Physical, chemical and mineralogical properties of mine spoil derived from the Wise Formation, Buchanan County, Virginia
Physical disintegration of the rocks is promoted by the closely spaced blast-hole grid used in the mining operation. Wet-dryfreeze-thaw forces are effective in causing disarticulation of the weakened rocks in 6 months or less. The silty spoils cause excessive dust, are crusted and support ponds. Application of organic amendments promotes infiltration. Some of the spoils contain enough salts to seriously retard growth of non-tolerant plant species. Exchangeable bases are overestimated, but the salts are a nutrient source. K is low, but adsorption isotherms indicate that, unlike the naturally occurring soils of the locality, there is no serious problem of K-fixation in the spoils. NaHCO₃ gives the most accurate measure of spoil P. A response to fertilization is likely. Adsorption isotherms suggest a problem with P-fixation by the goethite rocks.
There was no measurable pedogenic activity in the spoils after two years of weathering other than physical disintegration of rock fragments and weakly developed structure in some spoil surface layers. There was no evidence of leaching of salts during this period.
When regrading the spoils on the benches, maintenance of adequate drainage is essential to prevent nutrient depletion, Fe-generated toxicity and acidity and toxic accumulations of salts. A mixture of 70% sandstone, 20% siltstone and 10% shale should yield a well-drained sandy loam spoil upon weathering. The ferruginous and silty rocks should be regraded well below the surface.