Oxec II Hydroelectric Project
Powering Guatemala with green energy
Solel Boneh Guatemala
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Guatemala
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2014 - 2018
56 MW greenfield hydropower project in Guatemala.
First cellular cofferdam in Guatemala.
40% savings in spillway concrete volume.
4-month reduction in overall construction schedule.
Challenges
- A high-magnitude flood design complicated the spillway energy-dissipation design.
- A high-magnitude, temporary diversion flood complicated the diversion works.
- Unstable ground and a poor-quality foundation have been associated with landslides during excavation.
- A large volume of work had to be accomplished within a limited, compressed schedule.
Solutions
- Changed the spillway stilling-basin design to an optimized submerged roller bucket design, resulting in up to 40% savings in the concrete volume of the spillway.
- Reduced the length of the cofferdam and temporary works with the revised spillway design.
- Replaced the original conventional cofferdam with a cellular alternative, resulting in a much smaller footprint and smaller excavation.
Highlights
- The cofferdam eliminated a major phase in diversion, reducing the overall construction schedule by 4 months and achieving a remarkable reduction in bank excavation.
- The first of its kind built in Guatemala, the cofferdam has 29 cells, is nearly 300 metres long, and consists of 2,000 tons of steel and over 50,000 m3 of fill.
- The cofferdam resists fast flows, controls the release of sediment, and exhibited high reliability and safety during its installation and life in service, needing no remedial works after flood events.
- The fill material was processed with a view to removal methodology. The maximum size of the aggregate was limited so the cell fill can be mixed with water and pumped off the project site.
Project Numbers
56-MW greenfield hydropower project in Guatemala200-m-long concrete gravity dam
41 m high powerhouse
150,000 m3 of concrete construction in less than 30 months
4 spillway radial gates (12 m W x 16.5 m H) to pass an extreme flood of 6144 m3/s
29-cell cofferdam designed for a diversion flood of 2,810 m3/s
50,000 m3 of fill for Stage 1 cofferdam
1,800 sheet piles constructed in a 4-month period