Unusual mine waste dam shakes off magnitude 8.3 earthquake

On June 23, 2001 a Magnitude 8.3 earthquake struck the southern portion of Peru. The newly constructed 130 m high Torata River Diversion Dam was shaken by the tremor, undergoing a near-maximum design ground acceleration of 0.20 g. The concrete faced rockfill dam (CFRD) responded as expected, with only minor deformations and superficial movements. Most importantly, there was no increase in seepage through the dam or its foundation. The dam is part of a system of structures built to divert the entire Torata River around Southern Peru Copper Corporation’s Cuajone open pit copper mine and adjacent waste storage space. It was originally planned to be a conventional clay core/rock shell embankment with the rock to be quarried out of the reservoir area. However, by incorporating select mine waste into a uniquely designed embankment section, which included a 130 m wide crest, the construction cost was cut in half.