Last time we were here we bought the Tucson coupon book, which offered 2-for-1 discounts on many tourist sights. We did everything that interested us and visited many other tourist sites as well. Except for the Tubac artisan fair, we have not revisited any of these places and have to marvel as how much remains to be seen. When we first arrived, a two month stay felt like forever, but as our departure date nears, there's still much to see and do. It often takes time to discover what an area has to offer. We feel so fortunate to have that time to linger and discover and sample the many cultural and outdoor activities that make Tucson a favorite place for us to spend the winter.
Whenever we head south on I-19 we see massive mine tailings and were surprised to learn that we could visit a working mine. On this trip it feels like we have turned into mine aficionados, having visited many historic mine sites and related ghost towns. Usually, commercial enterprises do not want tourists wandering around and getting in the way. Mining is a dangerous and dirty business. The tour here included a bus ride that took us to the action and a guide who had worked here for thirty years and knew every step of the mining process. Every ton of ore produces about thirteen pounds of copper. But for every ton of ore, about three more tons of waste rock must be removed. Only the enormous scale and efficiency of an open-pit mining operation can make such a low-grade deposit economically viable.
People have been working the site we visited today since 1899. Today this strip mine is owned by ASARCO, a Mexican company. The main focus of the mining is copper, although many more rare and precious minerals such as gold and platinum and other minerals I have never heard of are also uncovered as massive quantities of rock are dug, crushed and processed. Massive is the operative word. This strip mine has uncovered so much land, that the piles created are carefully monitored to ensure that nothing collapses unexpectedly. To begin holes one foot in diameter and fifty feet deep are dug and filled with ammonium nitrate and fuel oil. The blasting crew detonates the charge during shift change when no one is in the pit. Blasting technology has steadily improved, and mine blasts are not as dramatic as in the past. This is because now more energy goes into fracturing the rock in place, so not as much rock and dirt gets thrown into the air. The explosions break the rock into pieces small enough to be loaded into massive trucks that have tires 11' tall. When you stand on a platform that overlooks the rock removal, the trucks and shovels look like toys and you have no sense of how huge it all is.
The tour took us inside the buildings where the rock is pulverized and the tailings are separated from the mineral rich ore. The copper is refined out of the rock with chemicals and leaves here 95% pure to be processed further for commercial use. We were surprised how few employees are employed here. Most of them appeared to be monitoring the machinery that was doing all the doing. That makes this place a relatively safe place to work. We heard a lot about how the ground water is monitored to ensure that the chemicals do not leach into the water table; most of the water used in the process is recycled. It is feasible to reclaim the land covered by the tailings, but in this climate it's a challenge. Mother Nature takes one hundred years to cover the hillsides with plants once again. To accelerate the process, the sterile tailings have to be covered with soil and planted and watered until things get going. Another approach is to cover the tailings with green alfalfa and bring in a herd of cows to graze. Their hoofs break up the soil and work the alfalfa seeds and manure into the rocky soil. Judging by all the tailings we saw, not a lot of effort is being put into reclamation. It might be one of those things that companies do not do unless government regulations require it.