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Milltown Dam Removal

Milltown Dam Removal. Patrick McCormick. Timeline. 1907 Milltown Dam Constructed 1908 Flood Scours mine and smelting tailings, which are high in Ar and Cu sediments settle in Milltown Reservoir 1981 Wells in Milltown are found to be contaminated with Ar

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Milltown Dam Removal

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  1. Milltown Dam Removal Patrick McCormick

  2. Timeline • 1907 Milltown Dam Constructed • 1908 Flood Scours mine and smelting tailings, which are high in Ar and Cu sediments settle in Milltown Reservoir • 1981 Wells in Milltown are found to be contaminated with Ar • 1983 Milltown Reservoir sediments found to cause contamination

  3. Timeline (con’t) • 1983 Milltown Reservoir declared superfund site • 1996 ice flows threaten to destroy dam, pool level is lowered, allowing scouring of contaminated sediments to take place • 1998/99 Bull Trout Listed under ESA • 1999 EPA recommends dam removal

  4. Timeline (con’t) • 2000 Milltown Dam classified as high hazard potential • 2003 Proposed plan released to public including dam removal, dredging and moving of most contaminated sediments • 2006 Pond drawn down permanently, dredging begins • March 28, 2008 Coffer Dam Breached

  5. The Problem • 7 million cubic yards of toxic sediment from mining operations in Butte and Anaconda trapped • Old dam, in need of serious repair, possibility of catastrophic breach high • Scouring events lead to surface water contamination downstream, causing fish kills • Ar plume in groundwater contaminating 120 acres • Dam impeding fish passage and causing predation of ESA listed bull trout

  6. Solutions Considered • Do Nothing • Dam Modification • Dam Modification and Partial Sediment Removal • Dam Breaching, Full Sediment Removal

  7. Do Nothing • Problem will continue to persist • Cheap

  8. Dam Modification • Modify the dam so it is safer, better able to control water release and allow fish passage • Could decrease toxic release events • Costly in the future • Would not address groundwater contamination

  9. Dam Modification and Partial Sediment Removal • Dredge sediments where scouring is likely to occur, modify dam • Would reduce downstream chemical release events • May improve groundwater • Not long term fix • Would be costly to maintain

  10. Dam and Sediment Removal • Remove Dam and sediments, reconstruct and vegetate channels • Would allow fish passage • Would remove pollution source • No chance of catastrophic dam failure • Would remove reservoir, important for recreation, land value etc. • Where to dump contaminated waste?

  11. Dam Removal 101 • Draw down reservoir • Remove contaminated sediments • Build coffer dam • Remove coffer dam • Let the river do its thing • http://www.youtube.com/watch?v=ISLInzprz3M&feature=related

  12. Sources • US EPA Milltown Reservoir SedimentsOperable Unit Record of Decision December 2008 • Envirocon Final Technical Memorandum Milltown Reservoir Dry Removal Scour Evaluation May 2004 • Grossman Elizabeth Watershed: the Undamming of America Centerpoint New York NY 2002

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