Injection of water into the silo was carried out to set a baseline for the post-gas comparison and to measure the effective properties of the buffer. In a series of tests water was injected into different parts of the silo and the overall responses were recorded by the installed instrumentation.

Water permeability tests were performed before (Test WT1) and after gas injection (Test WT2). Both tests involved injection and withdrawal tests from the silo and sinusoidal variation of the upper cavern injection rate.

• WT1: Water Test 1: Multi-event injection/withdrawal from silo - 15th Oct to 25th Nov 02
  
  
• CV-Rsin1: Sinusoidal variation in injection rate into upper cavern - 28th Nov to 2nd Dec 02
  
  
• WL1: Water test layer 1 - 9th to 17th January 03
  
  
• WT2 CVSIN1: Sinusoidal variation in injection rate into upper cavern - 4th to 8th Oct 03
  
  
• WT2: Water Test 2: Multi-event injection/withdrawal from silo - 10th Oct to 15th Dec 03

Comparison of the results of WT1 and WT2 showed increased storage during WT2 (probably due to the presence of residual gas) and a potential reduction in the transmissivity of the flow path in/out of the silo. No evidence of any increase in permeability of the EBS due to the gas injection was observed.