Artificial saturation of the sand/bentonite layers had to be carried out due to the low natural inflow rate.

• Initial saturation stages used low pressure injections into layer 1 and the upper cavern backfill
  
  
• Once the upper cavern was filled, the pressure was raised to about 580 kPa (this is similar to the ambient pressure prior to excavation)
  
  
• Once the target pressure was reached, the pressure was maintained by balancing injection with inflows to GMT drift and the VE shear zone
  
  
• The saturation stage ended on 15th October '02 when the water tests began
  
  
• High water saturation was achieved quickly in layers 8, 9 and 10. These high permeability layers may be due to the presence of the gas visualisation tracer
  
  
• Much slower saturation of layers 2 to 6 and layer 11 was observed.