BACKGROUND

Highway construction between Tellico Plains, Tennessee, and Robbinsville, North Carolina, began in 1965. More than a decade later, in 1977, acid drainage from completed sections of the Tellico-Robbinsville Highway altered water quality and reduced the abundance of trout in the adjoining North River and Citico Creek watersheds (1). These watersheds li~ within the Tellico Wildlife Management Area, where streams have typically been soft water--slightly acidic drainages supporting an excellent sport fishery of stocked and native trout species. The headwaters of streams affected by Anakeesta leachates--McNabb Creek, Hemlock Creek, and Grassy Branch Creek--are adjacent to highway embankments. These streams exhibited depressed pH values, increased concentrations of sulfates, heavy (toxic) metals, and acidity. Highway embankments containing sulfide-rich pyritic units of the Anakeesta formation were believed to be the sources of acid drainage< l• ll·

Neutralization of acid leachates in receiving streams was begun in May 1978 and continued through January 1979. An interim mitigation measure of sodium hydroxide (NaOH) additions was used. A 20 percent solution of NaOH was gravity-metered into the headwaters of affected streams in an attempt to maintain a pH level of approximately 5. 8 at the mouths of these streams. Additional remedial actions taken to reduce leachate runoff included asphalt curbing, ditching, and surface drain installa-