Hydrological dynamics following partial removal of an oil well pad undergoing restoration to a boreal peatland

Many peatlands on the North American Western Boreal Plain have been disturbed by industry, including through the construction of thousands of oil well pads. The introduction of fen mosses onto residual mineral well pads following their partial removal has been proposed as a novel technique to restore these sites. However, it has remained unclear whether this would support the requisite hydrological conditions for fen moss establishment. To assess this, a field study of hydrological function at a partially removed pad undergoing restoration near Slave Lake, Alberta, Canada was undertaken. Specifically, the hydrophysical properties of the residual fill and adjacent peatland (including hydraulic conductivity, bulk density, and porosity) were characterized, and related to subsurface flow and water table regulation within the partially removed pad and adjacent peatland. The results demonstrate that flow through the peatland was disrupted by the low saturated hydraulic conductivity of the residual fill (1.15 × 10^-5 m s^-1) and the compacted underlying peat (4.91 × 10^-6 m s^-1), resulting in preferential flow around the pad. On the residual pad, hydrological connectivity with the adjacent peatland resulted in a well-regulated, near-surface water table across nearly half of its surface area. However, limitations on subsurface flow through the pad footprint resulted in variable hydrological dynamics across much of its interior. These findings suggest that partially removed well pads have the potential to support requisite hydrological conditions for fen moss establishment, but further development of the technique should be undertaken to improve subsurface hydrological connectivity with adjacent peatlands.