In Northern Alberta, Canada, large volumes of low-grade ‘lean’ oil sand (LOS) overburden are translocated during the surface mining of oil sands and remain in future reclaimed landscapes. The objectives addressed in this paper are to (a) characterise the on-site petroleum hydrocarbon (PHC) content of LOS; (b) evaluate the effect of LOS temperature on rates of carbon dioxide (CO2) flux and PHC biodegradation and (c) evaluate the potential for PHC to leach from LOS into groundwater. The results show that LOS is predominantly composed of heavier F3 and F4 PHC fractions, the temperature appears to affect carbon dioxide fluxes and PHC degradation rates and it is unlikely that the presence of LOS in reclamation soils will release significant quantities of PHC into groundwater.