Natural Attenuation

For more information on Natural Attenuation, please contact:

Kathleen Yager
Technology Integration and Information Branch
(617) 918-8362
yager.kathleen@epa.gov

Overview Guidance Application Training Additional Resources

Overview

Natural attenuation relies on natural processes to clean up or attenuate pollution in soil and groundwater. Natural attenuation occurs at most polluted sites. However, the right conditions must exist underground to clean sites properly. If not, cleanup will not be quick enough or complete enough. Scientists monitor or test these conditions to make sure natural attenuation is working. This is called monitored natural attenuation or MNA.

When the environment is polluted with chemicals, nature can work in four ways to clean it up:

1. Tiny bugs or microbes that live in soil and groundwater use some chemicals for food. When they completely digest the chemicals, they can change them into water and harmless gases.
2. Chemicals can stick or sorb to soil, which holds them in place. This does not clean up the chemicals, but it can keep them from polluting groundwater and leaving the site.
3. As pollution moves through soil and groundwater, it can mix with clean water. This reduces or dilutes the pollution.
4. Some chemicals, like oil and solvents, can evaporate, which means they change from liquids to gases within the soil. If these gases escape to the air at the ground surface, sunlight may destroy them.

MNA works best where the source of pollution has been removed. For instance, buried waste must be dug up and disposed of properly. Or it can be removed using other available cleanup methods. After the source is removed, the natural processes get rid of the small amount of pollution that remains in the soil and groundwater. The soil and groundwater are monitored regularly to make sure they are cleaned up.

A Citizen's Guide to Monitored Natural Attenuation
EPA 542-F-01-004, 2001

Download Spanish Translation (130K/PDF)

The Citizen's Guide Series are 2-page fact sheets that provide a general description on approaches to clean up contaminated was sites. The fact sheets cover five questions about each clean up approach: What is it?, How does it work?, Is it safe?, How long will it take?, and Why use it?.

Guía del Ciudadano para la Reducción Natural Supervisada
EPA 542-F-01-004S, 2001

La Serie de Guías del Ciudadano son boletines de dos páginas con datos que proveen una descripción general en cómo sanear sitios contaminados. Estos boletines con datos que cubren cinco preguntas acerca de cada procedimiento de saneamiento: ¿Qúe es?, ¿Cómo trabaja?, ¿Es seguro?, ¿Cúanto tiempo requerirá?, y ¿Por qué debe de usarse?

Monitored Natural Attenuation of Chlorinated Solvents: U.S. EPA Remedial Technology Fact Sheet
EPA 600-F-98-022, 1998

This fact sheet explains what monitored natural attenuation means when the term is used to describe a potential strategy to remediate a contaminated site. It also describes the various physical, chemical and biological processes of natural attenuation that may occur at a site. This fact sheet is written for an audience with little or no scientific background and is meant to aid Federal, State, and local regulators in educating the public on complex environmental issues. Other informational materials are in preparation and will provide more specific details and scientific depth for the evaluation of monitored natural attenuation as a remedy at specific sites.

Monitored Natural Attenuation of Petroleum Hydrocarbons: U.S. EPA Remedial Technology Fact Sheet
EPA 600-F-98-021, 1998

This fact sheet explains what monitored natural attenuation means when the term is used to describe a potential strategy to remediate a contaminated site. It also describes the various physical, chemical and biological processes of natural attenuation that may occur at a site. This fact sheet is written for an audience with little or no scientific background and is meant to aid Federal, State, and local regulators in educating the public on complex environmental issues. Other informational materials are in preparation and will provide more specific details and scientific depth for the evaluation of monitored natural attenuation as a remedy at specific sites.

Natural Attenuation of Hazardous Wastes
2004. R. Surampalli, S.K. Ong, E. Seagren, and J. Nuno (eds.). American Society of Civil Engineers, Reston, VA. ISBN: 0784407401, 256 pp.

In addition to a discussion of the regulatory framework, this book covers major pollutants and basic scientific principles on physical, chemical, and biological processes involved in natural attenuation, and contains an extensive review of literature, examples of applications of natural attenuation, and site characterization and monitoring requirements and procedures.

Treatment Technologies for Site Cleanup: Annual Status Report (ASR), Twelfth Edition
EPA 542-R-07-012, 2007

The Twelfth Edition of this report, published by the EPA Office of Superfund Remediation and Technology Innovation (OSRTI) in September 2007, documents treatment technology applications at more than 1,900 soil and groundwater cleanup projects at National Priorities List (NPL) sites. The status of more than 1,200 projects included in the ASR Eleventh Edition is updated, and information about 192 new projects derived from Records of Decision (ROD) signed from 2002 through 2005 is added. The report also includes a special section about on-site containment remedies. The ASR is based on the analysis of nearly 3,000 RODs signed since 1982 at 1,536 NPL sites. The online version includes new downloadable spreadsheets with the data for several of the key tables and figures in the report. Specific information about each technology application included in the ASR Twelfth Edition is available in the ASR Remediation Database.

Disclaimer
http://clu-in.org/techfocus/default.focus/sec/Natural%5FAttenuation/cat/Overview/
Last updated on Thursday, December 18, 2008