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: March 22, 2010

Point of Contact:
Steve Chen
ARS Technologies, Inc.
98 North Ward Street
New Brunswick NJ 08901 
Tel: 732-296-6620 
Fax: 732-296-6625
Email: sc@
arstechnologies.com

1,1,1-TCA at an unknown industrial facility
Unknown, VA


Hydrogeology:

The site includes an underlying limestone bedrock aquifer. Water-bearing fractures exist at depths of 40 to 55 feet below ground surface. A highly conductive anomaly oriented in the direction of groundwater flow was identified near a leaking aboveground storage tank.

Targeted Environmental Media:
  • - Fractured Bedrock

Contaminants:

The references abstract did not identify plume characteristics however it is known that 75-gallons of 1,1,1-trichloroethane (TCA) were released from an aboveground storage tank and contaminated groundwater in the underlying limestone bedrock aquifer.

Major Contaminants and Maximum Concentrations:
  • - 1,1,1-Trichloroethane (20,000 µg/L)
  • - 1,1-Dichloroethane (0 µg/L)
  • - 1,1-Dichloroethene (0 µg/L)
  • - Chloroethane (0 µg/L)

Site Characterization Technologies:

  • - Coring
  • - Other (Electrical resistivity (ER) survey)

Comments:
Bedrock cores were taken to indicate the presence and depth of water-bearing bedrock fractures. The depth and location of bedrock fractures was confirmed through an ER survey.


Remedial Technologies:

  • - Fracturing
  • - Other (Zero-valent iron (ZVI))
Comments:
Prior to ZVI delivery, fracturing was performed under gas pressures of up to 650 pounds per square inch (psi). During June and September 2006, 13,100 pounds of ZVI was injected in conjunction with Pneumatic Fracturing to position a commercially available sponge ZVI (H-200). ZVI was introduced into a 15-foot thick bedrock zone in 3 to 3.5-foot sections and isolated by high-pressure packers. The ZVI was delivered under pressures that ranged between 60 to 280 psi with a maximum of 550 psi. Approximately 50% of the treatment zone did not have ZVI injected because the bedrock was competent.

Pressure monitoring took place during injection. As far as 200 feet from the injection area, pressure was observed. The pattern of pressure propagation was highly variable, probably determined by the existing fracture orientation.
Remediation Goals:

None provided


Status:

Over 12 months, TCA, 1,1-DCA, and 1,1-DCE concentrations within the source zone were decreased by 90%. Downgradient well concentrations of TCA and 1,1-DCE have decreased by 85% and 75% respectively, though 1,1-DCA concentrations increased.


Lessons Learned:

References:
Chen, Steve, David Sarr, and Kay Powell. Successful Treatment of 1,1,1-TCA in Bedrock by Pneumatic Fracturing and Zero-Valent Iron Injection, Poster Session E1 . Presented at the Sixth International Conference on Remediation of Chlorinated and Recalcitrant Compounds. Monterey, CA. May 19-22, 2008.

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