The El Tambolar Hydropower plant, is to be built on the San Juan River near the town of Pachaco, 145 km from the city of San Juan and 20 km upstream of the Los Caracoles dam.
The works involve an access road from the Los Caracoles power plant, the diversion channels for the San Juan River, a gravel concrete-faced dam with flood spillway and an open-air channel. Generation is pressure-driven and there is an external power plant.
The diversion of the river for the construction of the dam was undertaken by building two parallel tunnels lined with a reinforced concrete trunk section on the right bank of the river. Both tunnels are 6 meters in diameter and have a length of 492 meters. One of the two tunnels will later function as a bottom outlet, so a sluice gate will be built inside it with an access tunnel leading to it.