Principles to Consider When Reviewing and Using Natural Condition Provisions
EPA Region 10 completed an internal, educational document entitled “EPA Natural Conditions Workgroup Report on Principles to Consider When Reviewing and Using Natural Condition Provisions” (pdf file, 225 Kb, 54 pages) on April 1, 2005.
This document describes issues that have arisen and approaches that EPA Region 10 staff have taken in handling issues related to natural condition provisions in water quality standards (WQS) under the Clean Water Act (CWA), such as 303(d) listing (list of impaired waters), Total Maximum Daily Loads (water quality improvement plans) and NPDES (waste water discharge) permits.
This is a working document that will be revised as new information becomes available.
The purpose of this document is to 1) educate EPA staff on the development and application of the natural condition WQS provisions in CWA programs and 2) assist EPA staff in making sound decisions. This document advises EPA staff on how to implement CWA actions (involving natural condition WQ standard provisions) and review state and tribal CWA actions for EPA approval. The target audience for the document is EPA staff. The document recognizes the need for flexibility to address unique circumstances associated with individual waters, states and tribes, as long as water quality is protected.
This document describes basic principles underlying the creation and use of the natural condition provisions in water quality standards (WQS) under the Clean Water Act (CWA). These principles were derived from the collective experience of EPA staff who have worked on natural condition issues over the past decade. The document recognizes the need for flexibility to address unique circumstances associated with individual water bodies, states and tribes, as long as water quality is protected.
The purpose of this document is to share among EPA staff issues and approaches regarding the development and application of the natural condition WQS provisions in CWA programs. This document provides EPA staff advice on implementing CWA actions (involving natural condition WQ standard provisions), and on reviewing state and tribal CWA actions for EPA approval. The target audience for this document is EPA staff.
All four Region 10 states and many tribes have natural condition provisions in their EPA-approved WQS. Over the years, many questions have arisen over the wording, meaning and use of these natural condition provisions. EPA Region 10 convened a workgroup to develop a document to help its staff better understand and apply natural condition provisions. The workgroup included people with experience in developing and applying natural condition WQS provisions in CWA programs, such as 303(d) listing (list of impaired waters), Total Maximum Daily Loads (TMDLs or water quality improvement plans) and NPDES (wastewater discharge) permits.
The following principles are common to all CWA programs. Generally, decisions based on the application of a natural condition provision should be:
Furthermore, consider the following when using natural condition provisions:
- geographically specific;
- scientifically defensible;
- well-documented and supported with data and information;
- highlighted in a process that provides the public an opportunity for review and comment when natural condition provisions are applied [e.g., in a 303(d) listing decision, in the development of TMDL, in a NPDES permit];
- tracked and accessible to the public.
Ideally, WQS with a natural condition provision will include a definition of a natural condition (such as “the quality of surface water that exists in the absence of human-caused pollution or disturbance”); a provision that site-specific criteria may be set equal to a natural condition and a written procedure (e.g., Implementation Plan) on how the state or tribe will determine a natural condition of a water body and narrative natural conditions criteria for temperature that allows the natural condition temperature to become the criteria and supercede the numeric criteria when a natural condition determination is made on a case-by-case basis.
Water Quality Standards (WQS)
303 (d) ListingDecisions made using a natural condition provision (which allow a water body to be removed or not included on the list) should be based on existing and readily available data and information, supported by a site-specific, scientifically defensible rationale that does one of the following:
- explains why human activities in a watershed are not directly or indirectly the cause of the exceedance of WQS for the pollutant of concern;
- shows there has been virtually no human activity in the watershed that would affect the water quality parameter in question;
- explains how natural processes alone are adequate to account for the observed exceedance of the water quality standard for the pollutant of concern; or
- shows that the water quality in the watershed is similar to that measured in an undisturbed reference location.
TMDLs and NPDES PermitsWe encourage the states or tribes to discuss their preliminary approach for quantifying or determining natural conditions with EPA staff when developing a TMDL load or wasteload allocation. The following questions may help states and tribes in selecting a methodology to use in determining a natural condition:
- Does a suitable reference watershed or reference location (with similar size, elevation, geology, climate, fauna, flora, flow, etc.) exist?
- Are there adequate data from the reference location?
- Is there an appropriate model that meets the project objectives?
- Is there available expertise to run the model?
- Are there adequate data to use as model input parameters?
- What are the legal, resource and time constraints?
Frequently Asked Questions The U.S. Environmental Protection Agency (EPA) Region 10 has written a report for internal use entitled Principles to Consider When Reviewing and Using Natural Conditions Provisions. The report is designed to share among EPA staff issues that have arisen and approaches that EPA Region 10 staff have taken in handling issues related to naturally occurring water quality conditions. While the report is for internal use, EPA recognizes that people outside the Agency may want to read it. Below are answers to questions frequently asked about the report.
Q: What are natural conditions?
Natural condition is a term used to describe the quality of surface water untouched by human-caused pollution or disturbance. Natural conditions are rare and exist in limited settings.
Q: What is so important about natural conditions?
States define goals for their surface waters called water quality standards. These goals include a specific numeric pollutant concentration or a narrative description called water quality criteria. The criteria is designed to protect the uses that the state has set for the water such as drinking water, recreation, aquatic life. In some cases, a surface water may exceed the numeric criteria even though there have been no human disturbances in this water. As a result, states usually include a natural condition provision in their water quality standards. This provision explains how a state will handle situations where the natural condition of the water exceeds the numeric water quality standards. In many states, the natural condition provision sets the numeric criteria equal to the natural condition. For example, if the dissolved oxygen criterion states that dissolved oxygen should be no less than 5 mg/l. If the state determines that the natural condition of that water is actually 4 mg/l under the natural condition, then the criteria would be 4 mg/l for that water.
Q: How do you calculate natural conditions?
There is no single correct approach to calculating a natural condition. The two most common approaches used are measurement and modeling. In the measurement approach, the natural condition is calculated by using data from a reference water that has similar physical and geographic characteristics but that has not been disturbed by humans. Modeling is a mathematical tool used to estimate water quality conditions of a water in the absence of human disturbances. The report describes approaches for calculating natural conditions under “Determining Natural Conditions.”
Q: Why did EPA Region 10 write this report?
EPA Region 10 wrote this report to help EPA staff better understand and apply natural condition provisions and to help EPA staff review state and Tribal development and application of natural condition provisions for approval. The Region 10 states (Alaska, Idaho, Oregon, and Washington) and many Tribes have a natural conditions provision in their EPA-approved water quality standards. Over the years, many questions have come up about what the provisions mean and how they should be implemented.
Q: Is the report regulatory guidance?
No, the report is not regulatory guidance. It is an educational document. It does not impose binding requirements on EPA, states, Tribes, or the regulated community. It also does not substitute for Clean Water Act requirements, EPA’s regulations, or the obligations imposed by consent decrees or enforcement orders. Furthermore, information in the report does not apply to all situations.
Q: Am I required by EPA to use the report as a guide when reviewing and using natural conditions provisions?
No, you are not required to use the report. EPA recognizes the need for flexibility to address unique circumstances associated with individual water bodies and state and Tribes, as long as water quality is protected.
Q: How was the report developed?
The report was written by an EPA Region 10 workgroup. The principles and recommendations in the report are based on the experiences of EPA staff who have worked on state and Tribal water quality standards, and applied these provisions in Clean Water Act programs, such as 303(d) listing (list of impaired waters), Total Maximum Daily Loads (water quality improvement plans) and NPDES (wastewater discharge) permits over the past decade.
Q: Will the report be revised in the future?
Yes, the report is a working document and it will be revised and updated as new information becomes available. The most current version of this report is posted on this website.
Q: What are the major recommendations of the report?
When applying the natural condition provisions under any of the Clean Water Act programs, EPA recommends that:
Q: When are natural conditions not present?
As the term is used in this report, “natural conditions” are not present when: water quality has been or is altered by human activity or industry; irreversible human features, such as a dam, are present; or there have been influences from sources outside the watershed, such as atmospheric deposition of mercury. Further, ambient or best-attainable conditions are not necessarily natural. You can learn more about these topics in the section of the report entitled “Water Quality Standards and Natural Condition.”
Q: Will the report tell me when an Endangered Species Act (ESA) consultation is required by EPA?
No, the report does not provide guidance on this topic. It is beyond the scope of the report.
Q: Where do I send my comments, questions or suggestions?
E-mail your comments, questions and suggestions to firstname.lastname@example.org. EPA will be updating this document periodically and the most correct version will be posted on this website .
- Decisions are geographically specific, well-documented, and supported with data and information.
- The public is provided with opportunity to comment on the basis for applying any natural condition provision at the time of use and that natural condition provisions are tracked and accessible to the public.