Irape Dam is a rockfill dam with clay and gravel core. The maximum dam height is 208m and the total volume is 10.3 million m3. It is located in a place of very rugged topography, the type canyon with difficulties constructive associated with topographical aspects and local geochemical conditions. The tight 40-month construction schedule and the strict economic limitations of the job, made obligatory the use of the excavated materials in the dam embankment, including large amounts of weathered sulfide-rich rocks based on study results. The dam core was built with sandy-clay with the precaution to use a mixture of gravel and clay in the deep channels, to get higher rigidity modulus in this zone. A layer of more plastic, self-healing soil was placed along the clay/rock contact on the valley walls to help the redistribution of stresses. Natural sand was used in the fine filters, and crushed rock in the coarse filters and transitions. Consequently, with the exception of protection and covering rockfills, which were made of non-sulfide or sulfide-poor rocks, all the other embankment materials came from the required excavations. In addition, to reduce the amount of rain water seeping into the downstream zone, and prevent the production of acid effluents, a sort of “umbrella” was provided in the downstream slope, made up of 6 m wide sheets of HDPE (high density polyethylene).
The project is owned by Cemig Geração e Transmissão S.A..
