milltown dam removal
DESCRIPTION
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 - PowerPoint PPT PresentationTRANSCRIPT
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Milltown Dam Removal
Patrick McCormick
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Timeline
1907 Milltown Dam Constructed1908 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
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Timeline (con’t)1983 Milltown Reservoir declared
superfund site1996 ice flows threaten to destroy dam,
pool level is lowered, allowing scouring of contaminated sediments to take place
1998/99 Bull Trout Listed under ESA1999 EPA recommends dam removal
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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
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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
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Solutions Considered
Do NothingDam ModificationDam Modification and Partial Sediment
RemovalDam Breaching, Full Sediment Removal
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Do Nothing
Problem will continue to persistCheap
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Dam Modification
Modify the dam so it is safer, better able to control water release and allow fish passage
Could decrease toxic release eventsCostly in the futureWould not address groundwater
contamination
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Dam Modification and Partial Sediment RemovalDredge sediments where scouring is
likely to occur, modify damWould reduce downstream chemical
release eventsMay improve groundwaterNot long term fixWould be costly to maintain
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Dam and Sediment Removal
Remove Dam and sediments, reconstruct and vegetate channels
Would allow fish passageWould remove pollution sourceNo chance of catastrophic dam failure Would remove reservoir, important for
recreation, land value etc.Where to dump contaminated waste?
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Dam Removal 101
Draw down reservoirRemove contaminated sedimentsBuild coffer damRemove coffer damLet the river do its thinghttp://www.youtube.com/watch?
v=ISLInzprz3M&feature=related
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SourcesUS EPA Milltown Reservoir
Sediments Operable 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