A Case Study of Coal Resource Evaluation in the Canadian Rockies Using Digital Terrain Models

The purpose of this study was to evaluate the large-scale structure, and hence available reserves, of the Lower Cretaceous Luscar Formation near Mountain Park, in the Foothills of Alberta. Coal resource evaluation clearly requires information on the mineable tonnages, as well as the grade, of the coal strata. In open pit mining, the volume of coal economically extracted from a seam is directly related to the amount of overburden that must be removed in order to expose the coal. This may very conveniently be expressed as an "overburden ratio" map, a contour map of the ratio of the overburden thickness divided by the coal seam thickness at the same location. While the cutoff value for economic recovery varies due to many factors, it is relatively uncommon for coal with a ratio of greater than 10 to be economically mineable. The overburden ratio map may thus be of value in coal reserve estimation. The construction of an overburden ratio map requires three components: a topographic model, a model of the top of the coal seam, and a model of its base. In this study the coal seam was fairly consistent in its thickness (about 30 feet) and therefore no model of the base of the coal seam was needed for thickness estimation. With this assumption, the problem became one of producing an overburden isopach, or thickness, map.