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GROUND WATER SAMPLING FOR VERTICAL PROFILING OF CONTAMINANTS
Citation:
Paul*, C J. AND R W. Puls*. GROUND WATER SAMPLING FOR VERTICAL PROFILING OF CONTAMINANTS. Presented at Groundwater Conference, San Francisco, CA, 10/30/2000.
Description:
Accurate delineation of plume boundaries and vertical contaminant distribution are necessary in order to adequately characterize waste sites and determine remedial strategies to be employed. However, it is important to consider the sampling objectives, sampling methods, and sampling system used when interpreting any monitoring data. Traditional groundwater sampling methods can yield data which provide inaccurate pictures of plume shape, location, and extent of contamination. The quality of data collected using pumps and bailers is dependent upon the screen length, the purging and sampling technique used, and the volume purged prior to sampling. Comparisons were made using four different sampling approaches and devices to collect ground water from three conventional monitoring wells. Sampling devices used include an electric submersible pump using low-flow sampling techniques, a bailer using "traditional" sampling methods, and a passive multi-layer sampling system (DMLS?, Margan Ltd.). A Geoprobe? using short (30 cm) screens was used to determine aqueous contaminant concentrations in the formation adjacent to the monitoring wells at discrete depth intervals.
Both the submersible pump and bailer failed to provide accurate delineations of plume extent and concentration gradients. Data collected using low-flow purging and sampling techniques and the bailer generally provided averaged concentration values over the entire screened interval. However, data collected with the bailer consistently underestimated chromium concentrations when compared with the submersible pump data The Geoprobe? technology provides discrete contaminant distribution where monitoring wells are not available or for comparison purposes with other techniques. The DMLS? sampler provided data generally consistent with contaminant concentrations in the formation water acquired using the Geoprobe?.