What would you recommend for low-flow wells of less than 30 mL per minute?

If you are purging a low-flow well at rates that are significantly under 100 mL per minute, it may be time to consider using an alternate purging and sampling method. When wells are so low-yield that it's hard to get the water level to stabilize even at very low pumping rates, I recommend switching to a no-purge or passive sampling approach. With the no-purge approach you actually grab a water sample from the well using a device like a snap sampler or something similar, or if you are only looking at certain VOCs you might be able to use a diffusion-type device. You have to remember that the water in the formation in those extremely low hydraulic connectivity settings is not moving very fast or very far.  Diffusion actually has a tendency to be a greater factor when it comes to the contaminant redistribution or movement, and using a passive or no-purge approach and getting a sample from the water column will probably show the best representation under those very low-yield conditions.