Pollard, J, McKenna, GT, Fair, J, Daly, CA, Wytrykush, C & Clark, J 2012, 'Design aspects of two fen wetlands constructed for reclamation research in the Athabasca oil sands', in AB Fourie & M Tibbett (eds), Proceedings of the Seventh International Conference on Mine Closure
, Australian Centre for Geomechanics, Perth, pp. 815-829, https://doi.org/10.36487/ACG_rep/1208_67_Pollard
Suncor Energy Inc. (Suncor) and Syncrude Canada Ltd. (Syncrude) operate surface mines in the Athabasca oil sands region of northeastern Alberta, Canada. Regulations and corporate commitments require the companies to return the landscape to self-sustaining boreal forest land uses. Prior to disturbance, fen wetlands made up a considerable portion of the boreal forest ecosystem, and as a result, Suncor and Syncrude are both designing and constructing full scale fen research wetlands at their Athabasca oil sands leases. Prior to these projects, there has been considerable research into natural wetlands in the region and some construction of marshes and smaller wetlands. Syncrude and Suncor’s fen research wetlands projects expand on that knowledge base for construction at a full scale. The purpose of these constructed fen wetlands is to gain design, construction and operational experience which, in addition to research into performance of the wetland, can be used to guide future reclamation activities at a commercial scale. This paper describes the various design aspects of these multidisciplinary projects.
Both Suncor and Syncrude’s surface mining activities create a range of different landforms which require reclamation. The locations for the fen research wetlands are different; Suncor’s fen will be constructed on an overburden dump while Syncrude’s will be created on a sand-capped composite tailings (CT) deposit. Although the initial watershed geometries and underlying materials differ, there are similarities in the design components, which mainly originate from landscape design principles. Although both designs are for fen wetlands, both projects include a larger instrumented research watershed, where the main purpose is to study the interactions between the wetland and surrounding terrestrial uplands. One of the projects, the Syncrude Sandhill Fen, has recently completed construction, and moved to an operation, monitoring and surveillance phase. The other project (the Suncor Pilot Fen) construction is ongoing and planned to be completed at the end of 2012.
A characteristic of natural fen wetland systems is a stable water table maintained at a very stable elevation near peat surface and this, in turn, maintains the fen wetland vegetation. An important aspect of the design is the ability to monitor the hydrogeology and hydrology of the constructed system. Both of the fen wetlands are designed to mitigate against too much water at surface which would promote marsh vegetation (non-target species) and too little water at surface which would promote terrestrial plants (non-target species) and development of a wooded swamp or upland forest. Both designs incorporate model predictions for a dynamic climate system prone to periods of drought and flood; an important consideration for the boreal forest climate in this region. The resulting watershed design includes elements to maintain water elevations, promote recharge into the wetland and control salinity. These design features enhance the suitability of the hydrogeological regime of the site and likely the success of the wetland.
The designs incorporate robust measures to account for settlement of fill material or tailings which underlie the site. From predictions, these settlements were shown to be localised but are still accommodated as part of a robust fen wetland design. Reclamation placement has been designed to maximise the potential for establishment of a fen wetland.
The fen wetland projects have been a collaborative process involving graduate students, professors, and industry people working together to complete the design and construction and incorporate the combined knowledge into future fen wetland design and construction on reclaimed landscapes. The knowledge provided by the research team includes international knowledge of traditional wetland restoration techniques, processes in natural wetlands in the boreal forest and climatic regime and established experience of mine reclamation techniques in the Athabasca oil sands.
The projects described are specific case studies to the Athabasca oil sands and as such knowledge gained is biased towards the boreal forest environment and its specific climatic and geological conditions. The projects provide description of fen wetland creation where the initial conditions for wetland establishment are broadly absent and the construction team was required to establish a hydrological regime and provide carbon and plant sources from mining materials (i.e. there is no base case conditions to re-establish). A description of the design process to create these instrumented watersheds and conclusions from the design and construction are provided. While this paper provides a case history for a specific geographical location, the design process and key learnings will be of interest to wetland designers interested in mine reclamation.
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