Page 800 - The Toxicology of Fishes

780 The Toxicology of Fishes

115° 114° 113° 112°

Clark
Fork Blackfoot River
47°
Milltown
Dam
Turah
River
Flint Creek Deer Lodge
Rock
Montana Creek

Idaho Warm Springs Creek Warm Springs Ponds
Silver Bow Creek
46°
Butte

0 20 mi
0 30 km

FIGURE 19.1 Watershed of the Clark Fork River in Montana to the confluence of the Flathead River (not shown). The
Upper Clark Fork, upstream of Milltown Reservoir, is the subject of this chapter.

History of the Clark Fork Mining and Smelting Complex
In 1805, Meriwether Lewis and William Clark began exploration of what is now Montana. They described
the basin of the Clark Fork of the Columbia River as “a unique landscape of primitive beauty” filled
with vast resources (Moore and Luoma, 1990). Extraction of these resources began in 1864, with placer
mining for gold. By 1896, over 4500 tonnes of copper ore per day was being mined and smelted near
Butte in the headwaters of the Clark Fork (Figure 19.1). At the turn of the century, one of the world’s
largest smelting plants was constructed in Anaconda, 40 km west of the mining operations. In 1955,
underground mining of high-grade ores in Butte was superceded by large-scale open-pit mining. Under-
ground mining ceased in 1976. Depressed copper prices forced closure of the smelter in 1980, and
mining in the largest open pit slowed in 1983. Mining has resumed in recent years in adjacent pits, along
with limited underground operations. When the smelter at Anaconda stopped production, over 1 billion
tonnes of ore and waste rock had been mined from the district. The Butte district was touted as the
“richest hill on Earth” in its prime. The mining and smelting operations that produced this vast wealth
left behind deposits of waste covering an area one fifth the size of Rhode Island. The waste complex
comprises the largest Superfund hazardous waste site in the United States (Moore and Luoma, 1990).
The adverse environmental impacts found in the Clark Fork basin are typical of the legacy of historic
large-scale mining and smelting operations that occur all over the world. Large-scale mining creates
visually obvious impacts on surrounding landscapes and watersheds. Most macrofaunal life in a stream
can be literally exterminated over relatively small extremely contaminated areas, but less visible effects
are more common and more widespread. Evaluating the ecological effects of mine wastes over the
broader area, especially, is complicated. It can also be contentious when the stakes are high. In this
chapter, we address factors that influence the risks from mine wastes, emphasizing the effects of metal
contaminants.