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[Federal Register Volume 81, Number 74 (Monday, April 18, 2016)]
[Proposed Rules]
[Pages 22555-22566]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2016-08038]

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 131

[EPA-HQ-OW-2016-0012; FRL-9944-70-OW]
RIN 2040-AF60

Aquatic Life Criteria for Copper and Cadmium in Oregon

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: The Environmental Protection Agency (EPA) proposes to 
establish federal Clean Water Act (CWA) aquatic life criteria for 
freshwaters under the state of Oregon's jurisdiction, to protect 
aquatic life from the effects of exposure to harmful levels of copper 
and cadmium. In 2013, EPA determined that the freshwater acute cadmium 
criterion and freshwater acute and chronic copper criteria that Oregon 
adopted in 2004 did not meet CWA requirements to protect aquatic life 
in the state. Therefore, EPA proposes to establish federal freshwater 
criteria for cadmium and copper that take into account the best 
available science, EPA policies, guidance and legal requirements, to 
protect aquatic life uses in Oregon.

DATES: Comments must be received on or before June 2, 2016.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-HQ-OW-
2016-0012, at http://www.regulations.gov. Follow the online 
instructions for submitting comments. Once submitted, comments cannot 
be edited or removed from Regulations.gov. EPA may publish any comment 
received to its public docket. Do not submit electronically any 
information you consider to be Confidential Business Information (CBI) 
or other information whose disclosure is restricted by statute. 
Multimedia submissions (audio, video, etc.) must be accompanied by a 
written comment. The written comment is considered the official comment 
and should include discussion of all points you wish to make. EPA will 
generally not consider comments or comment contents located outside of 
the primary submission (i.e. on the web, cloud, or other file sharing 
system). For additional submission methods, the full EPA public comment 
policy, information about CBI or multimedia submissions, and general 
guidance on making effective comments, please visit http://www2.epa.gov/dockets/commenting-epa-dockets.
    EPA is offering two virtual public hearings so that interested 
parties may also provide oral comments on this proposed rule. The first 
hearing will be on Monday, May 16, 2016 from 4:00pm to 6:00pm Pacific 
Time. The second hearing will be on Tuesday, May 17, 2016 from 9:00am 
to 11:00am Pacific Time. For more details on the public hearings and a 
link to register, please visit http://www.epa.gov/wqs-tech/water-quality-standards-regulations-oregon.

FOR FURTHER INFORMATION CONTACT: Erica Fleisig, Office of Water, 
Standards and Health Protection Division (4305T), Environmental 
Protection Agency, 1200 Pennsylvania Avenue NW., Washington, DC 20460; 
telephone number: (202) 566-1057; email address: fleisig.erica@epa.gov.

SUPPLEMENTARY INFORMATION: This proposed rule is organized as follows:

I. General Information
    Does this action apply to me?
II. Background
    A. Statutory and Regulatory Authority
    B. EPA's Disapproval of Oregon's Freshwater Copper and Cadmium 
Criteria
    C. General Recommended Approach for Deriving Aquatic Life 
Criteria
III. Freshwater Cadmium Aquatic Life Criteria
    A. EPA's National Recommended Cadmium Criteria
    B. Proposed Acute Cadmium Criterion for Oregon's Freshwaters
    C. Implementation of Proposed Freshwater Acute Cadmium Criterion 
in Oregon
IV. Freshwater Copper Aquatic Life Criteria
    A. EPA's National Recommended Copper Criteria
    B. Proposed Acute and Chronic Copper Criteria for Oregon's 
Freshwaters
    C. Implementation of Proposed Freshwater Acute and Chronic 
Copper Criteria in Oregon
    D. Ongoing State Efforts To Develop Copper Criteria for Oregon's 
Freshwaters
    E. Incorporation by Reference
V. Critical Low-Flows and Mixing Zones
VI. Endangered Species Act
VII. Under what conditions will federal standards be not promulgated 
or withdrawn?
VIII. Alternative Regulatory Approaches and Implementation 
Mechanisms
    A. Designating Uses
    B. Site-Specific Criteria
    C. Variances
    D. Compliance Schedules
IX. Economic Analysis
    A. Identifying Affected Entities
    B. Method for Estimating Costs
    C. Results
X. Statutory and Executive Order Reviews
    A. Executive Order 12866 (Regulatory Planning and Review) and 
Executive Order 13563 (Improving Regulation and Regulatory Review)
    B. Paperwork Reduction Act
    C. Regulatory Flexibility Act
    D. Unfunded Mandates Reform Act
    E. Executive Order 13132 (Federalism)

[[Page 22556]]

    F. Executive Order 13175 (Consultation and Coordination With 
Indian Tribal Governments)
    G. Executive Order 13045 (Protection of Children From 
Environmental Health and Safety Risks)
    H. Executive Order 13211 (Actions That Significantly Affect 
Energy Supply, Distribution, or Use)
    I. National Technology Transfer and Advancement Act of 1995
    J. Executive Order 12898 (Federal Actions To Address 
Environmental Justice in Minority Populations and Low-Income 
Populations)

I. General Information

Does this action apply to me?

    Copper and cadmium naturally occur at low levels in surface waters 
but, at higher concentrations, can be toxic to aquatic life. 
Anthropogenic activities such as coal combustion, mining, 
electroplating, iron and steel production, and use of pigments, 
fertilizers and pesticides, can increase levels of cadmium in the 
environment. Sources of elevated copper in the environment include 
mining, fabrication of paper, metal products and electronics, and 
discharges from wastewater treatment plants.
    Entities such as industries, stormwater management districts, or 
publicly owned treatment works (POTWs) that discharge pollutants to 
freshwaters of the United States under the state of Oregon's 
jurisdiction could be indirectly affected by this rulemaking, because 
federal WQS promulgated by EPA would be applicable to CWA regulatory 
programs, such as National Pollutant Discharge Elimination System 
(NPDES) permitting. Citizens concerned with water quality in Oregon 
could also be interested in this rulemaking. Categories and entities 
that could potentially be affected include the following:

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                                      Examples of potentially affected
             Category                             entities
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Industry..........................  Industries discharging pollutants to
                                     freshwaters of the United States in
                                     Oregon.
Municipalities....................  Publicly owned treatment works or
                                     other facilities discharging
                                     pollutants to freshwaters of the
                                     United States in Oregon.
Stormwater Management Districts...  Entities responsible for managing
                                     stormwater runoff in the state of
                                     Oregon.
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    This table is not intended to be exhaustive, but rather provides a 
guide for readers regarding entities that could be indirectly affected 
by this action. Any parties or entities who depend upon or contribute 
to the water quality of Oregon's waters could be affected by this 
proposed rule. To determine whether your facility or activities could 
be affected by this action, you should carefully examine this proposed 
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.

II. Background

A. Statutory and Regulatory Authority

    CWA section 101(a)(2) establishes a national goal wherever 
attainable of ``water quality which provides for the protection and 
propagation of fish, shellfish, and wildlife and provides for 
recreation in and on the water . . . '' These are commonly referred to 
as the ``fishable/swimmable'' goals of the CWA.
    CWA section 303(c) (33 U.S.C. 1313(c)) directs states to adopt WQS 
for their waters subject to the CWA. CWA section 303(c)(2)(A) and EPA's 
implementing regulations at 40 CFR part 131 require, among other 
things, that a state's WQS specify designated uses of the waters, and 
water quality criteria that protect those uses. EPA's 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.'' 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 are required to review applicable WQS at least once every 
three years and, if appropriate, revise or adopt new standards (CWA 
section 303(c)(1)). Any new or revised WQS must be submitted to EPA for 
review and approval or disapproval (CWA section 303(c)(2)(A) and 
(c)(3)). If EPA determines that a WQS that a state submits to EPA for 
review does not meet the requirements of the CWA, EPA must notify the 
state of the changes necessary to meet CWA requirements (CWA section 
303(c)(3)). CWA section 303(c)(3) and (c)(4) further specify that if a 
state does not make those changes within 90 days of notification, EPA 
must promptly prepare and publish a revised or new WQS for the state. 
Under CWA section 303(c)(4)(B), the Administrator is authorized to 
determine, even in the absence of a state submission, that a new or 
revised standard is needed to meet CWA requirements.
    Under CWA section 304(a), EPA periodically publishes criteria 
recommendations for states to consider when adopting water quality 
criteria for particular pollutants to meet the CWA section 101(a)(2) 
goals. In establishing numeric criteria, states should adopt water 
quality criteria based on EPA's CWA section 304(a) criteria, section 
304(a) criteria modified to reflect site-specific conditions, or other 
scientifically defensible methods (40 CFR 131.11(b)(1)). Ultimately, 
whatever methods are used, criteria must protect the designated use and 
be based on sound scientific rationale (40 CFR 131.11(a)(1)).

B. EPA's Disapproval of Oregon's Freshwater Copper and Cadmium Criteria

    On July 8, 2004, Oregon submitted 89 revised aquatic life criteria 
for 25 toxic pollutants to EPA for review under CWA 303(c). Many of 
Oregon's revised criteria were the same as EPA's nationally recommended 
304(a) aquatic life criteria at the time. A subsequent consent decree 
between EPA and Northwest Environmental Advocates established deadlines 
for EPA to complete its CWA 303(c) review of Oregon's aquatic life 
criteria. Prior to taking a final action on the aquatic life criteria, 
EPA requested formal consultation with the National Marine Fisheries 
Service (NMFS) and the U.S. Fish and Wildlife Service (USFWS) on its 
proposed approval of the criteria, consistent with section 7 of the 
Endangered Species Act (ESA). EPA initiated this consultation on 
January 14, 2008, by submitting a biological evaluation to the NMFS and 
USFWS, which contained an analysis of the potential effects of EPA's 
proposed approval of Oregon's criteria on

[[Page 22557]]

threatened and endangered species in Oregon.\1\
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    \1\ EPA initiated consultation on Oregon's aluminum criteria 
based on its mistaken belief that Oregon's criteria were entirely 
equivalent to EPA's 1988 304(a) recommended criteria. However, 
Oregon's criteria specified that they applied ``to waters with pH 
values less than 6.6 and hardness values less than 12 mg/L (as 
CaCO3)'' whereas EPA's 1988 304(a) recommended criteria 
``apply at pH values of 6.5-9.0.'' EPA ultimately disapproved 
Oregon's criteria because the state had not supplied a scientific 
rationale for the difference between Oregon's statement of the 
conditions under which the criteria would be valid and EPA's 
specified pH range for the criteria. Since EPA was disapproving the 
aluminum criteria, it sent a letter to the NMFS and USFWS 
identifying this change. The USFWS had already completed and 
transmitted its non-jeopardy opinion to EPA by that point, so it was 
too late for EPA to withdraw the consultation request for aluminum. 
However, in the letter to the NMFS, EPA withdrew its request for 
consultation on Oregon's acute and chronic aluminum criteria.
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    On July 31, 2012, the USFWS provided its biological opinion to EPA. 
The biological opinion found that EPA's proposed approval of Oregon's 
aquatic life criteria would not jeopardize the continued existence of 
endangered species for which USFWS was responsible. However, on August 
14, 2012, the NMFS concluded in its biological opinion that seven of 
Oregon's revised freshwater criteria would jeopardize the continued 
existence of endangered species in Oregon for which the NMFS was 
responsible. These seven criteria were the freshwater criteria Oregon 
adopted to protect aquatic life from adverse acute and chronic effects 
from ammonia, copper, and aluminum,\2\ as well as the criterion to 
prevent adverse acute effects from cadmium. The NMFS biological opinion 
contained Reasonable and Prudent Alternatives (RPAs) for each of the 
four pollutants that would avoid the likelihood of jeopardy to the 
species. For acute ammonia and cadmium, and acute and chronic aluminum, 
the RPA specified a process for deriving revised freshwater criteria. 
For the chronic ammonia criterion, the RPA specified that Oregon's 
previously applicable chronic ammonia criterion, which was based on 
EPA's 1985 304(a) recommendation, should remain in place. The NMFS RPA 
for acute and chronic copper criteria was to establish ``a new acute 
criterion of 2.3 [micro]g/L for freshwater copper using EPA's 2007 
[Biotic Ligand Model (BLM)]-based aquatic life criteria'' and ``a new 
chronic criterion of 1.45 [micro]g/L for freshwater copper using EPA's 
2007 BLM-based aquatic life criteria.'' On January 19, 2016 the NMFS 
sent EPA a letter clarifying that ``. . . use of EPA's 2007 copper BLM 
to derive copper criteria that are specific to individual locations or 
ecoregions is appropriate under the RPA, provided that the state of 
Oregon has the appropriate data to input into the BLM and appropriate 
procedures to use the BLM.''
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    \2\ The NMFS acknowledged EPA's request to withdraw the aluminum 
criteria from consultation; however, they did not have time to 
modify the biological opinion to exclude acute and chronic aluminum 
from the document.
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    On January 31, 2013, EPA disapproved several of Oregon's revised 
aquatic life criteria under CWA 303(c), including the acute cadmium 
freshwater criterion, and the acute and chronic freshwater ammonia, 
copper, and aluminum criteria that the NMFS concluded would jeopardize 
endangered species in Oregon.\3\ Oregon made changes to its freshwater 
ammonia criteria in response to EPA's 2013 disapproval and submitted 
revised freshwater ammonia criteria to EPA on January 23, 2015. EPA 
evaluated the revised freshwater ammonia criteria's consistency with 
the RPA for ammonia contained in the 2012 NMFS biological opinion, 
concluded that the revised criteria would protect endangered species in 
Oregon, and approved the revised criteria on August 4, 2015. Although 
Oregon has been working closely with EPA to derive protective 
freshwater copper criteria that the state would adopt in a future 
rulemaking, the state has not yet addressed EPA's 2013 disapproval of 
its freshwater criteria for cadmium, copper, and aluminum. EPA is 
proposing the freshwater acute cadmium, and acute and chronic copper 
criteria in this rule in accordance with CWA section 303(c)(3) and 
(c)(4) requirements. EPA intends to propose freshwater acute and 
chronic criteria for aluminum in Oregon in a separate rulemaking at a 
later date following completion of updates to EPA's CWA section 304(a) 
recommended criteria for aluminum.
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    \3\ The NMFS determined that the criterion Oregon adopted to 
protect aquatic life from adverse chronic effects from cadmium would 
not jeopardize the continued existence of endangered species; EPA 
approved Oregon's chronic cadmium criterion in January 2013.
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C. General Recommended Approach for Deriving Aquatic Life Criteria

    Under the Agency's CWA section 304(a) authority, EPA develops 
methodologies and specific criteria to protect aquatic life and human 
health. These methodologies and criteria are subject to public as well 
as scientific expert review before EPA releases them as formal agency 
recommendations for states to consider when developing and adopting 
water quality criteria. To derive criteria for the protection of 
aquatic life, EPA follows its Guidelines for Deriving Numerical 
National Water Quality Criteria for the Protection of Aquatic Organisms 
and Their Uses (referred to as the ``1985 Guidelines'').\4\ These 
guidelines describe an objective way to estimate the highest 
concentration of a substance in water that will not present a 
significant risk to the aquatic organisms in the water.
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    \4\ 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. http://www.epa.gov/sites/production/files/2015-08/documents/guidelines_for_deriving_nnwqc_for_the_protectin_of_aquatic_organisms_and_their_uses.pdf.
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    Numeric criteria derived using EPA's 1985 Guidelines are expressed 
as short-term (acute) and long-term (chronic) values. The combination 
of a criteria maximum concentration (CMC), a one-hour average value, 
and a criteria continuous concentration (CCC), a four-day average 
value, protects aquatic life from acute and chronic toxicity, 
respectively.\5\ Neither value is to be exceeded more than once in 
three years. EPA selected the CMC's one-hour averaging period because 
high concentrations of certain pollutants can cause death in one to 
three hours, and selected the CCC's four-day averaging period to 
prevent increased adverse effects on sensitive life stages. EPA based 
its once every three years exceedance frequency recommendation on the 
ability of aquatic ecosystems to recover from the exceedances (when the 
average concentration over the duration of the averaging period is 
above the CCC or the CMC).\6\
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    \5\ In EPA's 2001 304(a) recommendation for cadmium and the 2007 
304(a) recommendation for copper, EPA specified that the acute 
cadmium and copper criteria (CMCs) had 24-hour (rather than one-
hour) durations. Subsequently, in the 2016 304(a) update for 
cadmium, EPA revised the cadmium CMC duration to one-hour to reflect 
the acute criteria duration recommended in the 1985 Guidelines. EPA 
proposes that the duration for both copper and cadmium CMCs in this 
rule be one-hour, to be consistent with the updated 304(a) 
recommendation for cadmium and with EPA's 1985 Guidelines. As 
articulated on page 35 of USEPA's 1991 Technical Support Document 
for Water Quality-based Toxics Control, March, 1991 (EPA/505/2-90-
001), a one-hour averaging period is expected to be fully protective 
for the fastest-acting toxicants, and even more protective for 
slower-acting toxicants.
    \6\ See USEPA, 1985. Pages. 5-7.
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    Since fresh and salt waters have different chemical compositions 
and different species assemblages, it is necessary to derive separate 
acute and chronic criteria for fresh and salt waters. Additionally, 
criteria may be based on certain water characteristics (e.g., pH, 
temperature, hardness, dissolved organic carbon (DOC), etc.), since 
water chemistry can influence a pollutant's

[[Page 22558]]

bioavailability and toxicity. For metals in particular, EPA recommends 
expressing the criteria as functions of chemical constituents of the 
water, since those constituents can form complexes with metals and 
render the metals biologically unavailable, or compete with metals for 
binding sites on aquatic organisms. Additionally, in 1995, EPA 
recommended that criteria for metals be expressed as dissolved (rather 
than total) metal concentrations, since the concentration of dissolved 
metal better approximates the toxic fraction.\7\
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    \7\ Water Quality Standards; Establishment of Numeric Criteria 
for Priority Toxic Pollutants; States' Compliance--Revision of 
Metals Criteria, May 4, 1995, 60 FR 22229.
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    The 1985 Guidelines specify that it is necessary to have toxicity 
test data from a minimum of eight families of aquatic organisms to 
derive criteria. These families are intended to be representative of a 
wide spectrum of aquatic life, and act as surrogates for untested 
species. Therefore, the specific test organisms do not need to be 
present in the water(s) where the criteria will apply. However, states 
may develop site-specific criteria using species residing at the site 
if they maintain similar broad taxonomic representation. EPA derives 
acute criteria from 48- to 96-hour tests of lethality or 
immobilization. EPA derives chronic criteria from longer term (often 
longer than 28-day) tests that measure survival, growth, or 
reproduction. If sufficient chronic toxicity data are not available, 
chronic criteria are set by determining a ratio of acutely toxic to 
chronically toxic concentrations. Where appropriate, EPA recommends 
that criteria are lowered to protect commercially or recreationally 
important species.
    For more detailed information on how EPA derives protective aquatic 
life criteria, see the 1985 Guidelines.\8\
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    \8\ See USEPA, 1985.
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III. Freshwater Cadmium Aquatic Life Criteria

A. EPA's National Recommended Cadmium Criteria

    Water hardness (determined by the presence of calcium and magnesium 
ions, and expressed as calcium carbonate, CaCO3) affects the 
toxicity of cadmium, as calcium and magnesium ions compete with cadmium 
for binding sites on aquatic organisms' gills. Organisms show more 
sensitivity to cadmium in lower hardness (soft) water than in hard 
water. EPA therefore expresses the national 304(a) recommended acute 
and chronic cadmium criteria as functions of water hardness.
    EPA previously published final 304(a) recommended aquatic life 
criteria for cadmium in 2001.\9\ In recent years, EPA embarked on an 
update to the science underlying the 2001 national cadmium criteria 
recommendations. This work included a literature search of 
toxicological databases, evaluation of those data, recalculation of the 
criteria based on those data updates, and revision of supporting 
documentation. In 2015, EPA completed an external peer review of the 
draft updated cadmium criteria and revised them accordingly. EPA then 
published the draft criteria for public comment in the Federal 
Register, and solicited comments for 60 days (December 1, 2015, 80 FR 
75097). EPA revised the criteria to respond to the public comments, and 
expects the final national updated 304(a) recommended cadmium criteria 
to be published in the Federal Register in April 2016.\10\
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    \9\ The 2001 304(a) national recommended freshwater cadmium 
criteria were the same criteria that Oregon adopted and submitted to 
EPA in 2004.
    USEPA. 2001. 2001 Update of Ambient Water Quality Criteria for 
Cadmium. U.S. Environmental Protection Agency, Office of Water, 
Washington, DC EPA-822-R-01-001. http://water.epa.gov/scitech/swguidance/standards/criteria/current/index.cfm#altable.
    \10\ See http://www.epa.gov/wqc/aquatic-life-criteria-cadmium.
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B. Proposed Acute Cadmium Criterion for Oregon's Freshwaters

    To protect aquatic life in Oregon's freshwaters from acute toxic 
effects from cadmium, EPA proposes the one-hour average CMC not exceed 
e(0.9789 x ln(hardness)-3.866) x CF ([micro]g/L, dissolved) 
more than once every three years. ``CF'' refers to the conversion 
factor and is used to convert the total recoverable concentration to a 
dissolved concentration, consistent with EPA's policy on criteria for 
metals. The equation for the acute cadmium CF is CF = 1.136672-[(ln 
hardness) x (0.041838)]. This is the same freshwater acute cadmium 
criterion (and associated CF) as in EPA's final 2016 national updated 
304(a) recommended cadmium criteria. The (ln hardness) term in both the 
CMC equation and the CF equation is the natural logarithm of the 
ambient water hardness in mg/L (CaCO3).
    Where site-specific hardness data are unavailable, EPA proposes to 
use a default hardness concentration of 25 mg/L (as CaCO3), 
which equates to a one-hour average dissolved cadmium concentration of 
0.49 [micro]g/L.\11\ As with other metals criteria in Oregon that are 
expressed as a function of hardness, the acute cadmium criterion 
equation requires ambient hardness data that represent the entire site 
to which the criterion will apply to calculate an acute cadmium 
criterion for a site. EPA strongly recommends that Oregon collect 
sufficiently representative ambient hardness data to determine the 
appropriate acute cadmium criterion for a site. However, EPA recognizes 
that, in certain situations, there will not be sufficiently 
representative ambient hardness data to adequately characterize the 
site; thus, EPA is proposing a default hardness concentration to 
provide clarity to NPDES permit writers and water body assessors on 
what acute cadmium criterion applies at the site. EPA evaluated the 
protectiveness of using a default hardness of 25 mg/L by calculating 
the 10th percentile of existing hardness concentrations in Oregon's 
waters, using U.S. Geological Survey (USGS) data on calcium and 
magnesium ion levels in waters within each of the nine Level III 
ecoregions in Oregon.\12\ EPA selected the 10th percentile as a 
statistic that is both protective and can be reliably determined from 
small sample sizes. The USGS dataset that EPA evaluated indicates that 
the lowest 10th percentile ecoregional hardness in Oregon is 28 mg/L, 
suggesting that a default hardness concentration of 25 mg/L would be 
protective of the majority of Oregon's waters. However, certain water 
bodies in Oregon, such as relatively un-impacted headwaters, could have 
hardness concentrations below 25 mg/L, and Oregon should prioritize 
collecting ambient hardness data in those waters to ensure the 
resulting acute cadmium criteria are protective of aquatic life.
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    \11\ Oregon currently uses a default hardness concentration of 
25 mg/L if no hardness data are available to calculate hardness-
dependent metals criteria. See Oregon Department of Environmental 
Quality. 2014. Methodology for Oregon's 2012 Water Quality Report 
and List of Water Quality Limited Waters (Pursuant to Clean Water 
Act Sections 303(d) and 305(b) and OAR 340-041-0046). Pages 76-77.
    \12\ EPA used 10th percentile calcium and magnesium data from 
USEPA's Draft Technical Support Document: Recommended Estimates for 
Missing Water Quality Parameters for Application in EPA's Biotic 
Ligand Model, February 16, 2016 (EPA 820-R-15-106), along with the 
following equation to relate calcium and magnesium to hardness: mg/L 
CaCO3 = 2.5*(calcium concentration in mg/L as Ca\2+\) + 
4.1*(magnesium concentration in mg/L as Mg\2+\).
    For a map of Level III ecoregions in the continental United 
States, see http://archive.epa.gov/wed/ecoregions/web/html/level_iii_iv-2.html#LevelIII.
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    EPA's proposal to use a default hardness of 25 mg/L in the absence 
of sufficiently representative ambient hardness data should not be 
confused with use of a low-end hardness floor

[[Page 22559]]

even when ambient data are available measuring hardness below 25 mg/L. 
Consistent with EPA guidance, a site's actual ambient water hardness 
should be used to calculate the criterion when sufficiently 
representative hardness data are available, even if the hardness is 
below 25 mg/L.\13\
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    \13\ USEPA. 2002. National Recommended Water Quality Criteria: 
2002. U.S. Environmental Protection Agency, Office of Water, 
Washington, DC EPA-822-R-02-047.
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    In describing potential remedies to address EPA's January 2013 
disapproval, EPA noted that ``new scientific data on the toxicity of 
cadmium [are] now available and would need to be reviewed regarding 
their quality and relevance prior to being considered in developing an 
updated recommendation for a specific numeric criterion protective of 
Oregon aquatic life.'' \14\ EPA's 2016 section 304(a) recommended 
cadmium criteria update represents a thorough review and incorporation 
of the latest scientific data on cadmium toxicity to aquatic life. The 
updated 304(a) recommended freshwater acute cadmium criterion, which 
EPA is proposing to apply in Oregon, now incorporates a more robust 
dataset on cadmium's acutely toxic effects, and was lowered to protect 
commercially and recreationally important salmonids, consistent with 
EPA's 1985 Guidelines. Additionally, EPA's proposal of a default 
hardness value as part of the criterion for Oregon will ensure that 
protective cadmium criteria can be easily derived for all freshwaters 
in the state. Therefore, EPA proposes that the 2016 section 304(a) 
recommended acute cadmium criterion, in combination with a protective 
hardness default that will apply in the absence of sufficiently 
representative ambient hardness data, will protect aquatic life in 
Oregon.
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    \14\ USEPA. 2013. EPA Clean Water Act 303(c) Determinations On 
Oregon's New and Revised Aquatic Life Toxic Criteria Submitted on 
July 8, 2004, and as Amended by Oregon's April 23, 2007 and July 21, 
2011 Submissions. Page 46.
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C. Implementation of Proposed Freshwater Acute Cadmium Criterion in 
Oregon

    When calculating a hardness-based criterion value, Oregon should 
consider the following when defining a site to which the acute cadmium 
criterion applies: (1) Metals are generally persistent, so calculating 
the criterion using hardness values from a small site at or near the 
discharge point could result in a criterion that is not protective of 
areas that are outside the defined site, and (2) 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.\15\ Additionally, pursuant to 40 CFR 131.10(b), Oregon 
must consider downstream WQS when calculating a protective criterion 
concentration in upstream waters.
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    \15\ USEPA. 1994. Interim Guidance on Determination and Use of 
Water-Effect Ratios for Metals. U.S. Environmental Protection 
Agency, Office of Water, Washington, DC EPA-823-B-94-001. February 
1994.
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    When setting Water Quality-Based Effluent Limitations (WQBELs), 
Oregon should determine the water body's ambient hardness level under 
critical conditions (i.e., low hardness) when cadmium toxicity is 
expected to be higher, such that the resulting cadmium criterion is 
protective of the entire site at critical and less than critical 
conditions. EPA's NPDES Permit Writers' Manual describes the importance 
of determining 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\ Because organisms are more sensitive to cadmium 
when corresponding hardness concentrations are low, Oregon should 
ensure that sufficiently representative ambient hardness data are 
collected to have confidence that critical conditions in the water body 
are being adequately captured.
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    \16\ USEPA. 2010. NPDES Permit Writers' Manual. U.S. 
Environmental Protection Agency, Office of Water, Washington, DC 
EPA-833-K-10-001. September 2010.
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    Substantial changes in a site's ambient hardness will likely affect 
the resulting acute cadmium criterion at that site. Therefore, EPA 
recommends that Oregon periodically revisit each water body's acute 
cadmium criterion and re-run the equation when changes in water 
hardness are evident or suspected at a site, and also as additional 
monitoring data become available.

IV. Freshwater Copper Aquatic Life Criteria

A. EPA's National Recommended Copper Criteria

    In 2007, EPA issued revised section 304(a) national recommended 
freshwater aquatic life criteria for copper that represent the best 
available science and understanding of the interaction between water 
chemistry and copper toxicity.\17\ These criteria recommendations 
incorporate use of a Biotic Ligand Model (BLM), which is a metal 
bioavailability model that uses receiving water body characteristics to 
develop water quality criteria on a site-specific basis. The BLM 
requires ambient data on ten water body-specific characteristics to 
calculate a freshwater copper criterion (temperature, pH, dissolved 
organic carbon (DOC), calcium, magnesium, sodium, potassium, sulfate, 
chloride, and alkalinity).
---------------------------------------------------------------------------

    \17\ USEPA. 2007. Aquatic Life Ambient Freshwater Quality 
Criteria--Copper. U.S. Environmental Protection Agency, Office of 
Water, Washington, DC EPA-822-R-07-001. http://water.epa.gov/scitech/swguidance/standards/criteria/aqlife/copper/upload/2009_04_27_criteria_copper_2007_criteria-full.pdf.
---------------------------------------------------------------------------

    Along with the criteria recommendations, EPA released supplementary 
materials related to using the BLM on a site-specific basis to derive 
criteria. Training materials that EPA released in 2007 discussed 
considerations such as collecting sufficiently representative data to 
account for a site's spatial and temporal variability, properly 
defining the site to which the BLM-derived criterion applies, 
reconciling multiple model runs, and estimating input parameters when 
site-specific data are lacking.\18\ To address situations where site-
specific data are not available for some of the BLM's ten input 
variables, EPA published for public comment the Draft Technical Support 
Document: Recommended Estimates for Missing Water Quality Parameters 
for Application in EPA's Biotic Ligand Model (EPA 820-R-15-106) on 
February 16, 2016 (81 FR 7784).
---------------------------------------------------------------------------

    \18\ USEPA. 2007. Copper Aquatic Life Criteria: Supplementary 
Training Materials. U.S. Environmental Protection Agency, Office of 
Water, Washington, DC http://water.epa.gov/scitech/swguidance/standards/criteria/aqlife/copper/faq_index.cfm. See ``Data 
Requirements.''
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B. Proposed Acute and Chronic Copper Criteria for Oregon's Freshwaters

    To protect aquatic life in Oregon's freshwaters, EPA proposes the 
CMC and CCC based on the 2007 304(a) recommended copper BLM. EPA 
proposes to express the CMC as a one-hour average dissolved copper 
concentration (in [micro]g/L) and the CCC as a four-day average 
dissolved copper concentration (in [micro]g/L), and that the CMC and 
CCC are not to be exceeded more than once every three years.
    As with hardness data used to determine the acute cadmium criterion 
discussed earlier, EPA recommends that Oregon collect ambient data to 
determine protective copper criteria by site. In the absence of 
sufficiently representative ambient data to run the BLM, EPA proposes 
default input values

[[Page 22560]]

for DOC, calcium, magnesium, sodium, potassium, sulfate, chloride, and 
alkalinity that are based on the 10th percentile of existing 
concentrations of these variables in waters within each of Oregon's 
Level III ecoregions.\19\ If information exists to characterize a water 
body's stream order (a measure of the relative size of a stream), EPA 
proposes to instead use the 10th percentile concentrations by stream 
order within each of Oregon's Level III ecoregions. These defaults (by 
ecoregion and by stream order within each ecoregion) are set forth in 
Tables 1 and 2 below and are described further in EPA's Draft Technical 
Support Document: Recommended Estimates for Missing Water Quality 
Parameters for Application in EPA's Biotic Ligand Model which can be 
found in the record for this rulemaking.\20\ Because EPA is proposing 
default input parameters, protective copper criteria can be easily 
derived for assessment and permitting purposes (even in the absence of 
ambient data). EPA solicits comments on the Agency's proposal to use 
the 10th percentile of existing concentrations to derive default input 
parameters. EPA also solicits comments on using default input 
parameters based on a different percentile, such as the 5th or 25th (or 
another percentile within that range). Calculations of default input 
parameters at the 5th and 25th percentiles can also be found in the 
record for this rulemaking (see Fifth and Twenty-fifth Percentile 
Estimates for Copper BLM Input Parameters by Oregon Level III 
Ecoregion).
---------------------------------------------------------------------------

    \19\ EPA is not proposing default input values for the other two 
BLM inputs, pH and temperature, because pH and temperature are 
highly variable and routinely monitored. EPA anticipates that 
sufficiently representative site-specific data will be available for 
these parameters. Even though EPA is proposing default values for 
DOC, EPA recommends that Oregon collect site-specific measurements 
of DOC if possible, because copper toxicity and BLM predictions are 
highly sensitive to DOC concentrations.
    \20\ See USEPA, 2016. EPA's proposed default inputs are from 
Tables 4, 8, 9, 10 and 20.
---------------------------------------------------------------------------

    Finally, EPA proposes that in order to calculate final acute and 
chronic copper criteria, Oregon use a value not to exceed the 10th 
percentile of individual BLM outputs for the site. While the 10th 
percentile should be protective in a majority of cases, certain 
circumstances may warrant use of a more stringent BLM output. When 10 
or fewer data points are available for a given site, EPA proposes that 
Oregon use the lowest individual acute and chronic BLM outputs as the 
final acute and chronic criteria. EPA solicits comment on this 
approach, as well as alternative percentiles or approaches to 
reconciling individual copper BLM outputs into final acute and chronic 
copper criteria values.
    EPA's proposed acute and chronic copper criteria for Oregon's 
freshwaters are as follows:

    Acute (CMC) and chronic (CCC) freshwater copper criteria shall 
be developed using EPA's 2007 Aquatic Life Ambient Freshwater 
Quality Criteria--Copper (EPA-822-R-07-001), which incorporates use 
of the copper biotic ligand model (BLM).
    Where sufficiently representative ambient data for DOC, calcium, 
magnesium, sodium, potassium, sulfate, chloride, or alkalinity are 
not available, the state shall use the 10th percentile estimated 
values from Table 1 based on the applicable ecoregion (or Table 2, 
based on the applicable ecoregion and stream order).
    The final copper criteria shall be calculated as no greater than 
the 10th percentile of the distribution of individual BLM outputs at 
a site. If 10 or fewer BLM outputs are available for a given site, 
the lowest individual acute and chronic BLM output values shall be 
used as the final acute and chronic copper criteria for that site.

                                           Table 1--BLM Default Inputs for Each Level III Ecoregion in Oregon
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                               Calcium    Magnesium     Sodium    Potassium  Alkalinity   Chloride   Sulfate
                     Level III Ecoregion                        (mg/L)      (mg/L)      (mg/L)     (mg/L)      (mg/L)      (mg/L)     (mg/L)      DOC
--------------------------------------------------------------------------------------------------------------------------------------------------------
1 Coast Range...............................................        8.4          3.2        4.1        0.64          33        3.2        4.8        0.7
3 Willamette Valley.........................................        8.2          2.9        4.4        0.90          30        4.7        3.8        0.4
4 Cascades..................................................        6.6          2.9        3.5        0.74          35        2.2        3.2        0.3
9 Eastern Cascades Slopes and Foothills.....................        8.2          3.8        6.0         1.0          44        3.2        5.0        0.5
10 Columbia Plateau.........................................         15          5.2        9.3         1.8          40        3.3         10        1.0
11 Blue Mountains...........................................         11          3.9        7.7         1.4          49        3.3        7.1        0.8
12 Snake River Plain........................................         33           10         13         2.3         109         10         22        1.2
78 Klamath Mountains........................................        8.7          4.6        4.0        0.66          44        2.1        3.5        0.6
80 Northern Basin and Range.................................         26          8.2         20         2.7          89         15         24        1.0
--------------------------------------------------------------------------------------------------------------------------------------------------------

                               Table 2--BLM Default Inputs for Each Stream Order Within Each Level III Ecoregion in Oregon
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                               Calcium    Magnesium     Sodium    Potassium  Alkalinity   Chloride   Sulfate
          Level III Ecoregion                Stream order       (mg/L)      (mg/L)      (mg/L)     (mg/L)      (mg/L)      (mg/L)     (mg/L)      DOC
--------------------------------------------------------------------------------------------------------------------------------------------------------
1 Coast Range..........................  SO 1-3.............        6.0          0.8        1.3         0.1          44        0.6        1.1        0.7
                                         SO 4-6.............        3.6          1.0        2.0         0.2          15        1.6        2.2        0.7
                                         SO 7-9.............         12          3.4        4.3         0.8          56        2.3        6.3        0.7
3 Willamette Valley....................  SO 1-3.............        9.9          3.8        5.6         1.5  ..........        2.3        1.5        0.4
                                         SO 4-6.............        7.1          2.5        4.3         0.8          29        4.6        2.8        0.4
                                         SO 7-9.............        5.0          1.6        3.4         0.6          20        2.7        2.3        0.4
4 Cascades.............................  SO 1-3.............        1.0          0.2        1.8         0.2  ..........        0.5        0.2        0.3
                                         SO 4-6.............        3.5          1.0        2.8         0.4          16        0.8        0.8        0.3
                                         SO 7-9.............         13          3.6        3.7         0.9          52        1.7        6.9        0.3
9 Eastern Cascades Slopes and Foothills  SO 1-3.............        4.4          0.9        2.3         0.4          35        0.2        0.2        0.5
                                         SO 4-6.............        5.5          0.8        2.4         0.5          22        0.9        2.2        0.5
                                         SO 7-9.............  .........  ...........  .........  ..........  ..........  .........  .........        0.5
10 Columbia Plateau....................  SO 1-3.............       24.0          9.4       10.2         1.4         127        4.6         11        1.0
                                         SO 4-6.............        8.6          3.2        4.0         0.9          33        1.4        3.1        1.0
                                         SO 7-9.............        5.7          1.5        2.0         0.7          16        0.8        4.2        1.0
11 Blue Mountains......................  SO 1-3.............        8.6          3.2  .........  ..........         169  .........  .........        0.8
                                         SO 4-6.............        3.7          0.8        1.6         0.7          16        0.3        0.7        0.8
                                         SO 7-9.............        8.5          1.5        3.3         0.7          32        0.8        5.0        0.8
12 Snake River Plain...................  SO 1-3.............         13          2.0        6.1         0.8          35        1.4        3.7        1.2
                                         SO 4-6.............         13          2.5        4.9         1.2          40        2.2        3.8        1.2
                                         SO 7-9.............         37           10         13         2.5         122         11         30        1.2
78 Klamath Mountains...................  SO 1-3.............  .........  ...........  .........  ..........  ..........        2.1  .........        0.6
                                         SO 4-6.............        7.9          3.2        4.0         0.6          36        2.1        2.4        0.6

[[Page 22561]]

 
                                         SO 7-9.............  .........  ...........  .........  ..........  ..........  .........  .........        0.6
80 Northern Basin and Range............  SO 1-3.............        6.3          1.1        4.3         2.2          24        0.2        2.5        1.0
                                         SO 4-6.............         15          5.7        4.1         0.8          54        2.0        9.3        1.0
                                         SO 7-9.............        8.9          2.4        7.7         2.1  ..........        2.1        5.1        1.0
--------------------------------------------------------------------------------------------------------------------------------------------------------

    EPA's 2007 copper BLM represents the latest scientific knowledge on 
copper speciation and bioavailability. In describing potential remedies 
to address EPA's January 2013 disapproval, EPA noted that Oregon could 
use the 2007 copper BLM. The model provides predictable and repeatable 
outcomes, and EPA is proposing protective default inputs to use in the 
absence of site-specific data. EPA proposes that the combination of the 
2007 copper BLM and default inputs will protect aquatic life in Oregon.

C. Implementation of Proposed Freshwater Acute and Chronic Copper 
Criteria in Oregon

    EPA's proposed copper criteria for Oregon will be the first BLM-
based criteria in Oregon and, therefore, the state does not have 
associated implementation methods. EPA strongly recommends that Oregon 
develop such methods, and give similar consideration to site selection, 
characterization of critical conditions, and data representativeness, 
as discussed for cadmium earlier in this proposed rule. Aquatic 
organisms are more sensitive to copper when corresponding DOC and pH 
levels in the water are low, so Oregon should ensure that sufficiently 
representative data are collected for the BLM's input parameters to 
have confidence that critical conditions are adequately characterized.
    When Oregon derives copper criteria using the BLM, to promote 
transparency and ensure predictable and repeatable outcomes, EPA 
recommends that the state make each criterion and the geographic extent 
of the site to which the criterion applies publicly available on the 
state's Web site along with information such as:
    1. The number of sampling events used to derive the criterion;
    2. Whether the criterion relied on site-specific data, estimated 
data, or a combination of both; and
    3. The date when the criterion was developed.
    Finally, as discussed earlier with respect to ambient hardness 
levels, substantial changes in a site's water chemistry will likely 
affect any resulting copper criterion at that site. In addition, with 
regular monitoring and a robust, site-specific dataset, criteria can be 
developed that more accurately reflect site conditions and copper 
bioavailability than criteria set using default values or limited data 
sets. Therefore, EPA recommends that Oregon periodically revisit its 
copper criteria and re-run the BLM when changes in water chemistry are 
evident or suspected at a site, and also as additional monitoring data 
become available.

D. Ongoing State Efforts To Develop Copper Criteria for Oregon's 
Freshwaters

    EPA's proposed methodology for deriving protective acute and 
chronic copper criteria described in the preceding paragraphs is not 
necessarily the only scientifically defensible and protective approach, 
and consistent with 40 CFR 131.11(b)(1)(iii), Oregon has the option to 
establish criteria based on other scientifically defensible methods. In 
2015, the Oregon Department of Environmental Quality (DEQ) conducted an 
analysis of the copper BLM in preparation for adopting revised copper 
criteria to address EPA's 2013 disapproval. DEQ has spent significant 
time and resources collecting BLM input parameters at 138 locations 
across the state, as well as evaluating various methods to develop 
defaults that can be used in the absence of sufficiently representative 
ambient data. To date, DEQ has generally modeled its approach after the 
methodology presented in EPA's Draft Technical Support Document: 
Recommended Estimates for Missing Water Quality Parameters for 
Application in EPA's Biotic Ligand Model (EPA 820-R-15-106), but is 
considering different data sources and alternative geographic groupings 
of water bodies. EPA is working closely with DEQ, and will continue to 
provide input on the state's copper criteria development efforts.

E. Incorporation by Reference

    EPA is proposing that the final EPA rule regulatory text will 
incorporate one EPA document by reference. In accordance with the 
requirements of 1 CFR 51.5, EPA is proposing to incorporate by 
reference EPA's 2007 Aquatic Life Ambient Freshwater Quality Criteria--
Copper (EPA-822-R-07-001), discussed in section IV.A. of this preamble. 
EPA has made, and will continue to make, this document generally 
available electronically through www.regulations.gov and/or in hard 
copy at the appropriate EPA office (see the ADDRESSES section of this 
preamble for more information).

V. Critical Low-Flows and Mixing Zones

    To ensure that the proposed criteria are applied appropriately to 
protect Oregon's aquatic life uses, EPA is proposing critical low-flow 
values for Oregon to use in 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. Low flows can 
exacerbate the effects of effluent discharges because, 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., values that are too 
high), the resulting ambient concentrations could exceed criteria when 
low flows occur.\21\
---------------------------------------------------------------------------

    \21\ 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'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.\22\ 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

[[Page 22562]]

specific duration and frequency associated with the criterion. For the 
acute cadmium and acute and chronic copper criteria, EPA proposes the 
following critical low-flow values:
---------------------------------------------------------------------------

    \22\ 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.\23\
---------------------------------------------------------------------------

    \23\ See USEPA, 2014.
---------------------------------------------------------------------------

    The criteria in this proposed rule, once finalized, would apply 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 CCC would apply at the 
defined boundary of the chronic mixing zone and the CMC would apply at 
the defined boundary of the acute mixing zone).\24\
---------------------------------------------------------------------------

    \24\ See USEPA, 1991.
---------------------------------------------------------------------------

VI. Endangered Species Act

    As noted earlier in this proposed rule, the NMFS 2012 biological 
opinion concluded that the acute cadmium and acute and chronic copper 
criteria that Oregon adopted in 2004 would jeopardize the continued 
existence of endangered species in Oregon. The opinion also contained 
RPAs for cadmium and copper that would avoid the likelihood of jeopardy 
to endangered species in Oregon. EPA will continue to work closely with 
the NMFS to ensure that the acute cadmium criterion that EPA ultimately 
finalizes is protective of federally listed species in Oregon. For 
copper, the NMFS further clarified in January 2016 that adoption of 
EPA's 2007 copper BLM, which EPA is proposing in this rule, would be 
consistent with the 2012 RPA.

VII. Under what conditions will Federal standards be not promulgated or 
withdrawn?

    Under the CWA, Congress gave states primary responsibility for 
developing and adopting WQS for their waters (CWA section 303(a)-(c)). 
Although EPA is proposing cadmium and copper aquatic life criteria for 
Oregon's freshwaters to remedy EPA's 2013 disapproval, Oregon continues 
to have the option to adopt and submit to EPA acute cadmium and acute 
and chronic copper criteria for the state's freshwaters consistent with 
CWA section 303(c) and EPA's implementing regulations at 40 CFR part 
131. EPA encourages Oregon to expeditiously adopt protective aquatic 
life criteria. Consistent with CWA section 303(c)(4), if Oregon adopts 
and submits cadmium and/or copper aquatic life criteria, and EPA 
approves such criteria before finalizing this proposed rule, EPA would 
not proceed with the promulgation for those waters and/or pollutants 
for which EPA approves Oregon's criteria.
    If EPA finalizes this proposed rule, and Oregon subsequently adopts 
and submits cadmium and/or copper aquatic life criteria, EPA proposes 
that once EPA approves Oregon's WQS, the EPA-approved criteria in 
Oregon's WQS would become the applicable criteria for CWA purposes and 
EPA's promulgated criteria would no longer be applicable criteria. EPA 
would undertake a rulemaking to withdraw the federal criteria for 
cadmium and/or copper, but that process would not delay Oregon's 
approved criteria from becoming the sole applicable criteria for CWA 
purposes.

VIII. Alternative Regulatory Approaches and Implementation Mechanisms

    Oregon will have considerable discretion to implement these aquatic 
life criteria, once finalized, through various water quality control 
programs. Among other things, EPA's regulations: (1) Specify how states 
and authorized tribes establish, modify or remove designated uses, (2) 
specify the requirements for establishing criteria to protect 
designated uses, including criteria modified to reflect site-specific 
conditions, (3) authorize states and authorized tribes to adopt WQS 
variances to provide time to achieve the applicable WQS, and (4) allow 
states and authorized tribes to include compliance schedules in NPDES 
permits. Each of these approaches are discussed in more detail below.

A. Designating Uses

    EPA's proposed cadmium and copper criteria apply to freshwaters in 
Oregon where the protection of fish and aquatic life is a designated 
use (see Oregon Administrative Rules at 340-041-8033, Table 30). The 
federal regulations at 40 CFR 131.10 provide information on 
establishing, modifying, and removing designated uses. 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,\25\ and EPA finds that removal to be consistent with 
CWA section 303(c) and the implementing regulations at 40 CFR part 131, 
then the federal cadmium and copper aquatic life criteria would no 
longer apply to that water body. Instead, any criteria associated with 
the newly designated highest attainable use would apply to that water 
body.
---------------------------------------------------------------------------

    \25\ 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 Act and attainable, based on 
the evaluation of the factor(s) in Sec.  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)).
---------------------------------------------------------------------------

B. Site-Specific Criteria

    The regulations at 40 CFR 131.11 specify requirements for modifying 
water quality criteria to reflect site-specific conditions. In the 
context of this rulemaking, a site-specific criterion (SSC) is an 
alternative value to the federal freshwater cadmium or copper aquatic 
life criteria that would be applied on a watershed, area-wide, or water 
body-specific basis that meets the regulatory test of protecting the 
designated use, being scientifically defensible, and ensuring the 
protection and maintenance of downstream WQS. A SSC may be more or less 
stringent than the otherwise applicable federal criteria. A SSC may be 
appropriate when further scientific data and analyses can bring added 
precision to express the concentration of cadmium and/or copper that 
protects the aquatic life-related designated use in a particular water 
body.

C. Variances

    40 CFR part 131 defines WQS variances at Sec.  131.3(o) as time-
limited designated uses and supporting criteria for a specific 
pollutant(s) or water quality parameter(s) that reflect the highest 
attainable conditions during the term of the WQS variance. WQS 
variances adopted in accordance with 40 CFR part 131 allow states and 
authorized tribes to address water quality challenges in a transparent 
and predictable way. Variances help states and authorized tribes focus 
on making incremental progress in improving water quality, rather than 
pursuing a downgrade of the underlying water quality goals through a 
designated use change, when the current designated use is difficult to 
attain. Oregon has

[[Page 22563]]

sufficient authority to use variances when implementing the criteria, 
as long as such variances are adopted consistent with 40 CFR 131.14. 
Oregon may use its currently EPA-approved variance procedures with 
respect to a temporary modification of its uses as it pertains to any 
federal criteria (see OAR 340-041-0059) when adopting such variances.

D. Compliance Schedules

    EPA's regulations at 40 CFR 122.47 and 40 CFR 131.15 allow states 
and authorized tribes to include permit compliance schedules in their 
NPDES permits if dischargers need additional time to meet their WQBELs 
based on the applicable WQS. EPA's updated regulations at 40 CFR part 
131 also include provisions authorizing the use of permit compliance 
schedules to ensure that a decision to allow permit compliance 
schedules includes public engagement and transparency (80 FR 51022, 
August 21, 2015). Oregon already has an EPA-approved regulation 
authorizing the use of permit compliance schedules (see OAR 340-041-
0061), consistent with 40 CFR 131.15. That state regulation is not 
affected by this rule, and Oregon is authorized to grant compliance 
schedules, as appropriate, based on the federal criteria.

IX. Economic Analysis

    EPA's proposed cadmium and copper criteria may serve as a basis for 
development of NPDES permit limits. Oregon has NPDES permitting 
authority, and retains considerable discretion in implementing 
standards. EPA evaluated the potential costs to NPDES dischargers 
associated with state implementation of EPA's proposed criteria. This 
analysis is documented in Economic Analysis for the Proposed Rule: 
Aquatic Life Criteria for Copper and Cadmium in Oregon, which can be 
found in the record for this rulemaking.
    Any NPDES-permitted facility that discharges cadmium or copper in 
Oregon could potentially incur compliance costs. The types of affected 
facilities could include industrial facilities and POTWs discharging 
treated wastewater to surface waters (i.e., point sources). EPA expects 
that dischargers would use similar process and treatment controls to 
come into compliance with the proposed cadmium and copper criteria as 
they would to comply with Oregon's existing aquatic life criteria for 
cadmium and copper (i.e., ``baseline criteria''). EPA estimates the 
incremental impacts of the proposed rule against a baseline of full 
implementation of currently approved criteria.
    For this analysis, EPA did not estimate the potential for costs to 
stormwater or nonpoint sources such as agricultural runoff. EPA 
recognizes that Oregon may require controls for nonpoint sources. 
However, it is difficult to model and evaluate the potential cost 
impacts of this rule to those sources because they are intermittent, 
variable, and occur under hydrologic or climatic conditions associated 
with precipitation events. Also, baseline total maximum daily loads 
(TMDLs) for waters with baseline impairment for cadmium or copper have 
not yet been developed. Therefore, determining which waters would not 
achieve standards based on the proposed aquatic life criteria after 
complying with existing (baseline) regulations and policies may not be 
possible.

A. Identifying Affected Entities

    For economic analysis purposes, EPA developed hypothetical 
applications of the proposed cadmium and copper criteria using 
conservative estimates for hardness and the BLM inputs, respectively. 
The criteria that EPA derived for the cost analysis would likely be 
different from and possibly lower (more stringent) than the actual 
criteria applications that Oregon would derive using ambient data from 
each water body. As described earlier in this proposed rule, EPA 
recommends that Oregon collect sufficiently representative ambient data 
to derive the most accurate and protective cadmium and copper aquatic 
life criteria.
    Using the criteria derived for the cost analysis, EPA identified 10 
point source facilities that could potentially be affected by the 
rule--all are major dischargers. Major facilities are typically those 
that discharge more than 1 million gallons per day (mgd). Of these 
potentially affected facilities, 7 are POTWs and 3 are industrial 
dischargers. EPA did not include facilities covered by general permits 
in its analysis because data for such facilities are limited, and flows 
are usually much lower. EPA did not have cadmium or copper effluent 
data to evaluate minor facilities for this preliminary analysis.

B. Method for Estimating Costs

    EPA estimated costs for the 10 potentially affected facilities. EPA 
evaluated existing baseline permit conditions, reasonable potential to 
exceed estimates of the aquatic life criteria based on the proposed 
rule, and potential to exceed projected effluent limitations based on 
available effluent monitoring data. In instances of exceedances of 
projected effluent limitations under the proposed criteria, EPA 
determined the likely compliance scenarios and costs. Only compliance 
actions and costs that would be needed above the baseline level of 
controls are attributable to the proposed rule.
    EPA assumed that dischargers would pursue the least cost means of 
compliance with WQBELs. Incremental compliance actions attributable to 
the proposed rule may include pollution prevention, end-of-pipe 
treatment, and alternative compliance mechanisms (e.g., variances). EPA 
annualized capital costs over an assumed technology lifespan of 20 
years, adding recurring Operation & Maintenance costs, and discounted 
using 3% and 7% discount rates to obtain total annual costs per 
facility.

C. Results

    Based on the results for 10 facilities, EPA estimated a total 
incremental annual cost attributable to the proposed criteria of 
approximately $0.1 million to $18.2 million at a 3% discount rate.\26\ 
The low end of the range reflects the assumption that achieving very 
low copper limits is infeasible (e.g., available treatment technologies 
cannot consistently achieve the limits) and dischargers will need to 
apply for variances. The high end of the range reflects the assumption 
that dischargers can achieve the projected effluent limits through end-
of-pipe treatment. All of the incremental costs are attributable to 
municipal and industrial dischargers for treatment of copper. There was 
no reasonable potential to exceed the proposed acute cadmium criterion.
---------------------------------------------------------------------------

    \26\ The estimated costs using a 7% discount rate range from 
$0.1 million to $22.6 million.
---------------------------------------------------------------------------

    If the revised criteria result in an incremental increase in 
impaired waters, resulting in the need for TMDL development, there 
could also be some costs to nonpoint sources of metals. Using available 
ambient monitoring data, EPA compared cadmium and copper concentrations 
to the baseline and proposed criteria, identifying waterbodies that may 
be incrementally impaired (i.e., impaired under the proposed criteria 
but not under the baseline). Baseline impairment ranged from 8 to 46 
stations, depending on whether EPA used impaired water body information 
from 2010 or 2012. Using available monitoring data, EPA identified 
copper impairments at 82 monitoring stations based on the proposed 
criteria. Therefore, water quality data indicate potential for 
incremental impairment at 36 to 74 stations. This increase suggests 
that

[[Page 22564]]

nonpoint sources may bear some compliance costs, although data are not 
available to estimate the magnitude of these costs. If the net increase 
in stations (36 to 74) is an indication of the potential increase in 
the number of TMDLs, then the costs for TMDL development could range 
from approximately $1.3 million (36 TMDLs x $37,000) to $3.0 million 
(74 TMDLs x $40,000) \27\. The control of nonpoint sources such as in 
the context of a TMDL could result in less stringent requirements, and 
thus lower costs, for point sources.
---------------------------------------------------------------------------

    \27\ U.S. EPA (2001) reports that the average cost to develop a 
TMDL for a single source of impairment ranges from $27,000 to 
$29,000 (in 2000 dollars), which becomes $37,000 to $40,000 using 
the Consumer Price Index to escalate to 2015 dollars.
---------------------------------------------------------------------------

X. Statutory and Executive Order Reviews

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

    This action is not a significant regulatory action and was 
therefore not submitted to the Office of Management and Budget (OMB) 
for review. The proposed rule does not establish any requirements 
directly applicable to regulated entities or other sources of toxic 
pollutants. However, these WQS may serve as a basis for development of 
NPDES permit limits. Oregon has NPDES permitting authority, and retains 
considerable discretion in implementing standards. In the spirit of 
Executive Order 12866, EPA evaluated the potential costs to NPDES 
dischargers associated with state implementation of EPA's proposed 
criteria. This analysis, Economic Analysis for the Proposed Rule: 
Aquatic Life Criteria for Copper and Cadmium in Oregon, is summarized 
in section IX of the preamble and is available in the docket.

B. Paperwork Reduction Act

    This action does not impose an information collection burden under 
the PRA. While actions to implement these WQS could entail additional 
paperwork burden, this action does not directly contain any information 
collection, reporting, or record-keeping requirements.

C. Regulatory Flexibility Act

    I certify that this action will not have a significant economic 
impact on a substantial number of small entities under the RFA. This 
action will not impose any requirements on small entities. Small 
entities, such as small businesses or small governmental jurisdictions, 
are not directly regulated by this rule.

D. Unfunded Mandates Reform Act

    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 governments. As these water quality criteria are not self-
implementing, the action imposes no enforceable duty on any state, 
local or tribal governments or the private sector.

E. Executive Order 13132 (Federalism)

    This action does not have federalism implications. It will not have 
substantial direct effects on the states, on the relationship between 
the national government and the states, or on the distribution of power 
and responsibilities among the various levels of government. This rule 
does not alter Oregon's considerable discretion in implementing these 
WQS, nor would it preclude Oregon from adopting WQS that meet the 
requirements of the CWA, either before or after promulgation of the 
final rule, which would eliminate the need for federal standards upon 
EPA approval. Thus, Executive Order 13132 does not apply to this 
action.
    In the spirit of Executive Order 13132 and consistent with EPA 
policy to promote communications between EPA and state and local 
governments, EPA specifically solicits comments on this proposed action 
from state and local officials.

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

    This action does not have tribal implications as specified in 
Executive Order 13175. This proposed 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.
    Many tribes in the Pacific Northwest hold reserved rights to take 
fish for subsistence, ceremonial, religious, and commercial purposes. 
EPA developed the criteria in this proposed rule to protect aquatic 
life in Oregon from the effects of exposure to harmful levels of 
cadmium and copper. Protecting the health of fish in Oregon will, 
therefore, support tribal reserved fishing rights, including treaty-
reserved rights, where such rights apply in waters under state 
jurisdiction.
    Consistent with the EPA Policy on Consultation and Coordination 
with Indian Tribes, EPA consulted with tribal officials during the 
development of this action. On November 23, 2015, EPA sent a letter to 
tribal leaders in Oregon offering to consult on the proposed cadmium 
and copper criteria in this rule. On December 15, 2015, EPA held a 
conference call with tribal water quality technical contacts to explain 
EPA's proposed action and timeline. Formal consultation on the proposed 
action was not requested by any of the tribes. EPA will continue to 
communicate with the tribes prior to its final action.

G. 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 EPA 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.

H. Executive Order 13211 (Actions That Significantly Affect Energy 
Supply, Distribution, or Use)

    This action is not subject to Executive Order 13211, because it is 
not a significant regulatory action under Executive Order 12866.

I. National Technology Transfer and Advancement Act of 1995

    This proposed rulemaking does not involve technical standards.

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

    The human health or environmental risk addressed by this action 
will not have potential disproportionately high and adverse human 
health or environmental effects on minority, low-income or indigenous 
populations. The criteria in this proposed rule will support the health 
and abundance of aquatic life in Oregon, and will therefore benefit all 
communities that rely on Oregon's ecosystems.

List of Subjects in 40 CFR Part 131

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

[[Page 22565]]

    Dated: March 31, 2016.
Gina McCarthy,
Administrator.
    For the reasons set forth in the preamble, EPA proposes to amend 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.  131.46 to read as follows:

Sec.  131.46  Aquatic Life Criteria for Copper and Cadmium in Oregon.

    (a) Scope. This section promulgates aquatic life criteria for 
cadmium and copper in freshwaters in Oregon.
    (b) Criteria for cadmium and copper in Oregon. The aquatic life 
criteria in Table 1 apply to all freshwaters in Oregon where fish and 
aquatic life are a designated use.

                Table 1--Proposed Cadmium and Copper Aquatic Life Criteria for Oregon Freshwaters
----------------------------------------------------------------------------------------------------------------
                                                                                                   Criterion
                                                                                                   Continuous
                   Metal                       CAS No.      Criterion Maximum Concentration      Concentration
                                                                 (CMC) \3\ ([micro]g/L)            (CCC) \4\
                                                                                                  ([micro]g/L)
----------------------------------------------------------------------------------------------------------------
Cadmium 1 2................................      7440439  [e (0.9789 x ln(hardness) - 3.866)]
                                                           x CF.
                                                          Where CF = 1.136672 - [(ln
                                                           hardness) x (0.041838)].
                                            --------------------------------------------------------------------
Copper 1...................................      7440508  Acute (CMC) and chronic (CCC) freshwater copper
                                                           criteria shall be developed using EPA's 2007 Aquatic
                                                           Life Ambient Freshwater Quality Criteria--Copper (EPA-
                                                           822-R-07-001), which incorporates use of the copper
                                                           biotic ligand model (BLM).
                                                          Where sufficiently representative ambient data for
                                                           DOC, calcium, magnesium, sodium, potassium, sulfate,
                                                           chloride, or alkalinity are not available, the state
                                                           shall use the 10th percentile estimated values from
                                                           Table 2 of paragraph (c) of this section based on the
                                                           applicable ecoregion (or Table 3 of paragraph (c) of
                                                           this section, based on the applicable ecoregion and
                                                           stream order).
                                                          The final copper criteria shall be calculated as no
                                                           greater than the 10th percentile of the distribution
                                                           of individual BLM outputs at a site. If 10 or fewer
                                                           BLM outputs are available for a given site, the
                                                           lowest individual acute and chronic BLM output values
                                                           shall be used as the final acute and chronic copper
                                                           criteria for that site.
----------------------------------------------------------------------------------------------------------------
\1\ The criteria for cadmium and copper are expressed as dissolved metal concentrations.
\2\ CF is the conversion factor used to convert between the total recoverable and dissolved forms of cadmium.
  The term (ln hardness) in the CMC and the CF equation is the natural logarithm of the ambient hardness in mg/L
  (CaCO3). A default hardness concentration of 25 mg/L shall be used to calculate cadmium criteria in the
  absence of sufficiently representative ambient hardness data. A hardness concentration of 25 mg/L equates to a
  one-hour average dissolved cadmium concentration of 0.49 [micro]g/L.
\3\ The CMC is the highest allowable one-hour average instream concentration of cadmium or copper. 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 instream concentration of copper. The CCC is not to be
  exceeded more than once every three years. The CCC is rounded to two significant figures.

    (c) Estimated Values to Derive Copper Criteria. The default inputs 
to calculate copper criteria using the BLM in the absence of 
sufficiently representative ambient data are shown in Tables 2 and 3.

                                           Table 2--BLM Default Inputs for Each Level III Ecoregion in Oregon
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                               Calcium    Magnesium     Sodium    Potassium  Alkalinity   Chloride   Sulfate
                     Level III Ecoregion                        (mg/L)      (mg/L)      (mg/L)     (mg/L)       (mg/L)     (mg/L)     (mg/L)      DOC
--------------------------------------------------------------------------------------------------------------------------------------------------------
1 Coast Range...............................................        8.4          3.2        4.1        0.64          33        3.2        4.8        0.7
3 Willamette Valley.........................................        8.2          2.9        4.4        0.90          30        4.7        3.8        0.4
4 Cascades..................................................        6.6          2.9        3.5        0.74          35        2.2        3.2        0.3
9 Eastern Cascades Slopes and Foothills.....................        8.2          3.8        6.0         1.0          44        3.2        5.0        0.5
10 Columbia Plateau.........................................         15          5.2        9.3         1.8          40        3.3         10        1.0
11 Blue Mountains...........................................         11          3.9        7.7         1.4          49        3.3        7.1        0.8
12 Snake River Plain........................................         33           10         13         2.3         109         10         22        1.2
78 Klamath Mountains........................................        8.7          4.6        4.0        0.66          44        2.1        3.5        0.6
80 Northern Basin and Range.................................         26          8.2         20         2.7          89         15         24        1.0
--------------------------------------------------------------------------------------------------------------------------------------------------------

                               Table 3--BLM Default Inputs for Each Stream Order Within Each Level III Ecoregion in Oregon
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                               Calcium    Magnesium     Sodium    Potassium  Alkalinity   Chloride   Sulfate
          Level III Ecoregion               Stream order        (mg/L)      (mg/L)      (mg/L)     (mg/L)       (mg/L)     (mg/L)     (mg/L)      DOC
--------------------------------------------------------------------------------------------------------------------------------------------------------
1 Coast Range.........................  SO 1-3                      6.0          0.8        1.3         0.1          44        0.6        1.1        0.7
                                        SO 4-6                      3.6          1.0        2.0         0.2          15        1.6        2.2        0.7
                                        SO 7-9                       12          3.4        4.3         0.8          56        2.3        6.3        0.7
3 Willamette Valley...................  SO 1-3                      9.9          3.8        5.6         1.5  ..........        2.3        1.5        0.4
                                        SO 4-6                      7.1          2.5        4.3         0.8          29        4.6        2.8        0.4
                                        SO 7-9                      5.0          1.6        3.4         0.6          20        2.7        2.3        0.4
4 Cascades............................  SO 1-3                      1.0          0.2        1.8         0.2  ..........        0.5        0.2        0.3
                                        SO 4-6                      3.5          1.0        2.8         0.4          16        0.8        0.8        0.3
                                        SO 7-9                       13          3.6        3.7         0.9          52        1.7        6.9        0.3

[[Page 22566]]

 
9 Eastern Cascades Slopes and           SO 1-3                      4.4          0.9        2.3         0.4          35        0.2        0.2        0.5
 Foothills.
                                        SO 4-6                      5.5          0.8        2.4         0.5          22        0.9        2.2        0.5
                                        SO 7-9                .........  ...........  .........  ..........  ..........  .........  .........        0.5
10 Columbia Plateau...................  SO 1-3                     24.0          9.4       10.2         1.4         127        4.6         11        1.0
                                        SO 4-6                      8.6          3.2        4.0         0.9          33        1.4        3.1        1.0
                                        SO 7-9                      5.7          1.5        2.0         0.7          16        0.8        4.2        1.0
11 Blue Mountains.....................  SO 1-3                      8.6          3.2  .........  ..........         169  .........  .........        0.8
                                        SO 4-6                      3.7          0.8        1.6         0.7          16        0.3        0.7        0.8
                                        SO 7-9                      8.5          1.5        3.3         0.7          32        0.8        5.0        0.8
12 Snake River Plain..................  SO 1-3                       13          2.0        6.1         0.8          35        1.4        3.7        1.2
                                        SO 4-6                       13          2.5        4.9         1.2          40        2.2        3.8        1.2
                                        SO 7-9                       37           10         13         2.5         122         11         30        1.2
78 Klamath Mountains..................  SO 1-3                .........  ...........  .........  ..........  ..........        2.1  .........        0.6
                                        SO 4-6                      7.9          3.2        4.0         0.6          36        2.1        2.4        0.6
                                        SO 7-9                .........  ...........  .........  ..........  ..........  .........  .........        0.6
80 Northern Basin and Range...........  SO 1-3                      6.3          1.1        4.3         2.2          24        0.2        2.5        1.0
                                        SO 4-6                       15          5.7        4.1         0.8          54        2.0        9.3        1.0
                                        SO 7-9                      8.9          2.4        7.7         2.1  ..........        2.1        5.1        1.0
--------------------------------------------------------------------------------------------------------------------------------------------------------

    (d) Applicability. (1) The criteria in paragraph (b) of this 
section are the applicable acute cadmium and acute and chronic copper 
aquatic life criteria in all freshwaters in Oregon where fish and 
aquatic life are a designated use. After the effective date of this 
rule, in cases where EPA determines that state cadmium or copper 
aquatic life criteria meet the requirements of Clean Water Act section 
303(c) and 40 CFR part 131, Oregon's cadmium or copper criteria will 
apply rather than the criteria in paragraph (b) of this section.
    (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 freshwaters in Oregon where fish and aquatic 
life are a designated use.
    (i) For all waters with mixing zone regulations or implementation 
procedures, the criteria apply at the appropriate locations within or 
at the boundary 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.
    (ii) The state shall not use a low flow value that is less 
stringent than the values listed below for waters suitable for the 
establishment of low flow return frequencies (i.e., streams and rivers) 
when calculating the available dilution for the purposes of determining 
the need for and establishing Water Quality-Based Effluent Limitations 
in National Pollutant Discharge Elimination System permits:

------------------------------------------------------------------------
 
------------------------------------------------------------------------
Acute criteria (CMC).....................  1Q10 or 1B3.
Chronic criteria (CCC)...................  7Q10 or 4B3.
------------------------------------------------------------------------
Where:
    1. 1Q10 is the lowest one-day average flow event expected to occur
     once every ten years, on average (determined hydrologically)..
    2. 1B3 is the lowest one-day average flow event expected to occur
     once every three years, on average (determined biologically)..
    3. 7Q10 is the lowest seven-consecutive-day average flow event
     expected to occur once every ten years, on average (determined
     hydrologically)..
    4. 4B3 is the lowest four-consecutive-day average flow event
     expected to occur once every three years, on average (determined
     biologically)..
------------------------------------------------------------------------

[FR Doc. 2016-08038 Filed 4-15-16; 8:45 am]
 BILLING CODE 6560-50-P
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