12-13-2010, 08:10 PM
fast car Wrote:Dgaken,
After completing my graduate work in microbiology at CMU, I worked for a environmental consulting group that did ground water analysis at the Yuma sand mining operation. The operation in the early to mid 70's, consisted of a 100 yd X 200 yd square pit that had at least two or three front end loaders dumping sand onto a moving conveyor belt that would move the sand to ground level. The conveyors ran about half the length of the open pit. After reaching the surface, sand was sifted and then washed with a combination of water and pine oil to float the organics (primarily woody plant material/insects) to the surface. This was then skimmed and the pure clean sand was then sent to a rotary kiln dryer. The hot dry sand was then conveyored to enclosed hopper cars and sent on its way south and almost entirely used as cast sand for engine blocks and other cast iron parts.
The unique aspect of this mining operation was the fact that Yuma was one of the only mines to take back spent sand from the casting plants. The returned material was very dark black in color and smelled like the old paste that kids used in grade school. The spent material contained various compounds and was the main reason we were on site for monitoring perimeter wells that circled the mine. The open pit mine was back filled with the spent sand. It wasn't uncommon for Yuma to fill fifteen to twenty hoppers per day. I'm not sure how many returned hoppers they received with spent material. I'm sure by now the returning of spent sand has ceased due to environmental concerns.
Larry
I wonder if they have found a method of cleaning the spent sand for reuse? Of course if there is a method that isn't too costly or difficult, the casting company may be doing it themselves. Of course, it the sand went south from Yuma, it probably went to Mexico. Does the Mexican Government even care about the possibility of pollution of ground water with the spent casting sand?