Bill and I grew up in Pittsburgh's Monongahela Valley, where mine drainage is an occasional problem for neighborhoods like ours built on top of abandoned coal mines. But there, most of the pollution is cleaned up and out of sight, in compliance with strict environmental laws. Potosí looks like Pittsburgh in the early 1900s. We spent lots of time hiking around on top of enormous piles of yellowish-orange or gray tailings, where tiny bits of metal glint in the sun. Next to the piles are small creeks in colors I've never quite seen before: gray, yellow, and red, with frothy piles of white sulfates on top. Running water is not supposed to look like an ice-cream float.
Because the mineral ore in Potosí is extracted on the cheap at local processing plants that don't treat all the nasty stuff, piles of mine tailings come out of processing with high concentrations of zinc, lead, cadmium, arsenic, iron, and chromium intact, not to mention the cyanide used in the processing. The pollutants inevitably enter the watershed, causing health problems and the presence of heavy metals in crops downstream from the mines. The rocks in local streams are evidence of the high metal content—most are colored bright red (from oxidized iron), yellow (from the many sulfates in the water), or even a greasy jet black (from oxidized manganese). Bill tells me that when he arrived in town a few weeks before, a large new mine was planned near Cerro Rico, but after local campesino farmers, angry at further potential water pollution, used a popular Bolivian protest tactic and blockaded the major road into Potosí, the plan was abandoned.
In Potosí, effective mine-drainage treatment is still mostly theoretical. Passive-treatment programs—which use constructed wetlands, bacteria, and other natural methods to raise the pH levels and precipitate some of the heavy metals in mine-contaminated water—are used in parts of the United States and Europe around both abandoned and working mines, and they help to clean up the pollution. But down here, water and money are scarce commodities, and the scale of cleanup required is immense.
Franz says the Bolivian government has promised to treat some of the water that flows into the surrounding farms and causes the most damage to the region's agriculture. The government has also begun reforestation of the hillsides around Potosí, which will help to slow the flow of materials down the mountains. But one of the best ways to clean up Potosí may be good old capitalism: The heavy metals in the area are prized for industrial use, and the cadmium, lead, and zinc in all those piles of tailings could make a nice profit for a company with the resources to extract them.
In the right economic conditions, even a small cleanup effort in Potosí could mean both profit and an improved environment. For all that Potosí's metals have bought for the world, clean water for its miners seems like the least we can do.