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Ecological Risk Assessment


Ecological risk occurs when a contaminant is in contact with any part of the ecosystem long enough and at a level that is able to cause an adverse effect. It is important to include stakeholders early on in the ecological risk assessment (ERA) process to identify the appropriate assessment endpoints and ecotoxicity benchmarks. If natural resources are potentially impacted by releases at a site, then the designated natural resource trustees should be included as well.

Jump to Resources to access Policies & Guidance, Publications, Related Sites, and Tools



The three-tiered ERA approach closely mirrors the United States Environmental Protection Agency (EPA’s) eight-step process defined in the Ecological Risk Assessment Guidance for Superfund (ERAGS): Process for Designing and Conducting Ecological Risk Assessments. The Department of the Navy (DON) ERA Guidance provides details on what should be included and considered in each tier of an ERA, discussion on technical issues, and description of tools available to assist in the completion of ERAs. The key elements of the three-tiered ERA approach are described below:

  • The Tier 1 screening ecological risk assessment (SERA) is conducted to identify chemicals of potential concern (COPCs) that may pose unacceptable risks to the environment, thus focusing efforts on those constituents most likely to drive ecological risks. The Tier 1 SERA is usually conducted during the SI phase using existing data and conservative assumptions. The evaluation consists of two steps as follows: 

    Step 1 includes conducting a site visit, identifying site-specific data needs (e.g., site chemical data, ecotoxicity), identification of assessment endpoints and representative receptors (e.g., surrogate species), determination of complete exposure pathways, and refinement of the conceptual site model (CSM).

    Step 2 includes calculating an exposure point concentration based on the CSM and characterizing risk through the use of hazard quotients. For each receptor/COPC combination having a complete exposure pathway, the maximum concentration detected is compared to the appropriate ecotoxicity benchmark using the hazard quotient approach.

    Chemical constituents having maximum concentrations that are below their benchmark are eliminated. If there are no    unacceptable ecological risks or no complete exposure pathways to all ecological receptors, the site may be closed out for ecological concerns and exit the ERA process. If the SERA demonstrates that potential exposure pathways and unacceptable risk may exist, an interim action can be taken and/or a Tier 2 evaluation initiated.

  • The Tier 2 baseline ecological risk assessment (BERA) is intended to be a more rigorous evaluation. Rather than relying on conservative assumptions and comparison to ecotoxicity benchmarks, Tier 2 incorporates site-specific information to calculate risk estimates for those COPCs posing potential risk in the Tier 1 SRA. The Tier 2 evaluation also screens out constituents that are consistent with background concentrations. The BERA is comprised of the problem formulation, study design and data quality objectives (DQOs), verification of the field sampling design, site investigation and analysis, and risk characterization. Planning for these activities involves extensive communication between DON, regulators, natural resource trustees, and other stakeholders. The BERA will characterize the ecological risk posed by the site as documented in the RI report. A risk management decision is made to determine either no further action (NFA) from an ecological perspective or if the site is found to pose an unacceptable ecological risk then remedial alternative development (including a Tier 3 risk evaluation) is appropriate.

  • The Tier 3 risk evaluation of remedial alternatives (RERA) for ecological receptors is an evaluation of the remedial alternatives with regards to: (1) the effectiveness of reducing risks to acceptable levels; (2) ecological impacts related to remedy implementation; and (3) residual risks that will remain at a site. The purpose of the RERA is to provide remedial project managers (RPMs) with an assessment of the potential short and long-term health risks associated with the remedial alternatives.


For more information, Chapter of the DON Environmental Restoration Program Manual provides a detailed description of the ERA approach.



Title and Description

ERP Manual

DON Environmental Restoration Program Manual: Chapter Ecological Risk Assessment (February 2018)

Describes the overall approach for conducting ERAs and specifies that a three-tiered risk assessment approach be implemented.

Background Chemicals

Navy Policy on the Use of Background Chemical Levels (January 2004)

Clarifies the Navy’s position on consideration of background chemical levels.

Natural Resource Injury and Damages

Navy Policy on Natural Resources Injury and Damages in the Installation Restoration Program (December 2001)

Provides policy considerations related to the investigation of potentially impacted natural resources during the ERA process and to the selections of response actions to reduce those impacts.

Ecological Risk Guidance

Tri-Service Remedial Project Manager's Handbook for Ecological Risk Assessment (February 2000)

Summarizes procedural guidelines for conducting ecological risk assessments, key terminology, oversight recommendations, and links to additional information.

 ERA Policy

Navy Policy for Conducting Ecological Risk Assessments (April 1999)

Provides the Navy's approach for implementing ERAs consistent with the requirements of the EPA ERA guidance.

ERA Policy

Navy Environmental Policy Memorandum: Use of Ecological Risk Assessment (May 1997)

Identifies key issues and directions for ERAs to be conducted in a manner that is consistent with and supportive of the remedial decision-making process.


Title and Description


ESTCP Effect of Soil Properties on Metal Bioavailability (June 2013)

Summarizes the results of a research project to validate and promote the use of in vitro bioavailability methods in support of human health and ecological risk assessments.

ERA Review

NAVFAC Risk Assessment Workgroup Issue Paper: Reviewing Ecological Risk Assessment (March 2012)

Provides tools to help efficiently and effectively review ERA deliverables to ensure they meet Navy policy and the project objectives. Standard deliverables are discussed along with common issues in the ERA process and strategies to overcome them.

COPC Screening


NAVFAC Risk Assessment Workgroup Issue Paper: Ecological Screening and COPC Refinement for Sediment, Soil, and Surface Water (February 2012)

Discusses the Navy and EPA approach for developing the initial list of the COPCs for ecological risk as the outcome of the SRA.

Amphibian Protocol

NAVFAC Demonstration and Certification of Amphibian Ecological Risk Assessment Protocol Final Report (April 2009)

Provides Navy protocols for conducting ERAs in relation to amphibians.


Biomonitoring: Guide for the Use of Biological Endpoints in Monitoring Species, Habitats, and Projects (November 2007)

Presents a framework for designing biomonitoring programs, including objectives, decision criteria, and the design of data collection and analysis methods.

Habitat Restoration

Guidance for Habitat Restoration Monitoring: Framework for Monitoring Plan Development and Implementation (August 2004)

Describes a framework for developing and documenting a habitat restoration monitoring plan, including objectives, hypotheses, and exit criteria.


Guide for Incorporating Bioavailability Adjustments into Human Health and Ecological Risk Assessments at U.S. Department of Defense Facilities Part 1: Overview of Metals Bioavailability (June 2003)

Defines bioavailability, discusses where bioavailability fits in the risk assessment process, and where it may be beneficial to perform the additional studies needed to assess bioavailability.


Guide for Incorporating Bioavailability Adjustments into Human Health and Ecological Risk Assessments at U.S. Department of Defense Facilities Part 2: Technical Background Document for Assessing Metals Bioavailability (June 2003)

Details technical information for designing bioavailability studies. Includes soil collection and characterization to support bioavailability studies, as well as in vitro and in vivo methods for assessing bioavailability.

Aquatic   Toxicity

Guide for Planning and Conducting Sediment Pore Water Toxicity Identification Evaluations (TIE) to Determine Causes of Acute Toxicity at Navy Aquatic Sites (March 2003)

Provides information to plan and conduct TIE studies that will aid in characterizing and managing toxic freshwater and marine sediments.


Title and Description



Ecological Risk Assessment ToolBox (EPA EcoBox)

A compendium of tools that provides links to guidance documents, databases, models, reference materials, and other related resources.



EPA ECOTOX Knowledgebase

The ECOTOXicology knowledgebase (ECOTOX) is a comprehensive, publicly available knowledgebase providing single chemical environmental toxicity data on aquatic life, terrestrial plants and wildlife.

Water Quality Criteria 

EPA National Recommended Water Quality Criteria – Aquatic Life Criteria Table

This table contains the most up-to-date criteria for aquatic life ambient water quality criteria.




Oak Ridge National Laboratory (ORNL) RAIS Ecological Benchmark Tool

Screening ecological benchmarks are used to identify chemical concentrations in environmental media that are at or below thresholds for effects to ecological receptors. Includes benchmarks for surface water, sediment, and surface soil for a range of aquatic organisms, soil invertebrates, and terrestrial plants.

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