Authors
Year of Publication: 1974
Abstract:
Extraction of bitumen from the Alberta Oil Sands by surface mining will have a major impact on the hydrology of the areas immediately adjacent to each mine, and an impact on any drainage system receiving discharge from the mining or processing areas. Conversely, the hydrology will have a major impact on the mining operations. The exact nature of the impacts is difficult to evaluate, because: (a) both surface and subsurface hydrologic systems of the lower Athabasca River basin are poorly known, (b) the exact nature, amounts and ultimate fate of effluent and tailings materials are uncertain, (c) the degree of utilization of the waters within each basin and the possible physical changes to each basin ate essentially unknown, and (d) the nature and stability of the post-mining landscape, including particularly the success of reclamation and revegetation is open to speculation. In fact, at present we cannot predict even the simpler natural hydrologic characteristics of the river, nor do we have any real idea of the effect of the effluents produced by the oil sands plants. In this context, we generally conclude that the main initial emphasis of hydrologic studies should be on gathering sufficient information that the questions implied in items (a), (b) and (c) can be answered, and hence item (d) appraised. Sufficient data are needed to simulate surface runoff through the mining areas and to simulate groundwater flow systems in the mining areas; background data are needed on the physical and chemical characteristics of rivers and streams to determine present status, and so that pollution loads and other changes can be monitored. It is necessary to know, among other things: flood flows, to decide on the needs for and designs of stream diversions; the low-flow characteristics streams, for pollution control; and the severity of ice runs, again for flood information and diversion designs. To obtain this information, a general two-phase approach is needed: (1) an inventory of the hydrologic resources in the drainage basins likely to be affected by mining in the near future, and also in the Peace-Athabasca delta, and (2) a detailed examination of existing operations, to study water use and water wastes, including drainage of mining areas, tailings ponds, etc. To achieve this, specific study topics are set out below (in outline only, due to time constraints). These research needs should be formulated more specifically as projects, including scope, method, precision and timing before they are allocated and funded. In this respect, to help ensure that the desired results will be obtained and to obtain some measure of continuity, task force members consider that their respective agencies should have the opportunity of contributing more specifically to project formulation. Beyond this, hydrologic research needs will become apparent from the results of the first-phase investigations and the detailed nature of the mining developments. Definition of these needs is thus a continuing process; this report should not be considered the definitive and final document, but rather the initiation of a spectrum of projects. It was particularly noted, however, that time and again discussion ultimately and inevitably led back to one key issue – the nature and disposition of the tailings and plant effluents. These will determine the size of development impact on the hydrologic system – either directly, or indirectly through the degree of success of reclamation, which is intimately dependent on the nature of the solids and liquids left in the mined-out regions. The research needs are set out in two groups – (1) describing existing hydrologic resources and (2) development impact studies. Within these two groups listing is in descending order of priority.
