Ground freezing for plugging water filled tunnel

Safe water emptying
of tunnel by ice plug
Change gate without lowering the reservoir water level by placing a Geofrost ice plug upstream the gate.
Specialized in AGF since 1986.


No lowering of the water level

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

Unaffected by weather

An ice plug is not affected by a sudden increase in water level. It's a safe and reliable soultion.

Minimal stop in the production

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


When refurbishment or rehabilitation of the waterways in a hydro power plant are to take place, the gates are closed. But as installations grow older also the gate needs to be replaced. As an alternative to the usual lowering of the water reservoir and building a cofferdam, Geofrost delivers an ice plug that may seal the tunnel upstream and enabling draining the tunnel without lowering the reservoir level.

Ice plug from surface

A cofferdam is not always easy to establish. It may be due to topography, regulations or large values beeing lost for the owner.

Geofrost delivers iceplug upstream the gate enabling the refurbishment beeing executed safely in a drained tunnel.

Drilling is performed from surface above the reservoir level, down through the tunnel for installation.

Ice plug from waterside

Sometimes the water way upstream the gate is a pipe or an intake construction that preferably should not be drilled through.

Geofrost may then install equipment from the water side, and the ice plug will be in the intake structure or close by. It is then presupposed that the surrounding structure is water proof.

What we deliver

We are a total supplier of ice plug 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 freezing and nitrogn freezing
  • Instrumentation
  • Surveillance
  • Excavation

Where we operate

We offer our services to hydro power plants worldwide.


Contact person

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

Send enquiry

With brief overall project info, we quickly provide rates and price estimates on request.