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 15, 2005

Point of Contact:
Paul G. Landry
1400 Weston Way
P.O. Box 2653
West Chester PA 19380-2653 
Tel: 610-701-3000 
Fax: 610-701-3168
Email: landryp@
ail.rfweston.com

Letterkenny Army Depot: Building 37
Chambersburg, PA


Hydrogeology:

The groundwater system beneath the site is a complex, folded and fractured limestone aquifer that exhibits wide variations in seasonal water levels and well yields and that contains a well-developed epikarstic zone. Groundwater beneath the site flows to the south, discharging in a series of off-post springs about 1.5 miles from the boundary of Letterkenny Army Depot (LEAD).

Targeted Environmental Media:
  • - Fractured Bedrock

Contaminants:

Major Contaminants and Maximum Concentrations:
  • - Trichloroethene (0 µg/L)
  • - 1,1,1-Trichloroethane (0 µg/L)
  • - Tetrachloroethene (0 µg/L)
  • - 1,2-Dichloroethane (0 µg/L)
  • - 1,1-Dichloroethene (0 µg/L)
  • - 1,1-Dichloroethane (0 µg/L)
  • - Vinyl chloride (0 µg/L)
  • - Chloroethane (0 µg/L)

Site Characterization Technologies:

No technologies selected.


Remedial Technologies:

  • - Bioremediation (In Situ)
    • Reductive Dechlorination (In Situ Bioremediation)
Comments:
A bench-scale microcosm study indicated that the microbial degradation of the VOCs could be greatly enhanced under anaerobic conditions through the addition of sodium lactate. A 6-month pilot scale study followed. The results indicated that the discharge of VOCs to the springs was nondetectable within 1 month of injection. Biological indicator compounds, particularly methane, also showed marked increases in concentration.

In late 2000, the Army implemented the enhanced bioremediation effort on a full-scale basis. The program involves the introduction of sodium lactate, with a tracer dye, into a series of injection wells over a 30-day period every 6 to 8 months. Bi-monthly groundwater samples are collected from a series of on-site and off-site locations for analysis of lactate, dye, VOCs, and dissolved gases to track the progress of cleanup.

Remediation Goals:

Not provided in information reviewed.


Status:

Analytical results indicate that the sodium lactate is distributed effectively throughout the source area and that the contaminant plume is continuing to biodegrade. VOC levels in off-post wells and springs have rapidly declined and remained below applicable or relevant and appropriate requirements (ARARs) since 2002. On-post production of medium and light molecular weight daughter products has shown a consistent decline to near ARAR concentrations in 2003, while primary solvents have generally declined and remained below ARARs since 2002.


Lessons Learned:

Reference:
Landry, Paul G.; Paul R. Stone III. 2005. Enhanced bioremediation of chlorinated solvents in karst limestone bedrock using sodium lactate. The Eighth International In Situ and On-Site Bioremediation Symposium, Baltimore, Maryland. June 6-9.

Top of Page

For more information on Fractured Bedrock, please contact:

Ed Gilbert
Technology Assessment Branch

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