One of the big mysteries in many western coal strip mining regions is how long the land will take to recover. According to the Bureau of Land Management’s 2003 Environmental Impact Statement for a South Powder River Basin coal lease covering expansions of the North Antelope/Rochelle Complex, Black Thunder Mine, Antelope Mine, and North Rochelle Mine:
Following reclamation, the average surface elevation would be lower due to removal of the coal. The reclaimed land surface would approximate premining contours and the basic drainage network would be retained, but the reclaimed surface would contain fewer, gentler topographic features. This could contribute to reduced habitat diversity and wildlife carrying capacity on the LBA (Lease by Application) tracts after mining and reclamation is (sic) completed….
Consequences to soil resources from mining each LBA tract that is leased would include changes in the physical, biological and chemical properties. Following reclamation, the soils would be unlike premining soils in texture, structure, color, accumulation of clays, organic matter, microbial populations, and chemical composition. The replaced topsoil would be much more uniform in type, thickness, and texture.
BLM takes the position that reclaimed land in this condition will immediately resume its previous functions without impairment. On the other hand, BLM acknowledges, it may take up to a century for sagebrush vegetation to return to pre-mining density, and large game wildlife habitat (think deer and antelope playing…) and carrying capacity “may be reduced due to flatter topography, less diverse vegetative cover, and reduction in sagebrush density.”
The table below, from the same 2003 EIS, shows anticipated elevation change after reclamation at several new leased tracts in the Powder River Basin:
Little study has emerged of the effect on aquifers. The coal seams themselves often hold significant amounts of groundwater, as do some geologic layers displaced as overburden and replaced as one homogeneous mass. The EIS offers speculation about impacts, but no studies of the actual condition of groundwater restoration in reclaimed land or effects on adjacent land where agricultural activity continues:
Mining … would enlarge the area of lowered groundwater levels in the coal and overburden aquifers associated with the existing mining operations, as well as the area where the existing coal and overburden aquifers would be removed and replaced by mine backfill. At each mine, drawdown in the adjacent continuous coal aquifer would be expected to increase roughly in proportion to the increase in area affected by mining and would extend farther than drawdown in the discontinuous overburden aquifers. The data available indicate that hydraulic properties of the backfill would be comparable to the premining overburden and coal aquifers. TDS (Total Dissolved Solids) concentration levels of groundwater in the backfill would initially be expected to be higher than in the premining overburden and coal aquifers, but would be expected to meet Wyoming Class III standards for use as stock water.