebe muscle was more enriched with 15N than adult Red-necked Grebe muscle by 1.5‰, indicating that Western Grebes foraged at a slightly higher trophic position on Lake Wabamun than Red-necked Grebes. Red-necked Grebe muscles and feathers were also less depleted in 13C than Western Grebe muscle, indicating that Red-necked Grebes likely spent more time foraging in the littoral zone than Western Grebes. There were no differences in muscle or feather isotopic signals between juvenile and adult Western Grebes, suggesting that both age groups fed on similar prey items and in similar habitats. Muscle tissues and primary feathers of larger Red-necked Grebes were more enriched in both 15N and 13C than smaller grebes likely because larger grebes consume more or larger fish.

Early prehistoric sties in Alberta and how they relate to Ahai Mneh (FiPp-33)

A number of projectile points found in the basal cultural deposits at Ahai Mneh are representative of the Early Prehistoric period. In addition to confirming a cultural presence previously only tentatively identifi ed at this hilltop site near Wabamun Lake in central Alberta, these fi ndings add to our understanding of the range of the Agate Basin/Hell Gap phase, a period that is very poorly represented in Alberta archaeolog y. Further, two fragmentary specimens thatare basally concave and exhibit attempts at fl uting or basal thinning appear to be Early Prehistoric in origin; these bear some resemblance to stubby points of the little-known Sibbald phase, although they could also be representative of the later Lusk complex. While only the most tentative of identifi cations can presently be made, they serve as an indicator of multiple Early Prehistoric occupations at Ahai Mneh and highlight a key area of interest for future research at the site.

Characterization of Biodegraded Wabamun Spill Oil Samples Incubated with Lake Fresh Sediment or Enrichment Culture

ABSTRACT On August 3, 2005, a Canadian National Railway train derailed within the Whitewood Sands community of the Wabamun Lake area. The derailment resulted in the release of 712,500 liters of Bunker C oil and 88,000 liters of pole treating oil from the rail cars into the adjacent Wabamun Lake water. To estimate the hydrocarbon-degrading capabilities of microbes naturally present in oil-contaminated Lake Wabamun sediment, laboratory tests were conducted at the University of Alberta under two incubation conditions. The tests incubated spilled Bunker C oil recovered from the lake and the reference oil, Alberta Sweet Mix Blend (ASMB), at 22°C for 4 weeks or at 4°C for 8 weeks. Residual oil was recovered and quantitatively characterized at the Oil Research Laboratory of Emergencies Science and Technology Section, Environment Canada. Biodegradation results demonstrated that Lake Wabamun sediment microbes were capable of degrading a significant proportion of the ASMB reference oil at both incubation temperatur...

Analysis of potential acid gas leakage from wellbores in Alberta, Canada

Deep geological disposal of acid gas reduces green house gas emissions and removes potentially toxic hydrogen sulphide from the accessible environment. Leakage of acid gas through abandoned wellbores could compromise greenhouse gas mitigation and could be toxic. In this study, simple analytical equations are developed to predict the worst case, post injection leakage rate from wellbores with intact casings such that the acid gas moves directly from the reservoir to the surface with no dissolution into surrounding formations. The U.S. EPA code, ALOHA and Lawrence Livermore code, SLAB, are used to estimate atmospheric concentrations of hydrogen sulphide for worst case acid gas leakage at two sites west of Edmonton, Alberta; one in the Pembina-Wabamun area and the other in Brazeau-Nisku area. Results indicate detrimental atmospheric concentrations at low wind speeds would be confined to within about 3.5km downwind for the Nisku site. Lethal concentrations would be confined to within about 10m downwind for the Wabamun site and about 30m downwind for the Nisku site.A semi-analytical model is used to predict long-term leakage rates and concentration of dissolved acid gas in formation fluids surrounding a wellbore with leakage through a failed casing at a site near Wabamun Lake. Two sequestration processes: geochemical reaction and convective mixing in the reservoir are shown to be important in decreasing the duration of long-term leakage from thousands of years to hundreds or years. Leakage confined to the annulus of the wellbore could result in complete acid gas dissolution into surrounding formations with no atmospheric leakage. The Joule–Thomson cooling effect is shown to be unimportant for passive leakage. Concentrations of dissolved acid gas above the odour and taste threshold could occur in potable aquifers such as the Paskapoo. Contamination of potable aquifers with heavy metals could not be ruled out.

Reservoir Characterization for CO2Sequestration: Assessing the Potential of the Devonian Carbonate Nisku Formation of Central Alberta

The Wabamun Lake area of Central Alberta, Canada includes several large CO<sub>2<sub/> point source emitters, collectively producing more than 30 Mt annually. Previous studies established that deep saline aquifers beneath the Wabamun Lake area have good potential for the large-scale injection and storage of CO<sub>2<sub/>. This study reports on the characterization of the Devonian carbonate Nisku Formation for evaluation as a CO<sub>2<sub/> repository. Major challenges for characterization included sparse well and seismic data, poor quality flow tests, and few modern measurements. Wireline porosity measurements were present in only one-third of the wells, so porosity and flow capacity (permeability-thickness) were estimated using wireline electrical measurements. The Archie cementation factor appears to vary between 2 and 3, creating uncertainty when predicting porosity using the electrical measurements; however, high-porosity zones could be identified. The electrically-based flow capacity predictions showed more favorable values using a correlation with core than the relation based on drill stem and production tests. This behavior is expected, since the flow test flow capacities are less influenced by local occurrences of very permeable vuggy and moldic rocks. Facies distributions were modeled using both pixel and object methods. The object models, using dimensions obtained from satellite imaging of modern day environments, gave results that were more consistent with the geological understanding of the Nisku and showed greater large-scale connectivity than the pixel model. Predicted volumes show considerable storage capacity in the Nisku, but flow simulations suggest injection capacities are below an initial 20 Mt/year target using vertical wells. More elaborate well designs, including fracture stimulation or multi-lateral wells may allow this goal to be reached or surpassed.

The Wabamun Area Sequestration Project (WASP): A multidisciplinary study of gigaton scale CO2 storage in a deep saline carbonate aquifer

The Wabamun Area Sequestration Project (WASP) is a major integrated, multidisciplinary study investigating the potential for large-scale CO2 sequestration (>20 Mt/yr) in a deep saline aquifer in the Wabamun Lake area, southwest of Edmonton, Alberta, Canada. Four large coal-fired power plants in the region produce on the order of 30 Mt CO2/yr, with the goal being to inject 1 Gt of these emissions over 50 years. The WASP project establishes the viability of the Devonian Nisku Formation carbonate for large-scale injection. Storage capacity is thought to be between 0.2 and 0.3 Gt using conventional drilling and reservoir pressure management methods, while the injection potential may be increased to >0.4 Gt using more advanced strategies. Geostatistical manipulation of existing well log data, core-derived rock properties, and available seismic data allowed construction of static geologic models that were used for simulation of CO2 injection into the target formation. Important considerations include interactions of dissolved H2S in the aquifer brine with injected CO2; the geomechanics of the target formation and caprock seal; and the likely need for pressure management schemes to optimize injectivity without compromising seal integrity or large-scale aquifer behaviour. Future work should include more complete and up-to-date sampling of the caprock seal and entire injection formation interval; better aquifer brine samples for geochemical analysis; and in-situ test programs for assessing the geothermal effects on fracturing and the leakage rates through abandoned well bore cements and casings.

Geomechanical modeling for CO2 Storage in Wabamun Lake Area of Alberta, Canada

Abstract Based on experience gained from existing sequestration pilot projects and enhanced oil recovery practices, geologic storage is a technically viable means to significantly reduce anthropogenic emissions of CO2. During CO2 injection, increasing pore pressure and temperature reduction create geomechanical deformation of both the reservoir and surrounding rocks. One of the most important concerns with respect to the long term CO2 storage is that stress changes caused by injection could lead to formation fracturing or reactivation of fracture networks and fault movements which could potentially provide pathways for CO2 leakage through previously impermeable rocks. The cumulative CO2 emission from power plants located in Wabamun lake area in central Alberta, Canada reaches 30 Mt/year. Nisku geological formation located in Wabamun lake area was chosen as storage target based on storage capacity, expected ease of injectivity, leakage risks and interference with current petroleum production in the area. In order to determine whether the post-injection stress changes affect the viability of this target formation to act as an effective storage unit, the geomechanical assessment model of the formation has been developed, which couples the flow model and geomechanical model covering all layers from the basement to the surface. This work was a part of a comprehensive feasibility study of large scale CO2 storage potential in the Wabamun area, called the Wabamun Area CO2 Sequestration Project (WASP). The model used rock mechanical properties, reservoir characterization and flow properties of the Nisku provided by extensive work in other teams of the WASP project. The present modeling work focused on evaluation of a single well injecting 1 Mt/year for 50 years, followed by simulation of 50 years of shut-in. The pressure and stress variations were modeled during and after CO2 injection utilizing geomechanical software, GEOSIM, commercial code of Taurus Ltd. In order to increase the well injectivity, the case of allowing fracture initiation and propagation in Nisku was considered. The results show that injection above the fracture pressure will have the potential to increase the well injectivity (to at least 2 Mt/year) but also create the possibility of fracturing the caprock. The possible upward fracture propagation strongly depends on the caprock stress state and mechanical properties. However, the results of the simulation of vertical propagation have been obtained under the most unfavorable assumption of constant minimum stress gradient and are only preliminary. Since injected CO2’s temperature is considerably lower than the formation temperature, thermal effects were incorporated into the models. Decreasing temperature due to CO2 injection will result in stress reduction and smaller surface deformations compared to the isothermal model. Thermal effects of cold CO2 injection will also reduce the fracture (injection) pressure and enhance the horizontal fracture propagation through Nisku. CO2 injection in the Nisku zone is not likely to cause any significant surface heave and is not likely to have any environmental impact associated with surface deformations. Surface deformation data can be used in conjunction with seismic measurements to validate mechanical properties of Nisku and overlying layers. It also can help to plan for the location of the instrumentation and surface monitoring. Given the best estimates of cohesion and friction angle, the probability of reaching shear failure in Nisku or in the caprock is low. However, the likelihood of fracturing due to thermal effects is high. The importance of modeling of thermal effects in CO2 storage is the most important contribution. The results of this study are in agreement with our research on CO2 storage in Ohio River Valley.

Spatial distribution of mercury and other trace elements in recent lake sediments from central Alberta, Canada: An assessment of the regional impact of coal-fired power plants

These have been growing concerns over the environmental impacts of the coal-fired power plants in the western Canadian province of Alberta, which collectively comprise one of the largest point sources of Hg and other trace elements nationally. The overall cumulative impact of the power plants since the beginning of their activities several decades ago has been a critical question for industry, government agencies, and the research community. This paper aims to delineate the cumulative geographic extent of impact by investigating the spatial distribution of mercury and other trace elements of environmental concern in nine freshwater lakes, which cover the large area surrounding the coal-fired power plants in central Alberta, Canada. 210-Lead dating was used in conjunction with physical evidence of deposited fly ash to determine the sediments' age and hence the depths corresponding to the onset of coal-fired power generation in 1956. Total mean concentrations and fluxes of elements of environmental concern with integrated values since 1956 were then determined. The concentration values do not reflect the catastrophic oil spill at Lake Wabamun in 2005. The post-1956 flux rates of As, Cd, Co, Cr, Cu, Hg, Mo, Ni, Pb, Sb, V, W, and Zn were generally highest in sediment cores obtained from two lakes adjacent to power plants. However, the variable prevailing wind directions played an important role in determining the aerial distribution of Hg and other trace elements to the southeast and to the west of the power plants. Post-1956 fluxes of most elements declined downwind (westward), consistent with strong easterly winds transporting metal pollution further to the west of the power plants. However, spatial interpolation of the data suggested a major southern extension to the area of maximum metal deposition, which has not been sampled by this or previous studies in the region. An atmospheric model estimate of total Hg flux in 2007 near the Genesee power plant was substantially lower than indicated by the most impacted lake sediments, which have integrated Hg fluxes since 1956. The most likely explanations for the model-sediment difference are either that a sharp spatial gradient of deposition exists in the region, and/or recent technology improvements by the power plants have substantially reduced Hg emissions.

Ambient air total gaseous mercury concentrations in the vicinity of coal-fired power plants in Alberta, Canada

The Lake Wabamun area, in Alberta, is unique within Canada as there are four coal-fired power plants within a 500 km 2 area. Continuous monitoring of ambient total gaseous mercury (TGM) concentrations in the Lake Wabamun area was undertaken at two sites, Genesee and Meadows. The data were analyzed in order to characterise the effect of the coal-fired power plants on the regional TGM. Mean concentrations of 1.57 ng/m 3 for Genesee and 1.50 ng/m 3 for Meadows were comparable to other Canadian sites. Maximum concentrations of 9.50 ng/m 3 and 4.43 ng/m 3 were comparable to maxima recorded at Canadian sites influenced by anthropogenic sources. The Genesee site was directly affected by the coal-fired power plants with the occurrence of northwest winds, and this was evident by episodes of elevated TGM, NO x and SO 2 concentrations. NO x /TGM and SO 2/TGM ratios of 21.71 and 19.98 µg/ng, respectively, were characteristic of the episodic events from the northwest wind direction. AERMOD modeling predicted that coal-fired power plant TGM emissions under normal operating conditions can influence hourly ground-level concentrations by 0.46–1.19 ng/m 3 . The effect of changes in coal-fired power plant electricity production on the ambient TGM concentrations was also investigated, and was useful in describing some of the episodes.

Effects of an Oil Spill on the Regrowth of Emergent Vegetation in a Northern Alberta Lake

Following a train derailment in August 2005, Wabamun Lake (Alberta, Canada) was exposed to approximately 149,500 L of bunker "C" oil, much of which became entrained in the abundant Schoenoplectus tabernaemontani (= Scirpus validus) beds in the eastern basin of the lake. We assessed the regrowth of emergent macrophytes during the subsequent two growing seasons. Postspill measures of productivity, including transect length, total cover, and biomass were within the variability of prespill data collected in 2001, with the exception of a few specific areas in which biomass appeared to be affected. We conclude that exposure to oil during the late growing season in August 2005 and through the winter senescent period and regrowth in the summers of 2006 and 2007 did not cause large-scale changes to S. tabernaemontani communities. Physical factors such as cleanup activities and vegetation management appeared to be responsible for the reduced regrowth observed at some locations. Few previous studies have been published on the effects of oil spilled into freshwater on macrophyte communities; thus, the results of this study are expected to provide useful information for the assessment of future freshwater oil spills.

Feasibility of Injecting Large Volumes of CO2 into Aquifers

Although it is recognized that deep aquifers offer a very large potential storage capacity for CO2 sequestration it is not clear how to fill the storage with a large volume of CO2 in a relatively short period of time. The typical benchmark for the rate of CO2 injection is 1 Mt/year when studying storage performance. This rate is very low compare to the scale necessary for the storage technology to play a significant role in managing global emissions. In this study we perform numerical simulations of a large volume of injection, 20 Mt/year during 50 years of continuous injection resulting in a total sequestration of 1 Gt CO2. A sensitivity analysis of the results (plume area and CO2 storage capacity) is presented within the range of aquifer parameters: thickness (50-100 m); permeability (25-100 mD); rock compressibility (from 9u10 -10 to 2u10 -9 (1/Pa)) as well as different injection arrangements. The implementation of this study to a particular case of injection of 1 Gt total over 50 years into the Nisku aquifer located in Wabamun Lake Area, Alberta, Canada [1] is presented. In this area, large CO2 emitters including four coal-fired power plants with emission between 3 to 6 Mt/year each are present. The Nisku aquifer is believed to be a suitable choice for future sequestration projects. In this case study a few injection scenarios (number of wells and their placement, which control the ability to inject without exceeding the aquifer’s fracture pressure) are presented. The evolution of plume size and pressure field in the aquifer for these scenarios is shown. As opposed to the generic sensitivity study, the case study includes the heterogeneity of the aquifer and its dip angle. Both generic and Nisku studies have shown that the capacity of the reservoir in the case of large injection volumes should be evaluated not by available pore volume, but by ability to inject some amount without exceeding fracture pressure of formation.