THE STREAM ENVIRONMENT 183 



TABLE 2 



CRITERIA FOR ACID MINE DRAINAGE 

 COMPARED WITH WATER QUALITY OF TROUT CREEK 



*A11 values except pH are in milligrams per liter. 

 fHerricks and Cairns (1974). 



tSingle values are annual means; ranges at sites above and below mine 

 spoils are in parentheses. 



Much of the stress on macro invertebrates associated with acid 

 mine drainage in eastern streams can be attributed to low pH, per se, 

 although ferric hydroxide precipitation and heavy metals also have 

 adverse effects. Napier and Hummon (1976) found that mayflies did 

 not occur in streams which had otherwise recovered from acid mine 

 drainage but which maintained low pH values. They concluded that 

 low pH was primarily responsible for the elimination of mayflies. 



From the results of a survey of Colorado sites receiving drainage 

 from mines, Wentz (1974) tabulated the percentage of sample sites 

 where concentrations of 15 heavy metals and pH exceeded stream 

 criteria for fish and other aquatic organisms (criteria were drawn 

 from various cited sources). Only one station associated with coal 

 mining, the drain from an adit of an abandoned mine, exceeded these 

 criteria and only for iron and manganese. Wentz found no macro- 

 invertebrates in the drain, the bottom of which had a bright-orange 

 coating. 



Concentrations of most heavy metals are low in Trout Creek and 

 in western energy-development areas generally (Skogerboe, 1976). 

 The solubilities of many heavy metals associated with acid produc- 

 tion processes in eastern mining areas are limited by hydroxide or 

 carbonate precipitation processes. An examination of the solubility 

 equilibria of metals showed that most are least soluble from pH 7.0 

 to 8.0, the range within which over 85% of all observed pH values in 

 western energy areas lie (Skogerboe, 1976). The well-buffered nature 



