Should samples be collected immediately after bailing three to five casing volumes?
Should samples be collected immediately after bailing three to five casing volumes, or after the water in the well is allowed to recharge to at least 80% of the original volume amount?
This is a classic example of another one of the numbers we have in groundwater monitoring that really has no basis in science. We need take a look at some of the numbers such as: three to five volumes, 80% recovery, 100 mL/minute for volatiles, etc. and find the origin of these numbers to determine if they really have any meaning.
“80% recovery prior to taking a sample” seems to be an artifact of the concept of pumping tests on formations to determine hydraulic connectivity. There it makes sense to pump the well down and then get 80% recovery, but in a lot of other applications, it really has no effect on the samples that are taken.
This is a classic example of another one of the numbers we have in groundwater monitoring that really has no basis in science. We need take a look at some of the numbers such as: three to five volumes, 80% recovery, 100 mL/minute for volatiles, etc. and find the origin of these numbers to determine if they really have any meaning.
“80% recovery prior to taking a sample” seems to be an artifact of the concept of pumping tests on formations to determine hydraulic connectivity. There it makes sense to pump the well down and then get 80% recovery, but in a lot of other applications, it really has no effect on the samples that are taken.