• Ecology of the Southwest

In the Eye of the Copper Mine

Today we toured the ASARCO "Mission" copper mine near Green Valley, only a half hour from the experimental range.

In operation the mid-1900s, the mine is now one of the biggest copper mines in the country, covering about 20,000 acres leased from the Tohona O'odham tribe's land. We got a nice introduction to copper production from our fantastically quirky tour guide, Claudette, and then drove around the mine. We drove past the giant pools where murky black-green "slurry" is spun with water and sent to the next step in the refining process, and saw the huge hole in the earth, spanning 2-3 miles across and nearly a mile deep.

At the bottom of the pit was a pond of water, which we later found out to be the water table exposed by the drilling and removal of earth. This is one of the parts of mining that most affects the environment: when the water table is exposed to air after being buried deep underground, it begins to evaporate, causing water from other parts of the table to run to the section the mine uncovered. This can quickly dry up streams and springs that depend upon the water table's current depth beneath the ground. It's a huge reason that the recently-approved Rosemont copper mine, which would be located much closer to the Santa Rita Experimental Range, faces much opposition from residents, government officials, and ecologists alike.

Another of mining's "side effects" are the tailings - the roughly 75% of ore removed that does not contain precious metals - which are ground to extremely fine grains after proccessing and dumped into "tailing mountains." These grains are apt to be taken up by gusts of wind and make for dusty air, which is harmful to the lungs of those who breath it. To avoid this health-threatening dust, mines must use gargantuan quantities of water to wet the dumped tailings so that they can't blow in the air. Mining companies in this region buy water from the Colorado River, whose water is already contracted to more buyers than it has water to offer.

It gave us a lot to think about. Copper - most of which is shipped away for rapidly-developing industry in China - makes up much of the technology that makes up our modern world. But it is devastating to its local environment.

Later this afternoon, we each came up with research project proposals that will keep us busy for the last leg of the trip. There are some pretty cool ideas going around; Mimi plans to measure burn time of different woods, Zoe and Kim will examine the effect of road proximity on plant diversity, Mitch will look at water temperatures and algae in different parts of Florida Stream, and Connor will monitor bird activity in different zones.

We had our discussion tonight, and popped outside to watch the moon rise over the mountains behind Florida Canyon. The stars are prime for watching, cards ready for playing, and hot cocoa ready for slurping. It has been a great weekend!

All our best!