Response to Liu et al Rebuttal to “Effect of sea

Authors: John Owolagba Shahid Azam

Publish Date: 2016/05/13

Volume: 75, Issue: 10, Pages: 891-

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Abstract

The research focused on developing a conceptual understanding of atmospheric evaporation for dewatering of surface deposits of tailings For this purpose a desiccation model was developed to couple material properties of treated oil sand fine tailings with climatic parameters using 30year monthly averages The climatic conditions of northern Alberta Fort McMurray allow that such a water escape occurs mainly during late summer through early fall During this time June–September the air temperature remains above zero 14 °C as reported in Fig 1b Owolagba and Azam 2015 thereby precluding ground freezing and ice lens formation in the deposited tailings Therefore the transient seepage model was based on an equation that used hydraulic conductivity and vapor conductivity only Further details of the governing relationships leading to the above equation can be found in Azam and Ito 2012The increase in degree of saturation during early winter September–December is attributed to the high overall precipitation during the preceding summer months Fig 1a Owolagba and Azam 2015 Whereas the average air temperature for these months was analyzed to be −7 °C Fig 1b Owolagba and Azam 2015 air temperature in September is shown to be generally above freezing and the subzero air temperature in October and December does not mean an abrupt ground freezing and ice lens formation in the tailings deposit Conversely the decrease in degree of saturation during late winter January–March may be attributed to ice lens formation albeit the preclusion of this phenomenon in the governing equation In this context it is important to note that the runoff closely matched the precipitation trend Fig 2 Owolagba and Azam 2015 because percolation within the deposit was negligible owing to the low saturated hydraulic conductivity 3 × 10−10 m/s of the materialFinally the cited work of Christensen et al 2013 is fundamentally different from the focus of this research These authors presented in situ measurements not longterm average values of snowmelt infiltration opposite of evaporation under various topsoil cover thicknesses different from oil sand fine tailings Furthermore the study area Fort Saskatchewan is about 400 km south of Fort McMurray where field monitoring was conducted over a period of about 1 year March 2011–April 2012 Therefore the authors feel that a comparison of their results with a shortrange data of only winter conditions for a different soil is not valid

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