ISSUES CONTRIBUTING TO THE DECISION TO REMOVETHE MILLTOWN DAM

摘要

The Milltown Dam, a timber crib gravity structure constructed in 1907 used forrnhydropower generation, is located about 2.5 miles upstream of Missoula, Montana at thernconfluence of the Blackfoot and Clark Fork Rivers. A 1908 flood filled the reservoirrnwith sediments contaminated with metals from upstream mining and smelting operations.rnArsenic contamination in area drinking water was discovered in 1981 by the MissoularnCity-County Health Department. The United States Environmental Protection Agencyrn(EPA) listed the area on the federal Superfund site list in 1983. In 2003 MontanarnGovernor Judy Martz, the United States Environmental Protection Agency (EPA) and thernMontana Department of Environmental Quality (DEQ) called for the removal ofrncontaminated sediments in the Milltown Reservoir and the removal of the Milltown Dam.rnFactors leading to the decision to remove the dam included:rn? A 1986 ice event scoured contaminated reservoir sediments and killed fish.rn? Bull trout in the river were listed under the federal Endangered Species Act.rn? The reservoir became populated with an invasive, predatory fish species.rn? Electric energy deregulation led to the sale of the dam to a new owner.rn? The dam became an unprofitable liability.rn? Missoula County proposed ambitious cleanup and restoration goals known asrnthe Two Rivers Restoration Project.rn? Strong public support developed for cleanup and dam removalrn? Dam safety evaluations caused concerns about leaving the dam andrncontaminated sediments in place.rn? EPA and DEQ determined that dam and sediment removal would restore thernpolluted aquifer, and prevent surface water and fisheries impacts from icescouring,rnfloods or dam failure.