Controlling Toxic Pollutants

Control of toxic pollution requires: 1) preservation of standards that control pollution; 2) enforcement of those standards in permits and regulatory action; and 3) development of new water quality standards as required by modern science.
WaterLegacy’s work to control pollution has included:
  • Preserving of Minnesota’s wild rice sulfate standard in the face of litigation, legislation, and rulemaking to repeal or weaken the standard.
  • Requiring enforcement of Minnesota water quality standards for existing mines, including both taconite mines (sulfate, hardness, toxic metals) and peat mines (mercury).
  • Opposing toxic pollution from the proposed PolyMet copper-nickel mine, by challenging inadequate environmental review, water pollution permits, and dam safety and control of reactive waste seepage in the PolyMet permit to mine.
  • Explaining the science that links sulfate discharge to increased mercury methylation and the serious harm to health in Minnesota from methylmercury contamination of fish.
Acid mine drainage near the Boundary Waters Canoe Area in Minnesota. Photo from Friends of the BWCA.
As described below, WaterLegacy has partnered with citizen scientists to develop a scientific basis for control of specific conductance pollution. We also successfully advocated to preserve the Minnesota Health Department rule that sets limits for manganese to protect human health. Both of these pollutants can be discharged as a result of mining in Minnesota.

Specific Conductance Pollution

Specific conductance (or specific conductivity) describes the concentration of various salts in water that makes water conduct electricity more readily. It is easily measured in the field. Mining activities increase specific conductance, as does other industrial discharge.

EPA 2011 Conductivity Report

In 2011, the U.S. Environmental Protection Agency (EPA) researched damaged streams of coal mining areas in Appalachia and determined that elevated conductivity led to impairment of water for aquatic life. Elevated conductivity kills sensitive aquatic insects (referred to as benthic macroinvertebrates in the research) and reduces biodiversity of fish in affected streams and lakes. In 2011, the EPA prepared a draft field report that set a benchmark to protect aquatic life limiting conductivity to 300 µS/cm (microSiemens per centimeter).

Minnesota sets no limit on conductivity to protect fish or other aquatic life. The state’s only water quality standard for conductivity is based on protecting the use of water for agricultural irrigation. The limit set by this specific conductance rule is equivalent to 1,000 µS/cm.

Johnson Report Recommending Conductivity Limits in Northeastern Minnesota

After the EPA’s field-based report was released, two retired scientists, chemist Bruce Johnson and Maureen Johnson, both of whom had worked for Minnesota regulatory agencies, collaborated with WaterLegacy to analyze specific conductance in Minnesota. The Johnsons applied the EPA’s methodology in Appalachian streams to data in northeastern Minnesota ecoregions. They analyzed data from the Minnesota copper-nickel studies done in the 1970’s as well as recent data on aquatic insects and pollution levels in both undisturbed waters and waters affected by mining.

After detailed review of data on pollution and aquatic insect life, in 2015 the Johnsons’ Report concluded:

In the Minnesota ecoregions discussed in this report, discharge of specific conductance above the level of 300 µS/cm, established as guidance for Appalachian streams is highly likely to result in extirpation of 5% or more of invertebrate genera [of aquatic insects]. Such discharge should be prohibited under Minnesota narrative standards preventing degradation and toxic pollution.

EPA Confirmation of Johnson Report Conclusions

EPA lead scientist, Susan Cormier, Ph.D., undertook a review of the Johnson Report and confirmed its conclusions using additional independent data. EPA concluded in 2016:
Independent data sets from different decades confirm Johnson and Johnson’s conclusion . .  a benchmark value for SC [specific conductance] in Ecoregion 50 is not expected to be greater than the benchmark for central Appalachia, i.e. 300 µS/cm.
After reviewing various data sets, the EPA calculated its own provisional hazardous concentration for specific conductance. Based on the need to protect extirpation (killing) of sensitive species of aquatic life, EPA recommended a water quality standard of 320 µS/cm for northeastern Minnesota ecoregions.

EPA scientists also published in peer-reviewed journals the step-by-step methodology that should be used to protect aquatic life from excessive specific conductance pollution.

Has conductivity science been used in Minnesota?


WaterLegacy has repeatedly advocated that the Minnesota Pollution Control Agency (MPCA) protect fish and aquatic insects from specific conductance caused by mining discharge when granting water pollution permits. Under the Clean Water Act, since Minnesota has a narrative standard preventing toxicity to aquatic life, water pollution permits for surface waters should limit specific conductivity when there is a reasonable potential that conductivity would be toxic to aquatic life. The scientific research indicates that conductivity over 300 µS/cm is toxic in northeastern Minnesota ecoregions. Following the science, permits in this region should include an enforceable limit to prevent conductivity over 300 µS/cm.

In fact, mining discharge often exceeds even the lax 1,000 µS/cm limit in existing Minnesota’s irrigation-based rule. As a result, the abundance and diversity of aquatic life is impaired in many waters downstream of mines. One of the reasons WaterLegacy and our allies opposed and overturned the Mesabi Nugget variance was the excessive levels of specific conductance that the variance would have allowed.

Science-based Standards

WaterLegacy has repeatedly requested that the MPCA initiate rulemaking to set a water quality standard to protect aquatic life from specific conductance pollution. MPCA has not done so. The following comments are one of several appeals to MPCA to adopt a specific conductance water quality standard.  
Although MPCA has not taken action to adopt a specific conductance rule, the Fond du Lac Band of Lake Superior Chippewa initiated a process in 2018 to set a water quality standard limiting specific conductance pollution on its reservation. Following the science and based on its own reservation data, the Fond du Lac Band has proposed to limit conductance to 300 µS/cm to protect aquatic life.

Manganese Pollution

The Minnesota Health Department (MDH) adopts rules setting Health Risk Limits for the levels of contaminants in drinking water that are unsafe. Although the MDH does not have the authority to place these limits in permits, the MPCA is supposed to use MDH rules to set water pollution permit controls to protect human health.

Manganese occurs naturally in rock, and mining activities that excavate and pulverize rock and allow seepage through tailings or other wastes can increase levels of manganese in groundwater aquifers.

MDH rules currently limit manganese to 100 micrograms per liter (µg/L). This limit is based on scientific research showing that children and adults who drink water with high levels of manganese over time may have problems with memory, attention, and motor skills. Infants (babies under one year old) may develop learning and behavior problems if they drink water with too much manganese in it. 

Preventing Repeal of the Manganese Limit

In 2010, the MDH proposed to repeal its Health Risk Limit preventing excessive manganese in drinking water. MDH proposed to retain only informal risk assessment “advice” for this important pollutant. MDH claimed that its 100 µg/L rule was outdated.

WaterLegacy mobilized citizens to request a contested case hearing and submitted detailed comments opposing the change. WaterLegacy comments stated:

  • MDH should not repeal the manganese Health Risk Limit.
  • Manganese is dangerous to human health, causing impacts to the nervous system.
  • Infants, elderly people, and people with reduced liver function are more susceptible and require preservation of the 100 µg/L Health Risk Limit.
  • There is a real and present danger of manganese toxicity in drinking water resulting from mining.

MDH agreed to conduct a scientific assessment of the manganese Health Risk Limit rather than proceeding with repeal. In May 2012, the MDH assessment upheld the need for a 100 µg/L Health Risk Limit to protect the health of infants. As of 2020, the rule is still in effect.

It may be just a coincidence, but in 2010 an effort was underway to develop a manganese mining project in northern Minnesota in the town of Emily. The mine proposed in Emily used unproven injection well technology. In addition, the mobility of groundwater in this location suggests that pollution from the operation could not be sequestered and would affect the aquifer.

The Brainerd Dispatch provided an update on the progress of the Emily manganese mine in January 2019:

So far, the company has spent $23 million on the mine’s development. Aside from a few drill tests and the construction of surface facilities, there hasn’t been any active mining at the site. Attempts to extract the manganese have been unsuccessful.