Changes in legislation, combined with improved and lower cost sampling instrumentation, have encouraged consultants, researchers, and government agencies to obtain higher quality groundwater samples.  No-purge, also known as passive or grab sampling, is one method that is gaining acceptance by many regulatory agencies for obtaining representative groundwater samples. <\/p>\n\n\n\n

The ITRC (Interstate Technology & Regulatory Council) define a \u201cpassive\u201d sampler as one that is able to acquire a sample from a discrete location without the active media transport induced by pumping or purge technologies.<\/p>\n\n\n\n

Methodology<\/h2>\n\n\n\n

Sampling methods are based on the principle that groundwater, which flows through a screen and into a well, is characteristic of the water outside the well at that depth.  Studies have shown that sampling at the screened interval should result in a representative sample, without the need for purging.  In order to get a sample representative of aquifer conditions, passive samplers must be submerged within the screened interval and remain in the well until groundwater conditions have re-equilibrated. Once equilibrium is reached, a sample can be taken. Samples can also be taken as soon as the target depth is reached to obtain a sample of current conditions in the well.<\/p>\n\n\n\n

When compared to conventional sampling methods, no-purge samplers typically require less costs and time to retrieve a sample.  Minimal labour is required as there is no purge water to manage, or dispose.  Normally, no-purge samplers do not require power, a compressor or control unit, and there is little or no well water agitation when the samplers are deployed and operated.<\/p>\n\n\n\n