The 690 MW Karahnjukar Hydroelectric Project harnesses two glacier rivers originating in the Vatnajökull Glacier. The larger river, providing about 2/3 of the flow to the plant, is dammed at the Karahnjukar Mountain with the 198m high Karahnjukar concrete face rock fill dam and two moraine core rockfill saddle dams, 69 m and 25 m high. With the three dams the 2100 million m3 storage reservoir is created with the maximum supply level at 625 m a.s.l. From the reservoir a 40 km long headrace tunnel was excavated, mainly with 3 tunnel boring machines, to a 420 m high pressure twin pressure shaft, feeding six high head Francis turbines in an underground powerhouse. A 1 km long tailrace tunnel leads the turbine water to the Fljotsdalur valley at an elevation of 25 m a.s.l.
The second river is dammed at an elevation 625 m a.s.l. and the water fed into the headrace tunnel with a 13 km long diversion tunnel. In addition, there are some diversions with smaller dams and tunnels.
The total cost of the project is about 2 billion USD. Construction started in 2003 and the units came online in November 2007. The annual generating output is 4.8 - 5.0 TWh.
The services included overall project management of the project including from site investigations, an environmental impact assessment, permitting, tendering, supervision of construction management, budgeting, cost control, reporting and commissioning.
