[Federal Register Volume 86, Number 52 (Friday, March 19, 2021)]
[Rules and Regulations]
[Pages 14834-14846]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2021-05428]


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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 131

[EPA-HQ-OW-2016-0694; FRL-10019-00-OW]
RIN 2040-AF70


Federal Aluminum Aquatic Life Criteria Applicable to Oregon

AGENCY: Environmental Protection Agency (EPA).

ACTION: Final rule.

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SUMMARY: The Environmental Protection Agency (EPA or Agency) is 
promulgating Federal criteria for fresh waters in the State of Oregon 
that are jurisdictional under the Clean Water Act (CWA) to protect 
aquatic life from the effects of exposure to harmful levels of 
aluminum. EPA disapproved of Oregon's freshwater acute and chronic 
aluminum criteria in 2013. The CWA directs EPA to promptly propose 
water quality standards (WQS) addressing the Agency's disapproval and 
to promulgate those WQS unless, prior to such promulgation, the state 
adopts WQS addressing EPA's disapproval that the Agency determines meet 
the requirements of the CWA and EPA approves. Since Oregon has not 
adopted and submitted revised freshwater acute and chronic aluminum 
criteria to address EPA's 2013 disapproval, EPA is promulgating Federal 
freshwater acute and chronic aluminum criteria to protect aquatic life 
uses in Oregon as the applicable WQS under the CWA. If, at some point 
in the future, Oregon submits and EPA approves revised freshwater acute 
and chronic aluminum criteria to address EPA's 2013 disapproval, EPA 
would withdraw this regulation.

DATES: This rule is effective on April 19, 2021. The incorporation by 
reference of certain publications listed in the rule is approved by the 
Director of the Federal Register as of April 19, 2021.

ADDRESSES: EPA has established a docket for this action under Docket ID 
No. EPA-HQ-OW-2016-0694. All documents in the docket are listed on the 
http://www.regulations.gov website. Although listed in the index, some 
information is not publicly available, e.g., confidential business 
information (CBI) or other information whose disclosure is restricted 
by statute. Certain other material, such as copyrighted material, is 
not placed on the internet and will be publicly available only in hard 
copy form. Publicly available docket materials are available 
electronically through http://www.regulations.gov.

FOR FURTHER INFORMATION CONTACT: Mimi Soo-Hoo, Office of Water, 
Standards and Health Protection Division (4305T), Environmental 
Protection Agency, 1200 Pennsylvania Avenue NW, Washington, DC 20460; 
telephone number: (202) 566-1192; email address: [email protected].

SUPPLEMENTARY INFORMATION: This final rule is organized as follows:

I. General Information
    A. Does this action apply to me?
    B. How did EPA develop this final rule?
II. Background
    A. Statutory and Regulatory Authority
    B. EPA's Disapproval of Oregon's Freshwater Aluminum Criteria
    C. General Recommended Approach for Deriving Aquatic Life 
Criteria
III. Freshwater Aluminum Aquatic Life Criteria
    A. EPA's National CWA Section 304(a) Recommended Freshwater 
Aluminum Criteria
    B. Final Acute and Chronic Aluminum Criteria for Oregon's Fresh 
Waters
    C. Implementation of Final Freshwater Acute and Chronic Aluminum 
Criteria in Oregon
    D. Incorporation by Reference
IV. Critical Low Flows and Mixing Zones
V. Endangered Species Act
VI. Under what conditions would Federal standards be withdrawn?
VII. Alternative Regulatory Approaches and Implementation Mechanisms
    A. Designating Uses
    B. WQS Variances
    C. NPDES Permit Compliance Schedules
VIII. Economic Analysis
IX. Statutory and Executive Order Reviews
    A. Executive Order 12866 (Regulatory Planning and Review) and 
Executive Order 13563 (Improving Regulation and Regulatory Review)
    B. Executive Order 13771 (Reducing Regulations and Controlling 
Regulatory Costs)
    C. Paperwork Reduction Act
    D. Regulatory Flexibility Act
    E. Unfunded Mandates Reform Act
    F. Executive Order 13132 (Federalism)
    G. Executive Order 13175 (Consultation and Coordination With 
Indian Tribal Governments)
    H. Executive Order 13045 (Protection of Children From 
Environmental Health and Safety Risks)
    I. Executive Order 13211 (Actions That Significantly Affect 
Energy Supply, Distribution, or Use)
    J. National Technology Transfer and Advancement Act of 1995
    K. Executive Order 12898 (Federal Actions To Address 
Environmental Justice in Minority Populations and Low-Income 
Populations)
    L. Congressional Review Act (CRA)

I. General Information

A. Does this action apply to me?

    Entities such as industrial facilities, stormwater management 
districts, or publicly owned treatment works (POTWs) that discharge 
pollutants to fresh waters of the United States under the State of 
Oregon's jurisdiction could be affected by this rule because Federal 
WQS promulgated by EPA in this rule will be the applicable WQS for 
fresh waters in Oregon for CWA purposes after the effective date of 
this rule. These WQS are the minimum standards which must be used in 
such CWA regulatory programs as National Pollutant Discharge 
Elimination System (NPDES) permitting \1\ and identifying impaired 
waters under CWA Section 303(d). Categories and entities that could 
potentially be affected by this rule include the following:
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    \1\ Before any water quality based effluent limit is included in 
an NPDES permit, the permitting authority (here, the State of 
Oregon), will first determine whether a discharge ``will cause or 
has the reasonable potential to cause, or contribute to an excursion 
above any WQS.'' 40 CFR 122.44(d)(1)(i) and (ii).

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           Category            Examples of potentially affected entities
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Industry.....................  Industrial point sources discharging
                                pollutants to fresh waters of the United
                                States in Oregon.
Municipalities...............  Publicly owned treatment works or similar
                                facilities discharging pollutants to
                                fresh waters of the United States in
                                Oregon.
Stormwater Management          Entities responsible for managing
 Districts.                     stormwater in the State of Oregon.
------------------------------------------------------------------------

    This table is not intended to be exhaustive, but rather provides a 
guide for readers regarding entities that could ultimately be affected 
by this action. Any parties or entities who depend upon or contribute 
to the water quality

[[Page 14835]]

of Oregon's fresh waters could be affected by this rule. To determine 
whether your facility or activities could be affected by this action, 
you should carefully examine this rule. If you have questions regarding 
the applicability of this action to a particular entity, consult the 
person listed in the FOR FURTHER INFORMATION CONTACT section.

B. How did EPA develop this final rule?

    EPA carefully considered the public comments and feedback received 
from interested parties on the proposal published in the Federal 
Register at 84 FR 18454 on May 1, 2019. EPA provided a 45-day public 
comment period and held two public hearings on June 11 and June 12, 
2019, to provide clarification on the contents of the proposed 
rulemaking and to accept verbal public comments.
    A total of eight organizations and individuals submitted comments 
either to the docket or during the public hearings on a range of issues 
prior to the close of the public comment period on June 17, 2019. Some 
comments addressed issues beyond the scope of this rule. Brief 
summaries of specific comments and EPA's responses are provided in this 
action. For a full accounting of the comments and the Agency's 
responses, see EPA's Response to Comments document in the official 
public docket for this rule.

II. Background

A. Statutory and Regulatory Authority

    CWA Section 303(c) (33 U.S.C. 1313(c)) directs states to adopt WQS 
for state waters subject to CWA jurisdiction. CWA Section 303(c)(2)(A) 
provides that WQS shall consist of designated uses of the waters and 
water quality criteria based on those uses. EPA's implementing 
regulations at 40 CFR 131.11(a)(1) provide that ``[s]uch criteria must 
be based on sound scientific rationale and must contain sufficient 
parameters or constituents to protect the designated use [and] [f]or 
waters with multiple use designations, the criteria shall support the 
most sensitive use.'' In addition, 40 CFR 131.10(b) provides that 
``[i]n designating uses of a water body and the appropriate criteria 
for those uses, the [s]tate shall take into consideration the water 
quality standards of downstream waters and shall ensure that its water 
quality standards provide for the attainment and maintenance of the 
water quality standards of downstream waters.''
    States review applicable WQS at least once every three years and, 
if appropriate, revise or adopt new WQS (CWA Section 303(c)(1); 40 CFR 
131.20). Any new or revised WQS must be submitted to EPA for review and 
approval or disapproval (CWA Sections 303(c)(2)(A) and (c)(3); 40 CFR 
131.20 and 131.21). If EPA disapproves a state's new or revised WQS as 
not consistent with CWA requirements, the state has 90 days to adopt a 
revised WQS that adopts the changes specified by EPA to meet CWA 
requirements. If the state fails to do so, EPA must promptly propose 
and then, within 90 days, promulgate such WQS unless the state has 
adopted a revised or new WQS that EPA determines to be consistent with 
CWA requirements (CWA Sections 303(c)(3) and (c)(4)).
    Under CWA Section 304(a), EPA periodically publishes national 
criteria recommendations for states to consider when adopting water 
quality criteria for particular pollutants to meet the CWA Section 
101(a)(2) goal. When EPA has published recommended criteria, states 
should establish numeric water quality criteria based on the Agency's 
CWA Section 304(a) recommended criteria, CWA Section 304(a) recommended 
criteria modified to reflect site-specific conditions, or other 
scientifically defensible methods (40 CFR 131.11(b)(1)). Water quality 
criteria must protect the designated use and be based on sound 
scientific rationale. For waters with multiple use designations, the 
criteria shall support the most sensitive use (40 CFR 131.11(a)(1)).

B. EPA's Disapproval of Oregon's Freshwater Aluminum Criteria

    As explained in the preamble of the proposed rulemaking, EPA 
disapproved the State's freshwater aluminum criteria in 2013 because 
the State had not supplied a scientific rationale for the pH range 
under which the State's criteria would apply, which differed from the 
applicable pH range specified in EPA's 1998 national CWA Section 304(a) 
recommended criteria for aluminum (84 FR 18456-57, May 1, 2019) that 
existed at that time but have since been updated.
    Under the terms of a consent decree (as amended) to resolve 
litigation in Northwest Environmental Advocates v. U.S. EPA, 3:15-cv-
00663-BR (D. Or. 2015), EPA is required, no later than six months after 
the date on which the National Marine Fisheries Service (also known as 
National Oceanic and Atmospheric Administration (NOAA) Fisheries) 
issues its Biological Opinion on the aluminum criteria previously 
proposed by EPA, to either approve aluminum criteria to protect aquatic 
life in fresh waters submitted by Oregon or sign a notice for 
publication in the Federal Register to finalize the aluminum criteria 
EPA proposed for Oregon. NOAA Fisheries transmitted its Biological 
Opinion to EPA on July 1, 2020. Since Oregon has not yet adopted 
freshwater aluminum criteria to meet CWA requirements, EPA is 
promulgating freshwater aluminum criteria for Oregon waters in 
accordance with CWA Sections 303(c)(3) and (c)(4).

C. General Recommended Approach for Deriving Aquatic Life Criteria

    Under the Agency's CWA Section 304(a) authority, EPA develops 
national recommended criteria and methodologies to protect aquatic life 
and human health for specific pollutants and pollutant parameters. EPA 
invites public comment on draft recommended criteria and methodologies 
and seeks scientific expert review before EPA finalizes them as formal 
national water quality criteria recommendations for states to consider 
when developing and adopting applicable water quality criteria. EPA's 
Guidelines for Deriving Numerical National Water Quality Criteria for 
the Protection of Aquatic Organisms and Their Uses (referred to as the 
``Aquatic Life Guidelines'') \2\ describe the systematic way in which 
EPA establishes concentrations for a pollutant in water that will 
support the aquatic life designated use.
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    \2\ USEPA. 1985. Guidelines for Deriving Numerical National 
Water Quality Criteria for the Protection of Aquatic Organisms and 
Their Uses. U.S. Environmental Protection Agency, Office of Research 
and Development, Duluth, MN, Narragansett, RI, Corvallis, OR. PB85-
227049. https://www.epa.gov/sites/production/files/2016-02/documents/guidelines-water-quality-criteria.pdf.
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    Numeric criteria derived using EPA's Aquatic Life Guidelines are 
expressed as acute and chronic values representing short-term and long-
term exposures, respectively. The combination of a criterion maximum 
concentration (CMC), typically expressed as a one-hour average value, 
and a criterion continuous concentration (CCC), typically specified as 
a four-day average value, protects aquatic life from acute and chronic 
toxicity, respectively. Neither value is to be exceeded more than once 
in three years. An exceedance occurs when the average concentration 
over the duration of the averaging period is above the CMC or the CCC. 
EPA based its maximum exceedance frequency recommendation of once every 
three years on the ability of aquatic ecosystems to recover from the 
exceedances.
    The Aquatic Life Guidelines recommend reliance on toxicity test 
data from a minimum of eight taxa of aquatic organisms in order to 
derive

[[Page 14836]]

criteria. These taxa are intended to be representative of a wide 
spectrum of aquatic life, such that the representative taxa serve as 
surrogates for untested species. Therefore, the representative test 
organism species do not need to be present in the water(s) where the 
criteria will apply. A state is not precluded from relying on toxicity 
data using resident species to develop site-specific criteria to apply 
at a localized site. In developing site-specific criteria, EPA 
recommends that the state maintain similar broad taxonomic 
representation in calculating the site-specific criteria to ensure 
protection of the most sensitive species at the site. If a state 
chooses to carry out the ``deletion of data'' portion of the species 
re-calculation process, the state should consider how to demonstrate 
that the species included in the derivation of EPA's national 
recommended criteria are not present and would not serve as surrogates 
for other species that occur at the site.\3\
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    \3\ USEPA. 2013. Revised Deletion Process for the Site-Specific 
Recalculation Procedure for Aquatic Life Criteria. U.S. 
Environmental Protection Agency, Office of Water, Washington, DC. 
EPA-823-R-13-001. https://www.epa.gov/sites/production/files/2015-08/documents/revised_deletion_process_for_the_site-specific_recalculation_procedure_for_aquatic_life_criteria.pdf.
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III. Freshwater Aluminum Aquatic Life Criteria

A. EPA's National CWA Section 304(a) Recommended Freshwater Aluminum 
Criteria

    EPA's 2018 national CWA Section 304(a) recommended freshwater 
aquatic life criteria for aluminum (Final Aquatic Life Ambient Water 
Quality Criteria for Aluminum 2018, EPA 822-R-18-001, as cited in the 
Federal Register at 83 FR 65663, December 21, 2018), referred to in 
this action as the ``2018 national recommended criteria,'' were 
developed following the Aquatic Life Guidelines. These recommended 
criteria update and replace EPA's 1988 national CWA Section 304(a) 
recommended freshwater aquatic life criteria for aluminum. The 2018 
national recommended criteria apply to fresh waters and include a 
calculator that takes into account three water chemistry 
characteristics that affect aluminum toxicity. The 2018 national 
recommended criteria reflect the latest scientific knowledge and 
understanding of the interaction between water chemistry and aluminum 
toxicity, and represent a scientifically defensible method upon which 
EPA is basing this CWA action to establish WQS for fresh waters in 
Oregon (83 FR 65663, December 21, 2018).
    The 2018 national recommended criteria are based upon Multiple 
Linear Regression (MLR) models for fish and invertebrate species that 
use site-specific pH, dissolved organic carbon (DOC), and total 
hardness inputs to quantify the effects of these water chemistry 
parameters on the toxicity of aluminum to aquatic organisms. The MLR 
models normalize the available toxicity data to accurately reflect the 
effects of the site-specific water chemistry (pH, DOC, total hardness) 
on the toxicity of aluminum to tested species. The normalized toxicity 
test data are then used in a criteria calculator to generate criteria 
for specific ambient water chemistry conditions. The numeric outputs of 
the 2018 national recommended criteria calculator for a given set of 
conditions vary depending on the site-specific pH, DOC, and total 
hardness entered into the calculator. The calculator outputs (CMC and 
CCC) for a given set of input conditions are numeric values that would 
be protective for that set of input conditions (i.e., water-chemistry-
condition-specific CMC and CCC outputs).
    Users of the 2018 national recommended criteria can generate 
criteria magnitude values in two ways: (1) Use the lookup tables 
provided in the criteria document to find the numeric aluminum CMC and 
CCC most closely corresponding to the local conditions for pH, DOC, and 
total hardness; or (2) use the provided Aluminum Criteria Calculator 
V2.0 Excel spreadsheet to enter the pH, DOC, and total hardness 
conditions at a specific site to calculate the numeric aluminum CMC and 
CCC corresponding to the local input conditions.
    In its 2018 national recommended criteria, EPA expressed the 
aluminum criteria as ``total recoverable'' metal concentrations. The 
primary reason for the expression of the criteria as total recoverable 
aluminum concentrations is because the laboratory toxicity tests used 
in the effects assessment in the development of the aluminum criteria 
reported the aluminum concentrations as total recoverable aluminum. The 
use of total aluminum concentrations is justified for laboratory 
toxicity test data where the total aluminum concentration is in either 
a dissolved monomeric form or precipitated forms (e.g., aluminum 
hydroxides) of aluminum. The laboratory dilution waters in tests used 
for EPA's criteria development did not contain suspended solids, clays, 
or particulate matter where aluminum could be bound. However, total 
recoverable aluminum concentrations measured in natural waters may 
overestimate the potential risks of toxicity to aquatic organisms if 
suspended solids, clays, or particulate matter to which aluminum may be 
bound are present, because total recoverable methods measure 
bioavailable and non-bioavailable forms of aluminum.
    As discussed in Section 2.6.2 of EPA's 2018 national recommended 
criteria document, the different forms of aluminum vary in toxicity. 
The criteria document discusses differences between aluminum toxicity 
in a controlled laboratory setting and the toxicity of aluminum in 
natural waters that contain suspended particles, clays, and 
aluminosilicate minerals not present in lab waters. Dissolved and 
particulate (e.g., aluminum hydroxides) aluminum, as well as small 
sized colloids containing aluminum, exhibit toxic effects on aquatic 
life depending on the pH, DOC, and total hardness of the waters. Total 
recoverable aluminum methods determine the total concentration of 
monomeric (both organic and inorganic) forms of aluminum, polymeric and 
colloidal forms, as well as particulate forms and aluminum sorbed to 
clays present in a sample. Total recoverable methods use a strong acid 
(pH <2) digestion step to prepare the sample for measurement. In 
contrast, methods to determine dissolved concentrations of aluminum 
involve filtering test samples prior to digestion, which excludes 
particulate forms of aluminum from the test sample. Methods to 
determine dissolved concentrations of aluminum, therefore, may 
underestimate the toxicity of the aluminum in a sample if the 
particulate forms including aluminum hydroxide precipitates that 
contribute to toxicity are not measured. In conclusion, dissolved 
aluminum measurements are not appropriate for comparison to the 
aluminum criteria that EPA is promulgating for Oregon. EPA 
acknowledges, as several commenters noted during the comment periods 
for both EPA's 2017 draft national CWA Section 304(a) recommended 
criteria for aluminum and EPA's proposed criteria for Oregon, that not 
all forms of aluminum that may be present in ambient waters are 
biologically available or ``bioavailable'' to aquatic species. 
Bioavailable aluminum (or the bioavailable fraction of aluminum) is 
defined as the amount of aluminum that is available to cause a 
biological response in an aquatic organism. The best measures of 
bioavailability involve interactions of aluminum with a membrane (e.g., 
aluminum binding to proteins of gill membranes), diffusion

[[Page 14837]]

through the cell membrane, and flocculation of precipitated aluminum on 
the gill. Bioavailable aluminum is the toxicologically relevant 
fraction of aluminum which results from a combination of dissolved and 
precipitated aluminum, in contrast to mineralized (non-toxic) forms of 
aluminum.\4\ The non-bioavailable fraction of aluminum includes large 
suspended particles, clays, and aluminosilicate minerals.
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    \4\ Per Rodriguez et al. 2019: ``To properly characterize the Al 
concentrations in the toxicity studies, a method was needed that 
could discriminate bioavailable Al from mineral forms of Al. An 
extraction method at pH 4 for bioavailable Al was developed and 
evaluated using C. dubia chronic toxicity studies in the presence of 
TSS. It is concluded that the proposed method is better able to 
discriminate chronic toxicity effects attributable to bioavailable 
Al from mineralized nontoxic forms of Al compared with existing 
methods using total or total recoverable Al (i.e., extraction at pH 
<= 1.5).''
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    EPA's 2018 national recommended criteria document (Section 2.6.2 
from pp. 22-25) explains the science behind this understanding of 
aluminum chemistry and toxicity in more detail. There is also relevant 
discussion of aluminum chemistry (Section 2.2 from pp. 7-10) and mode 
of action and toxicity (Section 2.3 from pp. 10-16) that help explain 
the factors affecting bioavailability and toxicity.

B. Final Acute and Chronic Aluminum Criteria for Oregon's Fresh Waters

    EPA is promulgating aluminum criteria for Oregon that incorporate 
by reference the calculation of CMC and CCC freshwater aluminum 
criteria values for a site using the 2018 national recommended 
criteria.\5\ Doing so means that the CMC and CCC freshwater aluminum 
criteria values for a site shall be calculated using the 2018 Aluminum 
Criteria Calculator V.2.0 (Aluminum Criteria Calculator V.2.0.xlsx) or 
a calculator in R or other software package using the same 1985 
Guidelines calculation procedure and underlying model equations as in 
the Aluminum Criteria Calculator V.2.0 Excel spreadsheet, as 
established in the 2018 national recommended criteria. Consistent with 
the 2018 national recommended criteria, the final water quality 
criteria for aluminum in Oregon fresh waters are expressed as the CMC 
as a one-hour average total recoverable aluminum concentration (in 
[micro]g/L) and the CCC as a four-day average total recoverable 
aluminum concentration (in [micro]g/L). The CMC and CCC are not to be 
exceeded more than once every three years.
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    \5\ USEPA. 2018. Final Aquatic Life Ambient Water Quality 
Criteria for Aluminum. U.S. Environmental Protection Agency, Office 
of Water, Washington, DC. EPA-822-R-18-001. https://www.epa.gov/sites/production/files/2018-12/documents/aluminum-final-national-recommended-awqc.pdf.
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    EPA is promulgating multiple footnotes to the criteria statement to 
provide clarification on the criteria's intended application, and 
highlights two in this paragraph. The first footnote specifies that to 
apply the aluminum criteria for CWA purposes, criteria values based on 
ambient water chemistry conditions must protect the water body over the 
full range of water chemistry conditions, including during conditions 
when aluminum is most toxic. The second footnote states that (1) these 
criteria are based on aluminum toxicity studies where aluminum was 
analyzed using total recoverable analytical methods; (2) Oregon may 
utilize total recoverable analytical methods to implement the criteria; 
(3) for characterizing ambient waters, Oregon may also utilize, as 
scientifically appropriate and as allowable by State and Federal 
regulations, analytical methods that measure the bioavailable fraction 
of aluminum, as described above, (e.g., utilizing a less aggressive 
initial acid digestion, such as to a pH of approximately 4 or lower, 
that includes the measurement of amorphous aluminum hydroxide yet 
minimizes the measurement of mineralized forms of aluminum such as 
aluminum silicates associated with suspended sediment particles or 
clays); and (4) Oregon shall use measurements of total recoverable 
aluminum where required by Federal regulations.
    Commenters were generally supportive of EPA's proposal to base its 
promulgation for Oregon on EPA's 2018 national recommended criteria for 
aluminum. EPA acknowledged in the preamble to the proposal that the 
Agency may consider future modifications to the criteria if warranted 
based on, among other things, further public input, tribal 
consultation, new data, or evaluations of listed species completed 
during Endangered Species Act (ESA) consultation, or the results of ESA 
consultation. On February 13, 2020 and July 1, 2020, EPA completed 
consultation with the U.S. Fish and Wildlife Service (USFWS) and NOAA 
Fisheries, respectively. After evaluating potential effects of the 
Agency's action on federally-listed species during ESA Section 7(a)(2) 
consultation with USFWS and NOAA Fisheries, in addition to 
consideration of comments received during the public comment period 
associated with the proposed rulemaking, EPA is promulgating aluminum 
criteria consistent with the 2018 national recommended criteria.
    The 2018 national recommended criteria represent the latest 
scientific knowledge on aluminum speciation, bioavailability, and 
toxicity, and provide predictable and repeatable outcomes. Consistent 
with the Aquatic Life Guidelines, the 2018 national recommended 
criteria protect aquatic life for acute effects (survival and 
immobility), as well as chronic effects (survival, growth, and 
reproduction) at a level of 20% chronic Effects Concentration (EC20) 
for the 95th percentile of sensitive genera. The docket for the 2018 
national recommended criteria document contains detailed information on 
the science underlying that recommendation (Docket ID: EPA-HQ-OW-2017-
0260).
Comments Regarding Total Recoverable Aluminum and Use of an Emerging 
Analytical Method
    As mentioned above, commenters pointed out that, as EPA had 
acknowledged in its 2018 national recommended criteria document, the 
current test methods for total recoverable aluminum may, in some 
waters, overestimate the amount of aluminum that will be toxic to 
aquatic life in ambient waters in Oregon. Commenters suggested that in 
order to better approximate the toxic fraction of aluminum, EPA should 
allow use of an emerging analytical method that measures bioavailable 
aluminum by using an initial digestion at pH 4. Commenters urged use of 
such an analytical method to characterize aluminum concentrations in 
ambient waters, particularly in waters with high levels of total 
suspended solids suggesting the presence of colloidal, particulate, and 
clay-bound aluminum. Some commenters requested that the final criteria 
for Oregon be expressed as ``bioavailable or total recoverable'' 
aluminum to confirm availability for use of an alternative analytical 
method.
    EPA acknowledges in the final rule that the promulgated criteria 
are based on aluminum toxicity laboratory studies where aluminum was 
analyzed using total recoverable analytical methods. However, EPA also 
acknowledges that under natural conditions not all of these forms of 
aluminum would be biologically available to aquatic species. All of the 
approved total recoverable methods require that samples be preserved in 
the field by acidifying to pH <2 and digested in the laboratory with 
strong acid solution that dissolves the monomeric and polymeric forms 
of aluminum, in addition to colloidal, particulate, and clay-bound 
aluminum. Over the last three decades, the

[[Page 14838]]

scientific consensus has been that the total recoverable method for 
aluminum potentially overestimates the biologically available fraction 
and that a method that better addresses concerns with including 
aluminum bound to particulate matter would be useful (e.g., He and 
Ziemkiewics 2016; Ryan et al. 2019).\6\
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    \6\ He YT, Ziemkiewicz PF. 2016. Bias in determining aluminum 
concentrations: Comparison of digestion methods and implications on 
Al management. Chemosphere 159:570-576; Ryan AC, Santore RC, 
Tobiason S, WoldeGabriel G, and Groffman AR. 2019. Total recoverable 
aluminum: Not totally relevant for water quality standards. 
Integrated Environmental Assessment and Management. 15(6): 974-987.
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    In an attempt to address concerns with measuring total recoverable 
aluminum concentrations, researchers recently investigated new 
analytical methods to measure biologically available forms of aluminum 
(Rodriguez et al. 2019).\7\ This approach does not digest the sample at 
pH of -0.05 to +0.7 but rather to pH 4 to better measure only the 
bioavailable fraction of aluminum. Rodriguez et al. reported that 
sodium acetate buffer is added to the sample to reach the desired pH, 
followed by sample agitation for a specified period of time, and 
finally 0.45-[micro]m sample filtration. The sample is then acidified 
with nitric acid before inductively coupled plasma-optical emission 
spectrometry analysis. These authors provided data that led them to 
conclude that their proposed method is better able to discriminate 
chronic toxicity effects attributable to bioavailable aluminum from 
mineralized nontoxic forms of aluminum compared with existing methods 
using total or total recoverable aluminum.
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    \7\ Rodriguez PH, Arbildua JJ, Villavicencio G, Urrestarazu P, 
Opazo M, Cardwell AS, Stubblefield W, Nordheim E, Adams W. 2019. 
Determination of bioavailable aluminum in natural waters in the 
presence of suspended solids. Environmental Toxicology and 
Chemistry. 38(8):1668-1681.
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    EPA expects that an analytical method that uses a less aggressive 
initial acid digestion that liberates bioavailable forms of aluminum 
(including amorphous aluminum hydroxide), yet minimizes dissolution of 
mineralized forms of aluminum such as aluminosilicates associated with 
suspended sediment particles and clays (referred to as a bioavailable 
analytical method), will better estimate the bioavailable fraction of 
aluminum in ambient waters. EPA is not prescribing use of any specific 
method and looks to further research and method standardization efforts 
to identify best practices.
    For the reasons articulated above, EPA is including the option for 
Oregon to use a bioavailable analytical method for characterizing 
aluminum concentrations in ambient waters, except where measurements of 
total recoverable aluminum are required by Federal regulations (e.g., 
NPDES permit limits for aluminum and compliance reports, by regulation 
at 40 CFR 122.45, 40 CFR 122.44, and 40 CFR 122.48, must be expressed 
as ``total recoverable aluminum'' and measured using analytical methods 
approved at 40 CFR part 136). Doing so, particularly when testing 
ambient samples expected to contain significant amounts of colloidal, 
particulate, and clay-bound aluminum, will better approximate the 
fraction of aluminum that is ``available'' to aquatic life in Oregon 
waters. The footnote in the criteria statement that speaks to Oregon's 
use of a bioavailable analytical method specifies that such a method 
may utilize ``a less aggressive initial acid digestion, such as to a pH 
of approximately 4 or lower, that includes the measurement of amorphous 
aluminum hydroxide yet minimizes the measurement of mineralized forms 
of aluminum such as aluminum silicates associated with suspended 
sediment particles or clays.'' Oregon may use such methods ``as 
scientifically appropriate and as allowable by State and [F]ederal 
regulations.'' For more discussion on analytical methods 
considerations, refer to Section C. Implementation of Final Freshwater 
Acute and Chronic Aluminum Criteria in Oregon of this preamble.
Comments Regarding Language Included in the Aluminum Criteria Table
    In addition to addressing comments pertaining to the use of 
analytical methods described above, EPA also addressed separate and 
unrelated comments regarding language included in the proposed criteria 
table. In the proposed rulemaking, the proposed criteria table included 
the following text: ``Calculator outputs shall be used to calculate 
criteria values for a site that protect aquatic life throughout the 
site under the full range of ambient conditions, including when 
aluminum is most toxic given the spatial and temporal variability of 
the water chemistry at the site.'' Commenters requested that the text 
be moved out of the criteria table because they suggested that it 
referred to implementation of the criteria and that the criteria 
regulation should only contain a reference to the 2018 national 
recommended criteria for aluminum. In response, the final rule removes 
the proposed text from the criteria table and instead includes a 
modification of EPA's statement as a footnote to the criteria table. 
The Agency is using Oregon's adopted water quality criteria for the 
copper Biotic Ligand Model (BLM) as its guide, specifically Endnote N, 
Subpart 3(a), which states that Oregon ``will apply the BLM criteria 
for Clean Water Act purposes to protect the water body during the most 
bioavailable or toxic conditions.'' \8\
---------------------------------------------------------------------------

    \8\ See Endnote ``N,'' https://www.oregon.gov/deq/RulemakingDocs/tables303140.pdf.
---------------------------------------------------------------------------

    Commenters also requested that EPA edit the above-referenced 
statement to avoid the implication that a static set of criteria values 
must be calculated for each site for CWA implementation purposes. EPA 
affirms that the State need not calculate static criteria values for 
each site and has revised the statement to provide that for CWA 
purposes, criteria values based on ambient water chemistry conditions 
must protect the water body over the full range of water chemistry 
conditions, including during conditions when aluminum is most toxic. 
The intention of the statement is to reflect that site-specific pH, 
DOC, and total hardness conditions vary both spatially and temporally 
and that the State must apply the criteria in a manner that ensures 
protection over the full range of variability.
    The State may ensure protection over the full range of water 
chemistry conditions in different ways for different CWA implementation 
purposes. For example, for NPDES permitting, the permit protects the 
water body during critical conditions and therefore under other 
foreseeable conditions. The State could use multiple outputs of the 
calculator to generate a static set of criteria values that would be 
protective for the range of ambient conditions at a site, and use these 
to calculate a water quality-based effluent limit (WQBEL) for an NPDES 
permit for a water body. For assessment, the State could concurrently 
measure the aluminum concentration and the input parameters at the 
site. The calculator would generate instantaneous criteria values 
against which the concurrently collected aluminum monitoring data would 
be compared.
Comments Regarding Default Criteria Values
    Regarding the topic of default criteria values, Oregon will need to 
use ambient water chemistry data (i.e., paired pH, DOC, total hardness) 
as inputs to the calculator in order to determine protective aluminum 
criteria values when implementing the criteria, unless the State 
provides protective default

[[Page 14839]]

values. To ensure that all subject waters will be protected by the 
aluminum criteria, EPA recommends the State have either protective 
default input values for DOC, default criteria magnitude values, or 
procedures for how to calculate criteria values for waters for which 
there are insufficient data to adequately characterize site-specific 
conditions in the water body. EPA recommends that pH values be directly 
measured rather than estimated, given the variability of pH in the 
environment and the sensitivity of criteria calculations to differences 
in pH. EPA solicited comment in the preamble to the proposed rulemaking 
on whether it should promulgate default criteria values for aluminum to 
ensure protection of the aquatic life designated use when available 
data are insufficient to characterize a site. EPA agrees with comments 
that while default values may be needed in some situations, it is 
preferable to collect the needed ambient data and use the calculator to 
calculate criteria values. Commenters supported the use of default 
ecoregional criteria values for situations when data for more than one 
input parameter are unavailable, but requested that the final rule not 
include promulgation of default criteria values. In consideration of 
these comments, EPA has elected not to finalize default criteria 
procedures or values in this rule.
    Although Oregon is not required to identify default input 
parameters or default criteria values for aluminum, the State is 
required to protect the designated uses of the waterbodies within its 
jurisdiction. As described in more detail below, EPA has elected to 
provide the procedures for developing default criteria values and 
default DOC inputs in the docket to this rulemaking. These procedures 
are available to Oregon to use at the State's discretion, in the event 
the State does not yet have sufficient site-specific ambient data upon 
which to rely for a particular location. EPA expects that the State 
will provide publicly available default procedures or values so that 
the public and implementing entities will be aware of how all of the 
State's fresh waters subject to the rule will be protected by the 
criteria when available data are insufficient to characterize a site.
    Per commenters' suggestions, this final preamble briefly describes 
a suggested procedure for calculating default ecoregional criteria, but 
does not include a table of pre-calculated values. Comments supported 
the option of ``ecoregional criteria default values'' based on the 10th 
percentile of the distribution of calculator outputs calculated within 
an ecoregion, which is similar to the approach that EPA suggested in 
the preamble to the proposal and described in a technical analysis 
included in the docket (``Analysis of the Protectiveness of Default 
Ecoregional Al Criteria Values'' Docket ID: EPA-HQ-OW-2016-0694-0114). 
In this procedure, EPA calculated ecoregional default aluminum criteria 
values based on publicly available data from each of Oregon's Level III 
Ecoregions.\9\ To calculate ecoregional default criteria values, (1) 
EPA identified paired measurements of the three calculator input 
parameters where available, and (2) where paired measurements of the 
three calculator input parameters were unavailable, EPA identified 
paired ambient data measurements for available input parameters along 
with estimated DOC and/or total hardness estimated from measured Total 
Organic Carbon (TOC) and specific conductivity, respectively as needed. 
EPA then calculated the 10th percentile CMC and CCC (and other 
percentiles) for each ecoregion from the distributions of calculator 
outputs. Finally, depending on the ecoregion and data censoring method, 
EPA selected the 5th or 10th percentile as a statistic that represents 
a lower bound of spatially and temporally variable conditions that will 
be protective in the majority (>90%) of cases. This procedure is 
available for the State to use to generate default criteria values for 
areas for which the Aluminum Criteria Calculator v.2.0 will be used and 
there are insufficient site-specific ambient data. The State may also 
use another scientifically defensible procedure to generate default 
criteria values.
---------------------------------------------------------------------------

    \9\ USEPA. 2013. U.S. Environmental Protection Agency, 2013, 
Level III ecoregions of the continental United States: Corvallis, 
Oregon, U.S. EPA--National Health and Environmental Effects Research 
Laboratory, map scale 1:7,500,000, http://www.epa.gov/wed/pages/ecoregions/level_iii_iv.h. Omernik, J.M. 1987. Ecoregions of the 
conterminous United States. Annals of the Association of American 
Geographers. 77:118-125.
---------------------------------------------------------------------------

    In addition to soliciting comment on including default ecoregional 
criteria, EPA also solicited comment on whether the final rule should 
include default DOC input values. Among the input parameters, ambient 
DOC data are the least likely to be available out of the three input 
parameters. DOC influences aluminum toxicity unidirectionally. Higher 
levels of DOC provide more mitigation of aluminum toxicity. For water 
bodies for which sufficient pH and total hardness data are available, 
but sufficient DOC data are not available, Oregon may develop default 
DOC input values to use with ambient pH and total hardness data, as an 
alternative to using default criteria values. Comments supported the 
use of default DOC inputs when DOC input parameter data are 
unavailable. Commenters requested the final rule afford the State the 
discretion to develop its own DOC defaults, including a comment 
requesting that the State be able to use its own DOC default inputs 
from its copper BLM criteria rule.\10\ EPA has elected not to finalize 
default DOC inputs for this aluminum rule so that the State may use its 
discretion to develop or apply its own.
---------------------------------------------------------------------------

    \10\ Oregon Administrative Rules, Copper Standard Implementatoin 
(Chapter 340, Division 041, Section 0033), https://www.oregon.gov/deq/wq/Pages/WQ-Standards-Copper.aspx.
---------------------------------------------------------------------------

    Per commenters' suggestions, EPA briefly describes a possible 
procedure for calculating default DOC input values. One such approach 
would be to mirror the approach EPA described in the preamble to the 
proposed rulemaking, which also is described in technical support 
materials associated with EPA's proposed rulemaking and included in the 
docket to this rulemaking (``Analysis of the Protectiveness of Default 
DOC Options'' Docket ID: EPA-HQ-OW-2016-0694-0116). In that analysis, 
EPA analyzed the State's DOC default procedures for its copper water 
quality standard and found that in most of the ecoregions, the default 
values those procedures would generate would be protective as default 
inputs for aluminum as well, with some exceptions and considerations. 
EPA derived its suggested default DOC input values as the 15th or 20th 
percentile of the distribution of data from a compilation of high 
quality data available for Oregon's georegions (aggregated ecoregions 
with similar water quality characteristics). Depending on the ecoregion 
and the data censoring method, EPA selected the 5th, 15th, or 20th 
percentiles as low-end percentiles of georegional DOC concentrations 
that represent a lower bound of spatially and temporally variable 
conditions that will be protective in the majority of cases. EPA 
encourages the State to continue refining its DOC default input 
procedures to ensure the calculated aluminum criteria values will be 
protective for all of Oregon's fresh waters subject to this rule.

C. Implementation of Final Freshwater Acute and Chronic Aluminum 
Criteria in Oregon

    EPA understands that states have certain flexibilities under 40 CFR 
part 131 regarding how each implements water quality standards, such as 
today's

[[Page 14840]]

freshwater aluminum criteria for Oregon. To support the State, the 
proposed rulemaking identified a range of acceptable approaches for the 
State and the commenting public to consider. The State may elect to 
utilize one or more of the approaches or to implement the final 
aluminum criteria in other ways that are consistent with 40 CFR part 
131.
    For CWA implementation purposes, the State will need to identify 
one or more outputs from the calculator or a value derived from a 
scientifically defensible percentile of the distribution of the output 
values as the magnitude(s) of the criteria, to be applied together with 
duration and frequency, to protect the water body under the range of 
water chemistry conditions at a site. In practice, EPA expects the 
State to collect sufficient data to characterize the most toxic 
conditions at a site. The State could collect samples for the input 
parameters concurrently or as close to the same time as possible while 
representing the same environmental condition, and could use default 
values if appropriate where data are unavailable or insufficient to 
capture the variability in conditions. The ways by which the State may 
evaluate sufficiency are described in more detail below.
    The proposal preamble described three example approaches that the 
State could use to calculate criteria values when multiple calculator 
outputs, representing different ambient conditions over time, are 
available (i.e., how to reconcile multiple calculator outputs). EPA 
agrees with commenters' suggestions that further development and 
implementation of these approaches should be left to the State's 
discretion, and that the term used to identify one or more protective 
values, ``reconcile,'' was not appropriate to describe how the State 
should manage multiple calculator outputs. The appropriate approach for 
each circumstance will depend primarily on data availability and on the 
programmatic purposes for which criteria values are being calculated. 
For purposes which require forecasting a protective loading allocation 
under varying ambient conditions, for example, the State could 
calculate a single set of numeric criteria values (CMC and CCC) by 
choosing the lowest output or a low percentile of the outputs of 
multiple calculator runs, or use conservative default values.
    Oregon should ensure that sufficiently representative data are 
collected for the calculator's input parameters (pH, DOC, and total 
hardness) to have confidence that the most toxic conditions are 
adequately characterized. To accomplish this, Oregon may evaluate the 
input parameter data and resultant criteria values that are calculated 
over time for different flows and seasons through the use of 
appropriate statistical methods, such as Monte Carlo \11\ simulation. 
One consideration when defining a site to which to apply criteria for 
aluminum is whether the concentration of metals are generally 
consistent throughout the area. As the size of a site increases, the 
spatial and temporal variability is likely to increase; thus, more 
water samples may be required to adequately characterize the entire 
site. Implementation materials that outline the State's approaches will 
help provide transparency for the public and predictable, repeatable 
outcomes. Additional transparency and public accountability will be 
achieved if Oregon makes publicly available each site's ambient water 
chemistry data, including the inputs used in the aluminum criteria 
value calculations, resultant criteria values, and the geographic 
extent of the site.
---------------------------------------------------------------------------

    \11\ Given sufficient data, Monte Carlo simulation or equivalent 
analysis can be used to determine the probability of identifying the 
most toxic time period for a series of monitoring scenarios. From 
such an analysis, the State can select an appropriate monitoring 
regime.
---------------------------------------------------------------------------

    Similarly, NPDES permit effluent limits that are derived from the 
aluminum criteria calculator should be sufficiently explained in Fact 
Sheets or Statements of Basis. This includes providing an explanation 
of how the aluminum criteria values were calculated; the input data or 
summary of input data and source of data; and how criteria values were 
used to determine whether the discharge would cause or have the 
reasonable potential to cause or contribute to an excursion above the 
aluminum criteria, and if so, how the values were used to derive WQBELs 
for aluminum. The State's assessment methodology and any TMDLs 
developed for waters impaired for aluminum criteria developed using the 
calculator should also be adequately explained for transparency and 
public accountability in TMDL documents and Integrated Reports, as 
appropriate.
    Substantial changes in a water body's ambient input parameter 
concentrations will likely affect aluminum toxicity at that site. In 
addition, as a robust, site-specific dataset is developed with regular 
monitoring, criteria values previously calculated by the State can be 
updated to more accurately reflect site conditions. The State may wish 
to revisit calculated aluminum criteria values periodically (for 
example, with each CWA Section 303(d) listing cycle or WQS triennial 
review) or when changes in water chemistry are evident or suspected at 
a site and as additional monitoring data become available. This will 
ensure that the criteria values used for implementing CWA programs 
accurately reflect the toxicity of aluminum and remain protective of 
the aquatic life designated uses including when aluminum is most toxic.
Analytical Methods Considerations
    As discussed earlier, the forms of aluminum introduced into the 
laboratory toxicity tests upon which EPA relied for criteria 
development do not include suspended solids or clays where aluminum may 
be bound. Aluminum bound in suspended solids or clays would be 
extracted when using total recoverable methods that have a strong acid 
(pH <2) digestion step, but these forms of aluminum would not be 
biologically available to aquatic species in ambient waters. Empirical 
laboratory chronic (7-day) testing with Ceriodaphnia dubia 
investigating survival and reproduction endpoints indicates that total 
recoverable (pH -0.05 to +0.7 digestion) and bioavailable measurements 
of aluminum in lab waters are essentially equal up to approximately 1 
mg/L of aluminum.\12\ Studies are currently being conducted at Oregon 
State University with test solutions with greater than 1 mg/L of 
aluminum to better understand the relationship between the total 
recoverable and bioavailable analytical methods at concentrations above 
1 mg/L. Initial studies indicate there is little variability between 
total recoverable and bioavailable aluminum above 1 mg/L in lab waters 
because the laboratory waters do not include clays or suspended solids.
---------------------------------------------------------------------------

    \12\ Rodriguez PH, Arbildua JJ, Villavicencio G, Urrestarazu P, 
Opazo M, Cardwell AS, Stubblefield W, Nordheim E, Adams W. 2019. 
Determination of bioavailable aluminum in natural waters in the 
presence of suspended solids. Environmental Toxicology and 
Chemistry. 38(8):1668-1681.
---------------------------------------------------------------------------

    It is not necessary to apply a conversion or translation factor to 
compare field measurements using a bioavailable method against the 
promulgated aluminum total recoverable criteria. This is because both 
bioavailable and total recoverable analytical methods quantify the 
toxic fraction of aluminum equivalently in laboratory test waters given 
that standard toxicity test waters do not include suspended solids or 
clays per test protocols. For NPDES compliance monitoring and 
reporting, total recoverable measurements for metals are required. By 
comparison, for ambient water measurements, analytical methods that 
measure bioavailable

[[Page 14841]]

aluminum should provide more accurate quantification of the toxic 
fraction of aluminum. EPA has included a footnote to the final criteria 
statement specifically noting that for characterizing ambient waters, 
Oregon may utilize, as scientifically appropriate and as allowable by 
State and Federal regulations, analytical methods that measure the 
bioavailable fraction of aluminum. The State's use of such a method 
would need to comply with other requirements in the State's own 
program, for example, any applicable Quality Assurance/Quality Control 
requirements. For assessment and listing purposes, ambient field 
measurements analyzed using a bioavailable analytical method may be 
compared directly to the criteria because both represent the toxic 
fraction of aluminum.
    EPA recognizes that in some circumstances, assessing waters using 
the total recoverable analytical method could result in the listing of 
some waters (i.e., those with high amounts of total suspended solids) 
as impaired even though the elevated aluminum measurements could be 
largely attributed to non-bioavailable forms of aluminum. EPA's 
existing regulations do not require use of analytical test methods 
promulgated at 40 CFR part 136 in the implementation of CWA Section 303 
programs, including assessment and listing of waters, nor in the 
determination of the need for a WQBEL. However, EPA's regulations 
require that states assemble and evaluate all existing and readily 
available water quality-related data and information for use in 
developing their CWA Section 303(d) lists. 40 CFR 130.7(b)(5). The 
requirement to assemble and evaluate all data and information for 
assessment and listing purposes includes situations where only total 
recoverable aluminum data and information are available. However, in 
those circumstances, the State is not required to rely on that data for 
listing purposes as long as it provides a technical, science-based 
rationale for not using the data and information. 40 CFR 
130.7(b)(6)(iii). This technical, science-based rationale documenting 
the State's consideration of existing and readily available data and 
information is referenced in the additional footnote language to the 
criteria statement, which speaks to Oregon's ability to use analytical 
methods that measure the bioavailable fraction of aluminum for 
characterizing ambient waters ``as scientifically appropriate.'' For 
example, the State may be able to demonstrate that total recoverable 
aluminum samples are not representative of water quality conditions 
because non-toxic, non-bioavailable forms of aluminum are leading to an 
exceedance above the criterion. When data and information are available 
for both total recoverable and bioavailable aluminum, the State must 
evaluate all of it, but need not rely on all of it for assessment and 
listing purposes. Applicable regulations do not prohibit the State from 
assigning more weight to data and information about bioavailable 
aluminum than total recoverable aluminum for assessment and listing 
purposes.
    For developing TMDLs and load allocations, field measurements 
analyzed using a bioavailable method also may be used as the basis for 
identifying allocations for TMDLs, both wasteload allocations (WLA) for 
point sources and load allocations (LA) for nonpoint sources. For 
implementing a WLA, the associated WQBEL must be assessed for NPDES 
compliance purposes using total recoverable methods just as would be 
the case for other NPDES applications consistent with permitting 
regulations (NPDES permit limits for aluminum and compliance reports, 
by regulation at 40 CFR 122.44, 40 CFR 122.45, and 40 CFR 122.48, must 
be expressed as ``total recoverable aluminum'' and measured using 
analytical methods approved at 40 CFR part 136). For implementing a LA, 
a bioavailable analytical method could be used to measure nonpoint 
source contributions because significant solids with colloid and clay-
bound aluminum could be present (He and Ziemkiewics 2016; Ryan et al. 
2019),\13\ and should not contribute to the measured aluminum for 
comparison to a LA.
---------------------------------------------------------------------------

    \13\ He YT, Ziemkiewicz PF. 2016. Bias in determining aluminum 
concentrations: Comparison of digestion methods and implications on 
Al management. Chemosphere 159:570-576; Ryan AC, Santore RC, 
Tobiason S, WoldeGabriel G, and Groffman AR. 2019. Total recoverable 
aluminum: not totally relevant for water quality standards. 
Integrated Environmental Assessment and Management. 15(6): 974-987.
---------------------------------------------------------------------------

    The contexts where use of an EPA approved method is required are: 
(1) Applications for NPDES permits, specifically, measurements of 
effluents, (2) reports required from dischargers, and (3) 
certifications issued by states under CWA Section 401. 40 CFR 136.1(a). 
NPDES permit limits for metals must be expressed as ``total 
recoverable'' metals with the exception of circumstances that would not 
apply for the aluminum criteria in this rule. 40 CFR 122.45(c).

D. Incorporation by Reference

    The regulatory text incorporates an EPA document by reference, 
specifically, EPA's Final Aquatic Life Ambient Water Quality Criteria 
for Aluminum--2018, December 2018 (EPA-822-R-18-001). The 2018 national 
recommended criteria document is an update to the 1988 recommended 
aluminum aquatic life ambient water quality criteria, in accordance 
with the provisions of CWA Section 304(a) directing EPA to revise 
criteria from time to time to reflect the latest scientific knowledge. 
The criteria for aluminum that protect aquatic life in fresh water 
depend on a site's water chemistry parameters. Using those inputs, 
users can enter a site's pH, DOC, and total hardness into the aluminum 
criteria calculator or use the lookup tables in the criteria document's 
appendix. Incorporating this document by reference will allow the State 
to access all of the underlying information and data EPA used to 
develop the 2018 national recommended criteria for aluminum. With 
access to this information, the State will have the flexibility to 
create its own version of the calculator built upon the underlying 
peer-reviewed models. EPA has made, and will continue to make, this 
document publicly available electronically through www.regulations.gov 
at the docket associated with this rulemaking and at www.epa.gov/wqc/aquatic-life-criteria-aluminum.

IV. Critical Low Flows and Mixing Zones

    To ensure that the final criteria for aluminum are applied 
appropriately to protect Oregon's aquatic life uses, EPA recommends 
Oregon use critical low flow values consistent with longstanding EPA 
guidance \14\ when calculating the available dilution for the purposes 
of determining the need for and establishing WQBELs in NPDES permits. 
Dilution is one of the primary mechanisms by which the concentrations 
of contaminants in effluent discharges are reduced following their 
introduction into a receiving water. During a low flow event, there is 
less water available for dilution, resulting in higher instream 
pollutant concentrations. If criteria are implemented using 
inappropriate critical low flow values (i.e., flow values that are too 
high), the resulting ambient

[[Page 14842]]

concentrations could exceed criteria values when low flows occur.\15\
---------------------------------------------------------------------------

    \14\ USEPA. 1991. Technical Support Document For Water Quality-
based Toxics Control. U.S. Environmental Protection Agency, Office 
of Water, Washington, DC EPA/505/2-90-001. http://www3.epa.gov/npdes/pubs/owm0264.pdf.
    \15\ USEPA. 2014. Water Quality Standards Handbook-Chapter 5: 
General Policies. U.S. Environmental Protection Agency, Office of 
Water. Washington, DC EPA-820-B-14-004. http://www.epa.gov/sites/production/files/2014-09/documents/handbook-chapter5.pdf.
---------------------------------------------------------------------------

    EPA notes that in ambient settings, critical low flow conditions 
used for NPDES permit limit derivation purposes may not always 
correspond with conditions of highest aluminum bioavailability and 
toxicity. EPA's NPDES Permit Writers' Manual describes the importance 
of characterizing effluent and receiving water critical conditions, 
because if a discharge is controlled so that it does not cause water 
quality criteria to be exceeded in the receiving water under critical 
conditions, then water quality criteria should be attained under all 
other conditions.\16\
---------------------------------------------------------------------------

    \16\ The same principle holds for developing a TMDL target, the 
total load.
---------------------------------------------------------------------------

    EPA's March 1991 Technical Support Document for Water Quality-based 
Toxics Control recommends two methods for calculating acceptable 
critical low flow values: The traditional hydrologically-based method 
developed by the USGS and a biologically based method developed by 
EPA.\17\ The hydrologically-based critical low flow value is determined 
statistically, using probability and extreme values, while the 
biologically-based critical low flow is determined empirically using 
the specific duration and frequency associated with the criterion. For 
the acute and chronic aluminum criteria, EPA recommends the following 
critical low flow values, except where modeling demonstrates that the 
most significant critical conditions occur at other than low flow:
---------------------------------------------------------------------------

    \17\ USEPA. 1991. Technical Support Document For Water Quality-
based Toxics Control. U.S. Environmental Protection Agency, Office 
of Water, Washington, DC EPA/505/2-90-001. http://www3.epa.gov/npdes/pubs/owm0264.pdf.

Acute Aquatic Life (CMC): 1Q10 or 1B3
Chronic Aquatic Life (CCC): 7Q10 or 4B3
Using the hydrologically-based method, the 1Q10 represents the lowest 
one-day average flow event expected to occur once every ten years, on 
average, and the 7Q10 represents the lowest seven-consecutive-day 
average flow event expected to occur once every ten years, on average. 
Using the biologically-based method, 1B3 represents the lowest one-day 
average flow event expected to occur once every three years, on 
average, and 4B3 represents the lowest four-consecutive-day average 
flow event expected to occur once every three years, on average.\18\
---------------------------------------------------------------------------

    \18\ See USEPA, 2014.
---------------------------------------------------------------------------

    The final criteria must be attained at the point of discharge 
unless Oregon authorizes a mixing zone. Where Oregon authorizes a 
mixing zone, the criteria would apply at the locations allowed by the 
mixing zone (i.e., the CMC would apply at the defined boundary of the 
acute mixing zone and the CCC would apply at the defined boundary of 
the chronic mixing zone).19 20
---------------------------------------------------------------------------

    \19\ See USEPA, 1991.
    \20\ Oregon Administrative Rules, Mixing Zones (Chapter 340, 
Division 41, Section 0053), https://secure.sos.state.or.us/oard/viewSingleRule.action?ruleVrsnRsn=68770.
---------------------------------------------------------------------------

V. Endangered Species Act

    Section 7(a)(2) of the ESA requires that each Federal agency ensure 
that any action authorized, funded, or carried out by such Agency is 
not likely to jeopardize the continued existence of any endangered or 
threatened species or result in the destruction or adverse modification 
of critical habitat. For this rule, EPA transmitted a Biological 
Evaluation to NOAA Fisheries Service and USFWS on September 20, 2019. 
NOAA Fisheries responded on October 18, 2019, that EPA's Biological 
Evaluation was insufficient to initiate formal consultation. EPA 
submitted a revised Biological Evaluation to NOAA Fisheries on January 
2, 2020. On February 13, 2020, EPA received a final Biological Opinion 
from USFWS that determined that EPA's proposed action is likely to 
adversely affect, but will not jeopardize the continued existence of 
bull trout and will not destroy or adversely modify its designated 
critical habitat. USFWS also concluded that the proposed action may 
affect, but is not likely to adversely affect, eight other federally-
listed species and is not likely to destroy or adversely modify the 
critical habitat for the other species that were included in the 
consultation. On July 1, 2020, EPA received a final Biological Opinion 
from NOAA Fisheries that determined that EPA's proposed action is 
likely to adversely affect, but will not jeopardize the continued 
existence of 18 listed species and will not destroy or adversely modify 
designated critical habitat for the species that were included in the 
consultation. The receipt of the NOAA Biological Opinion concludes the 
consultation for this rule under ESA Section 7(a)(2). Documents 
associated with ESA consultation are available in the docket associated 
with this rule (Docket ID: EPA-HQ-OW-2016-0694).

VI. Under what conditions would Federal standards be withdrawn?

    Under the CWA, Congress gave states and authorized tribes primary 
responsibility for developing and adopting WQS for their navigable 
waters (CWA Sections 303(a) through (c)). Although EPA is finalizing 
aluminum aquatic life criteria for Oregon's fresh waters subject to 
this rule on the basis of having disapproved Oregon's 2004 criteria in 
February 2013, Oregon retains the option to adopt and submit to the 
Agency acute and chronic aluminum criteria for the State's fresh waters 
consistent with CWA Section 303(c) and the Agency's implementing 
regulation at 40 CFR part 131. Indeed, EPA encourages Oregon to do so 
expeditiously. The Agency would approve the State's criteria if the 
criteria meet the requirements of CWA Section 303(c) and implementing 
regulation at 40 CFR part 131. If EPA's federally promulgated criteria 
are more stringent or prescriptive than the State's criteria, EPA's 
federally promulgated criteria are and will be the applicable water 
quality standard for purposes of the CWA until the Agency withdraws 
those federally promulgated standards (40 CFR 131.21(c)). EPA would 
expeditiously undertake such a rulemaking to withdraw the Federal 
criteria if and when Oregon adopts, and the Agency approves, 
corresponding criteria that meet the requirements of CWA Section 303(c) 
and implementing regulation at 40 CFR part 131. After such a withdrawal 
of EPA's federally promulgated criteria, the State's EPA-approved 
criteria would become the applicable criteria for CWA purposes (40 CFR 
131.21(c)).

VII. Alternative Regulatory Approaches and Implementation Mechanisms

    The Federal WQS regulation at 40 CFR part 131 provides several 
tools that Oregon has available to use at its discretion when 
implementing or deciding how to implement these aquatic life criteria, 
once effective. Among other things, EPA's WQS regulation: (1) Specifies 
how states and authorized tribes establish, modify, or remove 
designated uses (40 CFR 131.10); (2) specifies the requirements for 
establishing criteria to protect designated uses, including criteria 
modified to reflect site-specific conditions (40 CFR 131.11); (3) 
authorizes and provides regulatory guidelines for states and authorized 
tribes to adopt WQS variances that provide time to achieve the 
applicable WQS (40 CFR 131.14); and (4) allows states and authorized 
tribes to authorize

[[Page 14843]]

the use of compliance schedules in NPDES permits to meet WQBELs derived 
from the applicable WQS (40 CFR 131.15). Each of these approaches is 
discussed in more detail in the next sections. Whichever approach a 
state pursues, however, all NPDES permits would need to comply with 
EPA's regulations at 40 CFR 122.44(d)(1)(i).

A. Designating Uses

    EPA's final aluminum criteria apply to fresh waters in Oregon where 
the protection of fish and aquatic life is a designated use (see Oregon 
Administrative Rules at Chapter 340 Division 41). The Federal 
regulation at 40 CFR 131.10(g) provides requirements for establishing, 
modifying, and removing designated uses when attaining the use is not 
feasible for one of the six factors in the regulation. If Oregon 
removes designated uses such that no fish or aquatic life uses apply to 
any particular water body affected by this rule and adopts the highest 
attainable use,\21\ the State must also adopt criteria to protect the 
newly designated highest attainable use consistent with 40 CFR 131.11. 
It is possible that criteria other than the federally promulgated 
criteria would protect the highest attainable use. If EPA finds removal 
or modification of the designated use and the adoption of the highest 
attainable use and criteria to protect that use to be consistent with 
CWA Section 303(c) and the implementing regulation at 40 CFR part 131, 
the Agency would approve the revised WQS. EPA would then undertake a 
rulemaking to withdraw the corresponding Federal WQS for the relevant 
water(s).
---------------------------------------------------------------------------

    \21\ If a state or authorized tribe adopts a new or revised WQS 
based on a required use attainability analysis, then it must also 
adopt the highest attainable use (40 CFR 131.10(g)). The highest 
attainable use is the modified aquatic life, wildlife, or recreation 
use that is both closest to the uses specified in section 101(a)(2) 
of the CWA and attainable, based on the evaluation of the factor(s) 
in 40 CFR 131.10(g) that preclude(s) attainment of the use and any 
other information or analyses that were used to evaluate 
attainability. There is no required highest attainable use where the 
state demonstrates the relevant use specified in section 101(a)(2) 
of the Act and sub-categories of such a use are not attainable (see 
40 CFR 131.3(m)).
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B. WQS Variances

    Oregon's WQS provide authority to apply WQS variances when 
implementing federally promulgated criteria for aluminum, as long as 
such WQS variances are adopted consistent with 40 CFR 131.14 and 
submitted to EPA for review under CWA Section 303(c). The Federal 
regulation at 40 CFR 131.3(o) defines a WQS variance as a time-limited 
designated use and criterion, for a specific pollutant or water quality 
parameter, that reflects the highest attainable condition during the 
term of the WQS variance. A WQS variance may be appropriate if 
attaining the use and criterion would not be feasible during the term 
of the WQS variance because of one of the seven factors specified in 40 
CFR 131.14(b)(2)(i)(A), including if NPDES permit limits more stringent 
than technology-based controls would result in substantial and 
widespread economic and social impact. WQS variances adopted in 
accordance with 40 CFR 131.14 (including a public hearing consistent 
with 40 CFR 25.5) provide a flexible but defined pathway for states and 
authorized tribes to issue NPDES permits with limits that are based on 
the highest attainable condition during the term of the WQS variance 
thereby allowing dischargers to make water quality improvements when 
the WQS is not immediately attainable but may be in the future. When 
adopting a WQS variance, states and authorized tribes specify the 
interim requirements of the WQS variance by identifying a quantitative 
expression that reflects the highest attainable condition (HAC) during 
the term of the WQS variance, establishing the term of the WQS 
variance, and describing the pollutant control activities expected to 
occur over the specified term of the WQS variance. WQS variances 
provide a legal avenue by which NPDES permit limits can be written to 
comply with the WQS variance rather than the underlying WQS for the 
term of the WQS variance. If dischargers are still unable to meet the 
WQBELs derived from the applicable WQS once a WQS variance term is 
complete, the regulation allows the State to adopt a subsequent WQS 
variance if it is adopted consistent with 40 CFR 131.14. EPA is 
promulgating criteria that apply to the use designation that Oregon has 
already established. Oregon's WQS regulations currently include 
provisions to use WQS variances when implementing criteria, as long as 
such WQS variances are adopted consistent with 40 CFR 131.14 and 
approved by EPA. Oregon may use the State's EPA-approved WQS variance 
procedures when adopting such WQS variances.

C. NPDES Permit Compliance Schedules

    EPA's regulations at 40 CFR 122.47 and 131.15 address how 
permitting authorities can use schedules for compliance with a limit in 
the NPDES permit if the discharger needs additional time to undertake 
actions like facility upgrades or operation changes to meet a WQBEL 
based on the applicable WQS. EPA's regulation at 40 CFR 122.47 allows a 
permitting authority to include a compliance schedule in the NPDES 
permit, when appropriate and where authorized by the state, in order to 
provide a discharger with additional time to meet a WQBEL implementing 
applicable WQS. EPA's regulation at 40 CFR 131.15 requires that a state 
that intends to allow the use of NPDES permit compliance schedules 
adopt specific provisions authorizing their use and obtain EPA approval 
under CWA Section 303(c) to ensure that a decision to allow a permit 
compliance schedule is transparent and allows for public input (80 FR 
51022, August 21, 2015). EPA already has approved Oregon's State law 
provision authorizing the use of permit compliance schedules (see OAR 
340-041-0061), consistent with 40 CFR 131.15. Oregon's compliance 
schedule authorizing provision is not affected by this rule. Oregon is 
authorized to grant permit compliance schedules, as appropriate, based 
on the Federal water quality criteria for aluminum in Oregon, as long 
as such permit compliance schedules are consistent with EPA's 
permitting regulation at 40 CFR 122.47.

VIII. Economic Analysis

    To best inform the public of the potential impacts of this rule, 
EPA evaluated the potential costs associated with State implementation 
of the Agency's aluminum criteria based on available information. This 
analysis is documented in Economic Analysis for the Final Rule: Federal 
Aluminum Aquatic Life Criteria Applicable to Oregon, which can be found 
in the record for this rule. For this analysis, EPA assumed that Oregon 
fully implements its existing narrative water quality criteria for 
aluminum (i.e., ``baseline criteria'') and estimated the incremental 
impacts for compliance with the aluminum criteria in this rule. For 
point source costs, EPA assumed any NPDES-permitted facility that 
discharges aluminum would have reasonable potential and would be 
subject to effluent limits and would incur compliance costs if it chose 
to continue discharging. EPA also evaluated nonpoint sources that 
contribute aluminum loadings to waters that would be considered 
impaired for aluminum under the final criteria, which may incur 
incremental costs for additional best management practices (BMPs). The 
total cost annualized of this final rule would range from $1.2 million 
to $8.0 million at a 3% discount rate, and $1.2 million to $8.1 million 
at a 7% discount rate, for the first 10 years. See Economic Analysis 
for the Final Rule:

[[Page 14844]]

Federal Aluminum Aquatic Life Criteria Applicable to Oregon for a 
detailed summary of the information and assumptions EPA relied on to 
estimate potential costs for the final rule.

IX. Statutory and Executive Order Reviews

    Additional information about these statutes and Executive orders 
can be found at http://www2.epa.gov/laws-regulations/laws-and-executive-orders.

A. Executive Order 12866 (Regulatory Planning and Review) and Executive 
Order 13563 (Improving Regulation and Regulatory Review)

    This action is a significant regulatory action and was submitted to 
the Office of Management and Budget (OMB) for review. Any changes made 
during OMB's review have been documented in the docket. EPA prepared an 
analysis of the potential costs to NPDES dischargers associated with 
State implementation of the aluminum criteria in this rule. This 
analysis, Economic Analysis for the Final Rule: Federal Aluminum 
Aquatic Life Criteria Applicable to Oregon, is summarized in section 
VIII of the preamble and is available in the docket.

B. Executive Order 13771 (Reducing Regulations and Controlling 
Regulatory Costs)

    This action is considered an Executive Order 13771 regulatory 
action. Details on the estimated costs of this final rule can be found 
in EPA's analysis of the potential costs and benefits associated with 
this action.

C. Paperwork Reduction Act

    This action does not impose any new information-collection burden 
under the Paperwork Reduction Act. This action does not directly 
contain any information collection, reporting, or record-keeping 
requirements. OMB has previously approved the information collection 
requirements contained in the existing regulations 40 CFR part 131 and 
has assigned OMB control number 2040-0049.

D. Regulatory Flexibility Act

    The Agency certifies that this action will not have a significant 
economic impact on a substantial number of small entities under the 
Regulatory Flexibility Act. This action will not impose any 
requirements on small entities. The EPA-promulgated WQS are implemented 
through various water quality control programs including the NPDES 
program, which limits discharges to navigable waters except in 
compliance with a NPDES permit. CWA Section 301(b)(1)(C) \22\ and EPA's 
implementing regulations at 40 CFR 122.44(d)(1) and 
122.44(d)(1)(vii)(A) provide that all NPDES permits shall include any 
limits on discharges that are necessary to meet applicable WQS. Thus, 
under the CWA, EPA's promulgation of WQS establishes WQS that the State 
implements through the NPDES permit process. While the State has 
discretion in developing discharge limits, as needed to meet the WQS, 
those limits, per regulations at 40 CFR 122.44(d)(1)(i), ``must control 
all pollutants or pollutant parameters (either conventional, 
nonconventional, or toxic pollutants) which the Director determines are 
or may be discharged at a level that will cause, have the reasonable 
potential to cause, or contribute to an excursion above any [s]tate 
water quality standard, including [s]tate narrative criteria for water 
quality.'' As a result of this action, the State of Oregon will need to 
ensure that permits it issues include any limitations on discharges 
necessary to comply with the WQS established in the final rule. In 
doing so, the State will have a number of choices associated with 
permit writing. Oregon's implementation of the rule may ultimately 
result in new or revised permit conditions for some dischargers. EPA is 
unaware of any current permit holders or other entities that would be 
required to obtain new permits or update existing permits as a result 
of this action, including small entities. EPA's action, by itself, does 
not impose any requirements on small entities; that is, the 
requirements are not self-implementing.
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    \22\ CWA Section 301(b) Timetable for achievement of objectives. 
In order to carry out the objective of this chapter there shall be 
achieved--(1)(C): Not later than July 1, 1977, any more stringent 
limitation, including those necessary to meet water quality 
standards, treatment standards, or schedules of compliance, 
established pursuant to any State law or regulations (under 
authority preserved by section 1370 of this title) or any other 
Federal law or regulation, or required to implement any applicable 
water quality standard established pursuant to this chapter.
---------------------------------------------------------------------------

E. Unfunded Mandates Reform Act (UMRA)

    This action does not contain any unfunded mandate as described in 
UMRA, 2 U.S.C. 1531-1538, and does not significantly or uniquely affect 
small goverments. This action imposes no enforceable duty on any state, 
local, or tribal governments or the private sector.

F. Executive Order 13132 (Federalism)

    This action does not have federalism implications. EPA believes, 
however, that this action may be of significant interest to state 
governments. Consistent with EPA's policy to promote communications 
between EPA and state and local governemnts, EPA consulted with Oregon 
early in the process of developing this rulemaking to permit them to 
have meaningful and timely input into its development. EPA discussed 
with Oregon the Agency's development of the Federal rulemaking and 
clarified early in the process that if and when the State decided to 
develop and establish its own aluminum standards, EPA would assist the 
State in its process. During these discussions, EPA explained the 
scientific basis for the aluminum criteria to protect aquatic life for 
fresh waters in Oregon; the Agency's consideration of comments received 
during the public comment period associated with this rulemaking; and 
the overall timing of the Federal rulemaking effort. EPA took these 
discussions with the State into account during the drafting of this 
rule.

G. Executive Order 13175 (Consultation and Coordination With Indian 
Tribal Governments)

    This action does not have tribal implications as specified in 
Executive Order 13175. This rule does not impose substantial direct 
compliance costs on federally recognized tribal governments, nor does 
it substantially affect the relationship between the Federal Government 
and tribes, or the distribution of power and responsibilities between 
the Federal Government and tribes. Thus, Executive Order 13175 does not 
apply to this action.
    Consistent with EPA Policy on Consultation and Coordination with 
Indian Tribes, the Agency offered government to government consultation 
to potentially affected tribes during the development of this action. 
EPA sent letters to tribal leaders of potentially affected tribes in 
the Pacific Northwest offering government-to-government consultation on 
the proposed aluminum rule for fresh waters in Oregon. EPA held two 
conference calls (June 4 and June 13, 2019) with the interested tribal 
water quality staff to explain the Agency's proposed action and 
timeline. No tribes requested formal government-to-government 
consultation on this rulemaking. EPA has continued to apprise the 
tribes of the status of its final action.

H. Executive Order 13045 (Protection of Children From Environmental 
Health and Safety Risks)

    EPA interprets Executive Order 13045 as applying only to those 
regulatory actions that concern environmental health or safety risks 
that the Agency

[[Page 14845]]

has reason to believe may disproportionately affect children, per the 
definition of ``covered regulatory action'' in section 2-202 of the 
Executive order. This action is not subject to Executive Order 13045 
because it does not concern an environmental health risk or safety 
risk.

I. Executive Order 13211 (Actions that Significantly Affect Energy 
Supply, Distribution, or Use)

    This action is not a ``significant energy action'' because it is 
not likely to have a significant adverse effect on the supply, 
distribution, or use of energy.

J. National Technology Transfer and Advancement Act of 1995

    This rule does not involve technical standards.

K. Executive Order 12898 (Federal Actions To Address Environmental 
Justice in Minority Populations and Low-Income Populations)

    EPA believes that this action does not have disproportionately high 
and adverse human health or environmental effects on minority 
populations, low income populations and/or indigenous peoples, as 
specified in Executive Order 12898 (59 FR 7629, February 16, 1994). The 
freshwater criteria for aluminum in Oregon will support the health and 
abundance of aquatic life in Oregon, and will therefore benefit all 
communities that rely on Oregon's ecosystems.

L. Congressional Review Act (CRA)

    This action is subject to the CRA, and EPA will submit a rule 
report to each House of the Congress and to the Comptroller General of 
the United States. This action is not a ``major rule'' as defined by 5 
U.S.C. 804(2).

List of Subjects in 40 CFR Part 131

    Environmental protection, Incorporation by reference, Indians-
lands, Intergovernmental relations, Reporting and recordkeeping 
requirements, Water pollution control.

    This document of the Environmental Protection Agency was signed on 
December 30, 2020, by Andrew Wheeler, Administrator, pursuant to the 
Third Amended Consent Decree in Northwest Environmental Advocates v. 
EPA, No. 15-cv-0663-BR (D. Ore., Mar. 16, 2020). That rulemaking 
document with the original signature and date is maintained by EPA. For 
administrative purposes only, and in compliance with requirements of 
the Office of the Federal Register, the undersigned EPA Official re-
signs the document for publication, as an official document of the 
Environmental Protection Agency. This administrative process in no way 
alters the legal effect of this document upon publication in the 
Federal Register.

    Signed in Washington, DC.
Jane Nishida,
Acting Administrator.

    For the reasons set forth in the preamble, EPA amends 40 CFR part 
131 as follows:

PART 131--WATER QUALITY STANDARDS

0
1. The authority citation for part 131 continues to read as follows:

    Authority: 33 U.S.C. 1251 et seq.

Subpart D--Federally Promulgated Water Quality Standards

0
2. Add Sec.  131.47 to read as follows:


Sec.  131.47  Aquatic life criteria for aluminum in Oregon.

    (a) Scope. This section promulgates aquatic life criteria for 
aluminum in fresh waters in Oregon that are jurisdictional under the 
Clean Water Act.
    (b) Criteria for aluminum in Oregon. The aquatic life criteria in 
Table 1 to this paragraph (b) apply to all fresh waters in Oregon that 
are jurisdictional under the Clean Water Act to protect the fish and 
aquatic life designated uses.

                Table 1 to Paragraph (b)--Aluminum Aquatic Life Criteria for Oregon Fresh Waters
----------------------------------------------------------------------------------------------------------------
                                                            Criterion maximum           Criterion continuous
                  Metal                     CAS No.      concentration (CMC) \3\       concentration (CCC) \4\
                                                              ([micro]g/L)                  ([micro]g/L)
----------------------------------------------------------------------------------------------------------------
Aluminum 1 2.............................    7429905  Acute (CMC) and chronic (CCC) freshwater aluminum criteria
                                                       values for a site shall be calculated using the 2018
                                                       Aluminum Criteria Calculator (Aluminum Criteria
                                                       Calculator V.2.0.xlsx), or a calculator in R or other
                                                       software package using the same 1985 Guidelines
                                                       calculation approach and underlying model equations as in
                                                       the Aluminum Criteria Calculator V.2.0.xlsx, as defined
                                                       in EPA's Final Aquatic Life Ambient Water Quality
                                                       Criteria for Aluminum.\5\
----------------------------------------------------------------------------------------------------------------
\1\ To apply the aluminum criteria for Clean Water Act purposes, criteria values based on ambient water
  chemistry conditions must protect the water body over the full range of water chemistry conditions, including
  during conditions when aluminum is most toxic.
\2\ These criteria are based on aluminum toxicity studies where aluminum was analyzed using total recoverable
  analytical methods. Oregon may utilize total recoverable analytical methods to implement the criteria. For
  characterizing ambient waters, Oregon may also utilize, as scientifically appropriate and as allowable by
  State and Federal regulations, analytical methods that measure the bioavailable fraction of aluminum (e.g.,
  utilizing a less aggressive initial acid digestion, such as to a pH of approximately 4 or lower, that includes
  the measurement of amorphous aluminum hydroxide yet minimizes the measurement of mineralized forms of aluminum
  such as aluminum silicates associated with suspended sediment particles or clays). Oregon shall use
  measurements of total recoverable aluminum where required by Federal regulations.
\3\ The CMC is the highest allowable one-hour average ambient concentration of aluminum. The CMC is not to be
  exceeded more than once every three years. The CMC is rounded to two significant figures.
\4\ The CCC is the highest allowable four-day average ambient concentration of aluminum. The CCC is not to be
  exceeded more than once every three years. The CCC is rounded to two significant figures.
\5\ EPA-822-R-18-001, Final Aquatic Life Ambient Water Quality Criteria for Aluminum--2018, December 2018, is
  incorporated by reference into this section with the approval of the Director of the Federal Register under 5
  U.S.C. 552(a) and 1 CFR part 51. All approved material is available from U.S. Environmental Protection Agency,
  Office of Water, Health and Ecological Criteria Division (4304T), 1200 Pennsylvania Avenue, NW, Washington, DC
  20460; telephone number: (202) 566-1143, www.epa.gov/wqc/aquatic-life-criteria-aluminum. It is also available
  for inspection at the National Archives and Records Administration (NARA). For information on the availability
  of this material at NARA, email [email protected] or go to www.archives.gov/federal-register/cfr/ibr-locations.html.

    (c) Applicability. (1) The criteria in paragraph (b) of this 
section are the applicable acute and chronic aluminum aquatic life 
criteria in all fresh waters in Oregon that are jurisdictional under 
the Clean Water Act to protect the fish and aquatic life designated 
uses.
    (2) The criteria established in this section are subject to 
Oregon's general rules of applicability in the same way and to the same 
extent as are other federally promulgated and state-adopted numeric 
criteria when applied to fresh waters in Oregon that are jurisdictional 
under the Clean Water Act to protect the fish and aquatic life 
designated uses.
    (3) For all waters with mixing zone regulations or implementation 
procedures, the criteria apply at the

[[Page 14846]]

appropriate locations within or at the boundary of the mixing zones and 
outside of the mixing zones; otherwise the criteria apply throughout 
the water body including at the end of any discharge pipe, conveyance, 
or other discharge point within the water body.

[FR Doc. 2021-05428 Filed 3-18-21; 8:45 am]
BILLING CODE 6560-50-P