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• Chapter 2. Identifying Impaired and Threatened Waterbodies and Setting Priorities for Establishing TMDLs

Chapter 2. Identifying Impaired and Threatened Waterbodies and Setting Priorities for Establishing TMDLs

Note: EPA no longer updates this information, but it may be useful as a reference or resource.

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This chapter defines and clarifies the listing requirements of § 303(d) of the Clean Water Act (CWA). Its purpose is to help State, Territorial, or authorized Tribal water quality program managers better understand existing statutory and regulatory language so that lists are submitted to and approved by EPA in an efficient and timely manner. The chapter summarizes the necessary components of an approvable list and provides recommendations for the data elements to be reported for each impaired waterbody and pollutant or pollution combination. The relationship between the four parts of the list are discussed, and additional guidance is provided regarding EPA's expectation of the scope of the State's, Territory's, or authorized Tribe's listing methodology. Information is also provided on the meaning of the term "readily available data and information" and on interpreting narrative criteria and designated use impairments. The chapter also provides guidance regarding the role of monitoring and how data are interpreted to support listing decisions. Identifying minimum data requirements for making listing decisions and assessing the level of information quality are also discussed.

2.1 What is the § 303(d) List

The § 303(d) list is a comprehensive public accounting of all impaired or threatened waterbodies, regardless of the cause or source of the impairment or threat. An impaired waterbody is one that does not attain water quality standards (designated uses, numeric and narrative criteria and anti-degradation requirements defined at 40 CFR 131). The standards violation might be due to an individual pollutant, multiple pollutants, pollution, or an unknown cause of impairment. Where a waterbody receives a thermal discharge from one or more point sources, impairment means that the waterbody is not meeting the applicable State temperature criterion or does not have or maintain a balanced, indigenous population of shellfish, fish, and wildlife. A threatened waterbody is one that currently attains water quality standards but for which existing and readily available data and information on adverse declining trends indicate that water quality standards will likely be exceeded by the time the next list is required to be submitted to EPA.

A State's, Territory's, or authorized Tribe's list of impaired or threatened waterbodies must be submitted to EPA by October 1 of every [reserved] year, beginning in the year 2000 (40 CFR 130.30). State, Territorial, and authorized Tribal § 303(d) lists must include waterbodies impaired or threatened by pollutants, such as nitrogen, copper, and clean sediment, and by pollution, such as hydromodification and loss of habitat. Separate listings are required for each waterbody and pollutant or pollution combination. The source of impairment might be from point sources, nonpoint sources, atmospheric deposition, or a combination of these. Impaired or threatened waterbodies must be listed regardless of whether the pollutant or source of pollution is known and whether the pollutant/pollution source(s) can be controlled.

Federal agencies have an important role to play in helping to meet the goals of the CWA. Federal agencies should work cooperatively with States, Territories, and authorized Tribes to ensure that Federal lands comply with Federal, State, and local water quality requirements and to ensure that impaired and threatened waterbodies located on Federal lands are identified during the listing process. During its review of State, Territory, and authorized Tribe lists, EPA will verify that impaired or threatened waterbodies on Federal lands are identified and listed.

Summary of Statutory and Regulatory Requirements for
Identifying Impaired or Threatened Waterbodies and Setting Priorities for Establishing TMDLs

All existing and readily available data and information must be assembled and considered to identify impaired or threatened waterbodies (§ 130.22(a)). Existing and readily available data and information includes, but is not limited to, the data and information in (§ 130.22(a))

• Your most recent EPA approved § 303(d) list;
• Your most recent Clean Water Act § 305(b) report;
• Clean Water Act § 319 nonpoint source assessments;
• Drinking water source water assessments under § 1453 of the Safe Drinking Water Act where the assessment results demonstrate for one or more pollutants regulated as drinking water contaminants under § 1412 that (i) a water quality standard has been exceeded, or is at risk of being exceeded, or (ii) the concentration of a pollutant has increased since use of the waterbody as a public water supply began;
• Dilution calculations, trend analyses, or predictive models for determining the physical, chemical or biological integrity of streams, rivers, lakes, and estuaries; and
• Data, information, and water quality problems reported from local, State, Territorial, or Federal agencies, Tribal governments, members of the public, and academic institutions.

States, Territories, and authorized Tribes are required to develop a methodology that explains how existing and readily available data and information were assembled and considered to make listing and priority decisions regarding the § 303(d) list (§ 130.23 and § 130.24 ). The methodology must (§ 130.23 (b), (c) and (d)):

• Specify the factors used to consider and evaluate the following types of data and information when making listing decisions:
  • Physical/chemical data and information
  • Biological data and information
  • Aquatic and riparian habitat data and information
  • Waterbody impairment and drinking water susceptibility analyses required under § 130.22 (b)
• Identify the type of data and information considered to be "existing and readily available" and explain how the following are considered in making listing and priority ranking decisions:
  • Data quality and age
  • Degree of confidence in the information used to determine whether waterbodies are impaired or threatened
  • Number and degree of exceedances of numeric or narrative criteria and designated uses used to determine whether waterbodies are impaired or threatened
• Describe the selection factors used to include waterbodies on the list;
• Detail the process for resolving disagreements with other jurisdictions involving waterbodies crossed by State or authorized Tribal or international boundaries; and
• Describe the method and factors used to assign a priority ranking to waterbodies on Part 1 of the list.
• Describe how and for what reasons previously listed waterbodies will be removed from the list.
• Be made available for the public to make comments for at least 60 days (§ 130.23(a)).
• Be submitted to EPA by January 31 of every [reserved] year for review and comment, along with a summary of all comments received and the response of the State, Territory, or authorized Tribe to each comment (§ 130.24(a)).

States, Territories, and authorized Tribes are required to develop a comprehensive list of impaired or threatened waters (§ 130.25 through § 130.27 ). The list must

• Include all waterbodies that, based on all existing and readily available data and information, are impaired or threatened by individual pollutants, multiple pollutants, or pollution from any source regardless of whether the waterbodies are impaired or threatened by
  • a pollutant which is unknown at the time of the listing;
  • atmospheric deposition; or
  • point sources, only by nonpoint sources, or by a combination of point and nonpoint sources.
• Be divided into four parts:
  • Part 1 - Waterbodies impaired or threatened by one or more pollutants. TMDL required.
  • Part 2 - Waterbodies impaired or threatened by pollution, but not impaired or threatened by one or more pollutants. No TMDL required.
  • Part 3 - Waterbodies for which EPA has approved or established a TMDL and water quality standards have not yet been attained.
  • Part 4 - Waterbodies that are impaired, for which implementation of best practicable control technology for point sources and secondary treatment for publicly owned treatment works are expected to result in attainment of water quality standards by the next listing cycle. No TMDL required.
• Identify the pollutant or pollutants causing the impairment or threat of impairment for each waterbody on Parts 1, 3, and 4 of the list.
• Identify the class of pollutants (e.g., metals, pesticides, industrial chemicals, or nutrient), if the specific pollutant is unknown at the time of listing.
• Identify the type of pollution causing the impairment or threat of impairment for each waterbody on Part 2.
• Identify the geographical location of each waterbody on the list, using a nationally recognized georeferencing system such as reach codes.
• Priority rank all waterbody and pollutant combinations on Part 1 of the list.
• Include a schedule for completing TMDLs for all waterbody and pollutant combinations on Part 1 of the list in accordance with the priority ranking (§ 130.31)
• Be submitted to EPA for review and action by October 1 of every [reserved] year starting 2000 (§ 130.30).

A waterbody and pollutant or pollution combination must remain on the list until new data and information indicate that there is no longer an impairment or threat of impairment (§ 130.28)

Only Part 1 of the § 303(d) list must be prioritized (§ 130.25-27). The priority ranking

• Must assign a high, medium, or low priority ranking to each waterbody and pollutant combination on Part 1 of the list taking into account the severity of the impairment or threatened impairment and the designated uses of the waterbody.
• Must assign a high priority to waterbodies with water quality standards uses as public drinking water supplies and for waterbodies in which species listed as endangered or threatened under §4 of the Endangered Species Act (ESA) are present. When identifying high priority waterbodies, the presence of sensitive aquatic species and secondary factors such as the historical, cultural, economic, and aesthetic uses of the waterbody may also be considered.
• May assign a medium or low priority to waterbodies which have endangered or threatened species present, and have an approved Habitat Conservation Plan or other specific, enforceable mechanism developed in accordance with the Endangered Species Act, as long as the approved plan or other mechanism is specific to the pollutant and the waterbody of concern and demonstrates that water quality standards will be attained or maintained.
• Must explain how the severity of the impairment or threat of impairment and the designated use to be made of the waterbody were considered in assigning each priority ranking.
• May consider other factors in assigning each priority ranking, including efficiencies gained by developing TMDLs for waterbodies located in the same watershed; the value and vulnerability of particular waterbodies; the recreational, economic, and aesthetic importance of particular waterbodies; TMDL complexity; the degree of public interest and support; and State, Tribal, Territorial or national policies and priorities. Each additional factor must be identified and how it was used to assign priority rankings must be explained.

The schedule must reasonably pace the workload over time, ensuring that TMDLs are completed no later than 15 years from the date of the initial listing on Part 1 of the list.

States, Territories, and authorized Tribes must submit to EPA, and make public, information on how they assembled existing and readily available data and how those data were used in identifying impaired or threatened waterbodies. This requirement can be fulfilled by either applying an existing § 305(b) reporting methodology to the § 303(d) process or by using a different listing methodology for the § 303(d) list. In either case, this methodology must be made available to the public for review (for no less than 60 days) and then must be submitted to EPA by January 31 of each year in which a list is due. If States, Territories, or authorized Tribes fail to submit a § 303(d) list, EPA is required to identify and list impaired or threatened waterbodies for the State, Territory, or authorized Tribe.

2.1a Required Components and Format of the § 303(d) List

Each threatened or impaired waterbody and pollutant or pollution combination must be listed by States, Territories, and authorized Tribes on one of four distinct parts of the § 303(d) list. These parts are described below.

Part 1: Waterbodies impaired or threatened by a pollutant as defined in 40 CFR 130.2(d). EPA anticipates that the largest proportion of impaired and threatened waterbodies will be included on Part 1 of the list. TMDLs must be scheduled and established for all waterbodies listed in Part 1. If the cause of impairment is unknown at the time of listing, the waterbody should be included on Part 1 of the list and you must, to the extent possible, identify the class of pollutants, e.g., metals, pesticides, industrial chemicals, or nutrients.

Waterbodies are often impaired or threatened by more than one pollutant. It is important to recognize that each waterbody and pollutant combination must be listed separately on Part 1 of the list and TMDLs are to be scheduled for each waterbody and pollutant combination.

If you do not know whether a waterbody is impaired by a pollutant or some type of pollution, the waterbody must be included on Part 1and the class of pollutant identified. Supplemental data collection and analysis should assist in identifying the impairing pollutant so that the TMDL can be established. EPA anticipates that the pollutant will be identified when the TMDL is initiated.

Part 2: Waterbodies impaired or threatened by pollution as defined by 40 CFR 130.2(c) but notimpaired or threatened by one or more pollutants. Waterbodies impaired or threatened by pollution, not by a pollutant, are included on Part 2 of the list. Review of the available data and information for theparticular waterbody should show that no pollutants pose a significant threat or are a significant cause of impairment to the waterbody. If this is the case, the waterbody is listed on Part 2. EPA believes that in situations where the impairment is not caused by a pollutant, a TMDL is generally not the appropriate solution to the problem. In keeping with the principle that the § 303(d) list is an accounting of all impaired and threatened waterbodies, however, these types of waterbodies must remain on Part 2 of the list until water quality standards are attained by some other means.

EPA believes that Part 2 waterbodies will primarily consist of waterbodies impaired due to hydromodification. For example, a stream designated for aquatic use support might be impaired due to a dam that restricts flow. In this situation, there is no pollutant to allocate and a TMDL is not required. As well, there might be situations where water withdrawals eventually lead to some pollutant-related impairments (e.g., flow is so low that a pollutant concentration exceeds numeric criteria), EPA does not believe that TMDLs should be the solution to problems substantially caused by hydromodification. Other conditions that may cause listing under Part 2 include exotic species (e.g., zebra mussels), noxious aquatic plants, radiation, and taste and odor problems.

Part 3: Waterbodies for which EPA has approved or established a TMDL and water quality standardshave not yet been attained. Part 3 includes waterbodies and pollutant combinations for which TMDLshave been approved or established by EPA. These waterbodies must remain on the list until waterquality standards are attained. Procedures for tracking implementation and monitoring the water qualityconditions of these waterbodies are identified in the TMDL. These monitoring data must be consideredwhen evaluating Part 3 waterbodies for potential delisting.

Part 4: Waterbodies that are impaired, but for which implementation of best practicable control technology for point sources and secondary treatment for publicly owned treatment works or controlsenforceable by State or Federal law or regulation that are expected to result in attainment of water quality standards by the next listing cycle. Part 4 includes waterbody and pollutant combinations for which TMDLs are not required because other required CWA controls are expected to attain water quality standards by the next listing cycle. The only controls that justify not listing an impaired or threatened waterbody on the § 303(d) list are the point source controls identified in § 301 and § 402 of the CWA.The listing submittal should identify the specific controls, funding, and construction schedules that are expected to result in implementation of the identified treatment needs. Supplementary analysis that demonstrates that the implementation of the point source controls will result in attainment of water quality standards should also be included (e.g., permit applications and limits, dilution analyses, and other modeling results). If a waterbody and pollutant combination listed on Part 4 does not attain water quality standards by the time the next list must be submitted to EPA, the waterbody and pollutant combination must be moved to Part 1 of the list, unless it is documented that failure to attain water quality standards is due to failure to comply with applicable technology-based requirements.

2.1b Submitting the § 303(d) List

Figure 2-1 presents a sample format for organizing the four parts of the § 303(d) list. In identifying specific waterbody and pollutant/pollution combinations on the list, States, Territories, and authorized Tribes should use the common data elements identified in this table. These data elements include information on the location of the waterbody, including the code of the U.S. Geological Survey (USGS) hydrologic unit (HU) in which the waterbody is located, the type of waterbody and size of impairment, the pollutant or type of pollution causing the impairment, all identified sources of the pollutant or pollution, and the designated uses of the impaired waterbody. Many of these data elements are already available within State/Territory/Tribal § 305(b) Waterbody System databases. Appendix A summarizes relevant codes for identifying pollutants. Appendix B, Table B-1, summarizes codes for identifying sources. For Part 1 of the list, information on the priority ranking of each waterbody and pollutant combination and the scheduled date for TMDL submittals should also be reported. As shown in Figure 2-1, certain data elements will not be relevant for certain parts of the list.

Figure 2-1. Sample format for organizing the four parts of a § 303(d) list

Waterbody Name	303(d) ID**	305(b) ID*	HUC	Watershed ID	Waterbody Type	Waterbody Size	Pollutant	Type of Pollution	Source(s) of Impairment	Designated Uses	TMDL Establishment Priority	Anticipated Date of TMDL Submittal	Date First TMDL Established for Waterbody	Date Final TMDL Approved or Established by EPA
Part 1:
Eagle Creek	SX-ABC123(1)-2000	SX-ABC123	01234567	Basin A	RIVER	2	Pathogens	---	Agriculture, Septage Disposal	Primary Contact	High	2002	2000	.
Eagle Creek	SX-ABC123(2)-2000	SX-ABC123	01234567	Basin A	RIVER	2	Nitrogen	---	Municipal Point Sources	Aquatic Life	Medium	2003	2000	.
Make-Believe Bay	SX-E123-2000	SX-E123	23568972	Basin B	ESTUARY	15	Chlorine	---	Municipal Point Sources	Aquatic Life	Low	2002	.	.
.	.	.	.	.	.	.	.	---	.	.	.	.	.	.
.	.	.	.	.	.	.	.	---	.	.	.	.	.	.
Part 2:
Dog Creek	SX-(*)GHI789-2000	Multiple	04567910	Basin C	RIVER	3.5	---	Flow Alterations	Hydromodification (Dam Construction)	Aquatic Life	---	.	.	.
.	.	.	.	.	.	.	---	.	..	.	---	.	.	.
.	.	.	..	..	..	..	---	.	..	.	---	.	.	.
.	.	.	.	.	.	.	---	.	..	.	---	.	.	.
.	.	.	.	.	.	.	---	.	..	.	---	.	.	.
Part 3:
Horse Lake	SX-XYZ-2000	SX-YYY	88887526	Basin E	LAKE	200	Nutrients	---	Agriculture, Municipal Point Sources	Recreation	.	.	2000	2000
Eagle Creek	SX-ABC(3)-2000	SX-ABC123	01234567	Basin A	RIVER	2	BOD	---	Municipal Point Sources	Aquatic Life	.	.	2000	2000
.	.	.	.	.	.	.	.	---	.	.	.	.	.	.
.	.	.	.	.	.	.	.	---	.	.	.	..	.	.
.	.	.	.	.	.	.	.	---	.	.	.	..	.	.
Part 4:
Apple River	SX-KLM357-2000	SX-BBB	68792431	Basin E	RIVER	0.7	Cyanide	---	Industrial Point Source	Aquatic Life	.	.	.	.
.	.	.	.	.	.	.	.	---	.	.	.	.	.	.
.	.	.	.	.	.	.	.	---	.	.	.	.	.	.
.	.	.	.	.	.	.	.	---	.	.	.	.	.	.
.	.	.	.	.	.	.	.	---	.	.	..	..	.	.

¹ 303(d) ID and 305(b) ID are the same (except for the year suffix) if there is a 1:1 correspondence between a Waterbody ID and the geographic extent of the 303(d) waterbody.
² 303(d) listing ID should be cross-referenced by the State to the Reach File 3.0 system.

Part 1: Waterbodies impaired or threatened by one or more pollutants
Part 2: Waterbodies impaired or threatened by pollution
Part 3: Waterbodies for which EPA has approved or established a TMDL and WQ standards have not yet been attained
Part 4: Waterbodies that are impaired, for which implementation of best practicable control technology for point Sources and secondary treatment for publicly owned treatment plants are expected to result in attainment of WQ standards by next listing cycle

To specify a unique waterbody for the § 303(d) list, the same waterbody ID used in the State/Territory/Tribal § 305(b) Waterbody System database should be used, with a suffix added to the § 303(d) ID for the year of the listing cycle. To accommodate situations where the geographic scale of the § 303(d) waterbody is either larger or smaller than that of the reported § 305(b) waterbody, a separate § 303(d) ID may be derived. The resulting § 303(d) ID can then be used in association with other information on use attainment status or pollutant/pollution causes and sources and can be added to geographic information system (GIS) data layers to facilitate mapping of § 303(d) and other water quality information.

EPA has created a national TMDL Tracking System database from the States' 1998 § 303(d) lists. EPA used State-supplied § 303(d) IDs or developed new § 303(d) IDs where State IDs were not available. States, Territories, and authorized Tribes should use these existing IDs from the TMDL Tracking System whenever possible for their future § 303(d) lists. Doing so will save significant EPA and State, Territory, or authorized Tribe labor and avoid errors in georeferencing future § 303(d) lists to the EPA Reach File and its successor, the National Hydrography Dataset. TMDL Tracking System files including the existing § 303(d) IDs are available from the National 303(d) Coordinator.

EPA Reach File Version 3 (RF3) forms the basis for linking the § 303(d) ID to geographic information. RF3 is a national hydrologic database that uniquely identifies and interconnects more than three million stream segments or "reaches" that compose the nation's surface water drainage system. RF3 was created from digital hydrography data produced by the USGS. EPA enhanced these hydrography datasets by assigning a unique reach code to each stream segment, determining the upstream/downstream relationships of each reach, and, when possible, identifying the stream name for each reach. A variety of other reach-related attributes that support mapping, pollutant routing, and spatial analysis applications are also available. EPA and USGS are currently finalizing the National Hydrography Dataset (NHD). This successor to RF3 will have greatly improved accuracy and power.

Over the past four years, EPA has worked with several States, Territories, and authorized Tribes to georeference or reach index their § 305(b) waterbodies to RF3. Georeferencing means linking individual waterbodies to the coordinates of a hydrographic database like RF3. The process is done in a geographic information system (GIS) environment. Concurrent with this reach indexing, EPA is creating a national TMDL Tracking System database that contains all waterbodies listed on 1998 § 303(d) lists. The Tracking System and reach indexing products are linked by unique § 303(d) IDs for mapping and spatial analysis.

States, Territories, and authorized Tribes may either develop their own GIS coverages/ shapefiles of § 303(d) waterbodies and submit them to EPA with their § 303(d) lists or adopt the standardized approach (preferred by EPA) of georeferencing their waterbodies to RF3. This standardized approach relies on reach indexing tools and GIS-related data files (event tables) developed by EPA in coordination with the States, Territories, and authorized Tribes.

The advantages of EPA's standardized approach to reach indexing include the following:

• The States, Territories, and authorized Tribes, the public, and EPA will be able to view the locations of § 303(d) waterbodies and other features in a consistent format.
• The standardized approach allows spatial analysis of water quality problems across political boundaries (e.g., when a watershed crosses a State, Territory, or authorized Tribal jurisdiction). Without a standardized approach, agencies often have technical problems using each other's GIS coverages.
• Other approaches used by States, Territories, and authorized Tribes usually alter the underlying RF3 coverage, which destroys compatibility with other EPA, State, Territory, or authorized Tribe coverages. The EPA approach leaves the underlying RF3 (and eventually NHD) coverages unaltered to allow for EPA and the States, Territories, and authorized Tribes to have a common hydrographic dataset for all GIS-related activities in the future.
• The approach provides a link to other water quality data and permits coverages.
• EPA has developed user-friendly indexing tools and provides training and technical support. EPA will also support the transfer of locational information on § 303(d) waterbodies to the forthcoming NHD.
• RF3 segments in an event table can be broken to accurately delineate the waterbodies of a State, Territory, or authorized Tribe without altering the underlying RF3 coverage. Event tables can also accommodate certain complexities of some waterbodies, such as § 303(d) waterbodies that have overlapping extents.
• With updates of locational data each § 303(d) cycle will become more routine and timely.

Key Questions to Consider When Formatting a § 303(d) List

• Has the list been divided into four distinct parts?
• Are specific waterbody and pollutant or pollutant type combinations listed on parts 1, 3, and 4 of the list?
• Are specific waterbody and pollution combinations listed on Part 2?
• Have all listed waterbodies been georeferenced?
• Has each listed waterbody been assigned a unique identifier?

2.2 Methodology for Identifying Impaired or Threatened Waterbodies

EPA regulations require States, Territories, and authorized Tribes to submit a written methodology that describes their approach for considering and evaluating the data and information used to develop their lists, as well as methodologies for prioritizing and scheduling TMDLs. Each State, Territory, and authorized Tribe must provide the public the opportunity to review and comment on this methodology for no less than 60 days. After the review period, the methodology must be submitted to EPA by January 31 of each year the § 303(d) list is due. Following submittal, EPA will review the listing and priority ranking methodology and provide, as appropriate, comments on the methodology in advance of the list submission. EPA will not approve or disapprove a listing methodology, but will consider the methodology in its review of the list.

The methodology should include the "decision rules" used to identify impaired or threatened waterbodies and to put waterbodies on Parts 1 through 4 of the list. It should include a description of the State's, Territory's, or authorized Tribe's overall approach to listing, including priority setting and scheduling; a description of how existing and readily available data and information were assembled, evaluated, and considered; and an explanation of how the State, Territory, or authorized Tribe considered data and information from habitat assessments, bioassessments, physical/chemical monitoring, and waterbody impairment and drinking water susceptibility analyses required under § 130.22(b). The listing methodology must also include a description of a process for resolving disagreements involving the condition and priority of waterbodies crossed by State, Territory, authorized Tribal, or international boundaries. The decision process and justification for removing waterbody and pollutant or pollution combinations from the list must also be clearly explained.

Although EPA does not specify which information or rules States, Territories, and authorized Tribes must use to identify impaired and threatened waterbodies, the Agency does require, at a minimum, a description of existing and readily available data and information and an explanation of how the following factors are considered in making listing and priority ranking decisions:

• Data quality and age.
• Degree of confidence in the information used to determine whether waterbodies are impaired or threatened.
• Number and degree of exceedances of numeric or narrative criteria and designated uses used to determine whether waterbodies are impaired or threatened.

The purpose of submitting the listing methodology eight months prior to submitting the § 303(d) list is to ensure that the public and EPA know and understand how the State, Territory, or authorized Tribe is assembling and considering existing and readily available data and information to develop its list. EPA believes that the process most States, Territories, and authorized Tribes use for completing § 305(b) reports is sufficient to characterize the quality of their waterbodies, including those impaired and threatened waterbodies required to be listed under § 303(d).

Figure 2-2 describes the conceptual relationship between § 305(b) use support decisions and § 303(d) impaired or threatened waterbodies. In the past, different characterizations of the same waterbodies in these reports has caused confusion and led to questions concerning the integrity of all CWA assessment and listing requirements. In most situations, waterbodies identified as not supporting or partially supporting their designated uses in the § 305(b) report should be identified as impaired on the § 303(d) list. Similarly, waterbodies identified in the § 305(b) report as threatened should also be identified as threatened and considered for inclusion on the § 303(d) list.

Key Questions to Consider When Developing a Listing Methodology

• What are the "decision rules" for identifying impaired or threatened waterbodies?
• What sources of data and information will be used to identify impaired or threatened waters?
• How do data quality and age affect listing and priority ranking decisions?
• What are the specific minimum requirements for data used to support listing decisions?
• How does the degree of confidence in available data and information affect listing and priority ranking decisions?
• How do the number and degree of exceedances of numeric or narrative criteria and designated uses affect listing and priority ranking decisions?
• How are priorities established for the waterbody and pollutant combinations listed on Part 1?
• What factors are considered when establishing the schedule for completing TMDLs?
• How are data and information from habitat assessments, bioassessments, physical/chemical monitoring, and waterbody impairment and drinking water susceptibility analyses considered?

2.3 Identifying Impaired or Threatened Waterbodies

To develop a comprehensive list of all impaired or threatened waterbodies, as well as the scope of the impairment or threat, a State, Territory, or authorized Tribe is required to consider (see Section 1-3) all existing and readily available data and information. The monitoring programs and cooperative data collection efforts of States, Territories, and authorized Tribes form the basis for listing decisions. Other sources of existing and readily available data and information include the public and Federal, State, and local agencies.

2.3a How Does Monitoring Support Listing Decisions?

A well-designed monitoring program is vital to a State's, Territory's, or authorized Tribe's efforts to characterize, identify, and ensure the protection and restoration of impaired or threatened waterbodies. Monitoring supports both listing and TMDL establishment decisions, as well as post-TMDL evaluation and tracking of standards attainment. Monitoring is essential to accurate lists, strategic collection of data to support TMDL establishment, streamlined TMDL establishment, and an improved understanding of water quality concerns, sources, and processes. As experience is gained in the TMDL process and related monitoring efforts, the design of monitoring strategies and interpretation of data will continue to improve. Specific areas where monitoring provides information to support listing decisions are summarized below:

• Identifying impaired or threatened waterbodies, including evaluating the pollutant(s) or pollution causing the impairment, evaluating potential sources, examining the magnitude or severity of the problem, and confirming the need to list the waterbody.
• Assigning a priority ranking to Part 1 waterbody and pollutant combinations and determining efficient schedules for TMDL development.
• Tracking compliance with water quality standards for Part 3 and Part 4 waterbody and pollutant combinations.
• Determining whether TMDL refinement is needed for Part 3 waterbody and pollutant combinations.

Monitoring performed before and during the list development process also supports establishing the TMDL. Some of the key points at which monitoring supports TMDL analysis include

• Selection of target values and evaluation of deviation from target
• Evaluation of the pollutant sources
• Estimation of source loadings
• Data for modeling and analysis of the TMDL linkage between source and targets

Although different types and quantities of monitoring data might be collected to support the various components of the listing and TMDL establishment processes, data are often used to support multiple objectives (e.g., § 305(b), § 303(d), TMDL establishment, and compliance monitoring). By coordinating various data collection activities, these multiple objectives can be addressed efficiently.

One of the techniques used by States, Territories, and authorized Tribes to organize water quality evaluations and management is the rotating watershed or basin approach. This approach can lead to a more comprehensive assessment of problems in individual watersheds, increase stakeholder involvement in watershed restoration, and ensure more efficient use of staff and financial resources in the water quality agency. The rotating basin approach involves monitoring a delineated watershed or basin according to a predetermined cycle (e.g., for one full year every five years) and using the data (1) to identify impaired or threatened waterbody and pollutant combinations causing impairments or threats, (2) to prepare or update a basinwide plan including a schedule for establishing TMDLs, (3) to implement controls, and (4) to monitor progress toward attainment of water quality standards. Selection of monitoring sites for each rotating basin survey is based on various factors:

• Known and suspected areas of point and nonpoint source impacts
• Previous § 303(d) listed and § 305(b) reported impaired waterbodies
• Outstanding resource waters
• Location of water intakes, landfills, and other features

Use of a rotating basin approach helps ensure that key information sources and other tools will be organized in a way that facilitates timely identification of impaired or threatened waterbodies and establishment of TMDLs.

Meeting TMDL Requirements in Mississippi Using a Rotating Basin Approach

The Mississippi Department of Environmental Quality (MDEQ) is implementing a Basinwide Approach to Water Quality Management to enable the state to comprehensively assess its waters for segments needing TMDLs, and establish those TMDLs over the next 13 years. Mississippi's 1998 § 303(d) list contains approximately 180 waterbody segments in need of TMDLs, and includes several hundred more segments listed as "potential waters of concern" based on previously evaluated information (i.e., information that does not include sufficient monitoring data to support decisions about the need for TMDLs).

MDEQ has divided the state into five basin groups to coordinate and administer key water quality activities. For each basin group, MDEQ plans to work through a five-phased management cycle to develop and implement watershed management plans that detail TMDLs, including implementation strategies. The five phases are: (1) Planning; (2) Data Collection; (3) Data Assessment and TMDL Development; (4) Basin Plan and TMDL Implementation Strategy Development; and (5) Implementation.

It is not feasible or cost-effective for MDEQ to conduct the same phase in every basin group at the same time. Therefore, MDEQ has established a schedule for sequencing the phases across the basin groups to balance workloads and provide for more focus in any given year. For example, in 2002 MDEQ will be implementing basin plans and TMDLs in the Big Black/Tombigbee group, developing basin plans and TMDL implementation strategies in the Yazoo group, conducting § 305(b) assessment and TMDL development in the South Independent/Pearl group, collecting data in the Pascagoula group, and prioritizing issues and planning data collection for the Coastal/North Independent/Tennessee group. Under this schedule, the first full iteration of the management cycle will have been completed in all basin groups by the end of 2006.

MDEQ plans to use this repeating cycle to coordinate its update of the State's § 303(d) list and to develop all currently needed TMDLs by the end of the second iteration of the cycle. During the first iteration of the cycle, MDEQ will--to the extent that resources are available--develop TMDLs for all waterbody segments on the § 303(d) list that are based on assessments made using monitoring data. Segments identified as "potential waters of concern" will be monitored during the first iteration of the basin cycle to verify whether the segments are actually impaired. Those previously evaluated segments that are verified by monitoring data as impaired will then have TMDLs developed for them during the second iteration of the basin cycle (currently scheduled to end in 2011), along with lower priority TMDLs not completed during the first iteration. As the cycle proceeds, waters added to the § 303(d) list during one iteration will be prioritized for TMDL development during the next iteration.

For more information about the rotating basin approach and its advantages, refer to Watershed Protection: A Statewide Approach, (EPA-841-R-95-004) and Appendix B of the 1998 § 305(b) guidelines (EPA-841-B-97-002B), as well as the Watershed Management Facilitation and Academy 2000 Distance Learning pages on the EPA Watershed Academy website (http://www.epa.gov/owow/watershed/wacademy/).

2.3b Assembling Existing and Readily Available Data

EPA regulations require that States, Territories, and authorized Tribes assemble all existing and readily available data and information to develop a list of impaired or threatened waterbodies (40 CFR 130.22). EPA regulations also explain that existing and readily available data include, at a minimum, the following data and information:

• Most recent EPA-approved § 303(d) list.
• Most recent § 305(b) report.
• CWA § 319 nonpoint source assessments.
• Drinking water source water assessments under § 1453 of the Safe Drinking Water Act, where the assessment results demonstrate for one or more pollutants regulated as drinking water contaminants under § 1412 that either a water quality standard has been exceeded or is at risk of being exceeded, or the concentration of a pollutant has increased since use of the waterbody as a public water supply began.
• Dilution calculations, trend analyses, or predictive models for determining the physical, chemical, or biological integrity of streams, rivers, lakes, and estuaries.
• Data, information, and water quality problems reported by local, State, Territorial, or Federal agencies, Tribal governments, members of the public, and academic institutions.

In addition to these six categories of data and information, Table 2-1 identifies several other types of information to be considered for § 303(d) listing decisions. Many of these categories of information are included in States', Territories', or authorized Tribes' § 305(b) reports or databases.

Table 2-1. Other examples of existing and readily available data and information to be considered for § 303(d) listing decisions

1	Waterbodies where fishing or shellfish bans and/or advisories are currently in effect or are anticipated and waterbodies where there have been repeated fish kills or where abnormalities (cancers, lesions, tumors, etc.) have been observed in fish or other aquatic life during the last 10 years.
2	Waterbodies where there are restrictions on water sports or recreational contact.
3	Waterbodies identified by the State, Territory, or authorized Tribe as priority waterbodies. (Water quality management plans often include lists of priority waterbodies, which are those waterbodies which most need water pollution control decisions to achieve water quality standards or goals.)
4	Waterbodies where ambient data indicate potential or actual exceedances of water quality criteria due to toxic pollutants from an industry classified as a primary industry in Appendix A of 40 CFR Part 122.
5	Waterbodies for which effluent toxicity test results indicate possible or actual exceedances of State, Territorial, or authorized Tribal water quality standards, including narrative "free from" water quality criteria or EPA water quality criteria where State, Territorial, or authorized Tribal criteria are not available.
6	Waterbodies classified for uses that will not support the "fishable/swimmable" goals of the CWA.
7	Waterbodies identified by the State, Territory, or authorized Tribe as impaired in its most recent Clean Lake Assessment conducted under § 314 of the CWA.
8	Surface waterbodies impaired by pollutants from hazardous waste sites on the National Priority List prepared under § 105(8)(A) of the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA).

Existing and readily available data and information include both monitored data and evaluated data and information. Monitored data refers to direct measurements of water quality, including sediment and some fish tissue analyses. Evaluated data and/or information provides an indirect appraisal of water quality through such sources as information on historical adjacent land uses, riparian health and habitat, location of sources, results from predictive modeling, and some surveys of fish and wildlife.

For types of impairment amenable to assessment using monitored data, EPA prefers that States, Territories, and authorized Tribes base § 303(d) listing decisions on monitored data for all their waterbodies. EPA recognizes, however, that most environmental agencies' monitoring networks might not be comprehensive enough to provide such information, in terms of both the geographic scope and the types of data collected. In addition, some types of impairments might not be amenable to monitored data. As a result, agencies might sometimes need to use evaluated data and information. For example, evaluated data and information can be especially useful in determining attainment of uses. This information is appropriate to use in direct support of listing decisions only when it is reliable and in accordance with applicable data collection and/or QA/QC program requirements.

2.3c Using Dilution Calculations and Predictive Models to Support Listing

Dilution calculations and predictive models can also be used in some cases to identify impaired and threatened waterbodies. Models provide techniques for relating meteorologic conditions, pollutant loads, and waterbody characteristics to ambient water quality conditions. Some models are developed as statistical relationships between measured conditions and monitoring. Other more complex models evaluate and/or simulate in more detail environmental processes such as rainfall, snowmelt, runoff, or pollutant transport. Other models have been developed for specific applications. Discussion of the use of mixing zone and dilution models in TMDL development and wasteload allocation analyses is provided in Technical Support Document for Water Quality-based Toxics Control (USEPA, 1991a).

Models and supplementary analyses may be used by States, Territories, and authorized Tribes to support the following evaluations of existing or threatened impairments:

Evaluation of potential existing impairment under current loading conditions (i.e., based on existing permits and historic nonpoint source loadings). This evaluation is often used to examine the overlapping effects of multiple point source discharges.

• Evaluation of the threat of future impairment under proposed loading conditions based on revised permit limits, existing permit limits, and existing or future nonpoint source loading conditions.
• Evaluation of the applicability of old or outdated monitoring data to current conditions. If historic monitoring showed impairment and loading conditions have changed significantly over time, modeling can be used to consider the level of impairment under existing loading conditions.
• Evaluation of specific critical conditions, such as persistent low flow conditions, under various loading scenarios to determine whether water quality standards are likely to be violated. This analysis allows the extrapolation from existing monitoring data to the critical conditions under which problems are likely to occur and water quality standards need to be protected.
• Identification of waterbodies where high pollutant loads may affect sensitive receiving waters.

2.3d Decision Process for Identifying Impaired or Threatened Waterbodies

It is very important that § 303(d) listing decisions be based on sound, high-quality, scientific information. As a reflection of this, EPA is requiring States, Territories, and authorized Tribes to document the level of information quality (or rigor) used in making listing decisions. EPA is also requiring that States, Territories, and authorized Tribes use specific minimum data requirements for considering and evaluating chemical, physical, and biological data. The documentation regarding the level of information quality and specific minimum data requirements used in making listing decisions are to be explained in the listing methodology.

305(b) Aquatic Life Use Support Guidelines as a Decision Process

EPA believes that the aquatic life use support guidelines available in the § 305(b) guidelines (EPA-841-B-97-002A and -002B) are the best decision rules available for use by States, Territories, and authorized Tribes in assessing the quality of data. EPA recommends that States, Territories, and authorized Tribes consider the process developed by the EPA/State § 305(b) Consistency Workgroup for defining levels of information quality or rigor for assessing aquatic life use support (ALUS). The tables developed by the Workgroup show a hierarchy of information quality for bioassessment data, habitat data, and physical/chemical data. In these tables, level 3 or 4 data provide a relatively high level of certainty of aquatic life use support or impairment. Level 1 or 2 data represent less rigorous approaches adequate for ALUS determinations, although generally with a lower degree of certainty.

The tables illustrate an approach for evaluating rivers and streams, although a similar approach is appropriate and possible for other waterbody types. Table C-1 in Appendix C, for bioassessment approaches covers the range of bioassessment information needed for § 305(b) and § 303(d) determinations. It points out, for example, that the highest level of bioassessment information requires assessment of two assemblages (e.g., fish and macroinvertebrates) by professional biologists, the use of regional reference conditions, and broad spatial coverage of sampling sites. Some States, Territories, and authorized Tribes are achieving level 3 or 4 data in their biomonitoring programs, while several other State, Territorial, or authorized Tribal programs are at level 2. Habitat Approaches, Table C-2 in Appendix C, reflects the fact that habitat measures are important to assessing ALUS. The highest level of information is based on quantitative measurements of numerous instream and floodplain characteristics, comparisons to a reference habitat condition, and broad spatial coverage. Physical/chemical approaches, Table C-4 in Appendix C, requires broad spatial and temporal coverage with sufficient frequency to capture acute events to achieve level 3 certainty.

The § 305(b) guidelines also include recommendations for minimum data requirements for making ALUS determinations based on different types of monitoring data. Table C-5 in Appendix C summarizes these minimum data requirements and serves as a good example of the type of information that EPA expects States, Territories, and authorized Tribes to submit with their listing methodologies.

Interpreting Narrative and Designated Use Impairments

Narrative criteria and designated use impairments must also be interpreted in making listing decisions. Whenever possible this should be done by identifying a quantified target that more readily interprets a designated use or narrative criterion impairment. For example, a narrative criterion specifying no "nuisance algal growths" in a lake could be related to a specific average summer chlorophyll α concentration. Similarly, a spawning use might be quantified by identifying the specific percentage of cobble embeddedness associated with a decline in the fishery.

EPA's Advance Notice of Proposed Rulemaking (ANPRM) describes current requirements for States, Territories, and authorized Tribes to identify the procedures they intend to use to interpret and implement narrative criteria as they pertain to point source discharges of toxics (63 FR 36765, July 7, 1998). EPA believes that similar requirements are necessary for the interpretation of narratives as they pertain to nonpoint sources and pollutants in addition to toxics. As such requirements are developed in the future, they should be applied for § 303(d) listing decisions.

Interpreting Antidegradation Policies

State, Territorial, and authorized Tribal antidegradation policies are a part of a complete water quality standards program (40 CFR 131.3(i)). There are three tiers to such an antidegradation policy:

• Tier 1: Maintain existing uses of surface waterbodies and prevent degradation that could interfere with those uses.
• Tier 2: Protect high quality waters.
• Tier 3: Provide special protection for "Outstanding Natural Resource Waters," such as waters of national or state parks, waters of wildlife refuges, or other waters of exceptional recreational or ecological significance.

At 40 CFR 130.26, EPA explains how to apply a water quality standards antidegradation policy when developing your § 303(d) list. A Tier 2 waterbody is impaired and must be listed when the level of water quality that existed at the time the waterbody was designated as Tier 3 has declined. A Tier 3 waterbody is threatened and must be listed when adverse trend data and information indicates that a designated use will no longer be attained by the time of the next listing cycle. A Tier 1 waterbody is impaired and must be listed if it is not maintaining a designated or more protective existing use. A Tier 1 waterbody is threatened and must be listed when an adverse trend indicates that a designated use or a more protective existing use will no longer be attained by the time of the next listing cycle.

2.3e Geographic Scope of Listed Waterbodies

Listed waterbodies can vary in size from stream segments of a few miles to entire watersheds. The geographic extent of the listing should correspond to where water quality is impaired or threatened. When an impairment is caused by a single point source discharger or a nonpoint source issue affecting only a small area, the listed waterbody might encompass only a small geographic area (e.g., a 2-mile stream segment or a portion of an estuary). When impairments occur throughout a larger geographic area, as might be the case for impairments associated with some nonpoint sources, the size of a listed waterbody might involve larger segments of a stream, an entire lake or estuary or, in some cases, all waterbodies in a watershed.

It is important to recognize that the geographic extent of a listed waterbody and pollutant or pollution combination will not necessarily be the same as the geographic extent of the TMDL(s) developed for each combination. Many water quality impairments or threats are caused by multiple sources within a watershed and require complex solutions. The impairment of a lake due to excessive nutrient concentrations, for example, might require the allocation of load reductions to sources distributed throughout a watershed. In this situation the lake would be listed as impaired although the subsequent TMDL and implementation would be established to address the entire watershed.

Key Questions to Consider When Identifying Impaired or Threatened Waterbodies

• How can you monitoring program be used to help identify impaired or threatened waterbodies?
• Have all sources of the data and information used to identify impaired or threatened waterbodies been clearly identified?
• Do these include the minimum data and information sources that EPA requires to be used?
• If no, is there a sound explanation as to why a specific data/information source was not used?
• Has the process developed by the EPA/State § 305(b) Consistency Workgroup for defining levels of information quality or rigor for assessing aquatic life use support been used to identify impaired or threatened waterbodies?
• Has Antidegradation Policy been considered?

2.4 Developing the Four Parts of the List

Each threatened or impaired waterbody and pollutant or pollution combination must be listed by the State, Territory, or authorized Tribe on one of four distinct parts of the § 303(d) list. These parts are described in Section 2.1 and listed below:

• Part 1: Waterbodies impaired or threatened by a pollutant as defined in 40 CFR 130.2(d).
• Part 2: Waterbodies impaired or threatened by pollution as defined by CFR § 130.2(c) but not impaired or threatened by one or more pollutants.
• Part 3: Waterbodies for which EPA has approved or established a TMDL, and water quality standards have not yet been attained.
• Part 4: Waterbodies that are impaired, for which implementation of best practicable control technology for point sources and secondary treatment for publicly owned treatment works or controls enforceable by State, Territorial, authorized Tribal or Federal law or regulation are expected to result in attainment of water quality standards by the next listing cycle. A TMDL is not required for waterbodies on this part of the list. If a waterbody on Part 4 does not attain water quality standards by the time the next list is due to EPA, it must be included on Part 1 of the list.

Figure 2-3 illustrates the relationships among the four separate parts of a § 303(d) list. EPA anticipates that most waterbody and pollutant combinations will be reported on Part 1. TMDLs are to be established for these waterbody and pollutant combinations. At the time of the next listing cycle, waters will remain on the list, be removed from the list (if water quality standards have been attained) or moved to Part 3 of the list (if a TMDL is established and water quality standards have not been attained). Waterbody and pollutant combinations can also be removed from Part 1 of the list if new data or information indicate that the waterbody has attained water quality standards or is no longer threatened.

Waterbody and pollution combinations are reported on Part 2 of the list. The only way that these waterbodies can be removed from the list is if water quality standards are attained or if new data and information demonstrate that the waterbody was incorrectly identified as impaired by pollution.

Waterbody and pollutant combinations where a TMDL has been established are reported on Part 3 of the list. If monitoring demonstrates that water quality standards have been attained, the waterbody and pollutant combination is removed from the list. Under some conditions evaluation of new information might determine that the TMDL is not appropriate or sufficient to result in attainment of water quality standards. A Part 3 waterbody would then be returned to the Part 1 list for revision of the TMDL.

Waterbody and pollutant combinations identified on Part 4 of the list are expected to attain water quality standards before the next listing cycle because of the implementation of best practicable control technology for point sources or secondary treatment for publicly owned treatment works or controls enforceable by State or Federal law or regulation that are expected to result in attainment of water quality standards by the next listing cycle. No TMDLs are required for these waterbody and pollutant combinations. If a waterbody does not attain water quality standards by the time the next list is due to EPA, the waterbody and pollutant ombination must be moved to Part 1 of the list unless it can be documented that the failure to attain water quality standards is due to failure to comply with applicable technology-based requirements.

When deciding to remove a waterbody and pollutant or pollution combination from any part of the list, you must use at least the same level of data as used for making the initial listing decisions.

In developing the four-part list, a clear decision process should be established and described in the State's, Territory's, or authorized Tribe's methodology. The decision process should be well documented and clearly conform to the definitions and requirements set out in the regulation and guidance. An illustration of the steps in sorting waterbodies into the four parts of the list is provided in Figure 2-4. This illustration shows the sequential questions and the supporting data used at each point in the decision process. The first step differentiates between waterbodies impaired by pollution and waterbodies impaired by pollutants. Waterbodies may be listed as waterbody and pollutant and waterbody and pollution combinations on Part 1 and Part 2 of the list, respectively. The second step moves those waterbody and pollutant combinations with completed TMDLs to Part 3 of the list. The third step moves waterbody and pollutant combinations with point source management activities, where compliance with water quality standards is expected to occur before the next listing cycle, to Part 4 of the list. All remaining waterbody and pollutant combinations are placed on Part 1 of the list.

Key Questions to Consider When Developing the Four Parts of the List

• Is Part 1 of the list composed only of waterbodies impaired or threatened by a pollutant, as defined in 40 CFR 130.2(d)?
• Is Part 2 of the list composed only of waterbodies impaired or threatened by pollution, as defined by CFR § 130.2(c)?
• Is Part 3 of the list composed only of waterbodies for which EPA has approved or established a TMDL, but where water quality standards have not yet been attained.
• Is Part 4 of the list composed only of waterbodies that are impaired, but for which implementation of best practicable control technology for point sources and secondary treatment for publicly owned treatment works are expected to result in attainment of water quality standards by the next listing cycle?
• If deciding whether to remove a waterbody and pollutant or pollution combination from the list, is the new data/information at least the same level as that used to list the combination originally?

2.5 Priority Ranking

The goal of priority ranking is to focus attention on the right waterbodies at the right time, while enabling a State, Territory, or authorized Tribe to make efficient use of its available resources and meet the objectives of the CWA. Once waterbodies needing TMDLs have been identified, a State, Territory, or authorized Tribe should prioritize those waterbodies using established ranking procedures that consider all water pollution control activities within the State, Territory, or lands of the authorized Tribe. EPA anticipates that the priority rankings will reflect the relative value and benefit of those waterbodies within the State, Territory, or Tribal land and take into account the severity of the impairment or threatened impairment, especially threats to human health and endangered species, and the designated uses of the waterbody (CWA § 303(d)(1)(A); 40 CFR 130.28).

2.5a Minimum Requirements for Priority Ranking

Prioritization strategies may vary in complexity and design and should be thoroughly documented in the § 303(d) listing methodology. However, there are minimum requirements for such strategies, and regardless of their complexity and design, they are expected to result in a schedule for completing TMDLs that is realistic and distributed proportionately over time. These requirements, summarized below, must be submitted to EPA for review and approval as part of the § 303(d) list:

• A priority ranking of "high," "medium," or "low" for each waterbody and pollutant combination on Part 1 of the list, taking into account the severity of the impairment or threatened impairment and the designated uses (40 CFR 130.28(a)).
• A priority ranking of "high" for all waterbodies that are public water supplies for which there is a violation of an MCL and/or have pollutants that are causing an impairment or threat for species listed as threatened or endangered under § 4 of the Endangered Species Act, unless there is information showing that the impairment does not affect the species. When identifying your high priority waterbodies, you may also consider the presence of sensitive aquatic species and, as secondary factors, historical, cultural, economic, and aesthetic uses of the waterbody (40 CFR 130.28(b)).
• An explanation of how the State, Territory, or authorized Tribe has accounted for the severity of the impairment or threat of impairment and the designated uses of a waterbody in assigning priority rankings to each waterbody and pollutant combination on Part 1 of the list (40 CFR 130.28(c)).
• Identification of any additional factors that are considered in the prioritization strategy. These may include, but are not limited to, efficiencies gained by developing TMDLs for waterbodies located in the same watershed; the value and vulnerability of particular waterbodies; the recreational, economic, and aesthetic importance of particular waterbodies; TMDL complexity; the degree of public interest and support; and State, Tribal, Territorial, or national policies and priorities (40 CFR 130.28(e)).
• If these or any other factors are considered, each must include a clear, concise explanation about how it is used in assigning priorities (40 CFR 130.28(f)). A schedule for establishing TMDLs for all waterbodies and pollutant combinations on Part 1 at a reasonable pace that distributes the workload for TMDL establishment over the entire duration of the schedule. All waterbody and pollutant combinations should have TMDLs established within 15 years after the date of the initial listing of Part 1 of the list (40 CFR 130.31).

EPA recognizes that each waterbody and pollutant combination on Part 1 of the § 303(d) list may be at a different stage on the path to an approved TMDL. Some might require additional data collection to adequately define the problem and conduct an analysis. Some might need outreach to increase stakeholder involvement and buy-in. Others might need to have a technical strategy outlined, budgeted, and scheduled. Some could be ready for completion of the TMDL and its submittal to EPA for approval. Some might need additional consideration and data collection if establishment of the TMDL is expected to be complex or there is uncertainty regarding the listing. It is important to understand that the identification of a high-priority waterbody and pollutant combination means that TMDL should be established before TMDLs for lower-priority waterbody and pollutant combinations. It means that high priorities should be first to receive the resources needed to advance them to the next stage(s) of the TMDL process during the fiscal year under consideration. While there is flexibility in making decisions among a group of high priority waterbody and pollutant combinations; high priority waterbodies hould be addressed before a medium or low priorities.

2.5b Developing a Priority Ranking for Waterbodies Listed on Part 1

The prioritization strategy developed by a State, Territory, or authorized Tribe must thoroughly describe the procedures used. Some of the considerations in developing a priority ranking process are discussed below.

Identify Primary and Secondary Objectives of the Prioritization Process

Before developing the priority ranking and schedule for Part 1 of the list, it is helpful to restate and clarify the objectives of each activity.

Priority ranking clarifies the urgency for establishing TMDLs based on environmental, social, and political factors. Priority ranking should clearly reflect environmental concerns and place special emphasis on severity of the impairment or threatened impairment and the designated uses of the waterbody. Priority ranking is performed before developing a schedule. However, consideration should be given to how the information collected for the priority ranking process can be used to support the schedule development.

The schedule is the plan for establishing TMDLs at a reasonable pace over its duration. Its development provides an opportunity to synchronize and optimize management activities within the State's, Territory's, or authorized Tribe's overall water quality program. The schedule can be used to show how TMDLs will be coordinated with basin planning processes. The schedule is also where various economies of scale can be realized, either by grouping TMDLs within larger watersheds or developing methods to address specific categories of pollutants.

Identify and Explain the Ranking Factors Considered

EPA has identified factors to use when developing a priority ranking strategy. EPA has also provided the opportunity to identify additional factors as needed. Figure 2-5 is a conceptual diagram of the required and optional factors to be considered by the priority ranking process. It is helpful to group the factors used in reviewing Part 1 waterbody and pollutant combinations in order to evaluate the implication of each factor on the resulting priority.

The first step, as outlined by the regulation, is to identify the high priority waterbody and pollutant combinations. A high priority designation recognizes the severity of impact and need to protect uses. A high priority waterbody and pollutant combination is first identified by a designated use in water quality standards for the waterbody as a public drinking water supply (where MCL is exceeded) and/or an impairment or threat for species listed as threatened or endangered under §4 of the Endangered Species Act (unless data shows no affect). The presence of sensitive aquatic species or secondary factors such as historical, cultural, economic, and aesthetic uses may also be considered in determining high priority waterbodies. The combination of the primary and secondary factors will result in identifying the suite of high priority waterbodies for which TMDLs must first be established within the 15-year time frame. It is intended to determine the waterbody and pollutant combinations for which there is the highest urgency to make immediate progress. Therefore, high-priority waterbody and pollutant combinations are those where resources should first be targeted for monitoring, assessment, TMDL analyses, and ultimately establishment of the TMDL.

The second step is to evaluate the remaining waterbody and pollutant combinations based on a broader range of factors. In Figure 2-4, two categories of factors are presented--those related to use of the water and those related to practical and programmatic considerations.

Some of the waterbody uses and related factors identified in the regulation include value and vulnerability of particular waterbodies as aquatic habitat and recreational, economic, and aesthetic importance. Other factors that could be considered in this category include court orders and decisions relating to water quality, national policies and priorities, and imminence of any threat to the environment.

The practical and planning-level considerations identified in the regulation include public interest and support, TMDL complexity, and efficiencies gained by developing TMDLs for waterbodies located in the same watershed. Other factors that could be considered include

• Immediate programmatic needs such as wasteload allocations needed for permits that are coming up for revision or for new or expanding discharges, or load allocations for needed best management practices.
• Hardships to point sources from not having a TMDL in place to allow for increased pollutant loads.
• Opportunities to influence actions or decisions that will not be open for review or revision over a long (i.e., greater than 5-year) term (e.g., with Federal Energy Regulatory Commission [FERC] relicensing for dams).
• The complexity of correcting the water quality problem, including the availability of controls; the value of, or need for, a longer TMDL process to collect more data, identify sources, and/or refine analyses; the degree to which an iterative approach to the TMDL is likely to be needed (e.g., because efficacy of control measures is very uncertain); the number of different types of sources on listed waterbodies; the size and characteristics of the waterbody (e.g., physical complexity, bathymetry, tides, currents); and the number of jurisdictions involved in the TMDL development process (as with interstate and international waters).
• The ease with which TMDLs could be established for lower-priority pollutants at the same time as higher-priority pollutants for the same waterbody.
• Opportunities to "nest" TMDL processes geographically to more efficiently and effectively advance environmental protection goals, conduct monitoring, identify sources, select solutions, engage the public, and advance implementation.

  In some cases the States, Territories, and authorized Tribes may need to consider waterbody and pollutant combinations that are difficult to address. Some types of problems where priority ranking and scheduling should consider the resource implications include when TMDL establishment

  • requires the use of highly sophisticated and detailed analyses to evaluate the interrelationships between pollutant loading and achievement of water quality standards (i.e., complex estuarine systems).
  • involves the assessment of "legacy" pollutants. In this case the legacy pollutant is the predominant or only cause of the waterbody listing. This may include situations where the solution would cause more environmental harm than good (e.g., contaminated sediments for which a risk assessment performed pursuant to CERCLA, RCRA, or a similar clean-up authority demonstrates that natural recovery is the preferred approach). Management of these pollutants (i.e., chlordane) is limited due to adverse environmental impacts from disturbance or dredging.
  • involves a pollutant where the predominant or only source is atmospheric deposition or acid rain. Implementation of the TMDL allocation would require substantive reductions of atmospheric deposition or acid rain, (i.e., pH violation where source is acid rain).

Perform the Priority Ranking

States, Territories, and authorized tribes must submit to EPA a description of their rationale for supporting priority ranking decisions. When a strategy has been established, the priorities and associated rankings can then be developed for the remaining waterbodies. Some helpful references are listed in the box. Although the required submittal of the ranking requires only the high, medium, and low designation, the information used in developing the priority ranking strategy can also assist in the development of schedules for establishing TMDLs. In some cases States, Territories, and authorized Tribes might choose to perform watershed-wide characterization studies to evaluate the listed waterbodies. These characterization studies can then be used to illuminate factors to consider when priority ranking (e.g., related activities, public involvement, availability of data), to support the development of schedules and strategic planning, and to contribute to the TMDL analysis. Not only does this information result in more efficient scheduling of monitoring and analytical activities, but the effort expended in watershed characterization reporting also provides an opportunity to "front-load" some of the analysis required for establishing TMDLs. An example outline for watershed characterization studies to support priority ranking, scheduling, and planning for monitoring and analysis is shown in the box on the next page.

Key Questions to Consider When Establishing a Priority Ranking Strategy

• Are there opportunities to "nest" TMDL activities geographically?
• What are the primary factors to consider for priority ranking?
• What are the secondary factors to consider for priority ranking?
• What are the objectives of the prioritization process?
• Does each waterbody and pollutant combination on Part 1 of the § 303(d) list have a priority ranking?

2.6 Developing the Schedule

EPA requires that a schedule for establishing TMDLs for waterbody and pollutant combinations on Part 1 of the list be submitted with the § 303(d) list (40 CFR 130.31). Although EPA will not approve or disapprove the schedule, the schedule will be considered in reviewing the list and priority rankings. The schedule must be consistent with the following:

• The pace of establishing TMDLs must reasonably spread the workload over the entire duration of the schedule.
• TMDLs should be established in accordance with the priority rankings. That is, TMDLs for high-priority waterbody and pollutant combinations should be established before medium and low-priority waterbody and pollutant combinations.
• States, Territories, and authorized Tribes may alter the actual establishment of high-priority TMDLs, medium-priority TMDL, and low-priority TMDLs from the sequence provided in its schedule. High-priority TMDLs should be completed first, medium-priority TMDLs should be completed next, and low-priority TMDLs should be completed last; the overall pace of TMDL establishment remains reasonable; and all TMDLs are established within the 15-year timeframe.

The schedule for completing TMDLs can be provided as target numbers of TMDLs to be completed for each year or as more specific completion dates for individual TMDLs. The schedule is considered a plan, and individual TMDL establishment dates may vary as needs are more clearly identified, problems are encountered, or opportunities for combining TMDL efforts are identified. The development of the schedule is likely to consider management factors such as staff availability, training, technical capabilities, funding for monitoring and technical support, basin planning cycles, coordination with monitoring and analysis activities, geographic clusters of TMDLs, and types of waterbody and pollutant combinations listed.

The schedule is not intended to rigidly constrain the process of establishing TMDLs and should be considered an opportunity to explain how TMDLs for Part 1 waterbodies will be completed. When synchronized with the broader planning process of a State, Territory, or authorized Tribe, the schedule can be the basis for a practical plan for managing and completing the required TMDLs in order of priority. Modifications to the schedule should allow for public review and comment.

If the State, Territory, or authorized Tribe chooses to use the rotating basin approach, as in the box below, this decision will have implications for scheduling. For example, all the listed waterbodies in one basin can be scheduled for TMDL establishment and approval in one year. While the State, Territory, or authorized Tribe is working to complete and get approval for the TMDLs in one basin, it can be working concurrently on characterizing the problems for the listed waterbodies in another basin. It is recommended that funding and other resources be distributed in each basin, and throughout the State, Territory, or authorized Tribe's jurisdiction, according to the established priorities, with high-priority waterbodies given first consideration.

Key Questions to Consider When Establishing a Schedule for Completing TMDLs

• Is the schedule for completing TMDLs balanced over time?
• Are high-priority waters scheduled to be completed first before other waterbody and pollutant combinations on Part 1 of the list?
• Are all other waterbody and pollutant combinations scheduled to be completed no later than 15 years of being placed on Part 1 of the list?

2.7 Listing and the Public Participation Process

Communicating with the public and promoting public input into the § 303(d) listing process is an integral component of a successful TMDL Program. At a minimum, EPA regulations require that States, Territories, and authorized Tribes that will be used to develop the list. States, Territories, and authorized Tribes must also provide the public with at least 30 days to review and comment on the list itself, the priority rankings, and the schedule for TMDL establishment. This public comment period must occur before the list is submitted to EPA. States, Territories, and authorized Tribes must also provide a summary of all public comments received, a description of how they considered the comments, and whether they agreed with the comments. States, Territories, and Tribes must provide an explanation when they disagree with a comment (40 CFR 130.31).

In addition to meeting these regulatory minimums, States, Territories, and authorizes Tribes should take advantage of involving the public as often as possible during the listing process. Although this approach might initially result in the expenditure of more time and resources, in the long run it will lead to better-supported, more cost-effective and expeditiously implemented TMDLs. States, Territories, and Tribes should actively solicit data and information from the public and encourage the public to nominate waterbodies for inclusion on the list. Informal public meetings should be held to help explain the TMDL process and to solicit input from the public, especially in watersheds where public interest is high. States, Territories, and authorized Tribes should also encourage high-quality private citizen or private organization water quality monitoring and clearly communicate how and when such information can be incorporated into the listing and TMDL establishment activities. A State's, Territory's, or authorized Tribe's general approach for involving the public in § 303(d) listing decisions must be described in its Continuing Planning Process document.

2.8 EPA Action on the Methodology and List

EPA will not approve or disapprove the listing methodology of the State, Territory, or authorized Tribe but will, if appropriate, provide comments. EPA will consider the methodology when it reviews and approves or disapproves the § 303(d) list. EPA's comments on the methodology will include a description of whether the Agency believes that the methodology will result in the identification of impaired or threatened waterbodies. When EPA reviews the State's, Territory's, or authorized Tribe's list, it will review how the State, Territory, or authorized Tribe responded to EPA's comments on the methodology. EPA may cite any deficiencies it raised in comments to the State, Territory, or authorized Tribe as a factor in a decision to disapprove all or part of the State's, Territory's, or authorized Tribe's list.

Within 30 days of receipt of a complete listing package, EPA must approve or disapprove a State's, Territory's, or authorized Tribe's list and priority ranking (40 CFR 130.30(b)). EPA may approve or disapprove the entire list or it may disapprove deficient portions and approve the remaining portions. If EPA disapproves a portion of the list, including the identification of certain waterbody and pollutant or pollution combinations or priority rankings, the Agency must, within 30 days, identify all (or the disapproved portion of) waterbodies and pollutant or pollution combinations or priority ranking as needed to make the list consistent with EPA regulations. EPA will notify the public in the Federal Register and a general circulation newspaper of its actions and request public comment for at least 30 days. When the comment period concludes, EPA will evaluate the public comments and compile a revised list. In the absence of significant public comment, EPA will send the portion of the list that it has corrected back to the State, Territory, or authorized Tribe for incorporation into the water quality management plan (40 CFR 130.30(d)).

Contents

Chapter 3

Water | Wetlands, Oceans & Watersheds | Watershed Protection

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