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: December 10, 2007

Point of Contact:
Jeff Orient
661 Andersen Drive, Foster Plaza 7
Pittsburgh PA 15220 
Tel: 412-921-8778 
Email: Jeff.orient@
tetratech.com

Former Naval Air Warfare Center
Philadelphia, PA


Hydrogeology:

Below the site lies the Triassic age Stockton Formation. This formation consists of arkosic sandstone units that alternate with finer grained mudstone units. Depositional environments include alluvial fan, fluvial, lacustrine, and near-shore lacustrine. Ground water flows primarily through coarse-grained unit fractures with semi-confining units made up of the softer mudstones. Fine-grained lithologic units and coarse-grained units within the larger depositional sequences are found below the site. Bedrock units strike N72E and dip approximately 6 to 7 to the north-northeast.

Targeted Environmental Media:
  • - Dense Non-aqueous Phase Liquids (DNAPLs)
  • - Fractured Bedrock

Contaminants:

Major Contaminants and Maximum Concentrations:
  • - Trichloroethene (Not provided)

Site Characterization Technologies:

  • - Borehole Geophysics
    • Single Point Resistance
    • Natural Gamma
    • Caliper
  • - Fluid Loggings
    • Temperature
    • Conductivity/Resistivity
  • - Flow
    • Heat Pulse Flowmeter

Remedial Technologies:

  • - Pump and Treat
  • - Other (Waste and contaminated soils from the site were excavated and disposed.)
Comments:
The design pumping rate was 54 gallons per minute (gpm) and the average pumping rate was approximately 50 gpm. Currently, 12 extraction wells are operating at the site. An air stripping and carbon polishing treatment system was also constructed to treat contaminated ground water.
Remediation Goals:

Objectives of the pump and treat system were source area containment and contaminant mass removal.


Status:

Ground water extraction began in 1999. Since then, contaminant concentrations have decreased within the source area and downgradient of the source area. The concentration of TCE within the source zone varies, however, levels within the most contaminated wells have shown concentration decreases of approximately two orders of magnitude. TCE concentrations downgradient of the extraction zone are slightly above the maximum contaminant level. Concentration decreases are less pronounced in the area further downgradient than the area immediately downgradient; however, off-site source contributions are being investigated.


Lessons Learned:

The two lowest producing wells had the highest concentrations of TCE, which remained elevated compared to other wells. This information leads to the belief that the DNAPL remains within the source area fractures and that not using low-yielding wells for extraction may not contribute to the overall goal.

References:
Orient, Jeff, Monaco, Lonnie, David, Kathryn, and Sloto Ronald A. Remediation of a Fractured Rock Aquifer Containing Trichloroethylene Dense Nonaqueous Phase Liquid. Presented at the 2007 U.S. EPA/NGWA Fractured Rock Conference: State of the Science and Measuring Success in Remediation. Portland, ME. September 24-26, 2007.

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For more information on Fractured Bedrock, please contact:

Ed Gilbert
Technology Assessment Branch

PH: (703) 603-8883 | Email: gilbert.edward@epa.gov