Gregg In Situ, Inc. conducts groundwater sampling using a Hydropunch^® type groundwater sampler, Figure GWS.  The groundwater sampler has a retrievable stainless steel or disposable PVC screen with steel drop off tip.  This allows for samples to be taken at multiple depth intervals within the same sounding location.  In areas of slower water recharge, provisions may be made to set temporary PVC well screens during sampling to allow the drill rig to advance to the next sample location while the groundwater is allowed to infiltrate.

 The groundwater sampler operates by advancing 1 ¾ inch hollow push rods with the filter tip in a closed configuration to the base of the desired sampling interval.  Once at the desired sample depth, the push rods are retracted; exposing the encased filter screen and allowing groundwater to infiltrate hydrostatically from the formation into the inlet screen.  A small diameter bailer (approximately ½ or ¾ inch) is lowered through the push rods into the screen section for sample collection.  The number of downhole trips with the bailer and time necessary to complete the sample collection at each depth interval is a function of sampling protocols, volume requirements, and the yield characteristics and storage capacity of the formation.  Upon completion of sample collection, the push rods and sampler, with the exception of the PVC screen and steel drop off tip are retrieved to the ground surface, decontaminated and prepared for the next sampling event.