Suspended solids in an end pit lake: Potential mixing mechanisms

Abstract

The production of crude oil from the Canadian oil sands has generated tailings ponds that contain oil sands process-affected water and oil sands fluid fine tailings (FFT). One remediation strategy is to backfill a mined out pit with FFT and cap this with a mix of oil sands process-affected water and fresh water to form a lake, called an end pit lake. Here we discuss various mechanisms governing the vertical mixing of suspended solids in an end pit lake. Depending on the depth of the water cap, wind waves can cause mixing between the water cap and the FFT. Other potential mixing mechanisms include: convection due to salt-water exclusion during ice formation, penetrative convection due to surface cooling, gas emission from the FFT, and internal wave activity. Data collected at Syncrude Canada Limited’s Base Mine Lake in 2013 and 2014 are used to demonstrate the effects of some of these processes.