The Power of Commitment 12552081 5 Column Operation and Sample Procedure The columns should be left exposed to atmospheric conditions for a minimum of 10 weeks. This initial phase is to ensure that oxidation of the waste rock takes place and becomes acid producing. During this initial phase, leachate generated should be monitored weekly. Depending on the results, the monitoring frequency may be extended with time. Samples can be obtained by carefully removing the leachate tubing from the bucket and collecting leachate directly from the tubing into laboratory supplied containers suitable for the analysis of the parameters detailed in Table 2 and Table 3. The expanded and reduced analytical suite should be undertaken on alternate weeks. It is recommended that the expanded suite is utilised for the first flush sample (the first leachate collection event). Field parameters should be collected utilising a calibrated multi-parameter (or similar individual meters) and the following field parameters recorded: pH Conductivity Temperature It is recommended that calibration of pH and conductivity is undertaken using appropriate calibration solutions that cover the likely range of measured parameters. The remaining leachate should be left to drain into the bucket until the tubing runs dry. The volume of leachate within the bucket should be recorded and sampled before reconnecting the tubing to the empty bucket. If insufficient leachate drains from the tubing and base of column to enable the collection of water samples and/or accurate measurement of field parameters, static water within the bucket should be utilised. If no leachate water (or insufficient leachate water) is available, a measured volume of 500 mL of de- ionised water should be poured into the column at the top, and the leachate should be collected as described above. Where this is required, it should be recorded on the sampling sheet. In the event that there is frequently not enough leachate to sample within the tubing, a measured volume of deionised water should be added to the top of the column several days before sampling to ensure sufficient water is available. The water level of the columns and buckets should be monitoring during and after heavy rainfall events in order to prevent overflow. If leachate buckets need emptying in between the weekly sample cycle, it is recommended that field parameters (as above) be recorded prior to the disposal of the leachate water. The water level of the columns and buckets should be monitoring during and after heavy rainfall events in order to prevent overflow. If leachate buckets need emptying in between the weekly sample cycle, it is recommended that field parameters (as above) be recorded prior to the disposal of the leachate water.
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