Over the years groundwater monitoring has been performed by a variety of methods; from a glorified bucket on a string (bailer) to sophisticated pumps matched with high tech multi-meters assessing a variety of groundwater parameters to identify when the extracted water best represents subsurface conditions. All groundwater sampling methods have their pro and cons, both in the quality of the sample and the cost at which it is collected. The Indiana Department of Environmental Management (IDEM) recently released technical guidance on the use of Polyethylene Diffusion Bags (PDBs) for sampling groundwater, which can be downloaded here
http://www.in.gov/idem/landquality/files/remediation_tech_guidance_poly_diffusion.pdf
As detailed in the guidance, this method was developed by the US Geological survey, and it has been tested and utilized for years. If site conditions are appropriate for their use, PDBs have the potential to reduce groundwater monitoring costs by as much as 30%. Over the course of a project, the cumulative savings can be substantial. Alternatively, the cost reductions can allow more samples to be collected to provide a more robust demonstration of the groundwater plume’s behavior.
Wilcox has ample experience with the technology, and has even developed a customized PDB for use in projects where vapor intrusion is a significant concern (additional details to come).