Soils

Soils have been sampled for metal content in three different areas at the Flambeau Mine site:

  • Within the mine’s industrial outlot
  • Outside the mine’s industrial outlot and west of Highway 27 (on the mine site proper)
  • Close to the mine’s industrial outlot, but east of Highway 27 (across the road from the mine site)

Summary Tables:

The Wisconsin Department of Natural Resources, in an April 2012 report entitled: Surface Water Quality Assessment of the Flambeau Mine Site (Stream C Report), cited contaminated soils as one of the causes of contaminated surface waters at the mine site. I would like to highlight a few of the report’s more compelling points for your convenience:

  • In 2010-2011, WDNR conducted surface water sampling at a number of locations on Flambeau Mine property, in Stream C, and in the Flambeau River. WDNR concluded that “Surface water copper and zinc concentrations at multiple sites in the Stream C watershed exceed the acute toxicity criteria on a frequent basis” (Stream C Report, page 20). Nearby streams unaffected by past copper mining did not show any copper toxicity.
  • WDNR found a strong correlation between elevated copper in soils impacted by historic mining activities and elevated copper in stormwater runoff: “The southeast corner of the mine site that drains to Stream C was not fully reclaimed and soil sampling by FMC in this area found multiple locations with elevated copper concentrations. Areas with high soil copper concentrations were generally correlated with high runoff water copper concentrations” (Stream C Report, page 3).
  • WDNR concluded that even though active mining ceased more than 15 years ago, the runoff from the site into the stream from the mine area still exhibits elevated copper concentrations. (Stream C Report, page 10). This includes all monitoring points along Stream C, from the nearby Highway 27 all the way to the mouth of the stream where it enters the Flambeau River. At the mouth of the stream, WDNR found that even though the copper is diluted by cleaner water from other sources, it still exceeds the copper standard in 90% of the samples collected (Stream C Report, page 10).
  • WDNR also found that the “Flambeau River below the mouth of Stream C . . . had a slightly higher mean copper concentration (2.7 ug/l) than the Flambeau River above the mouth of Stream C (1.5 ug/l copper)” (Stream C Report, page 10). On one of WDNR’s sampling dates (April 25, 2008), the copper concentration in the Flambeau River immediately below Stream C exceeded the copper Acute Toxicity Criterion whereas the Flambeau River above Stream C did not. This suggests that, even given the Flambeau River’s large volume and capacity for dilution, the copper input from Stream C was enough to cause an increase in copper concentration in the Flambeau River.
  • Although WDNR conducted a single toxicity analysis and found “no significant acute or chronic toxicity” on aquatic species, it provides a caveat that “only two to three organisms were tested using water from a single point in time. ATC’s are based on a broader and varied group of aquatic organisms and are meant to be protective of a full range of aquatic life throughout their life cycles” and that while “fish species are present in Stream C, it is unknown if they can successfully reproduce” (Stream C Report, pages 16-17). FMC has not conducted its own toxicity tests; thus it cannot be concluded that the waters of Stream C are toxic-free to all species.
  • According to WDNR, the likely causes of the high concentration of copper discharged from the Flambeau Mine site to Stream C include deposition of windblown dust from the mine’s high-sulfide waste rock stock-pile, runoff from a former vehicle washing station, runoff from mine site soil carried offsite by vehicles, and losses of fine particulate ore and ore oxidation products from rail cars on the site (Stream C Report, pp. 12-14).

To access the results of soil analyses conducted by FMC and various work plans implemented by the company in efforts to correct the problem with contaminated soils at the Flambeau Mine site, click on the following links:

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