U.S. EPA Contaminated Site Cleanup Information (CLU-IN)

U.S. Environmental Protection Agency
U.S. EPA Technology Innovation and Field Services Division

Natural attenuation

Additional Resources

Sandia Natural Attenuation Project

The Sandia Natural Attenuation Project is a three year program by Sandia National Laboratories to identify the mechanistic controls on metal and organic attenuation by irreversible sorption in the subsurface. SNAP will provide a scientific basis for risk-based corrective actions by helping identify only those sites where contaminants can be expected to impact the biosphere and where Monitored Natural Attenuation (MNA) is likely to be most effective.

Interstate Technology and Regulatory Council (ITRC)

Monitored Natural Attenuation Toolbox (MNAtoolbox)

MNAtoolbox identifies primary attenuation pathways and points out processes that might mitigate against MNA for particular contaminants. Sandia National Laboratory has made the toolbox and a user's guide available on its web site.

Bioremediation of Chlorinated Solvents Consortium

The Consortium is one of seven Action Teams of the Remediation Technologies Development Forum (RTDF). It was established in May 1993, when representatives from various companies, universities, EPA, DoD, and DOE met to discuss their mutual interest in developing in situ bioremediation technologies to degrade chlorinated solvents in soils and ground water. The historical information concerning the consortium is available through the RTDF home page.

In 2004, the RTDF - Bioremediation Consortium initiated Phase III of its research activities when it joined forces with a multinational team to launch the In Situ Source Area Bioremediation project (SABRE). This project, which is being conducted in the United Kingdom, is scheduled to be completed in 2008 and has a budget of nearly $6 million, financed by industrial members and the DTI LINK Bioremediation program in the UK. The goal is to demonstrate the efficacy of accelerated anaerobic bioremediation as a treatment alternative for source areas contaminated with chlorinated solvent dense non-aqueous phase liquids (DNAPLs). The SABRE project team comprises: Archon Environmental; British Geological Survey (BGS); Celanese Acetate; Chevron; CL:AIRE; DuPont; ESI; GE; Geosyntec Consultants, Inc.; Golder Associates; Honeywell; ICI; Scientifics; SERDP; Shell; SiREM; Terra Systems, Inc; University of Edinburgh; and University of Sheffield. The Environment Agency (EA) of England and Wales and US EPA are also included. In addition, the University of Birmingham and BGS are conducting a complimentary research project (Streamtube) in the SABRE test cell. The project has completed initial characterization of DNAPL source zones, a laboratory microcosm study, installation of the test cell, and baseline data collection. Column studies are well advanced, and modelling is occurring throughout the project. Biostimulation and bioaugmentation of the test cell occurred in the Spring of 2007.

Technology Innovation News Survey

The Technology Innovation News Survey contains market/commercialization information; reports on demonstrations, feasibility studies and research; and other news relevant to the hazardous waste community interested in technology development. This report is updated every two weeks.

Adobe PDF LogoCORONA: Confidence in Forecasting of Natural Attenuation as a Risk-Based Groundwater Remediation Strategy
Lerner, D.N., P. Bjerg, J. Datel, A. Gargini, P. Gratwohl, C. Holliger, P. Morgan, T. Ptak, R. Schotting, H. Slenders, and S.F. Thornton. Final report of the EU research project EVK1-2001-00087. University of Sheffield, UK. 32 pp, 2005

The CORONA project hypothesizes that a common pattern of biodegradation activity can be found in most ground-water contaminant plumes. High-resolution field data were used to develop three mathematical models for estimating the length of pollution plumes. The models were built into an easy-to-use spreadsheet called CoronaScreen, which is accompanied by manuals for the software and a guidance document to explain how natural attenuation can be assessed in the field and quantified. These engineering tools were tested by practitioners outside the project before being made available for free download from the project website.

Adobe PDF LogoDissolved Hydrogen Analyzer: Cost and Performance Report
C. Lebron, et al.
NTIS: ADA451214, 40 pp, 2006

This report describes the demonstration at three DoD sites of a portable dissolved hydrogen analyzer, a novel analytical technology developed by Camp Dresser & McKee, Inc., to help determine natural attenuation potential.

Evaluation of the Role of Dehalococcoides Organisms in the Natural Attenuation of Chlorinated Ethylenes in Ground Water
EPA 600-R-06-029, 2006

This report was produced by the U.S. EPA Office of Research and Development. It is designed for technical staff in the EPA Regions and in state agencies that require information on the contribution of Dehalococcoides bacteria to MNA of chlorinated solvents, and information on the proper application and interpretation of the assays in an evaluation of MNA. This report includes sections on the role of biotransformation in evaluation of MNA of chlorinated solvents, the ecology of microorganisms that transform chlorinated solvents, tools to assay microorganisms that transform chlorinated solvents, the relationship between Dehalococcoides DNA in ground water and rates of natural attenuation at field scale, the relationship between geochemical parameters and the occurrence of Dehalococcoides DNA in ground water, and the relationship Dehalococcoides DNA in ground water and behavior of chlorinated solvents in laboratory treatability studies or microcosm studies done with water from the plume.

Consideration of Natural Attenuation in Remediating Contaminated Sites
Kabardin, B. and J. Frauenstein (eds.).
Federal Environment Agency of Germany, 42 pp, 2011

This position paper discusses how to consider natural attenuation in the context of practical remediation of contaminated sites in Germany and outlines a systematic approach to decision making.

Adobe PDF LogoStandardized Procedures for Use of Nucleic Acid-Based Tools: Recommendations for Groundwater Sampling and Analysis Using qPCR
Lebron, C., P. Dennis, C. Acheson, N. Barros, D. Major, E. Petrovskis, F. Loeffler, K. Ritalahti, C. Yeager, E. Edwards, J. Hatt, and D. Ogles. SERDP Project ER-1561, 12 pp, 2014

SERDP project ER-1561 focused on identifying and minimizing the causes of variability during quantitative real-time polymerase chain reaction (qPCR) enumeration of genes of interest in groundwater, with the goal of developing of the knowledge needed to standardize methods for collecting, preserving, transporting, storing, and processing environmental samples for qPCR analysis. This document summarizes the project conclusions and recommends procedures for using qPCR analyses that will provide data of sufficient accuracy and reproducibility to allow site management decisions regarding bioremediation or MNA. Further details are available in the ER-1561 Final ReportAdobe PDF Logo (Lebron et al. 2014, 220 pages).

Arsenic Cycling in Hydrocarbon Plumes: Secondary Effects of Natural Attenuation
Cozzarelli, I.M., M.E. Schreiber, M.L. Erickson, and B.A. Ziegler.
Groundwater 54(1):35-45(2015)

NA relies on biodegradation of hydrocarbons coupled with reduction of electron acceptors, including solid-phase ferric iron (Fe(III)). Because As adsorbs to Fe-hydroxides, a potential secondary effect of hydrocarbon NA coupled with Fe(III) reduction is a release of naturally occurring As to groundwater. Anaerobic biodegradation of hydrocarbons coupled to Fe(III) reduction has been well documented at a crude-oil-contaminated aquifer near Bemidji, Minn. Groundwater samples collected at the site annually from 2009 to 2013 showed As concentrations in groundwater in the plume reached 230 µg /L, whereas groundwater outside the plume contained <5 µg /L As. A conceptual model of secondary As release due to hydrocarbon NA can be applied to other sites where an influx of biodegradable organic carbon promotes Fe(III) reduction.

Superfund Remedy Report, 17th Edition
EPA 542-R-23-001, 2020

EPA prepares the Superfund Remedy Report to provide information and analyses on remedies EPA selected to address contamination at Superfund National Priorities List and Superfund Alternative Approach sites. This report is the latest in a series, prepared since 1991, on Superfund remedy selection. The latest edition focuses on the analysis of Superfund remedial actions selected in fiscal years 2018, 2019, and 2020.

The data that forms the basis of the analyses contained in SRR 17th Edition can be found at Superfund Data and Reports by downloading Contaminant of Concern Data for Decision Documents by Media and Remedy Component Data for Decision Documents by Media.

Adobe PDF LogoValidation of Biotechnology for Quantifying the Abundance and Activity of Vinyl-chloride Oxidizers in Contaminated Groundwater: Guidance Document
Mattes, T.
ESTCP Project ER-201425, 40 pp, 2018

The purpose of this project was to evaluate qPCR-based molecular diagnostic tools for the purpose of estimating the attenuation contribution of VC-oxidizing bacteria. Groundwater and aquifer samples were taken from several DoD sites. The method targeted functional genes used by etheneotrophic bacteria in the aerobic VC biodegradation pathway. Functional genes associated with both VC oxidation and VC reduction were found present and expressed in groundwater samples. The researchers determined this by analyzing the relationships between functional genes associated with VC biodegradation and geochemical parameters, as well as the bulk VC attenuation rate at these contaminated sites. This novel technology promises to reveal the abundance and functionality of etheneotrophs at VC-contaminated sites. When this information is provided alongside a site-wide VC degradation rate, it could provide evidence that aerobic VC biodegradation is a significant contributor to overall VC natural attenuation processes. Additional information: ESTCP Final Report Adobe PDF Logo.

Natural Source Zone Depletion (NSZD)
Rousseau, M. American Institute of Professional Geologists Virtual Forum, May 8, 2020

This presentation discusses the fundamentals of NSZD, provides an overview of the most commonly used methods to quantify it, and considers the different ways it may factor into managing petroleum-contaminated sites. Case studies are included from the U.S., Canada, and Australia illustrating different ways NSZD rates were quantified, how NSZD rates compared to conventional LNAPL recovery system performance, and how NSZD fit into the overall LNAPL site management strategies.

Rapid Field Approach to Evaluating Natural Source Zone Depletion for a Range of Light Non-Aqueous Phase Liquid Sites (Abstract)
Ririe, G.T. and R.E. Sweeney. | Groundwater Monitoring & Remediation 42(4):67-77(2022)

This article presents results from two sites that illustrate the benefit of using a rapid field approach (RFA) to supplement existing data and update site conceptual models (SCMs). Most natural source zone depletion (NSZD) guidelines follow a single generic SCM (aerobic oxidation of methane) as the primary NSZD contributor. Aerobic oxidation of LNAPL is also possible and can be documented by measuring subsurface soil-gas composition and/or heat generated from biodegradation. The RFA was developed to easily separate sites into those with and without a methane plume overlying LNAPL. This distinction defines the relative rates of oxygen transport into the soil and methane generation and releases from saturated zone anaerobic biodegradation. Evidence for direct LNAPL oxidation is the absence of methane (<0.1%-v) in the unsaturated zone above LNAPL, which indicates that NSZD is a result of direct biodegradation of LNAPL. This measurement can be readily made in the field using existing monitoring wells. This alternative SCM needs to be considered and evaluated before implementing more costly data collection or other remediation or site management options.