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C.J. Schexnayder / ENR
C.J. Schexnayder / ENR
San Antonio Dam’s site favors run-of-river design.
The Madeira River is a wide, shallow, muddy waterway wending through Brazil’s far western state of Rondônia. It is here, on the largest tributary of the mighty Amazon River not far from the border with Bolivia, where Brazil has staked its electrical future.
Large-scale hydroelectric work stalled in Brazil in the early 1990s, but now a pair of dam projects in the initial stages of construction and valued at $10.5 billion mark the first step toward meeting the country’s 21st-century energy demand. The hydroprojects are scheduled to begin feeding the energy grid in 2012. By 2016, they are to be fitted with their maximum combined generation capacity of 6,450 MW, approximately 8% of the country’s total electricity generation.
When complete, the San Antonio and Jirau installations will be the largest run-of-river dams ever built. Each will sport 44 of the largest bulb turbines ever built, with 8-meter-dia rotors. Each will generate 75 MW of power.
“It’s a question of scale, not technology,” says Jose Bonifacio Pinto, Odebrecht’s project director. “The know-how to build this kind of turbines is already there.”
Concerns about an energy shortage prompted Brazilian officials to fast-track the Madeira project despite environmental opponents who are not conceding anything. “We don’t accept [that the dams] are inevitable…there are a number of lawsuits,” says Glenn Switcks, Latin America program director of Berkeley, Calif.-based watchdog International Rivers. “While opponents have not been able to obtain restraining orders, the cases are still to be heard.”
The government chose a run-of-river design for the San Antonio dam at a wide site strewn with shallow rapids and an island that covers about half of the channel. The design also minimizes the reservoir footprint. But environmental groups still say more than 400 sq kilometers of rainforest will be inundated, hundreds of residents displaced and rare fish and mammals endangered.
Both projects still must be licensed by IBAMA, Brazil’s environmental protection agency, before preliminary site-clearing work can begin. Opponents are challenging this license and the legality of the one that predicated the bidding.
The process started last December, when the Brazilian electricity regulatory agency Agência Nacional de Energia Elétrica awarded the San Antonio dam contract to Consoricio Madeira Energia. It comprises Brazilian construction firm Odebrecht, along with local power utilities Furnas and Companhia Energetica de Minas Gerais (Cemig). It also includes construction firm Andrade Gutierrez and Spanish bank Santander and Portuguese bank Banif.
The consortium’s offer to sell electricity at $43.82 per MWh was approximately one-third less than the capped tender price. San Antonio dam will rise 30 meters and stretch 2,550 m to impound the river just a few miles south of Porto Vehlo, capital of Rondônia, with a population of 330,000 people.
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The dam is to comprise multiple components: two 300-m concrete structures, each housing 12 turbine generators; the main spillway; a 430-m concrete section housing 20 turbines, flanked by two roller-compacted concrete structures, followed by an auxiliary spillway and a small earthfill, on the right bank.
Consortium engineers say they will build the dam in two stages. Cofferdams on the left bank will divert the flow, allowing dry excavation and construction of roughly half the dam and the spillway.
The river will then be routed through the completed portion of the dam. New cofferdams will protect the works in what is now the riverbed. A new navigation canal is to be built later under a separate contract.
The 3,300-MW Jirau project followed a different path. In May, winning consortium Consorcio Energia Sustentável do Brasil (CESB) won the auction, offering $43.30 per MWh—almost 22% below the cap. The company’s low numbers were based on a location and design different from the one proposed. CESB is led by France’s Suez, with local engineering firm Camargo Corrêa.
CESB says the key to its low bid was moving the dam downstream from the proposed site, some 140 kilometers upriver of San Antonio. Jirau’s proposed location featured an overabundance of hills, says Camargo Corrêa project manager Luis Américo Rojo. The move will save almost $620 million.
“The cost to excavate the site would have cost as much as it would to build the dam itself,” Rojo says. “It’s a location better suited to a traditional dam, and we felt this new location was much more advantageous for a run-of-the-river dam.”
CESB estimates the original location would have required excavating some 62 million cu m of spoil, 50 million more than the 12 million cu m the team will remove from the new site.
Jirau’s main rockfill dam will be 35 m high and 550 m long, flanked by two compacted earthen dikes, one 930 m long and the other 1,140 m long. It will impound a 258-sq-mile reservoir. Powerhouses on each bank will house turbines.
The two projects will require about 24,000 workers. Both consortiums say they will hire locally, but the pool of qualified employees in the region is limited. Madeira Energia has already begun a government-backed 12-week training school in Porto Veilho. CESB plans to institute a labor training program.
The Madeira project also plans at least two additional dams upstream in Bolivian territory. If built, they would add more than 10,000 MW of capacity.
The Bolivian proposal is part of a larger plan by Initiative for the Integration of South American Infrastructure to use the Madeira to provide electricity and improve the transportation infrastructure of the remote area. If the entire Madeira program is completed, the river will provide Bolivia with water access to the Atlantic.