Background:
The Oxec II hydroelectric project supports Guatemala’s mandate to use clean power rather than imported fossil fuels. When approached to consult on the project, SBI proposed an alternate plan to the one initially proposed by the local general contractor that significantly reduced construction costs and improved the structure’s reliability.
Following the construction of the Oxec I hydroelectric project, Energy Resources Capital entered a joint venture with SBI Holdings International AG through our subsidiary, Hatch, to construct the Oxec II hydroelectric project: a generating station consisting of a concrete gravity dam, a close-coupled power block, and a gated spillway section. SBI managed every aspect of the project—from planning and financing to design and construction.
The project’s scope included:
● Construction of a two-stage diversion using cellular cofferdams
● Installation of sheet piles in the river
● Construction of a submerged roller bucket spillway
● Construction of a concrete gravity dam
● Construction of a power bank on the left bank
● Construction of a gated spillway section on the right bank
● Construction of an Ogee crest equipped with four radial gates
SBI finished construction of the project in 2019. The new Oxec II hydroelectric project not only brings sustainable energy to Guatemala, but serves as a precedent for future builds due to its unique features and innovative construction methodologies.
Challenge: Unstable ground, flooding, and space limitations
Due to frequent flash flooding and high seismicity, the construction site was unstable, making it a challenging setting in which to build. The fast-flowing Oxec River also posed a challenge, as it would have to be diverted during construction. The project’s space limitations and siting were further complications, as Oxec I is located directly downstream from the construction site and could potentially suffer damage.
SBI’s Solution: Quality Design and Build
Planning:
Rather than the original plan for three-stage diversion, SBI proposed using cellular cofferdams to temporarily divert the river during construction. This required installing 1200 tons of sheet piles in the river, and was a technique never used before in Central America. We also used high resistance concrete to withstand the high speed of the water flow.
To prevent any damage to the Oxec I facility, we proposed a submerged solid roller bucket for energy dissipation, rather than the original design’s stilling basin. To achieve this, SBI conducted 3D finite element analysis and used a sophisticated CFD model. Our alternative designs reduced both the size and cost of construction.
Construction:
Throughout the project, SBI employed high-quality materials and our own advanced machinery (to prevent any procurement delays), along with SBI’s unparalleled engineering, construction, and project management expertise.
SBI’s scope of work included:
● Diverting the river using cofferdams and sheet piles
● Constructing a concrete dam, power bank, and gated spillway
● Reinforcing the concrete structures with rebars
Frequent flooding and high hydrostatic thrust called for extra protective measures to ensure the safety and integrity of the project. Therefore, per SBI’s recommendations, the Oxec II facility features:
● A submerged roller bucket spillway to dissipate energy
● Radial gates with trunnion anchorage capable of handling high hydrostatic loads
● A dam deck 3 meters above the normal operating level
Corporate Social Responsibility
As part of SBI’s commitment to social responsibility (CSR)—and in compliance with Guatemalan law—we created a Community Development Agreement to give back to the host communities and minimize the project’s environmental impact. Our CSR initiatives included:
● Employment of local youths
● Financial empowerment for business owners and traders
● Respect for traditional courtesies and festive periods
Results: A source of sustainable energy
Completed in 2019, the Oxec II hydroelectric project features major structural innovations designed to reliably provide sustainable energy to Guatemala for years to come. Completed on schedule and under budget, the project received the 2019 Canadian Consulting Engineering Award of Excellence and, due to its progressive design and environmentally-sound construction methods, will serve as a model for future projects supporting Guatemala’s clean energy mandate.
