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Environmental Health - Toxic Substances

Toxics Program Remediation Activities

Borehole-Geophysical Monitoring of a Contaminated Fractured Rock Aquifer

Type

Site Characterization

Location Storrs, Connecticut
Partners University of Connecticut
Technology
  • Monitored Natural Attenuation
  • Source Area Capping
Contaminants
  • Pesticides
  • Chlorinated Solvents
  • Heavy Metals
  • Benzene
Description
View of test wells during blasting of the recovery trench at Loring Air Force Base, Maine. Water was ejected from wells as much as 12 to 15 meters into the air
View of test wells during blasting of the recovery trench at Loring Air Force Base, Maine. Water was ejected from wells as much as 12 to 15 meters into the air

U.S. Geological Survey (USGS) scientists used surface- and borehole-geophysical methods together with hydraulic and geochemical data to characterize lithology, fractures, and hydraulic properties of crystalline bedrock and to determine the nature and extent of ground-water contamination from a landfill and former chemical-waste disposal pits located in the Willimantic River Basin, Connecticut. Detection of volatile organic compounds (VOCs) in water from domestic bedrock wells during the mid-1980s led to this investigation.

USGS scientists developed and tested field techniques and interpretive methods to characterize ground-water flow and chemical migration at the Mirror Lake Fractured-Rock Research Site, New Hampshire. Surface geophysical methods, such as electromagnetic induction, two-dimensional direct-current resistivity, square-array direct-current resistivity, and seismic refraction that were tested at the Mirror Lake site were at the landfill site. These methods helped target potential discharge of contaminants from the landfill for further investigation.

Conventional geophysical logging, acoustic and optical imaging, single-hole directional radar reflection, flowmeter logging under ambient and pumped conditions, and discrete-interval hydraulic testing, sampling, and monitoring were conducted in 11 bedrock boreholes. Borehole-geophysical methods were used to investigate the conductive anomalies identified by surface-geophysical methods, the location and orientation of fractures that intersect and surround each well, the direction and magnitude of ambient flow in the well, and the transmissive fractures that could provide pathways for contaminant migration.

The Multifunction Bedrock-Aquifer Transportable Testing Tool (BAT3), a discrete-zone monitoring system, was used in bedrock wells to prevent cross contamination, obtain water samples, measure hydraulic head, and assess hydraulic gradients between the bedrock and the glacial-drift deposits. Water samples were collected quarterly and analyzed for VOCs, metals, inorganic constituents, and other parameters.

More Information
Contact Carole Johnson, USGS, Branch of Geophysics, Storrs, Connecticut, cjohnson@usgs.gov
Publications

See Applied Research at University of Connecticut Landfill Study Area for a more complete list of publications from this study.

Links

Geophysical Methods Research

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Page Last Modified: Tuesday, 04-Aug-2015 15:47:23 EDT