Evaluation of groundwater flow patterns around a dual-screened groundwater circulation well

Richard Johnson, Michelle A. Simon

Research output: Contribution to journalArticle

13 Citations (Scopus)

Abstract

Dual-screened groundwater circulation wells (GCWs) can be used to remove contaminant mass and to mix reagents in situ. GCWs are so named because they force water in a circular pattern between injection and extraction screens. The radial extent, flux and direction of the effective flow of this circulation cell are difficult to measure or predict. The objective of this study is to develop a robust protocol for assessing GCW performance. To accomplish this, groundwater flow patterns surrounding a GCW are assessed using a suite of tools and data, including: hydraulic head, in situ flow velocity, measured hydraulic conductivity data from core samples, chemical tracer tests, contaminant distribution data, and numerical flow and transport models. The hydraulic head data show patterns that are consistent with pumping on a dual-screened well, however, many of the observed changes are smaller than expected. In situ thermal perturbation flow sensors successfully measured horizontal flow, but vertical flow could not be determined with sufficient accuracy to be useful in mapping flow patterns. Two types of chemical tracer tests were utilized at the site and showed that much of the flow occurs within a few meters of the GCW. Flow patterns were also assessed based on changes in contaminant (trichloroethylene, TCE) concentrations over time. The TCE data clearly showed treated water moving away from the GCW at shallow and intermediate depths, but the circulation of that water back to the well, except very close to the well, was less clear. Detailed vertical and horizontal hydraulic conductivities were measured on 0.3 m-long sections from a continuous core from the GCW installation borehole. The measured vertical and horizontal hydraulic conductivity data were used to construct numerical flow and transport models, the results of which were compared to the head, velocity and concentration data. Taken together, the field data and modeling present a fairly consistent picture of flow and transport around the GCW. However, the time and expense associated with conducting all of those tests would be prohibitive for most sites. As a consequence, a sequential protocol for GCW characterization is presented here in which the number of tools used can be adjusted to meet the needs of individual sites. While not perfect, we believe that this approach represents the most efficient means for evaluating GCW performance.

Original languageEnglish (US)
Pages (from-to)188-202
Number of pages15
JournalJournal of Contaminant Hydrology
Volume93
Issue number1-4
DOIs
StatePublished - Aug 15 2007

Fingerprint

Groundwater flow
flow pattern
Flow patterns
groundwater flow
Groundwater
groundwater
well
Hydraulic conductivity
Trichloroethylene
hydraulic conductivity
Impurities
hydraulic head
Water
trichloroethylene
Hydraulics
evaluation
pollutant
tracer
Core samples
Boreholes

Keywords

  • Anisotropy
  • Breakthrough curves
  • GCW
  • Groundwater circulation wells
  • Groundwater recirculation wells
  • Heterogeneity
  • Hydrogeology
  • HydroTechnics
  • In situ flow meters
  • In-well air stripping
  • MODFLOW
  • Numerical flow modeling
  • Numerical transport modelling
  • Tracer

ASJC Scopus subject areas

  • Earth-Surface Processes
  • Water Science and Technology
  • Environmental Chemistry

Cite this

Evaluation of groundwater flow patterns around a dual-screened groundwater circulation well. / Johnson, Richard; Simon, Michelle A.

In: Journal of Contaminant Hydrology, Vol. 93, No. 1-4, 15.08.2007, p. 188-202.

Research output: Contribution to journalArticle

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