First impounding of Arenal dam in Honduras

Commissioning of the hydro­power facilities, totalling 61 MW, is expected in early 2022.

Impounding of the Arenal reservoir on the river Yaguala in central Honduras was launched in early November. Filling of the reservoir, which will have a maximum storage capacity of approximately 70 x 106 m3, is expected to take at least one month, depending on the river discharge, according to the Lombardi Group, Switzerland, who is acting as Owner’s Engineer.

The Arenal I-II project, in the municipalities of Arenal and Olan­chito in the north central department of Yoro, comprises a 93 m-high, 273 m-long RCC arch gravity dam with a concrete volume of 305 000 m3, a 4.6 km-long headrace tunnel with two tunnel adits, two 270 m-long steel penstocks with diameters of 2.40 m, a 94 m-high surge shaft, a main hydro station equipped with two 30 MW vertical axis Francis turbines, and a secondary plant at the toe of the dam with a capacity of 1.12 MW, which will generate power from environmental flows. Power will be supplied to the national grid through a 25 km-long, 230 kV transmission line.

The project is being developed on behalf of Energias Limpias Del Yaguala SA de CV, a subsidiary of one of the leading power producers in Honduras, by an international consortium. The construction of the RCC dam, hydraulic tunnels and related civil works were carried out by Sinohydro. The Chinese state-owned hydropower engineering and construction replaced in 2018 the original civil works contractor, a joint venture of Italian construction groups Astaldi and Ghella, whose €101 million (US$ 113 million) contract awarded in 2017 was revoked. A joint venture of GE and STE Energy of Italy supplied the electro-mechanical equipment (GE supplied two 30.7 MW Francis turbines and generators and STE Energy provided a 1 MW Francis turbine and the complete balance of plant). IIA Tec­nologías Especializadas of Hon­duras supplied the hydro-mechanical equip­ment and Spain’s Equinsa supplied the transmission line and HV switchyard. The hydro plant is expected to generate average annual net output of approximately 230 GWh, based on a load factor of around 44 per cent, under a net head of 130 m and a design flow of 51 m3/s. Lombardi has been in charge of the engineering services from prefeasibility study to detailed design and site supervision.

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