Technical Assistance and Guidance Documents

Stressor Identification Guidance

United States Environmental Protection Agency	Office of Water Office of Research and Development	EPA 822-F-00-012 December, 2000

FACT SHEET

STRESSOR IDENTIFICATION GUIDANCE DOCUMENT

Summary

The U.S. Environmental Protection Agency (EPA) is publishing the Stressor Identification Guidance Document (EPA 822-B-00-025). The Stressor Identification (SI) guidance leads you, the water resource manager or environmental investigator, through stressor identification and evidence assembly. You may find the SI guidance useful whenever you find biological impairment in an aquatic ecosystem and need to know the cause.

You may find this guidance useful if you are engaged in any activity where the biological condition of a waterbody is important. These activities include: Water Quality Assessments State of the Environment Reports 305(b) Reports 303(d) Lists and Total Maximum Daily Load (TMDL) Programs State/Local Watershed Management Programs Non-point Source 319 Management Programs National Pollutant Discharge Elimination System (NPDES) Permitting Programs Cooling Water Intake 316(b) Permitting Programs Dredge and Fill Permitting Compliance and Enforcement Actions Risk Assessments Wetlands Assessments Preservation and Restoration Programs Control Effectiveness Assessments

Background

Numerous States and Tribes are turning to biological assessments and biocriteria to help protect the biological integrity of the Nation's waters. Using these tools you may find sites that are biologically impaired. You will need to identify the stressors causing the impairment if you want to improve the biological condition.

About this Guidance Document

The SI guidance helps you evaluate the information you have to identify the main stressor(s) causing biological impairment. The guidance will help you see where evidence is weak or lacking and needs to be developed. When evidence is adequate, you will be able to estimate the likely cause, or causes. You may use this guidance for any type of aquatic ecosystem. The SI process is a logical way of evaluating evidence. The SI guidance is not a mandatory procedure. There is no effective date specified.

Environmental Benefits

You can target your resources best when you identify stressors accurately. You can make convincing arguments to others of the need for action when you can show the strength of your evidence.

What kinds of data will I need?

The SI process is iterative. You will begin by analyzing available data to see if you already have sufficient information. The kinds of information you will need include information on the type of impairment, the extent of the impairment, any evidence of the usual suspects (e.g., toxicants, habitat loss) and most any other information from the site. You will look at that evidence first and then look for other less direct kinds of evidence if needed, such as other situations that are similar and might provide useful insights.

How does the SI process work?

The SI process has three main steps:

1. list candidate causes of impairment,
2. analyze the evidence, and
3. characterize the causes.

First, list the candidate causes. You will want to describe the impairment and make a map to help you understand the problem more clearly. Next, look for information. You will want to obtain input from stakeholders and evidence of stressors, especially stressors that are unique to your particular situation.

Second, analyze your evidence by breaking it down into usable pieces. The guidance helps you organize the pieces of evidence according to whether they rely principally on site-specific evidence, or whether they are based on observations from other sites, situations, or biological knowledge.

Third, characterize the cause. When you compile and analyze your available evidence, the actual cause may be obvious. Or, you may need a more systematic method for reaching a conclusion. The SI process combines multiple methods to determine the causes. The methods are presented in order by the kinds of evidence used, going from site specific to more general information.

As you proceed through the methods, you may find that more information is needed. You may want to get more information either by collecting new data or by further communication with decision makers and stakeholders.

How to Get a Copy of the Document

Copies of the complete document, titled Stressor Identification (SI) Guidance Document can be downloaded from the web at http://www.epa.gov/OST. The document may also be obtained from EPA's Water Resource Center by phoning 202-260-7786, by e-mailing a request to center.water-resource@epa.gov, or by mailing a request to EPA Water Resource Center, RC-4100, 401 M Street SW, Washington, DC 20460.