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Chapter 15
North Carolina’s Impaired Waters List
15.1 Introduction to North Carolina’s Impaired Waters List
The North Carolina Water Quality Assessment and Impaired Waters List is an integrated report
that includes both the 305(b) and 303(d) reports. The 305(b) Report is compiled to meet the
Section 305(b) reporting requirement of the federal Clean Water Act (CWA). The 305(b)
portion of the integrated report presents how well waters support designated uses (e.g.,
swimming, aquatic life support, water supply), as well as likely stressors (e.g., sediment,
nutrients) and potential sources of impairment. The 303(d) List is a comprehensive accounting
of all Impaired waters and is derived from the 305(b) Report. North Carolina refers to the
Impaired Waters List as the Integrated Report because it fulfills both the 305(b) and 303(d)
requirements.
Section 303(d) of the CWA enacted in 1972 required States, Territories and authorized Tribes to
1) identify and establish a priority ranking for waters for which technology-based effluent
limitations are not stringent enough to attain and maintain water quality standards, 2) establish
total maximum daily loads (TMDLs) for the pollutants causing impairment in those waters, and
3) develop and submit the list of Impaired waters and TMDLs biennially by April 1st of every
even numbered year to the US Environmental Protection Agency (EPA). EPA is required to
approve or disapprove the state-developed 303(d) list within 30 days. For each segment
Impaired by a pollutant and identified in the 303(d) list, a TMDL must be developed. TMDLs
are not required for waters Impaired by pollution. Here, pollution is defined by the EPA as,
“man-made or man-induced alteration of the chemical, physical, biological, and radiological
integrity of the water,” and is related to water control structures.
15.2 Introduction to TMDLs
A TMDL is a calculation of the maximum amount of a pollutant that a waterbody can receive
and still meet water quality standards, and an allocation of that amount to the pollutant sources.
A TMDL is the sum of the allowable loads of a single pollutant from all contributing point and
nonpoint sources. The calculation must include a margin of safety to ensure that the waterbody
can still attain its designated uses. The calculation must also account for seasonal variation and
critical conditions in water quality.
For more information on TMDLs and the 303(d) listing process, visit the TMDL website at
http://h2o.enr.state.nc.us/tmdl/.
15.3 Contents of the Integrated Report
The Integrated Report includes descriptions of monitoring programs, the use support
methodology, and the Impaired waters list. New guidance from EPA places all waterbody
assessment units into one unique assessment category (EPA, 2001b). Although EPA specifies
five unique assessment categories, North Carolina elects to use seven categories. Each category
is described in detail below:
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Category 1: Attaining the water quality standard and no use is threatened. This
category consists of those waterbody assessment units where all applicable use support
categories are rated "Supporting". Data and information are available to support a
determination that the water quality standards are attained and no use is threatened.
Future monitoring data will be used to determine if the water quality standard continues
to be attained.
Category 2: Attaining some of the designated uses; no use is threatened; and
insufficient or no data and information are available to determine if the remaining
uses are attained or threatened. This category consists of those waterbody assessment
units where at least one of the applicable use support categories are rated "Supporting"
and the other use support categories are rated "Not Rated" or “No Data”. Also included
in this category are waters where at least one of the applicable use support categories,
except Fish Consumption, are rated "Supporting"; the remaining applicable use support
categories, except Fish Consumption, are rated "Not Rated"; and the Fish Consumption
category is rated "Impaired-Evaluated". Data and information are available to support a
determination that some, but not all, uses are attained. Attainment status of the remaining
uses is unknown because there are insufficient or no data or information. Future
monitoring data will be used to determine if the uses previously found to be in attainment
remain in attainment, and to determine the attainment status of those uses for which data
and information were previously insufficient to make a determination.
Category 3: Insufficient or no data and information to determine if any designated
use is attained. This category consists of those waterbody assessment units where all
applicable use support categories, except Fish Consumption, are rated "Not Rated", and
the Fish Consumption category is rated "Impaired-Evaluated". Measured data or
information to support an attainment determination for any use are not available.
Supplementary data and information, or future monitoring, will be required to assess the
attainment status.
Category 4: Impaired or threatened for one or more designated uses but does not
require the development of a TMDL. This category contains three distinct sub-
categories:
Category 4a: TMDL has been completed. This category consists of those waterbody
assessment units for which EPA has approved or established a TMDL and water quality
standards have not yet been achieved. Monitoring data will be considered before moving
an assessment unit from Category 4a to Categories 1 or 2.
Category 4b: Other pollution control requirements are reasonably expected to
result in the attainment of the water quality standard in the near future. This
category consists of those waterbody assessment units for which TMDLs will not be
attempted because other required regulatory controls (e.g., NPDES permit limits,
Stormwater Program rules, etc.) are expected to attain water quality standards within a
reasonable amount of time. Future monitoring will be used to verify that the water
quality standard is attained as expected.
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Category 4c: Impairment is not caused by a pollutant. This category consists of
assessment units that are Impaired by pollution, not by a pollutant. EPA defines pollution
as "The man-made or man-induced alteration of the chemical, physical, biological and
radiological integrity of the water." EPA staff have verbally stated that this category is
intended to be used for impairments related to water control structures (i.e., dams).
Future monitoring will be used to confirm that there continues to be an absence of
pollutant-caused impairment and to support water quality management actions necessary
to address the cause(s) of the impairment.
Category 5: Impaired for one or more designated uses by a pollutant(s) and
requires a TMDL. This category consists of those waterbody assessment units that are
Impaired by a pollutant and the proper technical conditions exist to develop TMDLs. As
defined by the EPA, the term pollutant means "dredged spoil, solid waste, incinerator
residue, sewage, garbage, sewage sludge, munitions, chemical wastes, biological
materials, radioactive materials, heat, wrecked or discarded equipment, rock, sand, cellar
dirt and industrial, municipal, and agricultural waste discharged into the water". When
more than one pollutant is associated with the impairment of a single waterbody
assessment unit in this category, the assessment unit will remain in Category 5 until
TMDLs for all listed pollutants have been completed and approved by the EPA.
Category 6: Impaired based on biological data. This category consists of waterbody
assessment units historically referred to as "Biologically Impaired" waterbodies; these
assessment units have no identified cause(s) of impairment although aquatic life impacts
have been documented. The waterbody assessment unit will remain in Category 6 until
TMDLs have been completed and approved by the EPA.
Category 7: Impaired, but the proper technical conditions do not yet exist to
develop a TMDL. As described in the Federal Register, "proper technical conditions”
refer to the availability of the analytical methods, modeling techniques and data base
necessary to develop a technically defensible TMDL. These elements will vary in their
level of sophistication depending on the nature of the pollutant and characteristics of the
segment in question" (43 FR 60662, December 28, 1978). These are assessment units
that would otherwise be in Category 5 of the integrated list. As previously noted, EPA
has recognized that in some specific situations the data, analyses or models are not
available to establish a TMDL. North Carolina seeks EPA technical guidance in
developing technically defensible TMDLs for these waters. Open water and ocean
hydrology fecal coliform Impaired shellfishing waters are included in this category.
Categories 5, 6 and 7 constitute the 2004 North Carolina 303(d) List for the State of
North Carolina. A table of waters on Categories 1 through 3 is available for downloading
on the DWQ website (http://h2o.enr.state.nc.us/tmdl/General_303d.htm).
15.4 How North Carolina Proposes Delisting Waters
Waters appearing on the previously approved Impaired waters list will be moved to Categories 1,
2, 3 or 4 under the following circumstances:
• An updated 305(b) use support rating of Supporting, as described in the basinwide
management plans.
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• Applicable water quality standards are being met (i.e., no longer Impaired for a given
pollutant) as described in either basinwide management plans or in technical
memoranda.
• The basis for putting the water on the list is determined to be invalid (i.e., was
mistakenly identified as Impaired in accordance with 40 CFR 130.7(b)(6)(iv) and/or
National Clarifying Guidance for State and Territory 1998 Section 303(d) Listing
Decisions. Robert Wayland, III, Director. Office of Wetlands, Oceans and
Watersheds. Aug 27, 1997).
• A water quality variance has been issued for a specific standard (e.g., chloride).
• Removal of fish consumption advisories or modification of fish eating advice.
• Typographic listing mistakes (i.e., the wrong water was identified).
• EPA has approved a TMDL.
15.5 Scheduling TMDLs
Category 5 waters, those for which TMDLs are required, are at many different stages on the
path to an approved TMDL. Some require additional data. Some require more outreach to
increase stakeholder involvement. Others need to have a technical strategy budgeted, funded and
scheduled. Some are ready for EPA submittal.
According to EPA guidance (EPA 2004), prioritization of waterbody assessment units for
TMDLs need not be reflected in a “high, medium or low” manner. Instead, prioritization can be
reflected in the TMDL development schedule. Generally, North Carolina attempts to develop
TMDLs within 8-13 years of the original pollutant listing. Other information for each
assessment unit is also utilized to determine the priority in the TMDL development schedule.
This information includes the following:
• Year listed. Assessment units that have been on the 303(d) list for the longest period
of time will receive priority for TMDL development and/or stressor studies.
• Reason for listing. (Applicable to Category 5 AUs only) AUs with an impairment
due to a standard violation will be prioritized based on which standard was violated.
Standard violations due to bacteria or turbidity currently receive priority for TMDL
development.
• Classification. AUs classified for primary recreation (Class B), water supply (Class
WS-I through WS-V), trout (Tr), high quality waters (HQW), and outstanding
resource waters (ORW) will continue to receive a higher priority for TMDL
development and/or stressor studies.
• Basinwide Planning Schedule. (Applicable to Category 6 AUs only). The basinwide
schedule is utilized to establish priority for stressor studies.
15.6 Revising TMDLs
Current federal regulations do not specify when TMDLs should be revised. However, there are
several circumstances under which it would seem prudent to revisit existing TMDLs. The
TMDL analysis of targets and allocations is based upon the existing water quality standards,
hydrology, water quality data (chemical and biological), and existing, active NPDES wastewater
discharges. Conditions related to any of these factors could be used to justify a TMDL revision.
Specific conditions that the Division will consider prior to revising an existing, approved TMDL
include the following:
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• A TMDL has been fully implemented and the water quality standards continue to be
violated. If a TMDL has been implemented and water quality data indicate no
improvement or a decline in overall water quality, the basis for the TMDL reduction
or the allocation may need to be revised;
• A change of a water quality standard (e.g., fecal coliform to Echerichia coli). The
Division will prioritize review of existing TMDLs and data to determine if a revision
to TMDLs will be required;
• The addition or removal of hydraulic structures to a waterbody (e.g., dams).
Substantial changes to waterbody hydrology and hydraulics have the potential to
change many aspects of target setting, including the water quality standard upon
which the TMDL was developed, the water quality data, and the water quality
modeling;
• Incorrect assumptions were used to derive the TMDL allocations. This would include
errors in calculations and omission of a permitted discharge.
Should a TMDL be revised due to needed changes in TMDL targets, the entire TMDL would be
revised. This includes the TMDL target, source assessment, and load and wasteload allocations.
However, the Division may elect to revise only specific portions of the TMDL. For example,
changes may be justifiable to the load and wasteload allocation portions of a TMDL due to
incorrect calculations or inequities. In these cases, revisions to the TMDL allocations would not
necessarily include a revision of TMDL targets.
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