 The mound is used for the storage of radioactive waste and residues, and the grass-covered "interim cap" is designed to retard both rainwater infiltration and radon emission.All of the contaminated and radioactive materials stored at the former LOOW site—including thorium, uranium, and the world's largest concentration of radium-226—were placed into the structure.In 1951, laboratory waste and animals that had been injected with plutonium during experiments at the University of Rochester were shipped to the LOOW site for burial.