![]() ![]() The Milltown Dam’s history illustrates a collision of two conflicting environmental concepts: the use of dam removals as a tool for river restoration and the release of significant quantities of contaminated sediment in rivers, especially the archive of legacy sediment in dams and reservoirs. This ultimately led to a multiyear remediation plan involving a phased reservoir drawdown, mechanical removal of 2 million cubic meters of contaminated sediment at a cost of $120 million, and a planned breaching and removal of the dam in 2008. An emergency drawdown of the reservoir, intended to settle the ice jam on the riverbed, released a large quantity of contaminated sediment into the river downstream from the dam, killing most of the river’s fish. Arsenic levels in nearby groundwater compelled the Environmental Protection Agency to designate the reservoir a Superfund site.ĭuring an unusually wet winter in 1996, a large ice jam flowed downstream and threatened to breach the dam. By the 1980s, the reservoir stored 5 million cubic meters of contaminated sediment. ![]() Within months of the dam’s construction, a 500-year flood deposited tons of metal-contaminated sediment behind the dam. In 1908, copper-mining tycoon William Clark built the Milltown Dam on the Clark Fork River in southwestern Montana to supply hydroelectric power to his sawmills. Take the hundred-year saga of the Milltown Dam, for example. These projects can also unleash new problems, however, if contaminated sediments are released downstream. Dam removal and river restoration projects can restore river health and clean water, revitalize fish and wildlife populations, provide public recreation opportunities, and boost local economies.
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