Soil Stockpile Density Investigation

It is common industry practice to design soil stockpiles using an estimated bulking factor of 15-20% as the common assumption is that soil volume increases from in-situ density once it is salvaged and placed in a stockpile. Starting in 2011, Imperial Oil identified discrepancies between anticipated volumes and real volumes of soil volumes, leading them to conduct a Reclamation Material Stockpile density investigation at the South Reclamation Material Stockpile on the Kearl Oil Sands lease. The resulting report informs subsequent stockpile design and to improve the ability to audit reclamation material salvage programs.

This investigation challenges the common assumption that stockpiled soils have lower densities than in-situ soils, showing instead that surface soil and subsoil stockpiles may actually be more compacted, requiring a compression factor rather than a swell factor in volume estimates. This unexpected increase in density may partly explain shortfalls in anticipated soil salvage volumes, with implications for material balance, stockpile design, and reclamation planning. However, other contributing factors—such as discrepancies in actual versus planned salvage depths, assumptions about uniform density in stockpiles, and limitations in survey-based volume estimates—may also affect volume calculations. To reduce project risk, it’s important to consistently track reclamation materials and improve understanding of all variables influencing soil volume estimates. Note: The values being reported are specific to the surface soil and subsoil stockpiles at the South Reclamation Material Stockpile on the Kearl Oil Sands Lease and may not be fully applicable to stockpiles of the same material types at other locations.