Monday, July 20

It's not everyday you get so see a Superfund site, but today we had a opportunity to tour the Midnite Mine, a uranium mine which was abandoned in 1982 when the price of uranium suddenly plummeted.

We met at Wellpinit High School to learn a little bit about the history of the Spokane Tribe, and their current projects in the Department of Natural Resources. One of the largest of these projects is the cleanup of the Midnite Mine, a uranium mine which operated from 1955 to 1982. Because the mine was quickly abandoned, not only were open pit mines left, but giant piles of ore and protore (ore that is not as rich) as well. Planning for the cleanup began a decade ago, and the cleanup will continue for several decades, at a cost of hundreds of millions of dollars, which will be paid for by the Newmont Mining Corporation which owned the majority share of the mine.

Our first location on site was along the south end, by the Dawn Millsite. This was where the uranium ore was processed, leaving behind millions of gallons of waste water contaminated with other heavy metals and radionuclides. Their solution is to evaporate off the waste water, and then cover over the tailings with 10 feet of clean fill taken from the diversion ditch that surrounds the site. As of now, there are only two evaporation ponds left, and they hope to have the millsite finished in 3-5 years.

After lunch, we went to Pit #3, the larger of the two open pits. While my students went to see the pit, I had the opportunity to see the waste water treatment facility. The water from the pit is very acidic, due to the bacteria and archaea which break down pyrite (iron sulfide) in the soil and produce sulfuric acid. When the water is that acidic, metals like iron, lead, arsenic, and uranium dissolve in the water, and need to be removed before the water can be discharged.

These dissolved metals are removed by increasing the pH to 10-11 by adding lime (calcium hydroxide) This causes the metals to precipitate out, turning the lime a sludgy brown.

The lime and contaminants are settled out in a settling tank, while the water is pumped from the top of the tank. The water has acid added back in until it reaches neutral pH, when it is ready to be piped back into the Spokane River.

The sludge is then sent to a pressing machine, where the water is pressed out and sent back through the decontamination process. The dry pressed sludge is then packaged and shipped to a facility in  Utah where it is processed further to remove any remaining uranium and make yellowcake.

 After touring the water treatment plant, we took a tour to an overlook to see the pit. This pit will eventually be filled in, first with the unprocessed ore and protore, and then with clean fill from the diversion ditch by the millsite.

 I was surprised by how beautiful the site was. The pond reminded me of the bright blue of glacier fed lakes, and the swirling rock formations with terrace steps cut in seemed like something from a tourist attraction, rather than a Superfund site. It will take many years before this pit can be filled in, and it will have to have water pumped out and treated for the foreseeable future.