Monitoring an Experimental Soil Waste Near London, Ontario, Canada

Abstract

An experimental soil cover was constructed near London, Ontario and monitored for more than a year for percolation and water content data. The cover was a multi-layer system consisting of compacted till barrier soil placed between gravel layers, and a final topsoil cap in one half and a coarse stone cap in the other half. The lower gravel layer was intended to provide a capillary break that would minimize gravity driven drainage in the till, while the capillary barrier created at the upper gravel-till interface would reduce evaporative losses in the till during dry periods. The results showed that while the compacted till maintained a relatively high degree of saturation and low hydraulic conductivity under the coarse stone, it desiccated under the topsoil and resulted in high water percolation rates. The textural or grain size contrast between the relatively fine topsoil and the underlying gravel layer created a capillary break which, together with the relatively low hydraulic conductivity of the topsoil, prevented infiltrating waters from recharging the underlying till. Thus the till was not able to rebound to its pre-desiccation water content. The saturated hydraulic conductivity of the till under the topsoil was about 1 × 10⁻⁸ m/s after one year, compared to 2.0 × 10⁻¹⁰ m/s at construction.