Water Quality District
Milltown Dam: Background
Milltown dam and reservoir were located in
was built in 1906-7. A large flood in 1908 filled the reservoir with
sediments containing wastes from upstream mining operations in
The reservoir held about 6.6 million cubic yards of sediments, about 3 million yards of which were heavily contaminated with metals, including 2,100 tons of arsenic, 13,100 tons of copper, 19,000 tons of zinc, 143,900 tons of iron, and 9,200 tons of manganese. The depth of contaminated sediments ranged from 1 to more than 25 feet. Water depth in the reservoir averaged about four to eight feet.
dam's powerhouse was removed in March 2008, and spillway removal was
completed in March 2009. Contaminated sediment removal and shipment by
rail was complete in September 2009. Additional sediment removal for
restoration of the site was done and will be completed in 2010.
River channel construction and restoration began in 2009 and will
continue through 2011. The