Gas-Permeable Seal Test - Remediation

Saturation with high pressure water injection has been temporarily stopped due to an unexpected outflow of water through the main duct on January 2014. A series of activities took place to identify the point of leakage at the main duct, including a gradual increase of the water pressure in the system to 6 bars with continuous visual inspection inside the main duct. No water inflow was observed at this pressure and it was decided not to continue with the pressure increase before countermeasures against such an event in the future were taken.

The remediation concept selected consists of:

  1. closing of the main duct with the installation of a tight well head at the front end with water and gas-tight throughputs for the instrumentation cables
  2. backfilling the main duct with a low-permeability material to prevent any potential loss of bentonite or sand/bentonite mixture in the future or a connection through the risers

gast remediation 001
Main duct inspection with video camera

 gast remediation 002
Preparation for well head emplacement

gast remediation 003
Well head is installed at main duct mouth

gast remediation 004
Sealing of cable ducts in upper well head

Gas-Permeable Seal Test (GAST)

The GTS underground facilities are also available to interested 3rd parties for underground testing and research. The GTS offers cost-effective access to a fully developed, well characterised underground research facility with round the year logistical support - please contact Dr. Ingo Blechschmidt, Head of the Grimsel Test Site, for further details.