What purging/sampling procedure would you recommend for low-yielding wells that have a limited volume screened interval?

In a situation where a low-yield well has very limited sample volume to begin with try to sample the water that is present in the well screen zone and don’t purge. In other words, you are going to want to use a no-purge or passive approach in those wells. The other alternative is to use what is called Minimum Purge Sampling. This means installing a very small pump or a pump inlet, for example, the tubing lines from a peristaltic pump or a very small volume bladder pump with small diameter tubing. Purge out the volume of the pump and tubing and then take groundwater samples from that water column. A few published papers have shown that sampling the water standing in the well is actually a better representation of what is in the groundwater as opposed to evacuating that well and ending up with two problems: affecting the groundwater chemistry and not potentially having sufficient sample volume to fill the bottles. I would also like to point out, it’s very important in situations with limited sample volume to work with your laboratory. Talk to the lab to determine the minimum volume of water needed for all your analyses at the detection limits that you require. You may find that the laboratory can get by with less of the volume of water that you are currently collecting. In essence, work with your lab, get the volumes down, and use a passive or no purge approach, possibly minimum purge sampling.