downgradient well ( 5.664 kg). As in the other settings, portions of
contaminant plumes migrated past the extraction wells in setting C, but
did not reach the downgradient site boundary (Figure 3).
Results outlined above suggest that low-energy wells, coupled with the
mitigating effects of dilution and hydrodynamic dispersion, are a viable
groundwater remediation alternative in the simulated settings. Enabling
portions of a contaminant plume to migrate past a low-capacity well,
but attenuate within an onsite buffer zone, can be an effective remediation strategy.
The best overall well did not necessarily coincide with the downgradient point or crossgradient midpoint of a contaminant plume. Moreover,
large differences in the minimum pumping rate necessary to contain a
plume were observed for wells located just a few meters apart. These
results are compelling, because smaller extraction rates require less
pumping energy, resulting in potentially significant cost savings. Additionally, low-energy wells coupled with above ground treatment do not
require costly excavation and disposal of spent filter media, as in permeable reactive barriers. Above-ground treatment is easier to monitor
and maintain than filter media in permeable reactive barriers.
However, there are limitations to the methods simulated in this study.
These methods, and many used in practice, require groundwater to
transport dissolved contaminants. Thus, they would tend to be less
effective in aquifers with low groundwater seepage velocities, and for
contaminants with low solubility. Such conditions would delay or prevent contaminants from moving into the extraction well. Importantly,
the efficiency of groundwater remediation systems is highly dependent
upon site conditions; these systems require careful monitoring to verify
The objective of this study was to evaluate the relative performance of
low-energy wells as a function of placement in heterogeneous settings
for containing and removing contaminant plumes. Results show that
low-capacity wells are a viable alternative for groundwater remediation
in some heterogeneous settings. The optimal location of these wells
does not necessarily coincide with the downgradient or crossgradient
midpoint of a contaminant plume. Location is critically important; even
small differences can result in large differences in minimum pumping
rate necessary to contain a contaminant plume.
Author: Paul F. Hudak
Department of Geography and the Environment
University of North Texas
1155 Union Circle #305279
Denton, TX 76203-5017
Blowes, D. W., Ptacek, C.J., Benner, S.G., McRae, C. W. T., Bennett, T.A. &
Puls, R. W. (2000). Treatment of inorganic contaminants using permeable reac-
tive barriers. Journal of Contaminant Hydrology, 45( 1), 123-137.
Cunningham, J.A. & Reinhard, M. (2002). Injection-extraction treatment well
pairs: An alternative to permeable reactive barriers. Ground Water, 40( 6), 599-
Cunningham, J.A., Hoelen, T.P., Hopkins, G.D., Lebron, C.A. & Reinhard, M.
(2004). Hydraulics of recirculating well pairs for ground water remediation.
Ground Water 42( 6), 880-889.
Elder, C.R., Benson, C.H. & Eykholt, G.R. (2002). Effects of heterogeneity on
influent and effluent concentration from horizontal permeable reactive barriers.
Water Resources Research, 38( 8), 1152, doi: 10.1029/2001WR001259.
EPA (US Environmental Protection Agency) (2002). Economic analysis of the
implementation of permeable reactive barriers for remediation of contaminated
ground water. Washington, DC: US Environmental Protection Agency.
Gilbert, O., De Pablo, J., Cortina, J-L., Ayora, C. & Cama, J. (2010). In situ
removal of arsenic from groundwater by using permeable reactive barriers of
organic matter/limestone/zero-valent iron mixtures. Environmental Geochem-
istry and Health, 32( 4), 373-378.
Guerin, T.F., Horner, S., McGovern, T. & Davey, B. (2002). An application of
permeable reactive barrier technology to petroleum hydrocarbon contaminated
groundwater. Water Research, 36( 1), 15-24.
Gupta, N. & Fox, T.C. (1999). Hydrogeologic modeling for permeable reactive
barriers. Journal of Hazardous Materials, 68( 1), 19-39.
Hemsi, P.S. & Shackelford, C.D. (2006). An evaluation of the influence of
aquifer heterogeneity on permeable reactive barrier design. Water Resources
Research, 42, W03402, doi: 10.1029/2005WR004629.
Hudak, P.F. (2007). Mass transport in groundwater near hanging-wall intercep-
tors. Journal of Environmental Science and Health, 42( 3), 317-321.
Hudak, P.F. (2009). Internal versus external configurations of passive wells
with filter cartridges for cleaning contaminated groundwater. Remediation,
20( 1), 133-141.
Hudak, P.F. (2014). Comparison of permeable reactive barrier, funnel and gate,
non-pumped wells, and low-capacity wells for groundwater remediation. Jour-
nal of Environmental Science and Health, 49( 10), 1171-1175.
Lai, K.C.K., Lo, I.M.C., Birkelund, V. & Kjeldsen, P. (2006). Field monitoring
of a permeable reactive barrier for removal of chlorinated organics. Journal of
Environmental Engineering, 132( 2), 199-210.
Ludwig, R.D., McGregor, R.G., Blowes, D. W., Benner, S.G. & Mountjoy, K.
(2002). A permeable reactive barrier for treatment of heavy metals. Ground
Water, 40( 1), 59-66.
Painter, B.D.M. (2004). Reactive barriers: Hydraulic performance and design
enhancements. Ground Water, 42( 4), 609-619.
Robertson, W.D., Blowes, D. W. & Cherry, J.A. (2000). Long-term performance
of in situ reactive barriers for nitrate remediation. Ground Water, 38( 5), 689-
USGS (US Geological Survey) (1999). Deep aquifer remediation tools
(DARTs): A new technology for ground-water remediation. Reston, VA: US
Geological Survey Fact Sheet 156-99.
Wu, M. Y., Smits, K.M., Goltz, M.N. & Christ, J.A. (2008). A screening model
for injection-extraction treatment well recirculation design. Ground Water,
28( 4), 63-71.
Zheng, C. & Wang, P.P. (1999). MT3DMS, a modular three-dimensional
multi-species transport model for simulation of advection, dispersion and
chemical reactions of contaminants in groundwater systems; documentation
and user’s guide. Vicksburg, MS: US Army Engineer Research and Development Center Contract Report SERDP-99-1.
Contaminated Groundwater in Heterogeneous Aquifers
Circle 107 on Card or http://pen.hotims.com/68942-107
Continued on page 25