Dams and Civil Structures

Consortium files to construct tunnels for Peru’s 150 MW Peihap project

A filing submitted to securities regulator Superintendencia del Mercado de Valores shows a Peruvian and Italian consortium will construct two tunnels as part of the first phase of the country’s 150 MW Peihap project.

The US$140 million job – to be completed within five years by Peru’s Obrainsa and Italy’s Astaldi – includes the construction of two tunnels that will be used to transport water to the 150 MW Cashapite and 150 MW Gramadal hydropower stations.

The plants are part of Peru’s Alto Piura project, which also seeks to improve the region’s agriculture through irrigation infrastructure.

Dam safety upgrade completed in NSW, Australia

A US$11 million Ajenti Data Management System developed by Entura, part of the Hydro Tasmania Group, is in place as a safety upgrade to Lake Endeavour Dam in Parkes Shire, New South Wales, Australia. It included upgrades to the dam wall and spillway and implementation of an early warning system (EWS) for downstream residents and emergency services.

The Ajenti system allows real-time observations to be combined with rainfall forecasts, using modelling to determine likely inflows to the dam and related changes in water level over a seven-day forecast period, said Andrew Francis, infrastructure director for Parkes Shire Council. The EWS at Lake Endeavour Dam combines water levels from two locations in the catchment area with data from the Bureau of Meteorology.

“An effective flood forecasting system is a vital tool for managing the significant risks that floods pose to communities, infrastructure and the environment,” said Dr. Fiona Ling, Entura’s principal consultant in hydrology, resource management and investigations. “If you can clearly understand the likelihood and scale of potential flooding and get accurate and timely warnings, you can better manage water infrastructure and implement safety plans in time to protect assets and communities at risk.

“Staff can monitor the system via a simple interface, but the system is designed to be ‘set and forget.’ If water levels are likely to reach a pre-determined level, the system automatically alerts staff.”

Hydro Tasmania has 55 major dams and is Australia’s largest renewable energy provider.

410 MW Xe-Pian Xe-Namnoy project in Laos includes three dams

Construction of Xe-Pian Xe-Namnoy Power Co.’s (PNPC) US$1.02 billion 410 MW Xe-Pian Xe-Namnoy hydroelectric project in Lao People’s Democratic Republic includes the construction of three dams: Houay Makchan Dam, Xe Pian Dam, and Xe-Namnoy Dam along the Mekong River.

Xe-Pian and Xe-Namnoy are rockfill dams that will be constructed on the Bolaven plateau, along with saddle dams and Houay Makchan Dam, while the powerhouse will be located at the plateau base, giving the scheme a head of more than 630 m. Water will be discharged to the Xe Kong River.

Developers think the project, about 20% complete, will annually generate about 1,860 GWh. Construction began in February 2013 and commercial operations are expected to begin in 2019 if the project does not experience any additional major delays.

Government says region of proposed 1,400 MW Baleh project safe from seismic activity

A study released in December by the Malaysian government concluded no significant risk for seismic activity exists in the region where the 1,400 MW Baleh hydropower facility could be constructed.

Baleh is scheduled for construction on the island of Borneo. The dam will be a 200 m-high concrete faced rockfill dam that has a total volume of 20 million m³ of embankment fill, making it one of the world’s largest concrete faced rockfill dams, according to published reports. Civil structures include two 12 m-diameter concrete lined diversion tunnels and a radial-gated spillway capable of discharging 20,000 m3/s.

Questions regarding the area’s geographic stability and its impact on Baleh Dam’s integrity were raised after a magnitude 6 earthquake struck in June, about 600 km away in Ranau, which is north and east on the tip of Borneo at Celebes Sea. However, a report made available in December by Malaysia’s Natural Resources and Environment Board cites numerous studies that show evidence of karstic limestone in the project’s reservoir area and that leakage in the reservoir is likely.

The document draws on geological and seismic assessments conducted by MWH Global Malaysia and the GHD Group in 2010 that establish the area meets International Commission on Large Dams (ICOLD) safety standards, along with similar studies conducted by the Seismology Research Centre of Australia for SMEC Malaysia during the past year.

The government has yet to determine whether it will proceed in building Baleh, although it maintains it wants to use hydropower to help make the Sarawak Corridor a “developed” region by 2020.

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Dams and Civil Structures

US$294 million funds emergency repairs at 1,830 MW Kariba hydroelectric facility

In the last quarter of 2015, the Zimbabwean and Zambian governments signed agreements for US$294 million with the European Union (EU), the World Bank, the African Development Bank and the Swedish government to finance emergency dam repairs at the 1,830 MW Kariba hydroelectric facility, according to the World Bank.

At it’s commissioning in 1960, “the water was only 10-meters-deep [33 ft] at the foot of Kariba Dam, but erosion of this plunge pool has increased the depth to 90 m [295 ft] and has been wearing away rock near the dam’s foundations,” according to “Impact of the Failure of the Kariba Dam,” a report released by the Institute of Risk Management (IRM) of South Africa.

Located on the Zambezi River about 260 miles downstream of Victoria Falls in southeran Africa, the Zambezi River Authority (ZRA) operates the project. IRM, along with the EU, said repairs are urgently needed.

“It was considered an emergency and the EU decided to mobilize funds as it was important to start the rehabilitation as soon as possible,” said Philipe Van Damme, the EU ambassador to Zimbabwe.

Kariba Dam, at a height of 397 ft (128 m) and a crest length of 2,024 ft (617 m), impounds Lake Kariba, the world’s largest manmade reservoir. The Kariba hydroelectric project has been central to regional energy security and economic development, the report said.

Repair and rehabilitation will include reshaping the Kariba Dam plunge pool – to limit scouring and erosion that could potentially undermine the dam’s foundations – and refurbishing the spillway and associated infrastructure to improve the dam’s stability and operations.

The report IRM released earlier this year warns that 181 billion cubic meters of water from the facility’s reservoir would careen downstream if the dam fails. During a period of 8 to 10 hours, until the flow dissipates, the report posits a wall of water would hit and likely destroy the dam at the 2,075 MW Cahora Bassa hydroelectric project downstream in Central Mozambique.

Published reports indicate Moises Machava ,Technical Director of Hidroelectrica de Cahora Bassa (HCB), the company that operates Cahora Bassa Dam, said HCB has been aware of the risk to Kariba Dam.

According to Machava, the latest information is that the risk exists, but is not imminent. “It won’t happen tomorrow, or next year,” he said. “But if nothing is done, then it will happen, but not for another couple of years at least.”

The repairs could take up to a decade to complete, according to Charity Mwansa, ZRA chairperson. “Reshaping of the plunge pool will take three years, while the rehabilitation of the spillway gates will take six years with minimal disruptions to normal operations.”

Machava said HCB does not know when these repairs will begin, but given the urgency of the situation, he expected that date to be later this year or in early 2016. HCB expects to be briefed on this at the next meeting of the dam operators in early December.

ACT’s Icon Water in Australia will manage the US$3 million Corin Dam rehabilitation

State-owned Icon Water Ltd. is managing the Corin Dam rehabilitation project.

Located on the Cotter River in Namadgi National Park in the Australian Capital Territory (ACT), Australia, the projected cost of the rehabilitiation to the Corin Dam is around US$3 million.

The work will ensure integrity of the dam’s spillway, the crest of its upstream wall and the road atop the dam.

Corin Dam is 243 ft high and 925 ft long. The earthen dam wall is built on a rock foundation and impounds 71 billion liters forming the Corin Reservoir, which has a surface area of about 780 acres. Water from Corin Reservoir eventually reaches Australia’s capital city, Canberra. Canberra sources major amounts of its water from three dams on the Cotter River – Corin, Bendora (upstream) and Cotton (further upstream); and Googong Dam on the Queanbeyan River.

ACT is an enclave within New South Wales in southeast Australia and the government of ACT owns Icon Water Ltd. Icon Water hired Melbourne-based GHD to investigate and design improvements to substantially mitigate the identified risks.

During construction of a crest wall in 1998, Australian dam safety officials found a 50-mm-wide gap between Corin Dam’s clay core and the spillway bridge right abutment. According to published reports, during a dam assessment in 2007, Corin Dam officials determined conditions at the gap promoted a piping risk. In terms of dam walls, piping occurs when water seepage causes dam wall material to erode.

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