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

1200 1000 800 Cu Cl 600 400 200 0 1965 1970 1975 1980 1985

Year

1990 1995 2000 2005

Dissolved Cu in Torch Lake

Areal picture of lake with bathymetric contours overlain

Post-mining sediments Mining-period sediments

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

Portage Lake Lake Superior Torch Lake Post-mining sediments Stamp sands Note the high water content and lack of cohesion in the Torch Lake sediments.

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

Brown, post-mining sediments Water with suspended clay Layer of stamp sand on top of “recovered” sediment Stamp sands underneath recent sediments

Canadian Interim Sediment Quality Guideline 0 500 0

Core 8, 13m Cu Conc. (

m

g/g)

1000 1500 10 2000 Stamp sands 2500 Cessation of mining 20 30 40 50 60 Probable effects level

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 activities http://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 Lake http://www.epa.gov/glnpo/sediment/realizing2/RR2report.PDF

- an EPA web page on remediation of sites with contaminated sediments