EPA Decision Document 2022 Triennial Review

Decision Document of the United States Environmental Protection Agency
Determination Under Section 303(c) of the Clean Water Act Review of
North Carolina’s 2020-2022 Triennial Review

North Carolina transmitted revisions to its water quality standards (WQS) on August 3, 2022 to the
Environmental Protection Agency by letter dated July 5, 2022. As described more fully below, the EPA
has reviewed and is approving the revisions pursuant to section 303(c) of the Clean Water Act (CWA or
Act). Regarding consultation activities for section 7 of the Endangered Species Act, the EPA Region 4
concluded that the revisions addressed by today’s action would either have no effect on or may affect,
but were not likely to adversely affect threatened and endangered species or their designated critical
habitat. As a result, the EPA transmitted biological evaluations to the United States Fish and Wildlife
Service (USFWS) and National Marine Fisheries Service (NMFS) on July 13 and August 17, 2022,
respectively. Concurrence was received from USFWS in a letter dated July 18, 2022. Following a
request for formal consultation by the EPA on October 5, 2022, a Biological Opinion (BiOp) was
received from NMFS on February 9, 2023, concluding the section 7 consultation on this action.

Part I - Overview of State and Federal Information

Background

North Carolina’s submittal reflects the state’s rulemaking effort to satisfy the federal CWA requirement
to review existing regulations as part of a triennial review. The revisions addressed in this document
were discussed in a virtual public hearing held on July 20, 2021. Following the May 17, 2021 public
notice in the North Carolina Register, the comment period closed on August 3, 2021. The revisions were
approved for adoption by the North Carolina Environmental Management Commission (EMC) on
March 10, 2022.

In a July 5, 2022 letter written to Regional Administrator Daniel Blackman, EPA Region 4, Richard E.
Rogers, Jr., Director for the Division of Water Resources for the North Carolina Department of
Environmental Quality (DEQ or the Department) submitted new and revised WQS for review pursuant
to section 303(c) of the CWA. The letter and supporting documentation were received electronically on
August 3, 2022. In a July 27, 2022 letter, North Carolina’s Senior Deputy Attorney General certified that
the WQS revisions were duly adopted pursuant to North Carolina law. The revisions became effective
under state law on June 1, 2022 and are further described below.

Clean Water Act and Regulatory Requirements

Under section 303(c) of the CWA and federal implementing regulations at 40 C.F.R. Part 131, states and
authorized tribes (states) have the primary responsibility for reviewing, establishing, and revising WQS,
which consist of the designated uses of a waterbody or waterbody segment, the water quality criteria
necessary to protect those designated uses, and an antidegradation policy. Section 303(c) of the CWA
also requires states to establish WQS and to submit any new or revised WQS to the EPA for review and
approval or disapproval. When the EPA approves a state or tribal WQS, it becomes the applicable WQS
for purposes of the CWA. 40 C.F.R. section l31.21(c)(2).

Consistent with the regulatory requirement for states to provide an explanation if not adopting new or
revised criteria for parameters for which the EPA has published new or updated CWA section 304(a)
criteria recommendations, the state has provided the necessary information (40 C.F.R. section
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131.20(a)). This change was made to foster meaningful and transparent involvement of the public and
intergovernmental coordination with local, state, federal and tribal entities in light of recent science
provided by the EPA through its criteria recommendations. The EPA does not approve or disapprove
this explanation. For this triennial review, North Carolina noted it “had numerous competing priorities to
consider and determined that resource and time constraints would limit the scope of the regulations that
could be revised by the EMC.” In addition, based on the directives of the EMC and feedback from EPA
and public comments, the state has committed to additional actions as part of the next triennial review or
in a separate rulemaking. Those activities include: (1) evaluating the 2012 recreational criteria for
statewide adoption in Class B waters, (2) updating the state’s human health exposure factors (body
weight, drinking water intake, and fish consumption rate) as defined in 15A NCAC 02B .0208 based on
the 2015 EPA human health criteria updates, and (3) re-evaluating the current freshwater chronic silver
standard as a result of a rulemaking petition requesting removal of the standard. The remaining National
Recommended Water Quality Criteria (e.g., acrolein, aluminum, ammonia, cyanotoxin criteria, revised
94 human health criteria) are also currently under examination for the next triennial review.

Endangered Species Requirements

In addition to the EPA’s review under section 303 of the CWA, section 7(a)(2) of the Endangered
Species Act (ESA) requires federal agencies, in consultation with the USFWS and NMFS, to ensure that
their actions are not likely to jeopardize the continued existence of federally listed species or result in
the destruction or adverse modification of designated critical habitat of such species.

On March 29, 2022, a letter was sent to Mr. Pete Benjamin, Field Office Supervisor, USFWS and Ms.
Cathy Tortorici, Chief of the ESA Interagency Cooperation Division, NMFS, requesting ESA section 7
technical assistance for the list of species and designated critical habitat within statewide waters of
North Carolina. USFWS and NMFS responded in email and conversations following receipt of the
March 29, 2022 letter. Following a review of the species, critical habitat and parameter specific
information, the EPA prepared biological evaluations (BEs) for USFWS and NMFS. With the exception
of the revisions to the cadmium and selenium criteria, which are the focus of the BEs, all other revisions
approved by the EPA were determined to not be subject to consultation because they were either
editorial or clarification type changes.

The EPA transmitted the USFWS BE by letter dated July 13, 2022 from Ms. Stacey L. Bouma, Branch
Chief of the Water Quality Planning Branch to Ms. Janet Mizzi, Field Supervisor of the Asheville
Ecological Services Field Office. In a letter dated July 18, 2022, the USFWS concurred with the EPA’s
determinations that the EPA’s approval of the revisions and additions to the state’s freshwater WQS
may affect but are not likely to adversely affect federally listed species or result in adverse modifications
to critical habitats in the state.

On August 17, 2022, the NMFS BE was transmitted to Ms. Lisamarie Carrubba, Acting Chief of the
ESA Interagency Cooperation Division. In response to the EPA’s determination that the EPA’s approval
of the revisions and additions to the state’s saltwater WQS (as well as the freshwater cadmium criteria,
considered for sturgeon present in freshwater) may affect but are not likely to adversely affect federally
listed species or result in adverse modifications to critical habitats in the state, NMFS provided a
September 27, 2022 letter indicating NMFS would be unable to concur with EPA’s not likely to
adversely affect findings. Pursuant to 50 C.F.R. § 402.12(c), the EPA requested formal consultation with
NMFS by letter dated October 5, 2022. On February 9, 2023, NMFS transmitted its Biological Opinion,
concluding consultation under section 7 of the ESA.
3

The BiOp explains the definition of take, incidental take, and the exposures described by NMFS.

Section 9 of the ESA and Federal regulations pursuant to section 4(d) of the ESA prohibit the
take of endangered and threatened species, respectively, without a special exemption. “Take” is
defined as to harass, harm, pursue, hunt, shoot, wound, kill, trap, capture or collect, or to attempt
to engage in any such conduct (16 U.S.C. 1532(19)). Harm is further defined by regulation to
include significant habitat modification or degradation that results in death or injury to ESA-
listed species by significantly impairing essential behavioral patterns, including breeding,
feeding, or sheltering (see 50 CFR §222.102).

Incidental take is defined as take that results from, but is not the purpose of, carrying out an
otherwise lawful activity (see 50 CFR §402.02). Section 7(b)(4) and section 7(o)(2) of the ESA
provide that taking that is incidental to an otherwise lawful agency action is not considered to be
prohibited taking under the ESA if that action is performed in compliance with the terms and
conditions of this incidental take statement.

Exposures of shortnose sturgeon and Carolina and migrating Gulf of Maine, New York Bight,
Chesapeake Bay, and South Atlantic DPSs of Atlantic sturgeon to cadmium and selenium within
criteria limits in the action area are likely to result in incidental take due to the reductions in
survival of early life stage fish and fitness of these species.
NMFS concluded that EPA’s approval of North Carolina’s adoption and implementation of its cadmium
and selenium criteria is likely to adversely affect (LAA) the respective species as follows:

The cadmium criteria are LAA the shortnose sturgeon and the Carolina DPSs of Atlantic
sturgeon and migrating Gulf of Maine, New York Bight, Chesapeake Bay, and South Atlantic
Atlantic sturgeon DPSs because:

1. Permitting and monitoring of North Carolina DEQ-regulated waters indicate that exposures to
cadmium will occur;
2. Current monitoring data indicate that the North Carolina DEQ practical quantitation limits are
insufficient to detect cadmium within chronic criteria limits in greater than 90% of samples and
within acute criteria limits for at least 15% of samples from Sturgeon Waters;
3. The toxicity of cadmium in surrogate species1 indicate that exposures within criteria limits
will likely result in adverse effects to the survival of early-life-stage shortnose and Atlantic
sturgeon;
4. With increasing temperatures under climate change (IPCC 2021), temperature-dependent
effects of cadmium exposure on growth in surrogate species indicates that exposures within
criteria limits are likely to affect growth of shortnose sturgeon and Atlantic sturgeon; and
5. The viability of ESA-listed sturgeon populations in North Carolina’s waters is highly sensitive
to juvenile mortality resulting in lower numbers of sub-adults recruiting into the adult breeding
population (NMFS 1998a, ASSRT 2007).

The selenium criteria are LAA the shortnose sturgeon and the Carolina DPSs of Atlantic
sturgeon at the population scale because:

1 Explained in [BiOp] Section 8.1.2.1, particularly the fifth paragraph.
4

1. Permitting and monitoring data for of North Carolina DEQ-regulated waters indicate that
exposures to selenium will occur.
2. Ash basins adjacent to Sturgeon Waters are classified as having high and significant hazard
potential but monitoring data are not available for surface water or benthic organisms that may
accumulate selenium and may be consumed by sturgeon.
3. The criteria are strongly influenced by EC10s for white sturgeon that were the most sensitive
species included in criteria calculation, but there is evidence that white sturgeon are less sensitive
to selenium exposure than the ESA-listed green sturgeon, and NMFS must give the species
considered in this Opinion, shortnose and Atlantic sturgeon, the benefit of the doubt.
4. Criteria derived to protect 95% of species are not expected to be sufficiently protective of
imperiled species that are likely more sensitive than white sturgeon, the most sensitive species
used in the criteria development.
5. The viability of ESA-listed sturgeon populations in North Carolina’s waters is highly sensitive
to juvenile mortality resulting in lower numbers of sub-adults recruiting into the adult breeding
population (NMFS 1998a, ASSRT 2007).

Based on the assessment by NMFS, they concluded that the proposed action to approve North Carolina’s
adoption of criteria for cadmium and selenium was likely to adversely affect, but is not likely to
jeopardize shortnose sturgeon and Atlantic sturgeon (Acipenser oxyrinchus oxyrinchus, Carolina
Distinct Population Segment (DPS), and migrating and foraging Gulf of Maine, New York Bight,
Chesapeake Bay, and South Atlantic DPSs. NMFS concluded the reasonable and prudent measures
(RPMs) described below are necessary and appropriate to minimize the impacts of incidental take on
threatened and endangered species resulting from exposure to cadmium or selenium within criteria
limits:

1. The EPA Region 4 will work within its authorities and consistent with its MOAs with the
Services and North Carolina to ensure implementation of the adopted criteria in NPDES,
monitoring, and listing programs.

2. The EPA will inform North Carolina DEQ in the Action Letter and Decision Document of the
prohibition of unauthorized take of ESA-listed species, of NMFS’ findings on the exposure of
cadmium and selenium on ESA-listed shortnose and Atlantic sturgeon species, and of the
conditions listed under 50 CFR §402.16(a). The EPA will encourage North Carolina DEQ to
enlist NMFS technical assistance as early as practicable.

In addition to RPMs, section 7(b)(4) of the ESA requires the Services to identify terms and conditions
(including, but not limited to, reporting requirements) that must be complied with by the Federal agency
or applicant, or both, to implement the RPMs.

1. The following terms and conditions implement RPM 1:
a. EPA will meet with NMFS at approximately six months from EPA’s action date on North
Carolina’s 2020-2022 Triennial Review and again once EPA receives North Carolina’s
submission of the 2024 303(d) list to discuss actions taken by both agencies to date as a
result of the RPMs and terms and conditions. The EPA will coordinate with R4 staff
working in monitoring, listing, and permitting to ensure a complete listing of actions for
both updates with NMFS.
5

b. The EPA will share with NMFS the Action Letter and Decision Document with
monitoring and Section 303(d) listing contacts in the R4 office and North Carolina DEQ.
i. As North Carolina develops its assessment methodology for cadmium or
selenium, as appropriate, following the approval of the criteria by EPA, EPA will
encourage the state to coordinate closely with NMFS and EPA R4 staff prior to
bringing the assessment methodology to the Environmental Management
Commission.
c. The EPA will implement the 2001 MOA between EPA and the Services to the extent
possible. While not binding, Section IX of the 2001 MOA establishes a framework for
coordinating actions for permitting program activities under the Clean Water Act section
402. Specifically, EPA and NMFS will follow the nine coordination procedures regarding
issuance of State permits specified in Section IX. A. of the 2001 MOA in a manner
consistent with statutory and regulatory procedures. This provides for NMFS’ review of
draft state-issued permits for discharges that may affect ESA-listed sturgeon species for
the purposes of technical assistance to ensure that permitted cadmium or selenium
discharges minimize take.
d. The EPA will, when reviewing permits under its regular permit review practices under
Section IV. B. of the 2007 NC MOA, evaluate draft NPDES permits prepared by North
Carolina’s DEQ for compliance with the approved cadmium and selenium criteria,
including the use of sufficiently sensitive methodology in determining monitoring
requirements and discharge limits.

To implement RPM 1, pursuant to the 2007 NC MOA, with respect to sources that
potentially discharge cadmium or selenium into streams with ESA-listed sturgeon or adjacent
catchments, based on industrial or hazard class or, for cadmium from urban areas, population
size and land use, EPA’s expectations are as follows:
a. North Carolina DEQ will anticipate notification from EPA about any permits that may
raise issues regarding impacts to federally listed species or critical habitats pursuant to
NPDES MOA Section IV.E.1.
b. North Carolina DEQ will provide notice and copies of draft NPDES permits, public
notices, fact sheets or rationale, and permit applications to the Services for review, in
accordance with the NPDES MOA Section IV.D.4 and Section IV.E.1.
c. North Carolina DEQ will provide the draft permit record; including supporting
records/analytical results to NMFS for review and anticipate notification by NMFS,
either directly or through EPA, if there are concerns about the effluent test and/or
sampling methods as supported by the NPDES MOA Section IV.E.2.
d. If the EPA determines that the effluent data submitted with the permit application have
not met the requirements under 40 CFR Part 136, the EPA will inform North Carolina
DEQ and copy NMFS in accordance with NPDES MOA Section IV.E.4.

2. To implement RPM 2, EPA is informing North Carolina DEQ of the following:
a. Unauthorized take of ESA-listed endangered species is prohibited under section 9 of the
ESA, and these prohibitions apply to all individuals, organizations, and agencies subject
to United States jurisdiction. These take prohibitions have also been extended to the Gulf
of Maine DPS of Atlantic Sturgeon under section 4(d) of the ESA (50 CFR §223.211).
“Take” is defined as to harass, harm, pursue, hunt, shoot, wound, kill, trap, capture, or
collect, or to attempt to engage in any such conduct. Harm is further defined by
6

regulation to include significant habitat modification or degradation that results in death
or injury to ESA-listed species by significantly impairing essential behavioral patterns,
including breeding, feeding, or sheltering.
b. Exposures to cadmium or selenium at or below the proposed criterion may adversely
affect ESA-listed shortnose and Atlantic sturgeon species under NMFS’ jurisdiction.
c. EPA is approving the adopted cadmium and selenium criteria. However, if scientifically
defensible data2 become available suggesting that exposures to cadmium or selenium
under the criteria, as implemented by North Carolina DEQ, results in surface water
quality conditions that are found to be more harmful to shortnose or Atlantic sturgeon
than anticipated, for example, through monitoring in receiving waters where discharges
are considered to be compliant with the cadmium or selenium criteria, EPA will work
with North Carolina and ensure compliance with Section 7 of the ESA and 50 CFR §
402.16(a).[3]
d. EPA’s approval does not foreclose either the formulation by NMFS, or the
implementation by the EPA, of any alternatives that might be determined to be needed to
comply with section 7(a)(2).

The EPA also strongly encourages North Carolina DEQ to enlist technical assistance from NMFS as
early as practicable in order to avoid prohibited take by any activities, authorizations, or decisions
regarding potential cadmium or selenium sources or concentrations in waters where ESA-listed species
under NMFS’ jurisdiction occur. For example, NMFS could advise North Carolina DEQ on any ESA
implications of 303(d)/305(b) monitoring and listing decisions affecting such waters.

Government to Government Consultation 

The EPA recognizes its unique legal relationship with Tribal Governments as set forth in the United
States Constitution, treaties, statutes, executive orders, and court decisions. Government-wide and EPA-
specific policies call for regular and meaningful consultation with Indian Tribal Governments when
developing policies and regulatory decisions on matters affecting their communities and resources. Due
to the nature of the revisions, the EPA determined that Tribal resources of the Eastern Band of Cherokee
Indians (EBCI) and Catawba Indian Nation (CIN) could be impacted by the revisions and therefore
concluded that consultation with both tribes was necessary. In an August 15, 2022 letter from Jeaneanne
M. Gettle, Water Division Director, to the Honorable Richard Sneed, Chief of the EBCI, and an August
23, 2022 letter from Jeaneanne M. Gettle, Water Division Director, to the Honorable Bill Harris, Chief
of the CIN, the EPA offered both tribes an opportunity to consult and coordinate on this decision, in
accordance with the EPA’s Policy on Consultation and Coordination with Indian Tribes and the EPA
Policy on Consultation and Coordination with Indian Tribes: Guidance for Discussing Tribal Treaty
Rights. For the EBCI, the process began on August 15, 2022 and ended on September 14, 2022. For the
Catawba, the process began on August 29, 2022 and ended on September 28, 2022. During the
consultation period, the EPA did not receive comments from the EBCI or the CIN.

Summary of EPA Approval Actions

2 Information and analyses that are consistent with the Service's Policy on Information Standards Under the Endangered
Species Act (59 FR 34271).
3 Section 12 of the BiOp provides information on conditions.
7

Each of North Carolina’s revisions is addressed in detail within Part II, along with the EPA’s analysis
and conclusions. The EPA is approving all of the revisions in 15 NCAC 02B, except those which it
considers to not be new or revised WQS.

Part II - EPA’s Analysis of the Triennial Review Revisions

New and revised provisions below will be shown verbatim using a strikeout or underline format to
highlight the content that was deleted or added, respectively, or summarized generally depending on the
complexity of the revision.

15A NCAC 02B .0202 Definitions

Three definitions were added (available cyanide, lentic, and lotic) and one definition was revised
(industrial discharge) during this triennial review and are addressed individually below.

Renumbering also took place to address the associated revisions to the definitions as well as some other
editorial changes. Such changes are considered minor revisions. These revisions do not alter the
meaning or intent of the previously approved corresponding provisions. The EPA approves these minor
revisions as being consistent with the CWA and the EPA’s implementing regulations. The EPA notes,
however, that its approvals of these editorial changes do not re-open the EPA’s prior approvals of the
underlying WQS.

15A NCAC 02B .0202(7) was revised as follows:

(7) “Available cyanide” means inorganic cyanides that are free (HCN and CN-) and metal-
cyanide complexes that are dissociated into free cyanide ions under mildly acidic conditions (pH
3 to 6).

The addition of this definition adds additional clarity to the revision to the cyanide criterion. The
definition is consistent with the CWA and the implementing regulations at 40 C.F.R. Part 131 and
therefore approved.

15A NCAC 02B .0202(33) was revised as follows:

(32)(33) "Industrial discharge" means the discharge of industrial process treated wastewater or
wastewater other than sewage. Stormwater shall not be considered to be an industrial wastewater
unless it is contaminated with industrial wastewater. Industrial discharge includes:
(a) wastewater resulting from any process of industry or manufacture or from the
development of any natural resource;
(b) wastewater resulting from processes of trade or business, including wastewater from
laundromats and car washes, but not wastewater from restaurants; and
(c) for the purpose of prohibiting discharges to waters classified as Water Supply (WS) in
accordance with Rules .0212, .0214, .0215, .0216, and .0218 of this Section, wastewater
discharged from a municipal wastewater treatment plant requiring required to administer
pretreatment program. program pursuant to 15A NCAC 02H .0904.

These revisions represent a clarification by the state. The responsiveness summary further explains that
this revision addresses a previous stakeholder comment and that the “proposed changes more precisely
8

reflect the definition as it has been implemented since its original introduction in 1989 and results in no
operational effects.” Since this revision does not alter the meaning or intent of the previously approved
corresponding provisions, the EPA approves these minor revisions as being consistent with the CWA
and the EPA’s implementing regulations. The EPA notes, however, that its approvals of these editorial
changes do not re-open the EPA’s prior approvals of the underlying WQS.

15A NCAC 02B .0202(36) was revised as follows:

(36) "Lentic" means an aquatic ecosystem with standing or slow flowing water such as a lake,
pond, or reservoir.

As noted in the March 2022 Hearing Officer’s Report, these revisions provide clarity regarding certain
aspects of the adopted criteria for selenium. The EPA’s Aquatic Life Ambient Water Quality Criterion
for Selenium – Freshwater, EPA 822-R-16-006, 2016 (2016 Selenium Criteria document) notes lakes
and impoundments as examples of lentic waters. This definition is consistent with the expectation for
lentic waters and helps clearly articulate what waters are associated with the lentic criteria discussed
later in this document. Therefore, the EPA approves the addition of the criteria as being consistent with
the CWA and 40 C.F.R. Part 131.

15A NCAC 02B .0202(38) was revised as follows:

(38) "Lotic" means an aquatic ecosystem with rapidly flowing water such as a stream or river.

As noted in the March 2022 Hearing Officer’s Report, these revisions provide clarity regarding certain
aspects of the adopted criteria for selenium. The EPA’s 2016 Selenium Criteria document notes rivers
and streams as examples of lotic waters. This definition is consistent with the expectation for lotic
waters and helps clearly articulate what waters are associated with the lotic criteria discussed later in this
document. Therefore, the EPA approves the addition of the criteria as being consistent with the CWA
and 40 C.F.R. Part 131.

15A NCAC 02B .0211 Fresh Surface Water Quality Standards for Class C Waters

Renumbering and other editorial changes were made in 15A NCAC 02B .0211. Such changes are
considered minor revisions. These revisions do not alter the meaning or intent of the previously
approved corresponding provisions. The EPA approves these minor revisions as being consistent with
the CWA and the EPA’s implementing regulations. The EPA notes, however, that its approvals of these
editorial changes do not re-open the EPA’s prior approvals of the underlying WQS.

15A NCAC 02B .0211(5) was revised as follows:

Cyanide, available or total: 5.0 µg/l;

The currently recommended water quality criteria for cyanide are expressed as µg free cyanide (CN/L).
However, as noted in the 1984 Ambient Water Quality Criteria for Cyanide document, at the time, no
EPA approved methods for such a measurement were available to implement the criteria. Therefore,
until such methods were available, EPA recommended applying the criteria using the total cyanide
method. This is consistent with North Carolina’s existing inclusion of total cyanide in 15A NCAC 02B
.0211(5). As noted in the March 2022 Hearing Officer’s Report, newer analytical methods have since
9

been provided. This update is the basis for the state’s revision to the cyanide to include the use of
available cyanide data, in addition to the existing total cyanide option. Although North Carolina
originally proposed a revision to include the phrase “free” in addition to total cyanide, based on
comments received during the comment process, the state went forward with a final revision to include
the term “available” instead. In conjunction with that change, the state also added a definition of
available cyanide, which is “[a]vailable cyanide refers to inorganic cyanides that are free (HCN and CN-
) and metal cyanide complexes that are dissociated into free cyanide ions under mildly acidic conditions
(pH 3 to 6).” The revision to 15A NCAC 02B .0211(5) is consistent with the CWA and the
implementing regulations at 40 C.F.R. Part 131 and therefore approved.

15A NCAC 02B .0211(11) was revised as follows to include EPA’s newer selenium criteria
recommendation:

Metals:
(a) With the exception of mercury and selenium, mercury, acute and chronic freshwater aquatic
life standards for metals shall be based upon measurement of the dissolved fraction of the metal.
Mercury and selenium water quality standards shall be based upon measurement of the total
recoverable metal;
(b) With the exception of mercury and selenium, mercury, aquatic life standards for metals listed
in this Sub-Item shall apply as a function of the pollutant's water effect ratio (WER). …
(c) Freshwater metals standards that are not hardness-dependent shall be as follows:
…
(viii) Selenium, total recoverable, chronic: 5 ug/l;
(ix)(viii) Silver, dissolved, chronic: WER∙ 0.06 ug/l;
(d) Selenium, chronic: The standard for chronic selenium has the following components: fish
egg/ovary tissue, fish whole body or muscle tissue, and water column (lentic and lotic). These
components shall be used in the following order of preference provided data is available:
(i) Fish egg/ovary tissue;
(ii) Fish whole body or muscle tissue;
(iii) Water column.
Fish tissue concentrations are determined as dry weight and water column concentrations are
based on the dissolved fraction of selenium. Fish tissue components are expressed as
steady-state concentrations and provide instantaneous point measurements that reflect
integrative accumulation of selenium over time and space in fish populations at a given site. Fish
tissue components supersede the water column component when both fish tissue and water
concentrations are measured. Egg-ovary tissue results, where available, supersede all other tissue
and water column components. The chronic selenium standards are as follows:

Component Magnitude Duration
Fish tissue
Fish egg/ovary tissue 15.1 mg/kg Instantaneous
Fish whole body or
muscle tissue
8.5 mg/kg whole
body Instantaneous
11.3 mg/kg muscle Instantaneous
Water column Lentic or Lotic 1.5 ug/l lentic 30-day average
3.1 ug/l lotic 30-day average
10

The criteria are consistent with Aquatic Life Ambient Water Quality Criterion for Selenium –
Freshwater, EPA 822-R-16-006, 2016. The EPA approves the revision of the criteria as being
consistent with the CWA and 40 C.F.R. Part 131.

The hardness-dependent freshwater cadmium criteria equations within 15A NCAC 02B .0211(11)(e)
were revised as follows:

Metal
Equations for Hardness-
Dependent Freshwater Metals
(ug/l)

Standard at 25 mg/l hardness
(ug/l)
Cadmium, Acute
WER∙ [{1.136672-[ln
hardness](0.041838)} ∙
e^{0.9151 [ln hardness]-
3.1485}] ∙ e^{0.9789 [ln
hardness]-3.443}]
0.82 0.75

Cadmium, Acute,
Trout waters
WER∙ [{1.136672-[ln
hardness](0.041838)} ∙
e^{0.9151[ln hardness]-
3.6236}] ∙ e^{0.9789 [ln
hardness]-3.866}]
0.51 0.49

Cadmium, Chronic
WER∙ [{1.101672-[ln
hardness](0.041838)} ∙
e^{0.7998[ln hardness]-
4.4451}] ∙ e^{0.7977[ln
hardness]-3.909}]
0.15 0.25

Similar to the previous revisions to the state’s cadmium criteria, North Carolina adopted two equations
that incorporate EPA’s recommended variables, but also include a modified equation to calculate a non-
trout, acute criterion. The result is that two of the criteria match EPA’s 2016 recommendations for
cadmium criteria and the other criterion reflects the option to modify EPA’s 304(a) recommendations
based on other scientifically defensible methods. The previous criteria for cadmium were based on the
2001 cadmium recommendations, but all three of the more recently adopted criteria consider the updated
science in the 2016 recommended criteria for cadmium. A comparison between the state’s existing
criteria concentrations, the state’s newly adopted criteria, and EPA’s current recommended criteria
values is provided in the table below.

Comparison of North Carolina’s Cadmium Criteria with
EPA’s National Recommended Criteria for Cadmium

State’s previous
criteria
calculated at a
hardness of 25
(ug/l)
State’s 2022
criteria
calculated at a
hardness of 25
(ug/l)
EPA’s National
Recommended
criteria calculated at a
hardness of 25 (ug/l)
Date of
Current EPA
National
Recommended
Document
Cadmium (acute) 0.82 0.75 EPA 2016
11

Cadmium (acute,
trout waters) 0.51 0.49
EPA only recommends
a single acute value of
0.49
Cadmium (chronic) 0.15 0.25 0.25

The EPA’s national recommended water quality criteria for cadmium were updated in 2016 using the
following equations:

CMC (dissolved) = (CF) exp{mA [ln(hardness)] + bA}
CCC (dissolved) = (CF) exp{mC [ln(hardness)] + bC}

The final row in the table below summarizes the variables that went into the equations above, along with
the values in place previously for the state and EPA’s current recommended variables.

Hardness-based
Equation Variable
mA (acute) bA (acute) mC (chronic) bC (chronic)
EPA Recommended
Variables for
calculating cadmium
criteria
0.9789 -3.866 0.7977 -3.909
Previous NC variables
approved by EPA in
2016
0.9151 (non-trout)
0.9151 (trout)
-3.1485 (non-trout)
- 3.6236 (trout)
0.7998 -4.4451
Current NC variables
used to calculate 2022
criteria
0.9789 (non-trout)
0.9789 (trout)
-3.443 (non-trout)
-3.866 (trout)
0.7977 -3.909

For the acute (trout waters only) and chronic criteria, the state’s values are consistent with the EPA’s
2016 cadmium recommendations. The EPA approves the addition of these criteria as being consistent
with the CWA and 40 C.F.R. Part 131.

For the acute criteria that applies to non-trout waters, which are also Class C waters, North Carolina
used the option under section 131.11(b)(iii) that allows states to establish numerical standards by using
other scientifically defensible methods. As noted in the above table, the bA variable used to derive the
non-trout waters acute criterion differs from the bA used to calculate the acute criterion for trout waters
(which is the same as the recommended bA for the EPA’s 2016 acute criterion). In EPA’s 2016 cadmium
document, the acute criteria calculation was adjusted to account for a specific species, the rainbow trout,
by lowering the Final Acute Value (FAV) from 5.733 µg/L total cadmium to an FAV of 3.727 µg/L total
cadmium. North Carolina’s acute criterion for trout waters ties back to the lower FAV, while the acute
criterion for non-trout waters ties back to the higher FAV. Both values are contained in the 2016
cadmium document, but as North Carolina further explains in the following excerpt from the March
2022 Hearing Officer’s Report, the use of the higher FAV still results in protection of cadmium sensitive
species in the state’s Class C non-trout waters:

The proposed acute cadmium standard for Class C waters is based on the original Final Acute
Value (FAV) determined by the EPA [US EPA. Aquatic Life Ambient Water Quality Criteria for
Cadmium – 2016. EPA-820-R-16-002. https://www.epa.gov/wqc/aquatic-life-criteria-cadmium].
This FAV of 5.733 ug/L, expressed as total recoverable cadmium at 100 mg/L water hardness,
12

results in a Criterion Maximum Concentration (CMC) of 2.867 ug/L, or one-half of the FAV, as
total recoverable cadmium. When the CMC is expressed as dissolved cadmium, using the
conversion factor of 1.136672 - [(ln hardness) (0.041838)] and the toxic effect is adjusted for
water hardness using the relationship e^(0.9789*ln(hardness) - 3.443), the final proposed
dissolved, hardness-dependent acute cadmium standards of 0.09 ug/L at 2.5 mg/L, 0.75 ug/L at
25 mg/L, and 1.99 at 70.9 mg/L are obtained. The 2.5 mg/L and 70.9 mg/L hardness values
correspond to the minimum and maximum hardness values reported between 2007 and 2013 for
mountain streams at NCDEQ Ambient Monitoring System (AMS) stations (see Appendix A). The
25 mg/L hardness corresponds to an average hardness that is typical of NC surface waters. At
these same water hardness values the species mean acute values (SMAVs) expressed as dissolved
cadmium for the brown trout, bull trout, shorthead sculpin, and mottled sculpin, shown in Table
3, are all above the proposed acute cadmium standard indicating that the proposed acute
cadmium standard for Class C waters will be protective of these cadmium sensitive species.

Table 3 – Comparison of proposed Class C cadmium standard to the SMAVs for sensitive species
Species
SMAV (total
recoverable
Cd)1
(ug/L)
SMAV (dissolved Cd)2
(ug/L) at varying
mountain stream
hardness
Proposed Class C acute
standard (ug/L) at
varying mountain
stream hardness
Bull trout,
Salvelinus
confluentus
4.190 4.6023 4.1984 4.0165
0.093 0.754 1.995
Shorthead
sculpin,
Cottus
confusus
4.404 4.8373 4.4134 4.2215
Mottled
sculpin,
Cottus
bairdii
4.418 4.8523 4.4274 4.2345
Brown trout,
Salmo trutta 5.642 6.1973 5.6534 5.4075
1 SMAV for each species as total recoverable cadmium per the 2016 EPA NRWQC document
2 SMAV for each species as dissolved cadmium per the conversion factor provided in the 2106 EPA NRWQC
document
3 Minimum recorded water hardness of 2.5 mg/L for mountain stream AMS stations for 2007-2013
4 Water hardness of 25 mg/L that is used as an average for NC surface waters
5 Maximum recorded water hardness of 70.9 mg/L for mountain stream AMS stations for 2007-2013

The purpose in discussing the sensitivity of these other cadmium sensitive species is to further support
the state’s conclusion that while the nationally recommended criteria are intended to protect the more
sensitive rainbow trout species, which does not occur naturally throughout all portions of the state, this
alternative acute value would be protective of these other species. The acute, non-trout criterion is
expected to be protective of the species naturally present in Class C waters. As noted in the regulatory
impact analysis, all of the criteria updates were made to reflect updated science on the toxic effects of
cadmium on aquatic life and updated science on the relationship between water hardness and toxicity.
Based on the EPA’s analysis of the information provided by the state, the acute, non-trout criterion is
consistent with the CWA and the implementing regulations at 40 C.F.R. Part 131 and therefore
approved.

13

15A NCAC 02B .0211(11) was revised as follows:

(e)(f) Compliance with acute instream metals standards shall only be evaluated using an average
of two or more samples collected within one hour. Compliance with chronic instream metals
standards, except for selenium shall only be evaluated using an average of a minimum of four
samples taken on consecutive days or as a 96-hour average;

In 2016, the EPA concluded that this provision was not a new or revised water quality standard, and the
current revisions to change the content to reflect the selenium revisions in this submission does not alter
the meaning or original conclusion of this provision. This provision still does not establish or change a
level of protection related to the magnitude, duration, or frequency of water quality criteria nor establish
designated uses or antidegradation requirements. Rather, this provision describes the sufficiency or
reliability of information necessary for the state to decide whether a water attains or does not attain a
water quality standard.

15A NCAC 02B .0220 Tidal Salt Water Quality Standards for Class SC Waters

15A NCAC 02B .0220 was revised as follows:

(c) Acute and chronic tidal salt water quality metals standards shall be as follows:
…
(iii) Cadmium, acute: WER∙ 40 33 µg/l;
(iv) Cadmium, chronic: WER∙ 8.8 7.9 µg/l;
…

North Carolina has updated their existing cadmium criteria by adopting EPA’s Aquatic Life Ambient
Water Quality Criteria for Cadmium – 2016 to revise the criteria that apply to saltwater Class SC waters
for the protection of aquatic life. The criteria are consistent with the CWA and the implementing
regulations at 40 C.F.R. Part 131 and therefore approved.

15A NCAC 02B .0300 Assignment of Stream Classifications

15A NCAC 02B .0301(f)(2) was revised as follows:

In addition to Subparagraph (f)(1)(1) of this Rule, Paragraph, for unnamed streams entering other
states states, tribes approved for treatment as a state and administering a U.S. Environmental
Protection Agency approved water quality standards program, or for specific areas of a river
basin, the following Rules shall apply:

This item was revised to recognize water quality standards programs for tribes approved for treatment as
a state, which for North Carolina’s purposes, applies to the Eastern Band of Cherokee Indians. This
revision is consistent with the CWA and the implementing regulations at 40 C.F.R. Part 131 and
therefore approved.

15A NCAC 02B .0311(m) was revised as follows:

14

The Cape Fear River Basin Classification Schedule was amended effective August 1, 2002 as
follows:
(1) Mill Creek [Index Nos. 18-23-11-(1), 18-23-11-(2), 18-23-11-3, 18-23-11-(5)] from
its source to the Little River, including all tributaries was reclassified from Class WS-III
NSW and Class WS-III B NSW to Class WS-III NSW HQW@ and Class WS-III B NSW
HQW@.
(2) McDeed's Creek [Index Nos. 18-23-11-4, 18-23-11-4-1] from its source to Mill
Creek, including all tributaries was reclassified from Class WS III NSW and Class WS-
III B NSW to Class WS-III NSW HQW@ and Class WS-III B NSW HQW@.
The "@" symbol as used in this Paragraph means that if the governing municipality has deemed
that a development is covered under a "5/70 provision" as described in Rule .0215(3)(b)(i)(E) of
this Subchapter Rule .0624 of this Subchapter, then that development is not subject to the
stormwater requirements as described in 15A NCAC 02H.1006 15A NCAC 02H .1021.

As noted in the March 2022 Hearing Officer’s Report, these revisions represent a minor technical
correction that was made to correct the associated references. Such changes are considered minor
revisions. These revisions do not alter the meaning or intent of the previously approved corresponding
provisions. The EPA approves the editorial changes as being consistent with the CWA and the EPA’s
implementing regulations. The EPA notes, however, that its approvals of these editorial changes do not
re-open the EPA’s prior approvals of the underlying WQS.

15A NCAC 02B .0311(o)(4) was revised as follows:

Weymouth Woods Sandhill Seep near Mill Creek [18-23-11-(1)] was reclassified to Class WL
UWL.

As noted in the March 2022 Hearing Officer’s Report, this revision represents a minor technical
correction that was made to correct the associated references. Such changes are considered minor
revisions. This revision does not alter the meaning or intent of the previously approved corresponding
provisions. The EPA approves the editorial change as being consistent with the CWA and the EPA’s
implementing regulations. The EPA notes, however, that its approvals of this editorial change do not
re-open the EPA’s prior approvals of the underlying WQS.

15A NCAC 02B .0311(u) was revised as follows:

The Cape Fear River Basin Classification Schedule was amended effective September 1, 2019
November 1, 2019 with the reclassification of a portion of Sandy Creek [Index No. 17-16-(1)]
(including tributaries) from a point 0.4 mile upstream of SR-2481 to a point 0.6 mile upstream of
N.C. Hwy 22 from WS-III to WS-III CA. The reclassification resulted in an updated
representation of the water supply watershed for the Sandy Creek reservoir.

As noted in the March 2022 Hearing Officer’s Report, this revision represents a minor technical
correction that was made to correct the associated references. Such changes are considered minor
revisions. This revision does not alter the meaning or intent of the previously approved corresponding
provisions. The EPA approves the editorial change as being consistent with the CWA and the EPA’s
implementing regulations. The EPA notes, however, that its approvals of this editorial change do not re-
open the EPA’s prior approvals of the underlying WQS.

15

Part III - EPA’s Conclusions

Based on the reasons outlined above, it is our conclusion that the requirements of the CWA and 40
C.F.R. Part 131 have been met for the new or revised WQS contained in North Carolina’s submission.
Therefore, the new or revised criteria addressed in this Decision Document are approved by the EPA
pursuant to section 303(c) of the CWA.

Date Denisse D. Diaz, Acting Director
Water Division