Controlling Toxic Pollutants
- 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.
Specific Conductance Pollution
EPA 2011 Conductivity Report
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 detailed review of data on pollution and aquatic insect life, in 2015 the Johnsons’ Report concluded:
EPA Confirmation of Johnson Report Conclusions
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.
Read S. Cormier, Ph.D., Office of Research and Development U.S. EPA, Review of “An Evaluation of a Field-Based Aquatic Benchmark for Specific Conductance in Northeast Minnesota,” Feb. 4, 2016.
Read S. Cormier, et al. Step-by-Step Calculation and Spreadsheet Tools for Predicting Stressor Levels that Extirpate Genera and Species, Integrated Env. Assess. & Mgt. (Oct. 2017)
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.
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: