A coal mining company in south-central Illinois desired to modify their NPDES permits. These modifications would affect the receiving waterways. At their request, Specialized Ecological Services performed comprehensive stream biotic inventories and correlated that information with individual species tolerances to the chemical constituents of concern. The biotic inventory included invertebrate, fish, amphibian, and reptile inhabitants, as well as mammalian and avian users of the receiving waterway. Analyses included comprehensive literature review, database searching, and computer modeling. The ultimate result was scientifically justifiable adjustments to recommended effluent limits for the protection of aquatic life.