Torch Lake: Enhanced Recovery. 1868 first stamp mill opened on Torch Lake; 1/3 of lake filled in...

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

TorchLake

PortageLake

LakeSuperior

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