Investigation of the Causes of Low Infiltration Rate and Hydrophobicity in Reclamation Soils

Soil hydrophobicity impairs water storage and infiltration capacity in both natural and reclaimed landscapes, potentially causing erosion and surface water ponding as observed in the Athabasca Oil Sands Region. The Critical Water Content is the threshold where soils transition between hydrophobic and hydrophilic states. Limited data exists on hydrophobicity patterns and CWC values for regional reclamation materials (fibric, mesic and humic peats, LFH, sandy mineral soils, and tailings sands).

Five natural sites and four reclaimed sites were identified in 2008 and 2009 to determine the range of hydrophobicity of surface soils. The water droplet penetration time test and hydrophobicity index showed that the range of persistence of hydrophobicity for reclaimed sites was very similar to that of natural sites. Peat and LFH were found to be more hydrophobic than mineral soils. For peat, no clear relationship between soil water repellency and moisture content was evident but water repellency decreased with increasing decomposition level. Most of soils and tailing sands showed hydrophobicity at low water content and had a critical water content range from 0% to 3%. At higher water content (>3%), the tested materials became hydrophilic, but the contact angle decreased sharply with the increase in soil water content. However, all materials showed subcritical water repellency. To prevent materials from becoming hydrophobic, maintaining their water content above 4% in stockpile is necessary.