Reclamation of Abandoned Mine Spoils in British Columbia, 1977-78
Paper 1978 - 7
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The 1977-78 program consisted of two parts. The first part focused on the assessement of vegetation growth and soil forming processes taking place on abandoned mine spoils. The mines selected for this study were Coal Creek, Emerald, H.B., Hedley and Velvet. The first, Coal Creek, is an abandoned coal mine; the remainder are metal mines. In addition monitoring studies continued at Endako, Granby and Lornex. This was conducted to help verify some of the earlier findings.
The second phase of the program was a continuation of the weathering, microbiological oxidation and greenhouse studies initiated in 1976-77, as well as a study concerning P-fixation capacity of spoil materials.
The field studies on soil-forming processes and their effects demonstrated that organic matter (measured as organic-carbon) is accumulating in the surface layers of the mine spoil samples examined. Coal spoil seemed to respond most quickly to a build up of organic matter. This accumulation of organic matter helps build up the nutrient pool for sustaining a vegetative cover. Physical conditions for growth, particularly moisture availability were optimum at the Coal Creek location, but moisture stress was extreme on some of the metal mine spoils. Poor aeration, especially at Hedley is another growth limiting factor. Irrigation and/or fertilization and seeding in combination with deep ploughing would much improve the spoil as a growth medium.
In laboratory studies, a less obvious but still evident observation is that weathering has occurred in the samples examined, releasing nutrients. The beginning of the formation of clay minerals, notably vermiculite, supports this. In Coal Creek samples physical breakdown of the coarse faction is also occurring.
Phosphorus is the main limiting mineral nutrient in all spoil samples examined. An evaluation of the trace element content of spoil material and supported vegetation did not show any universal problem with toxicities. Low Cu:Mo ratios did occur. This could be a potential problem with ruminants feeding on the vegetation.
Microbiological studies discuss the ecology of iron and sulfur oxidizing bacteria in iron sulfide mine tailings and their fole in its oxidation. From the analysis completed it aopears that there is a relationship between kinds of organisms and the state of weathering of the tailings material. Increase in elemental sulfur content with a decrease in pH appears to be linked to microbial oxidation of iron sulfides.
Greenhouse studies concentrate on soil test evaluation, copper-molybdenum relationships and organic matter amendments concerning selected tailings materials. Comparison of soil tests on the various tailings are made and the best methods for each type are suggested. Cu:Mo ratios for selected tailings are found to be generally <2 which is considered potentially hazardous for ruminant consumption. Keeping N fertilizer rates at a moderate level decreases the concentration of Mo in plant tissue, with the result of raising the Cu :Mo ratio.
The effects on acid tailings of a variety of organic amendments show that short-term effects on plant growth are beneficial in all cases but that chicken manure decreases Fe and Cu concentrations in plant tissue. Sawdust was not found to be particularly effective.
Results of the P adsorption studies are only preliminary, for the method is only being developed. It was found, however, that the capacity of P-fixation (or adsorption) for a variety of spoil materials can be predicted over time. This allows more accurate fertilizer additions to be estimated so that excess P is not subject to leaching, and costs can be minimized.
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