Isaw . . the milling operation that recycles and contains all processed water, and the huge [residue-collecting] pond that, over time, will become a 600-acre wetland. i saw the sophisticated monitoring system for the early detection of contamination in the groundwater.
—t. h. watkins, "hard rock legacy," national geographic, march 2000

the quotation describes the management techniques of a modern gold mining operation. what is the primary purpose of these techniques?