MICRO-PURGE LOW-FLOW SAMPLING OF URANIUM-CONTAMINATED GROUND-WATER ATTHE FERNALD ENVIRONMENTAL-MANAGEMENT PROJECT

Efforts to sample representative, undisturbed distributions of uranium in ground water beneath the Fernald Environmental Management Project (FEMP) prompted the application of a novel technique that is less inva sive in the monitoring well. Recent studies (Kearl et al. 1992; Barcel ona et al. 1994) indicate that representative samples can and should b e collected without prior well volume exchange purging or borehole eva cuation. Field experiments conducted at the FEMP demonstrate that unde r specific sampling conditions in a well-defined hydrogeologic system, representative ground water samples for a monitoring program can be o btained without removing the conventional three well volumes from the well. The assumption is made that indicator parameter equilibration ma y not be necessary to determine when to collect representative samples at the FEMP. Preliminary results obtained from the field experiments suggest that this may be true. The technique employs low purge rates ( < 1 L/min) with dedicated bladder pumps with inlets located in the scr eened interval of the well, while not disturbing the stagnant water co lumn above the screened interval. If adopted, this technique, termed m icro-purge low-flow sampling, will produce representative ground water samples, significantly reduce sampling costs, and minimize waste wate r over the monitoring life cycle at the FEMP. This technique is well s uited for sites that have been fully characterized and are undergoing long-term monitoring.