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Monitored Natural Attenuation for Ground Water Cleanups

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Guidance:

"Use of Monitored Natural Attenuation at Superfund, RCRA Corrective Action, and Underground Storage Tank Sites," April 1999.
Final OSWER Directive, Publication EPA/540/R-99/009. NTIS Order Number PB99 963 315, 41p.
Available on-line from OSWER HTML, PDF (41 pp, 278K)

This directive clarifies EPA's policy regarding the use of monitored natural attenuation (MNA) for the remediation of contaminated soil and ground water. It defines the term "monitored natural attenuation" and explains that EPA considers it a remedy, not a "no action" alternative. The directive outlines potential advantages and disadvantages of this remedy, under what conditions it should be selected, the type of site most suitable for this remedy choice, the site data required to support the decision, performance monitoring considerations, and the use of contingency remedies. The directive also has a lengthy bibliography, including EPA web sites with information on monitored natural attenuation.

Other Reports:

"Monitored Natural Attenuation of Inorganic Contaminants in Ground Water Volume 1 - Technical Basis for Assessment" October 2007.
National Risk Management Research Laboratory (NRMRL), Cincinnati, Ohio, Publication EPA/600/R-04/027, 94p.
Available on-line from ORD.
Document in Sections PDF (94 pp, 2.5MB)
Abstract Only: (HTML)

This document represents the first volume of a set of three volumes that address the technical basis and requirements for assessing the potential applicability of MNA as part of a ground-water remedy for plumes with non-radionuclide and/or radionuclide inorganic contaminants. Volume 1, titled "Technical Basis for Assessment," consists of three sections that describe 1) the conceptual background for natural attenuation for inorganic contaminants, 2) the technical basis for attenuation of inorganic contaminants in ground water, and 3) approaches to site characterization to support evaluation of MNA. Emphasis is placed on characterization of immobilization and/or transformation processes that may control contaminant attenuation, as well as technical approaches to assess performance characteristics of the MNA remedy. A tiered analysis approach is presented to assist in organizing site characterization tasks in a manner designed to reduce uncertainty in remedy selection.

"Monitored Natural Attenuation of Inorganic Contaminants in Ground Water Volume 2 - Assessment for Non-Radionuclides Including Arsenic, Cadmium, Chromium, Copper, Lead, Nickel, Nitrate, Perchlorate, and Selenium" October 2007.
National Risk Management Research Laboratory (NRMRL), Cincinnati, Ohio, Publication EPA/600/R-07/140, 124p.
Available on-line from ORD.
Document in Sections PDF (124 pp, 1.8MB)
Abstract Only: (HTML)

This document represents the second volume of a set of three volumes that address the technical basis and requirements for assessing the potential applicability of MNA as part of a ground-water remedy for plumes with non-radionuclide and/or radionuclide inorganic contaminants. Volume 2, titled "Assessment for Non-Radionuclides Including Arsenic, Cadmium, Chromium, Copper, Lead, Nickel, Nitrate, Perchlorate, and Selenium," consists of individual chapters that describe 1) the natural processes that may result in the attenuation of the listed contaminants and 2) data requirements to be met during site characterization. Emphasis is placed on characterization of immobilization and/or transformation processes that may control contaminant attenuation, as well as technical approaches to assess performance characteristics of the MNA remedy. A tiered analysis approach is presented to assist in organizing site characterization tasks.

"Monitored Natural Attenuation of Inorganic Contaminants in Ground Water Volume 3: Assessment for Radionuclides Including Tritium, Radon, Strontium, Technetium, Uranium, Iodine, Radium, Thorium, Cesium, and Plutonium-Americium" September 2010.
National Risk Management Research Laboratory (NRMRL), Cincinnati, Ohio, Publication EPA/600/R-10/093, 147p.
Available on-line from ORD.
Document in Sections PDF (147 pp, 5.56MB)
Abstract Only: (HTML)

This document represents the third volume of a set of three volumes that address the technical basis and requirements for assessing the potential applicability of MNA as part of a ground-water remedy for plumes with non-radionuclide and/or radionuclide inorganic contaminants. Volume 3, titled "Assessment for Radionuclides Including Tritium, Radon, Strontium, Technetium, Uranium, Iodine, Radium, Thorium, Cesium, and Plutonium-Americium," consists of individual chapters that describe 1) the natural processes that may result in the attenuation of the listed contaminants and 2) data requirements to be met during site characterization. Emphasis is placed on characterization of immobilization and/or radioactive decay processes that may control contaminant attenuation, as well as technical approaches to assess performance characteristics of the MNA remedy. A tiered analysis approach is presented to assist in organizing site characterization tasks.

"Performance Monitoring of MNA Remedies for VOCs in Ground Water" April 2004.
National Risk Management Research Laboratory (NRMRL), Ada, Oklahoma, Publication EPA/600/R-04/027, 92p.
Available on-line from ORD.
Document in Sections PDF (13 pp, 415K)
Abstract Only: (HTML)

This report identifies data needs and evaluation methods useful for monitoring the performance of MNA remedies selected for VOCs in ground water. The document discusses the design considerations for monitoring networks and methods for determining remedy effectiveness. Effective monitoring of natural attenuation processes involves a three-dimensional approach to network design and clearly defined performance criteria based on site-specific remedial action objectives. Objectives for the monitoring program will be met through routine evaluations of institutional controls and measurements of contaminant, geochemical, and hydrologic parameters. These data are used to evaluate changes in three-dimensional plume boundaries, contaminant mass and concentration, and hydrological and geochemical changes that may indicate changes in remedy performance.

"Technical Protocol for Evaluating Natural Attenuation of Chlorinated Solvents in Ground Water" October 1998.
National Risk Management Research Laboratory (NRMRL), Ada, Oklahoma, Publication EPA/600/R-98/128, NTIS Order Number PB99-130023, 214p.
Available on-line from OSWER (HTML)

This protocol provides guidance for environmental managers on the steps that must be taken to understand the rate and extent to which natural processes are reducing contaminant concentrations at sites that are contaminated by chlorinated solvents. The document identifies parameters that are useful in the evaluation of natural attenuation of chlorinated solvents (chlorinated aliphatic hydrocarbons and/or fuel hydrocarbons) and provides recommendations to analyze and interpret the data collected from the site characterization process. It also provides suggestions for integrating monitored natural attenuation (MNA) into an integrated approach to remediation that also includes an active remedy. It includes a useful list of definitions of terms related to the topic. It is a technical, not a policy, document. Data gathered using this protocol can be used to evaluate whether MNA by itself or in conjunction with other technologies is sufficient to achieve site remedial objectives, and to compare the relative effectiveness of MNA and other remedial methods. This protocol is the result of a collaborative field and laboratory research effort involving researchers from EPA's Office of Research and Development, the U.S. Air Force, and the U.S. Geological Survey.

 

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