Lean oil sand soil capping synthesis and risk assessment

2018 EPEA approval clauses received by CNRL require a risk assessment of elevated naturally-occurring petroleum hydrocarbon (NPHC) levels found in overburden and interburden on reclaimed landforms and covered by reclamation materials. The main overall objective of this project was to provide capping thickness and cover design guidance for overburden disposal structures to industry members. To this end, Paragon Soil and Environmental Consulting Inc compiled a suite of research information: (1) a literature review, (2) a conceptual site framework (CSF) that compiled risk elements from the literature review plus a two day workshop during which industry members, representatives from the Alberta Energy Regulator, and third-party experts collaborated to discuss lean oil sand (LOS) research and risk components, (3) a risk assessment matrix (RAM), also compiled from the workshop discussions, and (4) a report from a field program and analysis on tree growth on reclaimed sites containing elevated NPHCs.

Key Outcomes: (1) A literature review of the current state of knowledge of characteristics, environmental risk and reclamation performance related to NPHCs in oil sands mining reclamation; (2) A field study of mature tree growth on reclaimed overburden containing petroleum hydrocarbons found that growth rates (site indices) of trees were not correlated with petroleum hydrocarbon concentrations in the overburden and that site index values were in the range of growth of other oil sands reclamation substrates such as tailings sand and non-LOS overburden, as well as natural upland forest communities in the region; (3) A Risk Assessment Matrix which identified potential risk events of reclaimed overburden landforms containing NPHCs and ranked the probability and severity of those events, which could be used as an immediate guide to selecting an appropriate soil cover design and identifying areas for future research and monitoring; (4) A Conceptual Site Framework that can be used as a guidance tool to assess and implement capping depth decisions for reclamation of NPHC-containing overburden landforms, as well as identifying gaps for future research and monitoring.