Surface-mine Rehabilitation in the American West

Extract

The rehabilitation plan for a surface-mined area should be in detail and prepared as part of the mining plan. The area to be disturbed should be identified as to its vegetation-types and potential for rapid and complete restoration. The rehabilitation plan should show, by means of topographic maps or three-dimensional maps prepared before the advent of mining, the general lay of the terrain and the reconfiguration after mining. Such maps will indicate how soil-slope regulations are being met, how aesthetic acceptability can be evaluated, and how ecological response-units for revegetation can be characterized.

In order to prepare a detailed revegetation plan before mining, the following maps and information are needed: (1) a topographic map, (2) a soil-series map, (3) a vegetation-cover map, and details concerning (4) the wildlife that inhabits the area, (5) the prevailing climatic conditions such as wind and the amount and form of precipitation, and (6) the character of each geological stratum that lies above the coal-seams or whatever is to be mined—including its structure, depth, and possible toxicity.

The detailed revegetation plan should identify where the topsoil or other plant-growth medium will be obtained, so that it can be stockpiled to be redistributed over the spoil material. Fine sandy loams, silty clay soils, and soils that are high in toxic elements or low in organic matter, should be avoided. It is recommended that topsoil material be redistributed over the spoil material to a minimum depth of 18 to 24 inches (457 to 610 mm), in order to furnish adequate depth for root concentration and for storage of reserve moisture following the spring snow-melt. The seedbed should be firm and free from competitive weeds. On harsh sites, water-holding basins or contour trenches should be constructed.

The method of seeding should include either drilling or broadcasting the seed, with due provisions for seed coverage by soil, and the addition of fertilizers and mulches where appropriate. The selection of species should include both native and introduced species that are adapted to the site. A wide diversity of life-forms and species should be included, to ensure stabilization of the area and furnish the wildlife habitat requirements. The season of seeding should be the period prior to the incidence of the most dependable precipitation in the area. The quantities of different seeds in the mixture and the overall amount employed will vary from site to site and with the method of planting. Generally speaking, poorer sites require more seed than favourable sites, and broadcasting requires about twice as much seed as does drilling.

Direct on-site costs for reclamation may vary from $250 to as much as $2,750 per acre (0.405 ha), depending upon saving and distributing the topsoil, shaping the overburden, seed-bed preparation, planting, fertilization, drainage control, mulching, and irrigation.