• Testing of Remediation
• Performance Monitoring

• U.S. Navy, Naval Facilities Engineering Command (NAVFAC)
• Virginia Polytechnic Institute and State University

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 to:

• locate the source area with direct-push technology and field gas chromatography methods.
• 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 benzene concentrations.

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).

• New Version of NAS (Natural Attenuation Software) Available
• Processes that Control the Natural Attenuation of Chlorinated Solvents -- Microbial Degradation of Chloroethenes in Ground Water Systems
• Software Provides Estimates of How Long it Will Take for Remediation Efforts to Achieve Their Goals
• Natural Attenuation Software, Software that calculates estimates for the period of time required to achieve site-specific remediation goals at sites contaminated with either fuels or chlorinated solvents. Developed in partnership with the USGS.
• Oxygen Release Compound (ORC^®) Home Page, Regenesis
• Pensacola Naval Air Station, Installation Summaries, Environmental Restoration Program, U.S. Navy

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

• Using Oxygen to Enhance Biodegradation of Contaminants – Lessons Learned
• Solvent Plume Source Removal Test (Fenton's Reagent), Naval Submarine Base Kings Bay, Georgia
• Oxygen-Release Compound Remediation Tests, Laurel Bay, South Carolina
• Subsurface Reactive Barrier, Cape Cod, Massachusetts

Other USGS In-Situ Chemical Oxidation Projects

• Stopping Contamination in Its Tracks, Denver Federal Center Permeable Reactive Barrier
• Deep Aquifer Remediation Tools (DARTs) -- A New Technology for Ground-Water Remediation (pdf)
• Field Demonstration of Reactive Chemical Barriers to Control Radionuclide and Trace-Element Contamination in Ground Water

Natural Attenuation Software (NAS) Information

• New Version of NAS (Natural Attenuation Software) Available
• Software Provides Estimates of How Long it Will Take for Remediation Efforts to Achieve Their Goals
• Estimating Cleanup Times Associated with Combining Source-Area Remediation with Monitored Natural Attenuation (ER-0436), ESTCP Project Description
• Natural Attenuation Software (NAS) Web Site, A web site where potential users can download the latest NAS software, documentation, and tutorials