500+ Years of Treating Polluted Water

500-years (1)

Media coverage of the PolyMet mine plan revealed that computer models predict water pollution lasting hundreds of years. In fact, these models showed that 500 years after the mine would close, water at the plant site would exceed Minnesota’s standards for heavy metals and sulfates.

PolyMet has attempted to confuse this issue rather than address it in a straightforward way. PolyMet says that “it’s not known at this time” how long polluted water would require treatment. That’s not acceptable – Minnesotans deserve an answer to this critical question. Minnesota law requires that sulfide mines be “maintenance free” at closure, and a proposal that calls for hundreds of years of monitoring and treatment is not maintenance free. Minnesota law requires a company to post a damage deposit sufficient to cover the costs of closure, including the cost of long-term water treatment.

Minnesotans deserve an answer to the question “how long will polluted water require treatment after closure of PolyMet’s proposed mine?”

This question needs to be answered

“GLIFWC staff are gravely concerned that the lead agencies are attempting to minimize the issue of perpetual/long term treatment by using vague and confusing language in the SDEIS. In addition, the language the lead agencies have used has changed during the development of the document even though the model results have not. [...]

The SDEIS requires substantially more transparency on one of the most fundamental issues at stake for this project. The fundamental question is: how long will the company be required to operate and maintain expensive mechanical treatment to meet water quality standards? This singular issue has significant repercussions for the public interest determinations and the scale of required financial assurance.” - Great Lakes Indian Fish and Wildlife Commission

Recommendation: The [Final EIS] should clearly explain the timeframe during which water treatment is projected, for both the plant and the mine sites.” - U.S. Environmental Protection Agency

“…it appears that the co-lead agencies are attempting to minimize the significance of the necessity for long term/perpetual treatment by using vague and confusing language in the SDEIS. The specific language describing long term water treatment has changed during the development of the document, even though the model results have not. The co-lead agencies use creative wording to obscure the results of the modeling; this is misdirection at best and highly inappropriate for the co-lead agencies to present to the public.” - Fond du Lac Band of Lake Superior Chippewa

The length of time matters to Minnesota taxpayers

“…the modeling in the draft arbitrarily stops at 200 and 500 years, despite the fact that those models show that the water will still require treatment at that point. The models in the SDEIS need to be amended to project out to the point in time where the water meets Minnesota’s water quality standards, even if that is many hundreds of years further into the future. The difference between 200 years and 2000 years might seem to be an insignificant point to a business that may not be around in 50 years, but to the state, which would otherwise be forced to pick up the costs of virtually perpetual water treatment, it is an important distinction.” - Sen. John Marty, Chair of the Minnesota Senate Energy and Environment Committee

“While state law and prudence require that closed mines be maintenance free, the mine plan revealed in the SDEIS reveals that the NorthMet sites will require hundreds of years of monitoring and water treatment … The model needs to be run further out into the future, especially for persistent pollutants such as mercury and other heavy metals. The SDEIS currently fails to adequately address the full scope and duration of  impact to both water quality and contamination levels in fish.” - Minnesota Trout Unlimited

“The SDEIS, in fact, concludes that ‘[i]t is uncertain how long the project would require water treatment.’ No plan is presented that reasonably assures that water treatment will be possible and effective for the stated hundreds of years at a minimum [...] Because of long timeframes that remain unknown, there is similarly no meaningful demonstration that mine closure and reclamation will actually be possible.” - Environmental Law and Policy Center

Computer models in the draft environmental impact statement predict hundreds of years of pollution

Buried deep in the thousands of pages of supporting material for the SDEIS are charts that show predicted levels of pollution for water collected and sent to PolyMet’s proposed water treatment plants (“WWTF influent.”) There are charts for dozens of pollutants, but here are three that show that after 200 years, water at the site contains levels of pollution well above water quality standards.

  • Key: the red dashed line at the bottom of each chart (“modeled WWTF target”) is the water quality standard. If water pollution is above this level, it cannot be legally released into the environment without treatment.
  • P90 is a “worst case” line – the model predicts a 90% chance that levels of pollution will be less than this line. Similarly, P50 is a “middle case,” with a 50% chance that pollution will be higher and a 50% chance it will be lower. P10 is a “best case,” there is a 10% chance that pollution would be lower than this line, and a 90% chance it would be higher.
  • Cu = copper, Ni = Nickel, SO4 = sulfates

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