Why do environmental groups say water treatment will be required for 200 to 500 years?

Information about water models developed for PolyMet's environmental review is being used incorrectly.

The timeframes used in the water models have nothing to do with water treatment and everything to do with ensuring that downstream water resources are protected in the event untreated water leaks offsite.

The models were not designed to determine the duration of water treatment.

More specifically, the models were designed to determine impacts to water quality at key reference points in the watersheds downstream of the tailings basin (Embarrass River watershed) and downstream of the mine site (Partridge River watershed). Scientists determined the amount of potential leakage to be relatively small (about the flow of a 5/8 inch garden hose) and the rate of travel to be slow (about 3 inches per day) to these respective points, so the extended timeframes (200 years in one case and 500 years in the other) were needed in the models to represent the maximum potential impacts at the reference points.

The modeling years have no correlation to the years that will be required for actual treatment.