milltown dam removal

Milltown Dam Removal

Patrick McCormick

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

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

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

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

Solutions Considered

Do NothingDam ModificationDam Modification and Partial Sediment

RemovalDam Breaching, Full Sediment Removal

Do Nothing

Problem will continue to persistCheap

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

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

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?

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

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