There are practical limits and regulatory limits of drawdown written into many guidance documents. Unfortunately, the 1996 EPA groundwater issue paper on low-flow sampling seemed to indicate a 3/10 of a foot drawdown limit. The authors didn’t put an “e.g.” in front of the 3/10 to make it the example and not a stated limit. Another study looked at the practical limit, and the reality is as long as you can get the pumping water level in the well to stabilize at some point, low flow sampling will work. Until the water level is stabilized mixing is still occurring, so indicator parameters will not stabilize. If you have a regulatory limit you can address that with the regulators by providing data to support that the drawdown limit doesn’t matter, it really depends on the water column that is present. The critical thing is to get the water level to stabilize in the well before you can say that indicator parameters have stabilized.