Torch Lake: Enhanced Recovery

• 1868 first stamp mill opened on Torch Lake;• 1/3 of lake filled in with stamp sands;• 1968 last stamp mill on Torch Lake closed;• 1972 27,000 gal of leaching liquor spilled in lake;• 1973 fish with tumors found in lake;• 1983 fish advisory posted;• 1983 IJC lists Torch Lake as Area of Concern;• 1986 Torch Lake becomes Superfund site;

• 1992 EPA completes assessment and formulates remediation plan;• 1997 remediation performed in watershed (Scales Creek);• 1997 Public Action Committee formed;• 1998 fish spawning reef constructed;• 1999-2003 stamp sands on shore covered with top soil;• 2004 remediated shore areas delisted from EPA Superfund list

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Dissolved Cu in Torch Lake

Areal picture of lakewith bathymetric contoursoverlain

Post-miningsediments

Mining-periodsediments

X-rays of Torch Lake sediment coresshowing varves (layers) in stamp sands

Post-mining sediments

Stamp sands

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PortageLake

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Note the high water contentand lack of cohesion in theTorch Lake sediments.

Water withsuspended clay

Layer of stampsand on top of“recovered” sediment

Brown, post-miningsediments

Stamp sandsunderneath recentsediments

Sediment core from Torch Lakewith mine residues overlaying“fresh” sediments.

Core 8, 13m

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Stamp sands

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CanadianInterim SedimentQuality Guideline

Cessation ofmining

Current Lake Status

• Sediments are accumulating very slowly (~2 mm/yr)

• Copper concentrations remain ~ 2 orders of magnitude above recommended concentrations and 1 order of magnitude above known toxic effects level;

• Some evidence exists of resuspension and mixing of stamp sands into “fresh” sediments.

Useful Web Sites

http://www.epa.gov/glnpo/aoc/trchlke.html - EPA's web page on AOC, Superfund activitieshttp://www.torchlake.org/index.html - Public Advisory Counsel (PAC) web page http://www.ijc.org/rel/boards/annex2/tables/torchlak.html - IJC web information on Torch Lakehttp://www.epa.gov/glnpo/sediment/realizing2/RR2report.PDF - an

EPA web page on remediation of sites with contaminated sediments