Acid mine water and increased stream siltation are both attributable to Pennsylvania's coal mining and are significant polluters of their water resources. Coal mining affects Wyoming's waters minimally because there are no acid water and very little siltation of permanent streams. In Wyoming coal mining can improve groundwater recharge and store much needed water.

Pennsylvania's coal-mined land is adversely affected by (1) subsidence; (2) total disturbed, surface-mined acreage (350,000 acres) and its rate of increase (12,000 acres in 1971 for 27 million tons of coal); and (3) slides on hillsides. Wyoming's sparse population makes subsidence effects minimal. Disturbed surface land effects are minimized by the (1) small total acreage (3,936 acres) and small annual increase (averages 170 acres for 8 million tons); (2) low-relief, flat, basinal rangelands mined; (3) remoteness from population centers; and (4) similarity of mine spoils with some natural landforms.

Wind-blown dust and fumes from burning culm banks and mine fires are accentuated in Pennsylvania because of their closer proximity to populated areas.

Although at least 80% of the disturbed surface acreage in Pennsylvania is recreational woodland, most disturbed acreage is remote, sparsely vegetated rangeland in Wyoming. Although vegetation in both states can be reestablished by planting or more slowly by natural revegetation, toxicity of mine wastes in Pennsylvania commonly retards its reestablishment and kills vegetation adjacent to the mine as well.

In Wyoming, the adverse effects of coal mining other than subjective, esthetic criticisms of temporary surface land disturbances are less damaging than in Pennsylvania.

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