Chlorinated Benzene Plume Source Area Containment Test (Oxygen-Release Compound Injection)
- Testing of Remediation
- Performance Monitoring
Naval Air Station, Pensacola, FL
In-Situ Chemical Oxidation (Oxygen Addition to Ground Water)
Remediation of chlorinated benzenes by the direct addition of oxygen to ground water
is being tested at the Naval Air Station Pensacola, Florida. Ambient ground water at the
site is anoxic (without oxygen), which leads to
negligible biodegradation of chlorinated
benzenes. However, because chlorinated benzenes degrade rapidly under oxic conditions
(with oxygen), the addition of oxygen may significantly accelerate attenuation of the
contamination at this site, precluding the need for expensive pump-and-treat technology.
In August of 2000, the chlorinated benzene source area was delineated using direct-push
technology, and ground-water sampling confirmed the presence of highly chlorinated
benzenes and anoxic conditions. In April of 2001, a passive curtain of an oxygen-release compound was injected into
the aquifer immediately downgradient of the source area, and a second curtain was
injected into the contaminant plume one hundred feet downgradient of the source area.
Ground-water sampling in May of 2001 confirmed that oxic conditions had been established
downgradient of where the oxygen-release compound was injected, and that concentrations
of chlorinated benzenes had decreased from 4060 µg/L (micrograms per liter) to 98.5
µg/L, or a decrease of about 97%. These preliminary results suggest that source area
isolation and plume containment of chlorinated benzenes using an oxygen-release compound
may be an effective remediation strategy in anaerobic aquifers. Because of the lower
operation and maintenance costs with using an oxygen-release compound compared to
pump-and-treat technology, it is estimated that lifetime remediation costs can be
lowered by up to 75%. Performance monitoring will be used to document remediation
efficiency over time, and to document how long the oxygen-release compound can maintain
oxic conditions in the aquifer system.
USGS involvement with the remediation of chlorinated benzenes at Pensacola was
- locate the source area with direct-push technology and field gas chromatography
- inject the oxygen-release compound immediately downgradient of the source area,
and in a line across the center of the plume.
- monitor ground-water chemistry downgradient of each oxygen-release compound
injection site in order to document changes in dissolved oxygen and chlorinated
USGS scientists are now conducting performance monitoring to evaluate the efficiency
of this remedial strategy. Because the oxygen-release compound may need to be
replenished periodically, performance monitoring will also be used to document the
lifetime of the oxygen-release compound in this hydrologic system.
Water-quality monitoring data from the site's chlorinated benzene plume are being
used to evaluate the ability of the Natural Attenuation
Software (NAS) package to estimate cleanup times associated with combining the
remediation of a contaminant source-area with using Monitored Natural Attenuation (MNA)
to remediate the remaining downgradient contaminant plume. This site is one of eight
demonstration sites that make up a diverse set of geologic, hydraulic, and geochemical
environments. The evaluation is being conducted by the U.S. Navy, Virginia Polytechnic
Institute and State University (Virginia Tech), and U.S. Geological Survey (USGS), with
funding from the Environmental Security Technology
Certification Program (ESTCP).
Note: Trade names are used for information purposes only and do not denote
endorsement by the U.S. Geological Survey.
Frank Chapelle, South Carolina Water Science Center, Columbia, SC,
- Chapelle, F.H., and Bradley, P.M., 1998,
- Selecting remediation goals by
assessing the natural attenuation capacity of ground-water systems: Bioremediation
Journal, v. 2, no. 3-4, p. 227-238.
- Chapelle, F.H., and Bradley, P.M., 1999,
- Selecting remediation
goals by assessing the natural attenuation capacity of ground-water systems, in
Morganwalp, D.W., and Buxton, H.T., eds., U.S. Geological Survey Toxic Substances
Hydrology Program--Proceedings of the Technical Meeting, Charleston, South Carolina,
March 8-12, 1999--Volume 3 of 3--Subsurface Contamination from Point Sources: U.S.
Geological Survey Water-Resources Investigations Report 99-4018C, p. 7-19.
Other Toxics Program In-Situ Chemical Oxidation Projects
Other USGS In-Situ Chemical Oxidation Projects
Natural Attenuation Software (NAS) Information
Back to Toxics Program Remediation Activities Index
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