Optimal Time for Collecting Volatile Organic Chemical Samples from Slowly Recovering Wells

Sheng-Fu J. Chou, Beverly L. Herzog, John R. Valkenburg, Robert A. Griffin

Research output: Book/Report/Conference proceedingOther report


Determining the optimum time to sample slowly recovering wells for volatile organic compounds was the objective of this research. Three hundred samples from 11 wells finished in fine-grained glacial tills were analyzed for up to 19 volatile organic compounds. Each well was sampled before purging, and at intervals up to 48 hours after well purging. This combination of purging and sampling was conducted three to five times on each well. Samples were collected with dedicated point-source PTFE (polytetrafluoroethylene) bailers equipped with bottom~emptying devices designed for collecting samples for volatile organic chemical analysis. The wells were easily evacuated with a bailer because they were finished, at depths less than 40 feet, in materials with hydraulic conductivities of between 1 x1 0-6 and 7x10-5 cm/sec. Results of the volatile organic chemical analyses were examined using a general linear model and the Tukey honestly significant difference test to determine whether the changes in chemical concentrations with time after purging were statistically significant. At the 95% confidence level, there was no significant difference in concentrations in samples collected any time after well purging; however, samples collected 4 hours after purging had slightly higher concentrations than samples collected earlier or later during well recovery. Concentrations of volatile organics were significantly lower before purging than after purging. Samples collected before purging and 24 hours after purging also were analyzed to determine whether purging affected nonvolatile organic compounds. The results were analyzed using the pairwise Hest on the concentration data. This test showed that concentrations were statistically greater after purging.
Original languageEnglish (US)
Place of PublicationChampaign, IL
PublisherHazardous Waste Research and Information Center
Commissioning bodyHazardous Waste Research and Information Center; Project Number HWR 86019
StatePublished - 1991

Publication series

NameRR Series (Hazardous Waste Research and Information Center)
NameEnvironmental Geology (Illinois State Geological Survey)


  • Water -- Pollution -- Measurement
  • Groundwater -- Illinois -- Sampling

ASJC Scopus subject areas

  • Environmental Science(all)
  • Earth and Planetary Sciences(all)

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