Sixty kilometres of tunnel, as part of Iceland’s largest ever
industrial development
As lead consultant in a joint venture comprising Línuhönnun,
Fjarhitun and HNIT plus European companies Coyne et Bellier, SWECO
and Norconsult, Mott MacDonald is overseeing the construction of
60km of tunnel and a 190m high concrete faced rockfill dam in
eastern Iceland. The dam and tunnel are part of national power
company Landsvirkjun’s US$1.3 billion project, which includes the
Kárahnjúkar power station being built to supply energy to US
company Alcoa’s new aluminium smelter.
Development of the Kárahnjúkar power station entails harnessing the
glacial rivers Jökulsá á Dal and Jökulsá í Fljótsdal and creating
the 57km2 Hálslón water-storage reservoir and the
smaller Ufsarlón reservoir. From the Hálslón reservoir, water will
be conveyed through an underground headrace tunnel eastward joining
another tunnel from the Ufsarlón reservoir. The water will then be
carried in a single tunnel north eastward to the Teigsbjarg
escarpment, where it will drop through two steep penstocks to an
underground powerhouse. There the water will enter six generating
units in the powerhouse and then travel through a tailrace tunnel
and canal into the course of the glacial river Jökulsá í Fljótsdal.
The hydropower station will have an installed capacity of 630MW, a
harnessed flow rate of 126m³ per second and a power-generating
capacity of 4450GWh per year.
We’re providing specialist expertise for the 7.6m diameter tunnel –
33km of which will be created using TBM and the remaining 27km
using drill and blast techniques, representing one of the major
tunnel drives currently underway worldwide. As lead consultant in
the joint venture we’re also directing the single integrated team
based near the glacier supervising construction of the tunnel and
dam.
