Hydropower tunnels

Safe refurbishment work in hydropower tunnels.

Contracting services

Ice plug from surface

Geofrost delivers ice plugging of water tunnels upstream the first gate, so the tunnel can be emptied for water and refurbishment works carried out in a safe manner in a dry tunnel.

Drilling is performed from surface above the reservoir level, down through the tunnel for installation of freezing pipes and monitoring equipment.

A cofferdam is not always easy to establish. It may be due to topography, regulations for the lake, or large values being lost for the owner if the water level is lowered.

Ice plug from waterside

Geofrost may install the ice plug through the water intake so it gets placed in the intake construction or further into the tunnel.

Sometimes the water way upstream the gate is a pipe or an intake construction that preferably should not be drilled through, or it is not practical to drill into the tunnel.

The ice plug has high reliability and is frozen into the surronding rock or concrete. The ice plug is monitored as long as it functions and detailed capacity calculations are always part of the design.

Photo: Ice plug.


Figure: Cofferdam.

Geofrost delivers waterproof core in rock fill dams so it can be used as a cofferdam. Drilling is done through the rock fill and further down through permeable layers and fractured rock, ensuring a completely impermeable cofferdam.


No lowering

By plugging the water filled tunnel by a Geofrost ice plug, it may become unnecessary to lower the reservoir water level.

Minimal stop

The temporary ice plug is relatively quick to establish, and removal is even faster. Time without hydro power production is minimized.

Low impact

Installation of ice plug has low impact on the surroundings.

What we deliver

We are a total supplier of ice plugs and waterproofing of cofferdams with ground freezing and offer all related services within consulting and contracting.


  • Project management
  • Design and engineering
  • Numerical analyses
  • Design report, drawings, and specifications.


  • Planning and procurement
  • Site management
  • Drilling and surveying
  • Pipe installation
  • Plant and equipment for brine and nitrogen freezing
  • Instrumentation
  • Monitoring

Where we operate

We offer our services worldwide.


Contact person

Anne-Lise Berggren, Ph.D., M.Sc
Senior specialist geotechnics
 (+47) 95 29 29 30


If you have questions or would like more information, please contact us. With project info, we quickly provide price estimates.

Ground freezing services since 1986.