For example, the Waste Isolation Pilot Plant, located 660 m (2,170 ft) deep in a salt formation, achieves 1585 m.w.e. shielding. Soudan Mine, at 713 m (2,339 ft) depth is only 8% deeper, but because it is in denser iron-rich rock it achieves 2100 m.w.e. shielding, 32% more.