Impact of Landfill Closure Designs on Long-Term Natural Attenuation of Chlorinated Hydrocarbons

Site Name:

Altus Air Force Base Landfill (LF 3)

Location:

Altus, Oklahoma

Period of
Operation:

October 2003 — November 2005 (2 years)

Cleanup
Type:

Pilot-Scale

Technology:
Recirculation Bioreactor

  • The bioreactor was constructed by excavating a 30-foot (ft) x 30-ft x 11 ft deep portion of the landfill near a suspected trichloroethene (TCE) source area and backfilling with a mixture of organic material and sand.
  • A groundwater extraction trench was installed in the shallow aquifer (downgradient from the bioreactor cell) and was backfilled with gravel.
  • Groundwater from the trench was extracted and distributed within the bioreactor cell using a drip irrigation system.
  • Groundwater monitoring wells were installed within the bioreactor cell and in the aquifer adjacent to, and beneath, the test cell for monitoring concentrations of chlorinated aliphatic hydrocarbons (CAH) and geochemical/microbial indicator parameters.

Cleanup Authority:
Resource Conservation and Recovery Act (RCRA)

Contacts:

John Hicks
Parsons
Project Manager and Principal Investigator
1700 Broadway , Suite 900
Denver, CO 80290
Phone: 303-764-1941
john.hicks@parsons.com

Jason Bidgood, P.E.
Parsons
Project Engineer
1700 Broadway , Suite 900
Denver, CO 80290
Phone: 303-764-8836
jason.bidgood@parsons.com

Chuck Butchee
Altus AFB Technical Point of Contact
97 CES/CEVR
401 L Avenue
Altus AFB, OK 73523
Phone: 580-481-5187
charles.butchee@altus.af.mil

Andrea Leeson, Ph.D.
ESTCP Program Manager — Environmental Restoration
ESTCP Program Office
901 N. Stuart Street
Arlington, VA 22203
Phone: 703-696-2118
andrea.leeson@osd.mil

Contaminants:
Chlorinated Aliphatic Hydrocarbons (CAH) including trichloroethene (TCE), dichloroethene (DCE), and vinyl chloride (VC).

Waste Source:
The Altus Air Force Base, LF 3 received construction debris, concrete, brush, and several drums of paint waste during the 1950’s and 1960’s. Several remedial investigations have been completed since the 1960's and data show that TCE and cis-1,2-DCE are the two most prevalent contaminants associated with the former landfill.

Type/Quantity of Media Treated:
Groundwater (690,000 gallons)

Purpose/Significance of Application:
The primary performance criteria for the site include:

  1. Demonstrate the positive impacts of bioreactors in reducing the CAH concentration in groundwater.
  2. Evaluate process longevity and provide cost assessments for potential full-scale applications.

Regulatory Requirements/Cleanup Goals:
The cleanup objective for this demonstration includes:

  1. Achieve 90% reduction in total molar CAH concentration in shallow downgradient groundwater.

Results:
Data from the demonstration site indicated the following:

  • The removal efficiency for TCE in shallow groundwater adjacent to the test cell was 96-99.9% during the five performance monitoring events.
  • The bioreactor removal efficiency for TCE and chlorinated ethenes (sum of TCE, DCE, and VC) from recirculated groundwater ranged from 97 to 100% and 76 to 96%, respectively.
  • The goal of 90% reduction in CAH concentration was not achieved due to a continuing TCE source upgradient of the bioreactor and the accumulation of daughter products in the aquifer beneath and adjacent to the bioreactor.

Cost Factors:
The total cost for the demonstration was $171,872; $56,152 for capital costs; $2,880 for operation and maintenance costs; and $112,840 for monitoring costs for the 2-year duration.

Description:
Altus Air Force Base (AFB) Landfill #3 (LF 3) is located at the eastern portion of Altus AFB. LF 3 received waste materials including garbage, wood, paper, metal, and shop wastes, construction debris, concrete, brush, and several drums of paint waste, which was buried in trenches. Site investigation identified chlorinated solvents in the groundwater, including trichloroethene (TCE) and dichloroethene (cis-1,2-DCE). A TCE plume extending about 4,000 feet downgradient of LF 3 was identified at the site.

A 24-month demonstration took place at the LF 3 site staring in October 2003. The purpose of the demonstration was to evaluate the removal efficiency of bioreactors for the treatment of chlorinated aliphatic hydrocarbons (CAH) in groundwater at unlined, closed landfills. The bioreactor construction began in 2003 and consisted of excavating soil and groundwater and backfilling with various organic materials, sand and gravel. Monitoring wells were installed and five performance monitoring events were completed during the 2-year demonstration.

The results showed that the concentration of TCE in the groundwater generally decreased across five post-installation groundwater monitoring events. The primary cleanup objective of this demonstration was to achieve 90% reduction in total molar CAH concentration in shallow groundwater downgradient of the bioreactor. This goal was not achieved due to a continuing TCE source upgradient of the bioreactor and the accumulation of daughter products in the aquifer beneath and adjacent to the bioreactor.