Pit Lake Research

Focus

Research into the characteristics of various pit lakes

Potential

Ensure the oil sands industry has the best research possible for pit lake reclamation plans in the future

Introduction

When an oil sands mining operation reaches the end of its life, the operator is required to fully reclaim the land to its equivalent use. Before an operator is given approval to build their mining operation, they must have government approval for their site reclamation plan. All closure landscapes are designed to include pit lakes. These closure features can be used as a method for treating process-affected water, sequestering Mature Fine Tailings (MFT) as they settle and as a hydrologically and ecologically sustainable landscape component. Given their importance, the Alberta government requires that the oil sands industry undertake additional research on pit lakes.

COSIA has projects underway focused on building a greater body of scientific knowledge on pit lakes as part of oil sands reclamation.

The first commercial scale demonstration of the technology is Syncrude’s Base Mine Lake, which was commissioned at the end of 2012 and is currently being monitored and studied. Findings will be shared with all interested COSIA companies and will inform the future work of the Demonstration Pit Lakes Project.

The Demonstration Pit Lakes Project envisions a world-class demonstration scale research facility on a mine site in northern Alberta, studying over a dozen demonstration lakes and ponds of various sizes – and depths – with different contents, vegetation treatments and drainage approaches.

Technology and Innovation

The Demonstration Pit Lakes Project is currently undertaking feasibility studies to assess how best to address the diversity of characteristics that require research across the breadth of proposed pit lakes, including various pit lake/ pond configurations (depths, size and widths), combinations of materials used (tailings deposits, seepage, cap water and reclamation runoff), and will test the hydrologic uniqueness of each planned pit lake.

Coal and metal mines have reclaimed mined out pits and transformed them into lakes for decades, many of which now support active fisheries. Examples of mine pit lake reclamations include COSIA member, Teck’s Sphinx Lake at their Cardinal River steelmaking coal operations and the Heustis Pit Lake and Trojan Tailings Pond located at their Highland Valley Copper operations.

Sphinx Lake at Teck’s Cardinal River operations near Hinton, AB

Sphinx Lake at Teck’s Cardinal River operations near Hinton, AB

Fishing on Trojan Pond at Teck’s Highland Valley Copper operations near Kamloops, B.C.

Fishing on Trojan Pond at Teck’s Highland Valley Copper operations near Kamloops, B.C.

In addition to a number of other differences in comparison with metal mine pit lakes, oil sands pit lakes must take into account parameters that affect biodegradation of materials such as naphthenic acids, including water temperature, salinity and the amount of oxygen available for microbial activity.

Learn more about history of pit lakes in mining

Once through the feasibility stage, which addresses the necessary characteristics of the various pits and the nature of the research facilities, an assessment will be made on next steps of the project. If approved, after planning, peer review and engineering, phase one of the project could move to construction with potential operation by 2017.

An artist’s rendering of the planned Demonstration Pit Lake facility

An artist’s rendering of the planned Demonstration Pit Lake facility

At this early stage, the intended facility and research would consist of a series of model calibrations, predictions and validations in concert with tightly controlled filling management and hydrologic and water quality monitoring. The following tasks are proposed to accomplish the objectives of this study:

  • Design the physical dimensions of the test pit lakes. This will involve determining appropriate dimensions for the pit lakes.
  • Determine appropriate filling conditions for the lakes. Previous modelling (CEMA 2007) has shown that the filling conditions can have a dramatic effect on the water quality of pit lakes. Some of the filling parameters that should be examined include:
    • total dissolved solids in inflow during and after filling;
    • proportion of process-affected waters in inflows;
    • duration of filling period; and
    • residence time of the pit lake.
  • Monitor water quality and ecosystem dynamics in the lakes. The objectives of the proposed water quality monitoring of the test pit lakes are to determine:
    • the water quality of the inputs to the pit lake;
    • the in-lake water quality; and
    • the driving forces behind the lake hydrodynamics
  • Calibrate and validate hydrodynamic and water quality models. While the water quality modelling may show that the pit lake effectively treats reclamation waters, a fully calibrated model(s) will be necessary for extrapolating the results to larger, planned pit lakes.

See our plans for the Demonstration Pit Lakes facility

While the Demonstration Pit Lakes Project is still in its planning stages, the Syncrude Base Mine Lake is an active COSIA Joint Industry Project (JIP). The data gathered from studying Syncrude’s Base Mine Lake will create the basis for future studies undertaken through the Demonstration Pit Lake Project. The Demonstration Pit Lake Project will be complimentary to Syncrude’s Base Mine Lake program and will help address regulatory and knowledge gaps in the research currently under way.

Base Mine Lake is Syncrude’s commercial scale demonstration of pit lake technology. It was one of the company’s original mine pits – hence the name “Base Mine” lake. After the mining operation finished in the area in 1995, Syncrude started the process of placing the fluid fine tailings (FFT) – which are the fine clay and silt particles suspended in the water left over from the extraction process – at the bottom of the mined out pit. When placement was complete in 2012, there was about 45 metres of this material at the bottom of Base Mine Lake, as well as approximately five metres of process-affected water on top of the FFT. In 2013, Syncrude added additional fresh water to bring the level to the final designed elevation. The shallow water zones along the shoreline can now develop vegetation and biological communities. The depth of the water will increase as the clays at the bottom of the lake dewater and settle. The Base Mine Lake is designed to hold water long enough to remediate constituents in the water. Fresh water was sourced from the nearby Beaver Creek Reservoir and the Mildred Lake Reservoir, bringing nutrients and seeds which will help spur the growth of aquatic vegetation. Water will also flow out to a recycle water pond where it will be reused in the extraction process, in order to keep the surface elevation approximately constant.

Learn about Base Mine Lake

Extensive monitoring of Base Mine Lake, supported by more in-depth research and computer modeling, will help researchers better understand the processes through which the lake undergoes natural biological development. The data and knowledge gained through the monitoring program will be shared with government, academia and peer industry partners.

Environmental Benefits

The outcome of this demonstration pit lake work will provide operators with invaluable information on the design and operating parameters for their intended pit lakes. This includes calibrated and validated models that could be applied to a range of design and operational strategies.

Collaboration

COSIA’s approach to coordinated pit lake research is alleviating the need for operators to individually carry out extensive research programs. This collaborative research approach is saving time, as well as tens of millions of dollars. It will also help ensure that all operators have access to a broader base of knowledge around future pit lakes.

Syncrude is the lead operator of the Base Mine Lake Project. The project was contributed by Syncrude to the Tailings Environmental Priority Area (EPA). The work being undertaken in the Base Mine Lake and Demonstration Pit Lake Projects cross over three COSIA EPAs, with collaboration and contribution across the Tailings, Water and Land EPAs.

The Demonstration Pit Lakes Project is a JIP within the Water EPA which includes all seven of COSIA’s mining operators; Canadian Natural Resources Ltd., Imperial Oil, Shell Canada, Suncor, Syncrude, Teck and Total E&P Canada.