Development of the new 690-mw Kárahnjúkar project in Iceland required numerous innovations to deal with unique site conditions, project requirements, and a challenging climate. The involvement of more than 1,300 construction workers from 42 countries highlights the international collaboration used to bring this project to fruition.
Completion of the 690-mw Kárahnjúkar Hydroelectric Project in late 2007 raised the total generating capacity for its owner, Landsvirkjun, to 1,902 mw — a 57 percent increase. In addition to this new project, Landsvirkjun, Iceland’s state power utility, has 12 hydro and two geothermal projects. Power from Kárahnjúkar primarily will supply a newly constructed aluminium smelter owned by Alcoa. The smelter is receiving the power under a 40-year contract. Power sales are expected to repay the project’s cost in 25 years, thereafter providing Iceland with a valuable legacy of additional decades of sustainable energy.
In September 2007, Kárahnjúkar’s completion was celebrated at a two-day technical seminar in Reykjavik, Iceland. Landsvirkjun brought together experts involved with the various aspects of the project, giving them an opportunity to share information about the special situations they encountered and how their efforts and those of their colleagues contributed to meeting project goals. Owing to the diverse character of the technical activities, many attendees learned for the first time about challenges faced and overcome.
The project was completed in four and one-half years — a notable accomplishment, especially owing to the harsh arctic winter environment in remote eastern Iceland where the project is located. The main dam for the Kárahnjúkar project is a 200-meter-high concrete-faced rockfill dam (CFRD), the highest dam of this type in Europe.
Kárahnjúkar houses six 115-mw Francis turbines in an underground powerhouse. The units receive water, at 600 meters gross head, from two vertical, 420-meter-high penstocks — among the highest in the world. (By comparison, New York City’s Empire State Building is 443 meters tall.) The Kárahnjúkar project harnesses two rivers — Jökulsá á Dal and Jökulsá í Flótsdal.
During construction of the Kárahnjúkar project, several challenges arose. One was that, after diversion of the Jökulsá á Dal River and excavation in the river canyon, rockbed faults were discovered that crossed the main dam’s foundation. This required major redesign of the dam, including relocation of a massive 80,000-cubic-meter concrete toe wall. Months of delay ensued and — instead of planned summer construction — the toe wall was constructed during the winter of 2004-2005.
Tunnel construction posed another major challenge. In fact, with 72 kilometers of tunnels, Kárahnjúkar is certainly exceptional and may lead the world in total tunnel length. The headrace tunnel itself is 40 kilometers long. Three tunnel boring machines (TBMs) were used to bore tunnels up to 7.6 meters in diameter. All three machines encountered difficulties due to heavy water ingress, fractured rock, and soft and loose material. Far more remedial effort was required than had been anticipated — including the use of conventional drilling and blasting (and use of concrete linings rather than excavated rock as tunnel walls). Nonetheless, overall, the use of TBMs proved quite effective. During the construction process, several new world daily TBM boring records were established, eventually achieving extension rates exceeding 400 meters per day.
Belt conveyors were used to remove the muck from behind the TBMs, and this was effective. However, Landsvirkjun now believes that including mucking in the drilling contract could have improved coordination of these critical activities. (Instead, separate contracts had been used for the TBM and mucking operations.)
More than 30 main contracts were used to complete Kárahnjúkar’s construction. Landsvirkjun provided overall project management and coordination, and both Icelandic and international firms participated in designing, supplying equipment to, and constructing the project. At the peak of construction, more than 1,300 construction workers from 42 countries were engaged.
The 690-mw Kárahnjúkar project in Iceland, built to supply electricity to an aluminium smelter, was completed in four and one-half years. The project increased owner Landsvirkjun’s generating capacity by 57 percent.
Meeting the challenges posed during construction required innovation on many fronts. For example, owing to delays in the construction of key project civil features, it appeared that Kárahnjúkar might be unable to meet its timetable for initiating a supply of power to the aluminium smelter. However, Landsvirkjun developed and implemented a creative plan to meet the requirement. Because the powerhouse was being built on the original schedule and the first unit would be available for service (even though it could not be supplied with water), the Unit 1 turbine and generator were physically decoupled and the generator operated in the synchronous condensing mode to supply the smelter. The unit took power from the eastern Iceland electrical grid that had been strengthened in anticipation of Kárahnjúkar’s completion and, in turn, supplied power in accordance with the terms of the smelter supply agreement.
Not unlike other major hydro construction projects, Kárahnjúkar faced environmental opposition both prior to its approval and during construction. Prior to project approval, hard-line opponents gave little credence to the enormous long-term economic and energy-independence benefits the project offered Iceland. Yet the project was ultimately approved.
To address issues and concerns raised by both opponents and citizens, Landsvirkjun has established programs and activities for ensuring that environmental matters are appropriately addressed, as well as to respond to concerns and complaints. Careful monitoring of environmental conditions is being conducted, from pre-project conditions going forward, to enable assessment of actual effects and to enable comparison with predicted effects.
Reaching a milestone,moving forward
The Kárahnjúkar project did not “just happen.” In fact, it is an outcome from decades of investigation of prospective project configurations in its eastern Iceland locale. Initial geologic exploratory investigations had been performed in the region 30 years earlier. Completion of the Kárahnjúkar hydroelectric project represents a major milestone. Yet, Landsvirkjun is not simply resting on its laurels for successfully completing this major project. The utility has three smaller hydro projects it’s now pursuing for future development. s
The main dam for the 690-mw Kárahnjúkar project in Iceland is a 200-meter-high concrete-faced rockfill dam. This is the highest dam of this type in Europe.
Pétursson, Guðmundur, and Sigurður Arnalds, “Some Innovations in Design, Engineering, and Construction of the Kárahnjúkar Project,” HRW, Volume 14, No. 6, December 2006, pages 20-25.
This report was compiled by HRW publisher Leslie Eden from her participation in the Kárahnjúkar Hydroelectric Project Technical Seminar and site visit, September 17-19, 2007.