U.S. EPA Contaminated Site Cleanup Information (CLU-IN)

U.S. Environmental Protection Agency
U.S. EPA Technology Innovation and Field Services Division

Fractured Bedrock Project Profiles

Last Updated: January 29, 2004

Point of Contact:
Graham Stevens
Connecticut DEP Remediation
79 Elm St.
Hartford CT 06106 
Tel: 860-424-4166 
Email: graham.stevens@

Norden Systems Inc.
Norwalk, CT


The site has only a thin soil cover, ranging in thickness from 0 to 7 feet (glacial till or fill), underlain by a very weathered saprolitic layer up to 30 feet in thickness. The saprolitic layer is underlain by fairly competent fractured metamorphic gneisses and schists.

Targeted Environmental Media:
  • - Fractured Bedrock


The major contaminants are TCE and breakdown products, and freon, from former degreasing operations. The lateral and vertical extent of the plume have not been completely delineated. Two source areas, one beneath the existing manufacturing building, and one just outside the building in a loading dock area, have been identified. Shallow wells in the highly weathered bedrock show evidence of shallow contamination in specific areas, apparently flowing with the topographic gradient to the southeast, and contamination has been found in wells up to 500 feet away. Certain deeper wells (up to 65 feet)in the fractured bedrock have historically shown contamination, although the horizontal and vertical extent is complex and has not been completely delineated at this time. Deeper wells (130 to 200 feet) were recently drilled and discrete sampling at the flowing fractures will be conducted in the fourth quarter of 1999.

Major Contaminants and Maximum Concentrations:
  • - Trichloroethene (var)

Site Characterization Technologies:

  • - Borehole Geophysics
    • Single Point Resistance
    • Natural Gamma
    • Caliper
    • Acoustic Televiewer
    • Video Camera Televiewer
    • Other
  • - Fluid Loggings
    • Temperature
    • Conductivity/Resistivity
  • - Flow
    • Heat Pulse Flowmeter
  • - Vertical Chemical Profiling
    • Packer Isolation
    • Multi-sampling port
  • - Fracture Trace Analysis
  • - Surface Conductivity Surveys (EM)
  • - Coring
  • - Other

We have done downhole radar in individual wells, as well as crosshole radar between closely spaced wells. We have also done crosshole heatpulse flowmeter work between wells that are hydraulically connected.

Remedial Technologies:

  • - Multi Phase Extraction

Remediation Goals:

Source area removal


A multi-phase extraction system was installed in the summer of 2003. Nine shallow wells were installed in the overburden and and five open hole deep wells were installed in the bedrock (20' to 60' deep). Ground water is treated in an air stripper. The technology will be evaluated in the summer of 2004.

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