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4 The Hartford Study -- Under directive from the Department of Energy Operable Unit Manager to investigate methodologies which could obtain superior data and cut costs, the No- purge KABIS Sampler TM technique was tested against the Low-flow Purge technique at the Hanford Operable Unit in Richland Washington. In an unprecedented cooperative effort, a multi-agency, multi-contractor study was conducted in 1996 on a limited number of wells to evaluate the benefits and inherent drawbacks associated with each sampling method and device In this unpublished study, M. Darrach, et al, noted that, ". the KABIS Sampler TM provides superior sampling results where large sample volumes are not required " and that, using the KABIS SamplerTM, purging appears unnecessary in wells which exhibit a measurable flow through the screened interval Aquifer flow evaluation was conducted on each well selected for this study using colloidal tracer methodology Hall et al, has shown that flow through the screened portion, and at any interval along the screened portion, of any groundwater monitoring well can be effectively identified and characterized using colloidal tracer"methodology The results of flow tracer testing at the Hanford Operable Unit on the wells selected for this study indicated that flows as low as 1-2 gpd were sufficient to affect refreshing of the water inside the screened portion of the well Discrete Multi-layer Sampling Studies -- Some success has been achieved using a new discrete multi-layer sampling (DMLS) system in the no-purge scenario The DMLS system resembles an elongate "bird house" with numerous chambers, each filled with de-ionized water, extending radially outward from a central stem; each chamber is covered with a semi- permeable membrane which is exposed to the water within the well The DMLS system is lowered down a well and allowed to reside within the well for up to several months before it is retrieved and the various chambers analyzed for whatever constituents have been equilibrated into the chamber Studies conducted in Israel and several European countries using the DMLS system have shown that reliable DPIS samples are achievable without benefit of purging Widdowson, and Orne demonstrated in their 1995 paper that metals and organic constituents could be successfully modeled in an aquifer in three dimensions There is a single obvious drawback to the DMLS sampler, however, expressed by the extraordinary amount of time necessary for equilibration of the sample cells and the well water across the semipermeable membrane. In situations where expediency is required, this sampler may not be a correct choice. Conclusions Obtaining representative groundwater samples, without benefit of well purging, from most groundwater monitoring wells using newly designed sampling equipment is now possible. A review of current published and unpublished literature has revealed a new, growing, and viable trend in the groundwater investigation industry Owing to the most recent move in both government and the private sector to spend less on environmental clean-up activities, and since the act of purging is, in and of itself a very costly enterprise, the no-purge scenario is gaining wide acceptance Recent studies conducted at sites in several states have all reached the same conclusion, that purging a groundwater monitoring well when using a sampling instrument