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Ron Yasurek, Mosaic general manager of phosphate operations, stands Tuesday, Jan. 29, 2019, on a roadway atop an enormous, 200-foot-high pile of white waste material called phosphogypsum. The gypsum supports and encases giant cooling ponds for process water at the company's fertilizer complex in Convent next to the Mississippi River. The 140-acre pond on the left is at on top of the mountain of waste. The pond on the right is part of the same waste pile but at a significantly lower elevation than the pond on the left.