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:
Bryon Dahlgren
Earth Tech, Inc.
Ste 170, 1455 Old Alabama Road
Roswell GA 30076-2167 
Tel: 770-990-1420 
Email: Bryon.dahlgren@
earthtech.com

Unknown chloroform-contaminated site
Unknown


Hydrogeology:

Bedrock with overlying saprolitic soils.

Targeted Environmental Media:
  • - Fractured Bedrock

Contaminants:

Most of the chloroform plume was down gradient of an existing groundwater extraction system which had proved ineffective and was shut down.

Major Contaminants and Maximum Concentrations:
  • - Chloroform (15,000 µg/L)

Site Characterization Technologies:

  • - Other

Comments:
No site characterization technologies were identified within the abstract for this reference.


Remedial Technologies:

  • - Bioremediation (In Situ)
    • Reductive Dechlorination (In Situ Bioremediation)
Comments:
A groundwater extraction system had been previously installed for the site; however, it was determined to be ineffective. Several extraction and monitoring wells from the prior system were transformed into injection wells through which a sodium lactate solution was gravity fed during two injection events. The first injection took place in 2003 during which a solution of sodium lactate and water was injected at approximately 60,000 mg/L. Equal portions of the solution were fed into 10 wells in order to afford an average lactate concentration of 1,000 mg/L within the plume. A second injection took place between July 2004 and February 2005 during which the same mass of lactate was injected as the first event, however one sixth of the mass was injected every sixth week in order to extend the duration of the treatment to thirty weeks. Site monitoring took place from 2005 to 2007.
Remediation Goals:

None provided


Status:

After the first injection, reducing conditions and a rapid decline in chloroform were observed, including several locations having non-detectable levels. Some locations showed a rebound in chloroform concentration while others remained low. After the second injection event, most locations are non-detect with the remaining locations showing a decline in chloroform concentrations by at least 95 percent.


Lessons Learned:

Reductive treatment can be used to remediate chloroform contamination in a bedrock aquifer. The project also showed that using existing wells, highly miscible and mobile (non-viscous) substrates, and gravity-fed injection can result in minimized technology costs. The project will be completed by the application of supplemental injections downgradient of the initial application as well as in some locations where minor rebound needs to be addressed.

References:
Dahlgren, Bryon. Reductive Dechlorination of Chloroform in Fractured Bedrock Aquifer: A Success Story, Platform Abstract Session A4. Presented at the Sixth International Conference on Remediation of Chlorinated and Recalcitrant Compounds. Monterey, CA. May 19-22, 2008.

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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