The Arroyito dam, opened in 1979 downstream of El Chocón, was born to optimize the use of water. It is an embankment about 3,500 metres long, with a homogeneous and permeable section of sandy gravel.
The average height of the dam, measured from its foundation, is 13 metres and the maximum height reaches 26 metres. The crown width varies between 6 and 10 metres, according to the purposes of the road.
The embankment behavior supervision, as well as the foundation and pillars, is carried out through different types of control instruments, since it is vital to determine the average filtration flow, measured by 6 flow meters at the bottom of the dam.
The hydroelectric power station is made up of four independent modules. Three of them, are equipped with a 42,660 KW power generator each. The fourth is used as service unit or a discharge, assembly and maintenance dock.
The hydraulic power station is equipped with three turbines of 61,623 CV of nominal power each, with a nominal jump of 16.85 meters.
The turbines are vertical axis Kaplan, rotating clockwise at 90.9 rpm, and with two bearings: one upper thrust combined bearing and guide located under the generator and another lower guide bearing located in the neck of the turbine, close to the runner.
The generators coupled to the turbines are protruding and pole-type, with a maximum generation voltage of 13.8 KV, elevated at 132 KV by the main transformers. These are connected to the Maneuver and Sectioning Station of 132 KV through an aerial line per group.