Sediment Diagenesis Module for CE-QUAL-W2. Part 1: Conceptual Formulation Jerry A. Vandenberg & Shwet Prakash & Edward M. Buchak Received: 8 February 2013 /Accepted: 22 September 2014 # Springer International Publishing Switzerland 2014 Abstract This paper presents a conceptual framework for a sediment diagenesis model that was developed as an add-on module to the hydrodynamic and water quality model CE- QUAL-W2. The module was designed for oil sand pit lakes, but has been developed such that it is applicable to other waterbodies, particularly those with subaqueously placed mine waste or organic-rich sediments. The module includes important physical and chemical processes such as the follow- ing: tailing consolidation coupled with lake bed deepening and pore-water release, biogenic gas production (build-up and release of methane, hydrogen sulfide and ammonia), bubble release through the water column, unconsolidated sediment resuspension during bubble ebullition, dynamic oxygen con- sumption at the sediment-water interface and in the water column from bubbles, and salt rejection during ice formation. Keywords Athabasca oil sands . End pit lakes . Mature fine tailings . Methane . Diagenesis . Gas release . Bubbling . Bed consolidation . Oil sands 1 Introduction This paper presents a sediment diagenesis module that was written as an add-on to the hydrodynamic and water quality model CE-QUAL-W2 (Corps of Engineers, water QUALity model for Waterbodies of 2-dimensions). The module was originally developed for predicting the physical and chemical behavior of submerged tailings in pit lakes developed as closure waterbodies for the oil sand industry. Both the con- ceptual formulations presented herein, and numerical formu- lations presented in Prakash et al. [21] of the module, howev- er, were based on generic diagenesis processes that are appli- cable to other waterbodies, particularly lakes with submerged tailings or lakes that have sediments with high organic con- tent, whether natural or contaminated. The module can also predict greenhouse gas emissions from such systems. 1.1 Background The oil sands of Alberta, Canada, contain approximately 170 billion barrels of proven oil reserves. In the Athabasca Oil Sands Region, north of Fort McMurray, the highly viscous hydrocarbon resource, bitumen, is near the surface and suffi- ciently concentrated to be recovered using conventional sur- face mining and chemical extraction. Presently, six surface mining projects are operating in the Athabasca Oil Sands Region; other projects are at various stages of the regulatory approval process. Similar to most mining operations, oil sand mines include pit lakes in their closure and reclamation plans. Approximate- ly 35 pit lakes are proposed for the region (Fig. 1). About half of these will have permits that specify that Mature Fine Tailings (MFT) be placed in the pit before the pit is flooded with fresh water to create a pit lake. MFT is a mixture of fine clay materials that settle much more slowly than the coarser tailings [18] and therefore pose This is a two-part paper, along with Sediment Diagenesis Module for CE- QUAL-W2 Part 2: Numerical Formulation J. A. Vandenberg (*) Golder Associates, Ltd., 220-1755 Springfield Road, Kelowna, BC V1Y 5V5, Canada e-mail: jvandenberg@golder.com S. Prakash : E. M. Buchak 75 Valley Stream Parkway, Suite 200, Malvern, PA 19355-1406, USA S. Prakash e-mail: shwet.prakash@erm.com E. M. Buchak e-mail: edward.buchak@erm.com Environ Model Assess DOI 10.1007/s10666-014-9428-0