Canada
Boreal peatland restoration through partial removal of an oil and gas well pad
Murdoch McKinnon, University of Waterloo
Peatlands cover over 30% of the landscape on Canada’s Western Boreal Plains, where oil and gas extraction has resulted in considerable ecosystem disturbance. Because peatlands are characterized by near-surface water tables and compressible organic soils, industrial features called well pads must be constructed to provide a stable base for surface equipment when oil and gas wells are drilled in these environments. Well pads are constructed with mineral fill (clay or sand) placed onto the peat surface, resulting in burial of the native vegetation community which is associated with peatland ecosystem function. In Alberta, there is a legal requirement to return well pads to a state of equivalent land capability post-decommissioning. In peatlands, this has been recently defined as including the reestablishment of hydrological and biogeochemical conditions which can support a peat-accumulating vegetation community.
One technique that has the potential to provide these conditions involves partially removing the mineral fill, such that the pad surface elevation is lowered to the level of the water table in the surrounding peatland. Here, we present the results of a four-year post-restoration assessment undertaken following the partial removal of a well pad near Slave Lake, Alberta. Specifically, we sought to assess whether partial removal resulted in a sufficiently wet residual mineral substrate for the establishment of peatland vegetation either introduced as donors or naturally revegetated from nearby sources. Our results demonstrate that groundwater connectivity with the adjacent peatland maintained near-saturated soil moisture conditions across just under half of the pad. This resulted in biogeochemical conditions similar to those observed in the adjacent rich fen. However, limited groundwater connectivity within the interior of the pad resulted in a reliance on snowmelt and early-season rainfall to maintain high soil moisture levels away from pad edges. In these drier interior patches, water availability to mosses typically became limiting by mid-summer. As such, potential modifications to the technique with the potential to improve surface and groundwater connectivity will be discussed.
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