What purging and sampling procedure would you recommend for low-yielding wells
What purging and sampling procedure would you recommend for low-yielding wells that have limited volume in the screen interval?
If I have a limited volume in the well screen in a very low-yield situation where I can't even pump the well at 50 to 100 mm a minute and get the water level to quickly stabilize then my recommendation would be to go a passive or no-purge sampling approach. That’s really at that point in the game if either through well construction or just through the National Formation Hydraulic Conductivity, you have a well that produces so little water and has so little water stored in it that you can't pump it then the water that’s standing in the well is unfortunately about the best representation you are going to get of what's in the formation. It's not perfect and it has to be considered as such. We know that it's really just essentially the lessor of two evils. But I would go with the passive or no-purge sampling device in that application. If I needed much sample volume or if I am looking for analytes beyond VOCs I am probably going to be using an equilibrated-grab sampler like HydraSleeve, a snap sampler or a camera sampler something like that. If I am looking at just VOCs, that’s where the passive diffusion devices might come into play.
If I have a limited volume in the well screen in a very low-yield situation where I can't even pump the well at 50 to 100 mm a minute and get the water level to quickly stabilize then my recommendation would be to go a passive or no-purge sampling approach. That’s really at that point in the game if either through well construction or just through the National Formation Hydraulic Conductivity, you have a well that produces so little water and has so little water stored in it that you can't pump it then the water that’s standing in the well is unfortunately about the best representation you are going to get of what's in the formation. It's not perfect and it has to be considered as such. We know that it's really just essentially the lessor of two evils. But I would go with the passive or no-purge sampling device in that application. If I needed much sample volume or if I am looking for analytes beyond VOCs I am probably going to be using an equilibrated-grab sampler like HydraSleeve, a snap sampler or a camera sampler something like that. If I am looking at just VOCs, that’s where the passive diffusion devices might come into play.