[Federal Register Volume 82, Number 247 (Wednesday, December 27, 2017)]
[Proposed Rules]
[Pages 61213-61229]
[FR Doc No: 2017-27621]

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 131

[EPA-HQ-OW-2017-0010; FRL-9972-46-OW]
RIN 2040-AF69

Water Quality Standards for the State of Missouri's Lakes and
Reservoirs

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: The Environmental Protection Agency (EPA or Agency) proposes
to establish federal nutrient criteria to protect designated uses for
the State of Missouri's lakes and reservoirs. On August 16, 2011, EPA
disapproved most of the numeric criteria for total nitrogen, total
phosphorus, and chlorophyll a that the State submitted to EPA in 2009.
EPA acknowledged the importance of Missouri's proactive efforts to
address nutrient pollution by adopting numeric nutrient criteria.
However, EPA concluded that the Missouri Department of Natural
Resources (MDNR) had failed to demonstrate the criteria would protect
the State's designated uses and were not based on a sound scientific
rationale. The Clean Water Act (CWA) directs EPA to promptly propose
water quality standards (WQS) that meet CWA requirements if a state
does not adopt WQS addressing EPA's disapproval. On February 24, 2016,
the Missouri Coalition for the Environment (MCE) filed a lawsuit
alleging that EPA failed to satisfy its statutory obligation to act
``promptly.'' On December 1, 2016, EPA entered into a consent decree
with MCE committing to sign a notice of proposed rulemaking by December
15, 2017 to address EPA's 2011 disapproval, unless the State submits
and EPA approves criteria that address the disapproval on or before
December 15, 2017. As of the date of this proposed rule, Missouri has
not submitted new or revised standards to address EPA's 2011
disapproval and EPA has not approved such water quality standards.
Therefore, under the terms of the consent decree, EPA is signing a
notice of proposed rulemaking that proposes new water quality standards
addressing EPA's August 16, 2011 disapproval. In this proposal, EPA
seeks comment on two primary alternatives. Under the first alternative,
EPA proposes nutrient protection values and eutrophication impact
factors in a combined criterion approach. Under the second alternative,
EPA proposes a similar combined criterion approach that would mirror
the State of Missouri's October 2017 proposal for lake nutrient water
quality standards. EPA will not proceed with final rulemaking (or will
withdraw its final rule, if applicable) to address its 2011 disapproval
if Missouri adopts and submits criteria to address EPA's 2011
disapproval and EPA approves them as meeting CWA requirements.

DATES: Comments must be received on or before February 26, 2018.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-HQ-OW-
2017-0010, 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 online public hearings so that interested
parties may provide verbal comments on this proposed rule. The first
public hearing

will be on February 7, 2018. The second public hearing will be on
February 8, 2018. For more details on the public hearings and a link to
register, please visit https://www.epa.gov/wqs-tech/proposed-nutrient-criteria-missouri-lakes-and-reservoirs.

FOR FURTHER INFORMATION CONTACT: Mario Sengco, Standards and Health
Protection Division, Office of Water, Mailcode: 4305T, Environmental
Protection Agency, 1200 Pennsylvania Avenue NW, Washington, DC 20460;
telephone number:<PHONE_NUMBER>; email address: [email protected].

SUPPLEMENTARY INFORMATION:

Table of Contents

I. General Information
    A. Does this action apply to me?
    B. What action is EPA taking?
II. Background
    A. Nutrient Pollution
    B. Statutory and Regulatory Background
    C. Deriving and Expressing Numeric Nutrient Criteria
    D. Missouri's 2009 Nutrient Criteria Submission and EPA's Clean
Water Act Section 303(c) Action
    E. Missouri Coalition for the Environment (MCE) Lawsuit and
Consent Decree
    F. Missouri's 2017 Proposed Nutrient WQS
III. Proposed Nutrient Combined Criterion for Lakes and Reservoirs
in Missouri
    A. Proposed Combined Criterion Approaches
    B. Proposed Combined Criterion Alternative 1
    C. Derivation of Nutrient Protection Values for Alternative 1
    D. Proposed Combined Criterion Alternative 2
    E. Additional Alternative Approaches Considered
    F. Applicability of Combined Criterion When Final
IV. Tributary Arms
V. Endangered Species Act
VI. Under what conditions will federal standards be either not
finalized or withdrawn?
VII. WQS Regulatory Approaches and Implementation Mechanisms
    A. Designating Uses
    B. Site-Specific Criteria
    C. WQS Variances
    D. NPDES Permit Compliance Schedules
VIII. Economic Analysis
IX. Statutory and Executive Order Reviews
    A. Executive Order 12866: Regulatory Planning and Review and
Executive Order 13563: Improving Regulation and Regulatory Review
    B. Executive Order 13771: Reducing Regulation and Controlling
Regulatory Costs
    C. Paperwork Reduction Act
    D. Regulatory Flexibility Act
    E. Unfunded Mandates Reform Act
    F. Executive Order 13132 (Federalism)
    G. Executive Order 13175 (Consultation and Coordination With
Indian Tribal Governments)
    H. Executive Order 13045 (Protection of Children From
Environmental Health and Safety Risk)
    I. Executive Order 13211 (Actions That Significantly Affect
Energy Supply, Distribution, or Use)
    J. National Technology Transfer Advancement Act of 1995
    K. Executive Order 12898 (Federal Actions To Address
Environmental Justice in Minority Populations and Low-Income
Populations)

I. General Information

A. Does this action apply to me?

    Citizens concerned with water quality in the State of Missouri may
be interested in this proposed rulemaking. Entities discharging
nitrogen or phosphorus to lakes and reservoirs, or to flowing waters
emptying into lakes or reservoirs, could be affected directly or
indirectly by this rulemaking because WQS are used in determining
National Pollutant Discharge Elimination System (NPDES) permit effluent
limits. Stakeholders that rely on lakes and reservoirs for recreation
or as a source of drinking water likewise may be interested in the
proposed criteria. Table 1 lists categories that ultimately may be
affected by this proposal.

      Table 1--Categories Potentially Affected by Proposed Criteria
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           Category            Examples of potentially affected entities
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Industry.....................  Factories discharging pollutants to lakes/
                                reservoirs or flowing waters emptying
                                into downstream lakes/reservoirs in
                                Missouri.
Municipalities...............  Publicly-owned treatment works
                                discharging pollutants to lakes/
                                reservoirs or flowing waters emptying
                                into downstream lakes/reservoirs in
                                Missouri.
Stormwater Management          Entities responsible for managing
 Districts.                     stormwater runoff in Missouri.
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    This table is not intended to be exhaustive; rather, it provides a
guide for entities that may be affected directly or indirectly by this
action. Nonpoint source contributors and other entities not listed in
the table also could be affected indirectly. Any party or entity that
conducts activities within the watersheds affected by this rule, or
that relies on, depends upon, influences, or contributes to the water
quality of the lakes, reservoirs and flowing waters of Missouri, also
may be affected by this rule. To determine whether your facility or
activities may 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
preceding FOR FURTHER INFORMATION CONTACT section.

B. What action is EPA taking?

    The EPA is proposing two alternatives to establish federal nutrient
criteria to protect designated uses for the State of Missouri's lakes
and reservoirs. Under the first alternative, EPA proposes nutrient
protection values (total nitrogen, total phosphorus, chlorophyll a) and
eutrophication impact factors in a combined criterion approach. Under
the second alternative, EPA proposes a combined criterion approach that
would mirror the State of Missouri's October 2017 proposal for lake
nutrient water quality standards. This action fulfills EPA's obligation
under its consent decree entered on December 1, 2016 to prepare and
publish proposed regulations for nutrient criteria to address the
Agency's August 16, 2011, disapproval of the State's nutrient criteria
by December 15, 2017.

II. Background

A. Nutrient Pollution

1. What is nutrient (i.e., nitrogen and phosphorus) pollution?
    Excess loading of nitrogen and phosphorus compounds \1\ is one of
the most prevalent causes of water quality impairment in the United
States. Nitrogen and phosphorus pollution problems have been recognized
for some time in the U.S. For example, a 1969

report by the National Academy of Sciences \2\ noted ``[t]he pollution
problem is critical because of increased population, industrial growth,
intensification of agricultural production, river-basin development,
recreational use of waters, and domestic and industrial exploitation of
shore properties. Accelerated eutrophication causes changes in plant
and animal life--changes that often interfere with use of water,
detract from natural beauty, and reduce property values.'' Inputs of
nitrogen and phosphorus lead to over-enrichment in many of the Nation's
waters and create a widespread, persistent, and growing problem.
Nitrogen and phosphorus pollution in fresh water systems can
significantly impact aquatic life and long-term ecosystem health,
diversity, and balance. More specifically, high nitrogen and phosphorus
loadings result in harmful algal blooms (HABs), reduced spawning
grounds and nursery habitats, fish kills, and oxygen-starved hypoxic or
``dead'' zones. Public health concerns related to nitrogen and
phosphorus pollution include impaired surface and groundwater drinking
water sources from high levels of nitrate-nitrogen, formation of
nitrogenous disinfection byproducts in drinking water, and increased
exposure to toxic microbes such as cyanobacteria.3 4
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    \1\ To be used by living organisms, nitrogen gas must be fixed
into its reactive forms; for plants, this generally includes either
nitrate or ammonia (Boyd, C.E. 1979. Water Quality in Warmwater Fish
Ponds. Alabama Agricultural Experiment Station, Auburn, AL).
Eutrophication is defined as the natural or artificial addition of
nitrogen/phosphorus to bodies of water and to the effects of added
nitrogen/phosphorus (National Academy of Sciences (U.S). 1969.
Eutrophication: Causes, Consequences, Correctives. National Academy
of Sciences, Washington, DC).
    \2\ National Academy of Sciences (U.S). 1969. Eutrophication:
Causes, Consequences, Correctives. National Academy of Sciences,
Washington, DC.
    \3\ Villanueva, C.M. et al., 2006. Bladder cancer and exposure
to water disinfection by-products through ingestion, bathing,
showering, and swimming in pools. American Journal of Epidemiology
165(2):148-156.
    \4\ USEPA. Environments and Contaminants: Drinking water
contaminants U.S. Environmental Protection Agency, Office of
Research and Development. Accessed December 2017. https://www.epa.gov/sites/production/files/2015-10/documents/ace3_drinking_water.pdf.
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    Elevated nitrogen and phosphorus levels can occur locally in a
stream or groundwater aquifer, or can accumulate much further
downstream leading to degraded lakes, reservoirs, and estuaries and
material impacts on fish and other aquatic life.5 6 Excess
nitrogen and phosphorus in water bodies come from many sources, which
can be grouped into five major categories: (1) Urban stormwater
runoff--sources associated with urban land use and development, (2)
municipal and industrial waste water discharges, (3) row crop
agriculture, (4) livestock production, and (5) atmospheric deposition
from the production of nitrogen oxides in electric power generation and
internal combustion engines.
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    \5\ National Research Council. 2000. Clean Coastal Waters:
Understanding and Reducing the Effects of Nutrient Pollution.
National Academies Press, Washington, DC.
    Howarth, R.W., A. Sharpley & D. Walker. 2002. Sources of
nutrient pollution to coastal waters in the United States:
Implications for achieving coastal water quality goals. Estuaries
25(4b):656-676.
    Smith, V.H. 2003. Eutrophication of freshwater and coastal
marine ecosystems. Environmental Science and Pollution Research
10(2):126-139.
    Dodds, W.K., W.W. Bouska, J.L. Eitzmann, T.J. Pilger, K.L.
Pitts, A.J. Riley, J.T. Schloesser & D.J. Thornbrugh. 2009.
Eutrophication of U.S. freshwaters: Analysis of potential economic
damages. Environmental Science and Technology 43(1):12-19.
    \6\ State-EPA Nutrient Innovations Task Group. 2009. An Urgent
Call to Action: Report of the State-EPA Nutrient Innovations Task
Group.
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2. Adverse Impacts of Nitrogen and Phosphorus Pollution on Aquatic
Life, Human Health, and the Economy
    The causal pathways that lead from human activities to excess
nutrients to impacts on designated uses in lakes and reservoirs are
well established in the scientific literature (e.g., Vollenweider,
1968; NAS, 1969; Schindler et al., 1973; Schindler, 1974; Vollenweider,
1976; Carlson, 1977; Paerl, 1988; Elser et al., 1990; Smith et al.,
1999; Downing et al., 2001; Smith et al., 2006; Elser et al., 2007).\7\
When excessive nitrogen and phosphorus loads alter a waterbody's
complement of algal and plant species, the corresponding changes in
habitat and available food resources can induce cascading effects on
the entire food web. Algal blooms block sunlight that submerged plants
need to grow, leading to a decline in the availability of submerged
aquatic vegetation and a reduction in habitat for juvenile fish and
some other aquatic organisms. Algal blooms can also increase turbidity
and impair the ability of sight-feeding fish and other aquatic life to
find food.\8\ Large concentrations of algae can also damage or clog the
gills of fish and certain invertebrates.\9\ Excessive algal blooms can
lead to shifts in a waterbody's production and consumption of dissolved
oxygen (DO) resulting in reduced DO levels that are sufficiently low to
harm or kill important recreational species such as walleye, striped
bass, and black bass.
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    \7\ Vollenweider, R.A. 1968. Scientific Fundamentals of the
Eutrophication of Lakes and Flowing Waters, With Particular
Reference to Nitrogen and Phosphorus as Factors in Eutrophication
(Tech Rep DAS/CS/68.27, Organisation for Economic Co-operation and
Development, Paris. National Academy of Science. 1969.
Eutrophication: Causes, Consequences, Correctives. National Academy
of Science, Washington, DC.
    Schindler D.W., H. Kling, R.V. Schmidt, J. Prokopowich, V.E.
Frost, R. A. Reid & M. Capel. 1973. Eutrophication of Lake 227 by
addition of phosphate and nitrate: The second, third, and fourth
years of enrichment 1970, 1971, and 1972. Journal of the Fishery
Research Board of Canada 30:1415-1440.
    Schindler D.W. 1974. Eutrophication and recovery in experimental
lakes: Implications for lake management. Science 184:897-899.
    Vollenweider, R.A. 1976. Advances in Defining Critical Loading
Levels for Phosphorus in Lake Eutrophication. Memorie dell'Istituto
Italiano di Idrobiologia 33:53-83.
    Carlson R.E. 1977. A trophic state index for lakes. Limnology
and Oceanography 22:361-369.
    Paerl, H.W. 1988. Nuisance phytoplankton blooms in coastal,
estuarine, and inland waters. Limnology and Oceanography 33:823-847.
    Elser, J.J., E.R. Marzolf & C.R. Goldman. 1990. Phosphorus and
nitrogen limitation of phytoplankton growth in the freshwaters of
North America: A review and critique of experimental enrichments.
Canadian Journal of Fisheries and Aquatic Science 47:1468-1477.
    Smith, V.H., G.D. Tilman & J.C. Nekola. 1999. Eutrophication:
Impacts of excess nutrient inputs on freshwater, marine, and
terrestrial ecosystems. Environmental Pollution 100:179-196.
    Downing, J. A., S. B. Watson & E. McCauley. 2001. Predicting
cyanobacteria dominance in lakes. Canadian Journal of Fisheries and
Aquatic Sciences 58:1905-1908.
    Smith, V.H., S.B. Joye & R.W. Howarth. 2006. Eutrophication of
freshwater and marine ecosystems. Limnology and Oceanography 51:351-
355.
    Elser, J.J., M.E.S. Bracken, E.E. Cleland, D.S. Gruner, W.S.
Harpole, H. Hillebrand, J.T. Ngai, E.W. Seabloom, J.B. Shurin & J.E.
Smith. 2007. Global analysis of nitrogen and phosphorus limitation
of primary production in freshwater, marine, and terrestrial
ecosystems. Ecology Letters 10:1135-1142.
    \8\ Hauxwell, J., C. Jacoby, T. Frazer, and J. Stevely. 2001.
Nutrients and Florida's Coastal Waters. Florida Sea Grant Report No.
SGEB-55. Florida Sea Grant College Program, University of Florida,
Gainesville, FL.
    \9\ NOAA. 2017. Ocean Facts: Are All Algal Blooms Harmful?
National Oceanic and Atmospheric Administration, National Ocean
Service. <https://oceanservice.noaa.gov/facts/habharm.html>.
Accessed December 2017.
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    Excessive algal growth also contributes to increased oxygen
consumption associated with decomposition (e.g., large quantities of
senescing and decaying algal cells), in many instances reducing oxygen
to levels below that needed for aquatic life to survive and
flourish.10 11 Mobile species, such as adult fish, can
sometimes survive by moving to areas with more oxygen. However,
migration to avoid hypoxia depends on species mobility, availability of
suitable habitat (i.e., refugia), and adequate environmental cues for
migration. Less mobile or immobile species, such as mussels, cannot
move to avoid low oxygen and are often killed during hypoxic
events.\12\ While certain mature

aquatic animals can tolerate a range of dissolved oxygen levels that
occur in the water, younger life stages of fish and shellfish often
require higher levels of oxygen to survive.\13\ Sustained low levels of
dissolved oxygen cause a severe decrease in the amount of aquatic life
in hypoxic zones and affect the ability of aquatic organisms to find
necessary food and habitat.
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    \10\ NOAA. 2017. Ocean Facts: Are All Algal Blooms Harmful?
National Oceanic and Atmospheric Administration, National Ocean
Service. https://oceanservice.noaa.gov/facts/habharm.html.
    \11\ USEPA. 2017. What is Hypoxia and What Causes It? U.S.
Environmental Protection Agency. <https://www.epa.gov/ms-htf/hypoxia-101>. Accessed December 2017.
    \12\ ESA. 2017. Hypoxia. Ecological Society of America <https://www.esa.org/esa/wp-content/uploads/2012/12/hypoxia.pdf>. Accessed
December 2017.
    \13\ USEPA. 1986. Ambient Water Quality Criteria for Dissolved
Oxygen Freshwater Aquatic Life. EPA-800-R-80-906. Environmental
Protection Agency, Office of Water, Washington, DC.
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    In freshwater lakes and reservoirs, blooms of cyanobacteria
(sometimes referred to as blue-green algae),\14\ can produce toxins
that have been implicated as the cause of a number of fish and bird
mortalities.\15\ These toxins have also been tied to the death of pets
and livestock that may be exposed through drinking contaminated water
or grooming themselves after bodily exposure.\16\ Cyanobacterial toxins
can also pass through normal drinking water treatment processes and
pose an increased risk to humans or animals.\17\
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    \14\ CDC. 2017. Harmful Algal Bloom (HAB)-Associated Illness.
Centers for Disease Control and Prevention. <https://www.cdc.gov/habs/> Accessed December 2017.
    \15\ Ibelings, B.W. & K.E. Havens. 2008. Chapter 32:
Cyanobacterial toxins: A qualitative meta-analysis of
concentrations, dosage and effects in freshwater, estuarine and
marine biota. In: Cyanobacterial Harmful Algal Blooms: State of the
Science and Research Needs. From the Monograph of the September 6-
10, 2005 International Symposium on Cyanobacterial Harmful Algal
Blooms (ISOC-HAB) in Durham, NC. <http://www.epa.gov/cyano_habs_symposium/monograph/Ch32.pdf>. Accessed August 19, 2010.
    \16\ WHOI. 2008. HAB Impacts on Wildlife. Woods Hole
Oceanographic Institution. <http://www.whoi.edu/redtide/page.do?pid=9682>. Accessed December 2009.
    \17\ Carmichael, W.W. 2000. Assessment of Blue-Green Algal
Toxins in Raw and Finished Drinking Water. AWWA Research Foundation,
Denver, CO.
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    Elevated nitrogen and phosphorus levels in lakes and reservoirs can
impact human health and safety and otherwise detract from the outdoor
recreational experience. For example, nutrient pollution in lakes
typically promotes higher densities of phytoplankton, which can reduce
the clarity of the water column to the detriment of swimmer safety.
Cyanobacterial blooms frequently result in high algal toxin (e.g.,
microcystin) concentrations, leading to swimming beach closures and
issuance of health advisories/warnings. In areas where recreation is
determined to be unsafe because of algal blooms, warning signs often
are posted to discourage human contact with the affected waters.
    Many other states, and countries for that matter, are experiencing
problems with harmful algal blooms (HABs).18 19 Scientific
assessments and numerous studies have shown an increase of HAB
occurrence, distribution and persistence in the U.S. and globally in
recent years.20 21 22 In a recent scientific assessment,
reviewers found that observed increases in water temperatures alter the
seasonal windows of growth and the geographic range of suitable habitat
for freshwater toxin-producing harmful algae and marine toxin-producing
harmful algae.\23\ These changes may increase the risk of exposure to
waterborne pathogens and algal toxins that can cause a variety of
illnesses. In addition, runoff from more frequent and intense extreme
precipitation events may increasingly compromise recreational waters,
shellfish harvesting waters, and sources of drinking water through
increased prevalence of toxic algal blooms. An example of an algal
bloom event occurred on August 10, 2017,\24\ when officials from the
Oakland Country Health Division located near Detroit, Michigan issued a
warning for residents and their pets to avoid two local lakes due to
the presence of an algal bloom. People were advised to avoid contact
with the water through recreation and to avoid drinking the water. In a
July 7, 2017 article,\25\ the number of reports of harmful algal blooms
affecting lakes and ponds in New York, as tracked by the New York State
Department of Environmental Conservation, were increasing early in the
season. Reducing nutrient input is one of the strategies lake managers
are employing throughout the State to address the growing problem of
algal blooms. Species of cyanobacteria commonly associated with
freshwater algal blooms include: Microcystis aeruginosa, Anabaena
circinalis, Anabaena flos-aquae, Aphanizomenon flos-aquae, and
Cylindrospermopsis raciborskii. Under certain conditions, some of these
species can release neurotoxins (affect the nervous system),
hepatotoxins (affect the liver), lipopolysaccharide compounds inimical
to the human gastrointestinal system, and tumor promoting
compounds.\26\ One study showed that at least one type of cyanobacteria
has been linked to cancer and tumor growth in animals.\27\
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    \18\ FWCC. 2017. What is a Harmful Algal Bloom? <http://myfwc.com/research/redtide/general/harmful-algal-bloom/>. Accessed
December 2017.
    \19\ Trevino-Garrison, I., DeMent, J., Ahmed, F.S., Haines-
Lieber, P., Langer, T., M[eacute]nager, H., Neff, J., van der Merwe,
D., Carney, E. 2015. Human illnesses and animal deaths associated
with freshwater algal blooms--Kansas. Toxins 7:353-366.
    \20\ Scientific American (2016) https://blogs.scientificamerican.com/guest-blog/toxic-algae-blooms-are-on-the-rise/.
    \21\ Lopez, C.B., Jewett, E.B., Dortch, Q., Walton, B.T.,
Hudnell, H.K. 2008. Scientific Assessment of Freshwater Harmful
Algal Blooms. Interagency Working Group on Harmful Algal Blooms,
Hypoxia, and Human Health of the Joint Subcommittee on Ocean Science
and Technology. Washington, DC.
    \22\ Lopez, C.B., Dortch, Q., Jewett, E.B., Garrison, D. 2008.
Scientific Assessment of Marine Harmful Algal Blooms. Interagency
Working Group on Harmful Algal Blooms, Hypoxia, and Human Health of
the Joint Subcommittee on Ocean Science and Technology. Washington,
DC.
    \23\ USGCRP, 2016: The Impacts of Climate Change on Human Health
in the United States: A Scientific Assessment. Crimmins, A., J.
Balbus, J.L. Gamble, C.B. Beard, J.E. Bell, D. Dodgen, R.J. Eisen,
N. Fann, M.D. Hawkins, S.C. Herring, L. Jantarasami, D.M. Mills, S.
Saha, M.C. Sarofim, J. Trtanj, and L. Ziska, Eds. U.S. Global Change
Research Program, Washington, DC, 312 pp.
    \24\ The Detroit News. Toxic algal blooms spotted in Waterford,
White Lake by Stephanie Steinberg. August 10, 2017. http://www.detroitnews.com/story/news/environment/2017/08/10/toxic-algal-blooms-spotted-waterford-white-lake/104463128/.
    \25\ The New York Times. Beware the Blooms: Toxic Algae Found in
Some City Ponds by Lisa W. Foderaro. July 7, 2017. https://www.nytimes.com/2017/07/07/nyregion/beware-the-blooms-toxic-algae-found-in-some-city-ponds.html.
    \26\ CDC. 2017. Harmful Algal Bloom (HAB)-Associated Illness,
Centers for Disease Control and Prevention. <https://www.cdc.gov/habs/>. Accessed December 2017.
    \27\ Falconer, I.R. & A.R. Humpage. 2005. Health risk assessment
of cyanobacterial (blue-green algal) toxins in drinking water.
International Journal of Research and Public Health 2(1):43-50.
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    Human health also can be impacted by disinfection byproducts
(DBPs), formed when disinfectants (such as chlorine) used to treat
drinking water react with organic carbon produced by algae in source
waters. Some DBPs have been linked to rectal, bladder, and colon
cancers; reproductive health risks; and liver, kidney, and central
nervous system problems.28 29 In their study of 21 water
supply lakes and reservoirs in New York, Callinan et al. (2013)
concluded that ``autochthonous [algal] precursors contribute
substantially to the DBP precursor pool in lakes and reservoirs and the
. . . establishment of [numeric nutrient criteria] for the protection
of [potable water supply] source waters is warranted and feasible.''
\30\
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    \28\ USEPA. 2017. Drinking water Requirements for States and
Public Water Systems, Public Water Systems, Disinfection Byproducts,
and the Use of Monochloramine. U.S. Environmental Protection Agency.
Accessed <https://www.epa.gov/dwreginfo/public-water-systems-disinfection-byproducts-and-use-monochloramine>. December 2017.
    \29\ National Primary Drinking Water Regulations: Stage 2
Disinfectants and Disinfection Byproducts Rule, 40 CFR parts 9, 141,
and 142. U.S. Environmental Protection Agency, FR 71:2 (January 4,
2006). pp. 387-493. Available electronically at: <http://www.epa.gov/fedrgstr/EPA-WATER/2006/January/Day-04/w03.htm>.
Accessed December 2009.
    \30\ Callinan, C.W., J.P. Hassett, J.B. Hyde, R.A. Entringer &
R.K. Klake. 2011. Proposed nutrient criteria for water supply lakes
and reservoirs. Journal of the American Water Works Association
105(4):E157-E172.

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    Implementation of nutrient criteria help to protect lakes and
reservoirs from the negative effects of nutrient pollution, which
frequently include, but are not limited to (a) the occurrence and
spread of toxic algae, (b) the proliferation of certain fish species
that are less desirable to sport anglers (i.e., ``rough'' fish), (c) a
general decline in sensitive aquatic plant and animal populations, (d)
the occurrence of taste and odor problems in drinking water derived
from lakes and reservoirs, (e) Safe Drinking Water Act violations
related to the occurrence of disinfection by-products (e.g.,
trihalomethanes, haloacetic acids) in finished drinking water, (f) a
decline in waterbody transparency with accompanying recreational safety
concerns, (g) the occurrence of unsightly scums and objectionable
odors, (h) the depreciation of lakefront property values,\31\ and (i)
an overall reduction in the functional life expectancy of reservoirs,
with a corresponding loss of return on society's economic investment in
these systems.
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    \31\ USEPA. 2015. A Compilation of Cost Data Associated with the
Impacts and Control of Nutrient Pollution, EPA 820-F-15-096, United
States Environmental Protection Agency, May 2015.
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3. Nutrient Pollution in Missouri Lakes and Reservoirs
    Lake water quality impairments attributable to nutrient pollution
have not been quantified with any degree of precision in Missouri.
Long-term monitoring data are available for about 10 percent of the
State's classified lakes and reservoirs (representing approximately 90
percent of overall lake acreage), and about 15 percent of these
monitored waters already have EPA-approved numeric nutrient criteria.
    Missouri adopted site-specific chlorophyll a, total phosphorus and
total nitrogen criteria for 25 lakes and reservoirs on July 1, 2009,
which were approved by EPA on August 16, 2011. Currently, eleven of
these waterbodies (44 percent) are listed for nutrient pollution-
related impairments. This percentage is consistent with nation-wide
estimates of lakes in the most disturbed category obtained through the
2012 National Lakes Assessment (NLA). Specifically, the NLA estimates
that 40 percent of all lakes and reservoirs in the conterminous U.S.
are considered most disturbed based on elevated phosphorus
concentrations, and 35 percent are considered most disturbed based on
elevated nitrogen concentrations (https://www.epa.gov/national-aquatic-resource-surveys/nla).
    MDNR acknowledges that lake and reservoir eutrophication is
occurring at a detectable rate throughout much of the state.\32\ Over
the past 20 or more years, chlorophyll a levels in monitored
waterbodies have increased by an average of 3.5, 13, 28 and 2.6
[micro]g/L in the Glaciated Plains, Osage Plains, Ozark Border and
Ozark Highlands, respectively.\33\
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    \32\ MDNR. 2016. Missouri Integrated Water Quality Report and
Section 303(d) List, 2016. Missouri Department of Natural Resources,
Jefferson City, Missouri. http://dnr.mo.gov/env/wpp/waterquality/303d/docs/2016-ir-305b-report.pdf.
    \33\ Id.
---------------------------------------------------------------------------

B. Statutory and Regulatory Background

    Section 303(c) of the CWA (33 U.S.C. Sec.  1313(c)) directs states
and authorized tribes \34\ to adopt WQS for their navigable waters.
Section 303(c)(2)(A) and EPA's implementing regulations at 40 CFR part
131 require, among other things, that state WQS include the designated
use or uses to be made of the waters and criteria that protect those
uses. EPA regulations at 40 CFR Sec.  131.11(a)(1) provide that states
and authorized tribes shall ``adopt those water quality criteria that
protect the designated use'' and that such criteria ``must be based on
sound scientific rationale and must contain sufficient parameters or
constituents to protect the designated use. For waters with multiple
use designations, the criteria shall support the most sensitive use.''
---------------------------------------------------------------------------

    \34\ Hereafter referred to as ``states and authorized tribes''.
``State'' in the CWA and in this document, refers to a state, the
District of Columbia, the Commonwealth of Puerto Rico, the U.S.
Virgin Islands, Guam, American Samoa, and the Commonwealth of the
Northern Mariana Islands. ``Authorized tribes'' refers to those
federally recognized Indian tribes with authority to administer a
CWA WQS program.
---------------------------------------------------------------------------

    Additionally, 40 CFR Sec.  130.10(b) provides that ``[i]n
designating uses of a waterbody and the appropriate criteria for those
uses, the state shall take into consideration the water quality
standards of downstream waters and ensure that its water quality
standards provide for the attainment and maintenance of the water
quality standards of downstream waters.''
    States and authorized tribes also are required to hold one or more
public hearings consistent with 40 CFR Sec.  25.5 to review their WQS
at least once every three years and, as appropriate, modify or adopt
new standards and to hold public hearings when revising or adopting new
WQS. (See 33 U.S.C. Sec.  1313 (c)(1) and 40 CFR Sec.  131.20). Any new
or revised WQS must be submitted to EPA for review and approval or
disapproval. 33 U.S.C. Sec.  303(c)(2)(A), (3)). If EPA determines a
state's new or revised standard does not meet the requirements of the
CWA, EPA ``must specify the changes to meet such requirements.'' Sec.
303(c)(3). If the state does not adopt such changes within ninety days,
EPA ``shall promptly prepare and publish proposed regulations'' and
promulgate any revised or new standard within ninety days unless the
state has adopted and EPA has approved a WQS as meeting CWA
requirements. Id.

C. Deriving and Expressing Numeric Nutrient Criteria

    Under CWA section 304(a), EPA periodically publishes criteria
recommendations for use by states and authorized tribes in setting
water quality criteria for particular parameters to protect the
designated uses for their surface waters. Where EPA has published
nationally-recommended criteria, states and authorized tribes have the
option of adopting water quality criteria based on EPA's CWA section
304(a) criteria guidance, section 304(a) criteria guidance modified to
reflect site-specific conditions, or other scientifically defensible
methods. (See 40 CFR 131.11(b)(1)). For nitrogen and phosphorus
pollution, EPA finalized in 2001-2002 numeric nutrient criteria
recommendations (i.e., total nitrogen, total phosphorus, chlorophyll a,
and turbidity) for lakes and reservoirs, and for rivers and streams for
most of the aggregated Level III Ecoregions in the United States. These
were based on EPA's previously published series of peer-reviewed, water
body specific technical guidance manuals regarding the development of
numeric criteria for lakes and reservoirs \35\ and rivers and
streams.\36\
---------------------------------------------------------------------------

    \35\ USEPA. 2000a. Nutrient Criteria Technical Guidance Manual:
Lakes and Reservoirs. EPA-822-B-00-001. U.S. Environmental
Protection Agency, Office of Water, Washington, DC.
    \36\ USEPA. 2000b. Nutrient Criteria Technical Guidance Manual:
Rivers and Streams. EPA-822-B-00-002. U.S. Environmental Protection
Agency, Office of Water, Washington, DC.
---------------------------------------------------------------------------

    In general, there are three types of empirical analyses that
provide distinctly different, independent and scientifically
defensible, approaches for deriving nutrient criteria from field data.
These include (1) the ``reference condition approach,'' which derives
criteria based on the observed water quality characteristics of
minimally disturbed or least disturbed waterbodies, (2) the
``mechanistic modeling approach,'' which employs mathematical
representations of ecological systems, processes and parameters using
equations that can be calibrated using site-specific data, and (3) the
``stressor-response-based

modeling approach,'' \37\ which uses available data to estimate
statistical relationships between nutrient concentrations and response
(ecological, recreational, human health) measures relevant to the
designated use to be protected. Each of these approaches is appropriate
for deriving scientifically defensible numeric nutrient criteria. Other
approaches may be appropriate depending on specific circumstances.
Numeric nutrient criteria also may be based on well-established (e.g.,
peer-reviewed, published, widely recognized) nutrient response
thresholds relating to the protection of a given designated use.\38\
---------------------------------------------------------------------------

    \37\ USEPA. 2010. Using Stressor-response Relationships to
Derive Numeric Nutrient Criteria. EPA-820-S-10-001. U.S.
Environmental Protection Agency, Office of Water, Washington, DC.
    \38\ USEPA. 2000a. Nutrient Criteria Technical Guidance Manual:
Lakes and Reservoirs. EPA-822-B-00-001. U.S. Environmental
Protection Agency, Office of Water, Washington, DC.
---------------------------------------------------------------------------

    EPA has long recommended that states adopt numeric criteria for
total nitrogen (TN) and total phosphorus (TP),\39\ the nutrients that
in excess can ultimately cause adverse effects on designated uses. For
this reason, TN and TP are often referred to as ``causal'' parameters.
However, EPA recognizes that the specific levels of TN and TP that
adversely affect designated uses, including harm to aquatic life as
indicated by various measures of ecological responses, may vary from
waterbody to waterbody, depending on many factors, including
geomorphology and hydrology among others. As a result, EPA has worked
with several states as they developed a combined criterion approach
that allows a state to further consider whether a waterbody is meeting
designated uses when elevated TN and TP levels are detected. Under this
approach, an exceedance of a causal variable, acts as a trigger to
consider additional physical, chemical, and biological parameters that
serve as indicators to determine protection or impairment of designated
uses; these additional parameters are collectively termed ``response''
parameters.
---------------------------------------------------------------------------

    \39\ Id.
---------------------------------------------------------------------------

    EPA's articulation of this combined criterion approach \40\ is
intended to apply when states wish to rely on response parameters to
determine whether a designated use is impaired, once a causal variable
has been found to be above an adopted threshold. As with any criteria,
states should make clear at what point it has determined that a
waterbody is meeting or not meeting its designated use. EPA has
expressed that numeric values for all parameters must be set at levels
that protect these uses (i.e., before adverse conditions occur that
would require restoration).\41\
---------------------------------------------------------------------------

    \40\ This approach is sometimes referred to as a
``bioconfirmation'' approach despite the fact that response
parameters may not all be ``biological,'' although they typically do
reflect biological activity.
    \41\ USEPA. Guiding Principles on an Optional Approach for
Developing and Implementing a Numeric Nutrient Criterion that
Integrates Casual and Response Parameters. September 2013.
---------------------------------------------------------------------------

    EPA has worked extensively with states that have adopted a combined
criterion approach, resulting in CWA section 303(c) approvals of
combined criterion approaches for Florida's streams,42 43
Minnesota's rivers and streams,\44\ and Vermont's lakes and
reservoirs.\45\ Although each of these combined criterion approaches
differ from one another in terms of the applicable causal parameters
and suite of response parameters as applied to various waterbody types,
the combined criterion construction can provide greater precision when
there is heightened variability in waterbodies' responses to nutrients.
---------------------------------------------------------------------------

    \42\ USEPA. Letter from James D. Giattina, Director, Water
Protection Division, EPA Region 4, to Herschel T. Vinyard,
Secretary, Florida Department of Environmental Protection. November
30, 2012.
    \43\ USEPA. Letter from James D. Giattina, Director, Water
Protection Division, EPA Region 4, to Herschel T. Vinyard,
Secretary, Florida Department of Environmental Protection. June 27,
2013.
    \44\ USEPA. Letter from Tinka Hyde, Director, Water Division,
EPA Region 5, to Commissioner John Line Stine, Minnesota Pollution
Control Agency. January 23, 2015.
    \45\ USEPA. Letter from Kenneth Moraff, Director, Office of
Ecosystem Protection, EPA Region 1 to Alyssa Schuren, Commissioner,
Vermont Department of Environmental Conservation. September 15,
2015.
---------------------------------------------------------------------------

    EPA notes that once appropriate numeric criteria are developed,
assessment of the impairment status of individual water bodies is
dependent on data; this is true for any set of numeric criteria
addressing any pollutant. EPA further recognizes that it is the
responsibility of States to determine the pace and prioritization of
data collection, as this is primarily an implementation issue rather
than a criteria development issue. However, EPA recommends that states
consider such implementation issues at the time of criteria development
as this may lead to a more successful water quality standards program
generally. In the case of nutrient criteria, EPA has recommended that
states interested in this approach develop a biological assessment
program that can measure biological responses and other nutrient-
related response parameters with confidence through a robust monitoring
program to account for spatial and temporal variability to document the
effects of nutrient pollution. EPA reiterates, however, that States
have significant discretion in determining the appropriate pace and
prioritization of such a monitoring program.
    In developing combined criteria, States and EPA have previously
identified the following as response parameters that are indicative of
nutrient pollution in streams: measures of primary productivity (e.g.
benthic chlorophyll a, percent cover of macrophytes), measures of algal
assemblage (e.g. algal assemblage indices), and measures of ecosystem
function (e.g. continuously monitored pH and dissolved oxygen). EPA
recognizes that this may not be an exhaustive list of appropriate
response parameters. The approach is generally applicable to lakes and
reservoirs, as well as other waterbody types. For lakes and reservoirs,
chlorophyll a has typically been measured as sestonic (open water)
concentration rather than as a benthic (bottom surface) concentration.
Appropriate biological response parameters should directly link
nutrient concentrations to the protection of designated uses. The
appropriate type and quantity of response parameters may vary by state,
ecosystem, and waterbody type.
    In previous guidance, EPA has recommended that a combined criterion
approach should make clear the impairment status of waterbodies in the
following situations.\46\ Specifically, EPA has recommended that if all
causal and response parameters are met, then the water quality
criterion is met and the waterbody is deemed to be meeting its
designated uses. If all response parameters are met, but one or more of
the causal parameters is exceeded, then the criterion is met and the
waterbody is deemed to be meeting its designated uses (though the state
may wish to flag this water body for further scrutiny in the future).
If a causal parameter is exceeded and any applicable response parameter
is exceeded, then the criterion is not met and the waterbody is deemed
to not be meeting its designated uses. If a causal parameter is
exceeded and data are unavailable for any applicable response
parameters, then the criterion is not met and the waterbody is deemed
to not be meeting its designated uses. If a causal parameter is not
exceeded but an applicable response variable is exceeded, then the
criterion is not met and the waterbody is deemed to not be meeting its
designated uses (in this scenario, further

investigation may be warranted to determine if nutrient pollution is
the cause).
---------------------------------------------------------------------------

    \46\ USEPA. Guiding Principles on an Optional Approach for
Developing and Implementing a Numeric Nutrient Criterion that
Integrates Casual and Response Parameters. September 2013.
---------------------------------------------------------------------------

    One situation deserves special consideration. If a causal parameter
is exceeded and data are unavailable for any applicable response
parameters, EPA has previously recommended that the criterion be deemed
not met and the waterbody be deemed to not be meeting its designated
uses. Under one of EPA's co-proposed approaches (which mirrors the
State's 2017 proposal), such waterbodies would be deemed
``undetermined'' with respect to impairment status. Under the other co-
proposed approach, which matches EPA's prior recommendations, the water
body is deemed to be impaired, until all response variables have been
assessed, at which point the water body status may be changed to non-
impaired if no response variable is exceeded. EPA has recommended this
approach in the past on the grounds that an exceedance of a causal
variable will generally correlate with impairment of aquatic life uses,
but we preserve the flexibility for states to conclude that a waterbody
is not impaired if information indicates the absence of a response in
the waterbody supporting the conclusion that the use is being
protected. EPA recognizes there are alternative views of how this
comports with requirements that criteria be based on a sound scientific
rationale and protective of designated uses, believing if data on some
response variables are missing, then it may not be known whether the
water body is meeting its designated use or not, and an
``undetermined'' status with respect to impairment may be appropriate.
EPA solicits comment on whether response variables are the best
indicators of impairment or non-impairment, and the science policy
considerations relevant to determining whether a water body is meeting
its designated use if data on some or all response variables are
missing.
    The approach described above ensures protection of designated uses
by taking into account critical information about the pollutant load in
the waterbody, as well as the response. Although the terminology of the
combined criterion approach more closely aligns with assessment and
listing terminology, the combined criterion is also the applicable WQS
for NPDES permitting purposes whereby permits must contain limits for
any pollutant parameters that are or may be discharged at levels that
will cause, have reasonable potential to cause, or contribute to an
excursion above any WQS (40 CFR 122.44(d)(1)).

D. Missouri's 2009 Nutrient Criteria Submission and EPA's Clean Water
Act Section 303(c) Action

    On November 5, 2009, Missouri submitted revised WQS containing
nutrient criteria for a large subset of the State's classified lakes
and reservoirs. These standards contained the following language at 10
CSR 20-7.031(4)(N)2: ``This [nutrient criteria] rule applies to all
lakes and reservoirs that are waters of the state and that are outside
the Big River Floodplain Ecoregion and have an area of at least ten
(10) acres during normal pool.'' Table G in Missouri's WQS regulations
listed 453 classified lakes and reservoirs, 25 of which were deemed
``high quality'' and were assigned site-specific nutrient criteria
separately in Table M. Of the remaining waters, 96 were smaller than
ten acres and/or located in the Big River Floodplain Ecoregion and
exempted from the application of nutrient criteria under 10 CSR 20-
7.031(4)(N)2. Conversely, 332 lakes and reservoirs not listed in Table
M were subject to the application of nutrient criteria under 10 CSR 20-
7.031(4)(N)2 and (4)(N)3 at the time Missouri submitted its nutrient
criteria to EPA. On August 16, 2011, EPA approved all nutrient criteria
assigned to the 25 waterbodies listed in Table M but disapproved
nutrient criteria that would have applied to the remaining waterbodies.
Additionally, EPA disapproved site-specific criteria for total
phosphorus assigned to the tributary arms of two large reservoirs (Lake
of the Ozarks and Table Rock Lake) per 10 CSR 20-7.031(4)(N)3.A.IV.
    The disapproved water quality standards defined ``prediction
values,'' ``reference values'' and ``site specific-values'' and derived
total phosphorus (TP) criteria based on how these values compared to
one another. This approach involved a set of input variables and site-
specific data requirements. For example, the regulation established
that TP prediction values for lakes and reservoirs in the Plains must
be calculated based on site-specific coefficients for the (a)
percentage of watershed originally in prairie, (b) hydraulic residence
time in years, and (c) dam height in feet. To apply the appropriate TP
criterion, the State would have had to know how the TP prediction value
compared to both the TP reference value and the actual (empirically
determined) TP concentration. Total nitrogen (TN) and chlorophyll a
criteria were calculated as multiples of the selected TP criterion.
    EPA's disapproval action was based on a determination that
Missouri's proposal did not include the data and other necessary
information needed for EPA to independently reproduce the State's work
and that the State had failed to demonstrate that the criteria would
protect the designated aquatic life support and recreational uses as
required by 40 CFR 131.6(b) and (c).\47\
---------------------------------------------------------------------------

    \47\ US EPA. (2011) Letter to Sara Parker Pauley (Director,
Missouri Department of Natural Resources) from Karl Brooks (USEPA
Region 7), Decision document on Missouri Water Quality Standards,
August 16, 2011.
---------------------------------------------------------------------------

    On March 19, 2014, Missouri submitted revised water quality
standards (the designated uses component) that incorporated, for the
first time, the Missouri Use Designation Dataset (MUDD) (10 CSR 20-
7.031(2)(E); see also Table G of WQS which references the MUDD \48\).
This dataset assigned designated uses to the State's classified lakes
and reservoirs (and streams) and was approved by EPA on October 22,
2014. Altogether, MUDD identified 3,081 waterbody segments, including
2,757 lakes and reservoirs, and assigned the following designated uses
to these waters: aquatic life support, whole body contact recreation,
secondary contact recreation, fish consumption, livestock and wildlife
watering, irrigation, and industrial water supply. In addition to these
uses, 123 lakes and reservoirs are also designated in the 2014 MUDD
dataset for drinking water supply. Missouri also revised its water
quality standards to provide that its specific criteria applies to all
waters consistent with the designated uses identified in Table G and
MUDD. 10 CSR 20-7.031(5). EPA approved this change on November 17,
2015. EPA's proposed rule addresses the same generic class of waters
included in Missouri's disapproved rule. However, consistent with
Missouri's subsequent actions, EPA's proposal would apply to a larger
group of enumerated lakes and reservoirs, specifically those in Table G
and MUDD that are ten acres or more, not located in the Big River
Floodplain Ecoregion, and not otherwise listed in Table M of the WQS.
This includes 967 waterbodies. EPA requests comment on whether this
scope is appropriate for the current rule.
---------------------------------------------------------------------------

    \48\ The Water Body Name, Missouri Use Designation Dataset
Version 1.0, August 20, 2013 (8202013 MUDD V1.0), refers to all
lakes in the Missouri Use Designation Dataset Version 1.0, August
20, 2013, that are not otherwise listed in Table G.
---------------------------------------------------------------------------

E. Missouri Coalition for the Environment (MCE) Lawsuit and Consent
Decree

    On February 24, 2016, the Missouri Coalition for the Environment
Foundation (MCE) filed a lawsuit alleging that EPA failed to perform
its

nondiscretionary duty to propose and promulgate new or revised water
quality standards for lakes and reservoirs in Missouri after
disapproving the State's submission in 2011. On December 1, 2016, EPA
entered into a consent decree with MCE that stipulates that EPA shall
sign a notice of proposed rulemaking by December 15, 2017, to address
EPA's 2011 disapproval, unless the State submits and EPA approves new
or revised standards that address the disapproval on or before December
15, 2017; and that EPA shall sign a notice of final rulemaking on or
before December 15, 2018, unless the State submits and EPA approves new
or revised standards that address the disapproval. In the years
following the 2011 disapproval action, EPA has endeavored to work
closely with Missouri to develop approvable nutrient criteria.

F. Missouri's 2017 Proposed Nutrient WQS

    On October 16, 2017, MDNR continued to develop revised numeric
nutrient criteria and formally issued its proposed WQS that are
intended to address EPA's August 16, 2011 disapproval. Based on EPA's
examination of the State's proposed rule, Missouri has characterized
its revised nutrient WQS as a combined criterion. Missouri's proposed
rule applies to lakes and reservoirs.\49\ The State's lakes and
reservoirs are impounded and have been assigned an aquatic life use of
either: Warm water habitat, cool water habitat, or cold water habitat.
Each subcategory is defined as ``waters in which naturally-occurring
water quality and habitat conditions allow [for] the maintenance of a
wide variety of [warm, cool or cold water] biota.'' \50\ The State
takes the position that ``health of sport fish populations can be
interpreted as an indicator of overall ecosystem health and the
presence of a ``wide variety'' of aquatic biota.'' \51\ Missouri's
proposed rule establishes three ecoregions and sets forth for each
ecoregion chl-a criteria above which waters would be deemed impaired,
and a combination of TN, TP, and chl-a ``screening values'' and five
``eutrophication impacts'' (i.e., response parameters) where a
waterbody would be deemed impaired if at least one screening value and
at least one eutrophication impact are exceeded in the same year. When
data are unavailable for the eutrophication impacts despite information
indicating that at least one screening value is exceeded, Missouri
intends waters to be listed on Category 3 of the 305(b)/303(d)
Integrated Report, meaning there is insufficient information to
determine impairment status. In Missouri's expression of the combined
criterion approach, the chl-a parameter functions as both a screening
value, requiring evaluation of the eutrophication impacts, and at a
higher level as a stand-alone criterion that would determine in and of
itself that a water body is impaired, without the need to further
assess eutrophication impacts. If chl-a is exceeded at the screening
level but there is inadequate information on the other response
variables, the water is placed in category 3 and not listed as
impaired.
---------------------------------------------------------------------------

    \49\ See 10 CSR 20-7.031(5) and the October 2017 draft language
proposed for 10 CSR 20-7.031(5)(N)(2) (``This rule applies to all
lakes that are waters of the state and have an area of at least ten
(10) acres during normal pool conditions. Big River Floodplain lakes
shall not be subject to these criteria'').
    \50\ 10 CSR 20-7.031(1)(C)1.A.VI, B.V and C.V.
    \51\ See Missouri Department of Natural Resources, Rationale for
Missouri Reservoir Nutrient Criteria Development, November 2016,
Section 6.1, pages 33-39.
---------------------------------------------------------------------------

Table 2. Excerpts From Missouri's October 16, 2017 Nutrient Proposal

                 Table L--Lake Ecoregion Chl-a Criteria and Nutrient Screening Values ([mu]g/L)
----------------------------------------------------------------------------------------------------------------
                                                                            Screening Values ([mu]g/L)
                 Lake Ecoregion                        Chl-a     -----------------------------------------------
                                                     Criterion          TP              TN             Chl-a
----------------------------------------------------------------------------------------------------------------
Plains..........................................              30              49             843              18
Ozark Border....................................              22              40             733              13
Ozark Highland..................................              15              16             401               6
----------------------------------------------------------------------------------------------------------------
5. Lakes with water quality that exceed Nutrient Criteria identified in Tables L and M are to be deemed impaired
  for excess nutrients.
6. Lakes with water quality that exceed screening values for Chl-a, TN, or TP are to be deemed impaired for
  excess nutrients if any of the following eutrophication impacts are documented for the respective designated
  uses within the same year. Eutrophication impacts for aquatic life uses include:
(I) Occurrence of eutrophication-related mortality or morbidity events for fish and other aquatic organisms;
(II) Epilimnetic excursions from dissolved oxygen or pH criteria;
(III) Cyanobacteria counts in excess of 100,000 cells per milliliter (cells/ml);
(IV) Observed shifts in aquatic diversity attributed to eutrophication; and
(V) Excessive levels of mineral turbidity that consistently limit algal productivity during the period May 1-
  September 30

    At the time of this proposal, Missouri's proposal is still under
consideration and the State has not submitted to EPA for CWA 303(c)
review a final rule with supporting information to address EPA's 2011
disapproval.

III. Proposed Nutrient Combined Criterion for Lakes and Reservoirs in
Missouri

A. Proposed Combined Criterion Approaches

    Today EPA is proposing two alternatives to establish nutrient
criteria in a combined criterion approach to address its 2011
disapproval. Under the first alternative, EPA proposes nutrient
protection values and eutrophication impact factors in a combined
criterion approach. Under the second alternative, EPA proposes a
combined criterion approach that would mirror the State of Missouri's
October 2017 proposal for lake nutrient water quality standards. EPA
seeks public comment on the two alternatives described below in light
of the federal regulations at 40 CFR part 131.11 requiring that
criteria must be based on a sound scientific rationale and protective
of the designated uses of the waters.

B. Proposed Combined Criterion Alternative 1

    Alternative 1 is presented in Table 3 below and appears as
regulatory text at the end of this proposal.

    Table 3--Alternative 1 Lake Ecoregion Nutrient Protection Values ([micro]g/L) and Eutrophication Impacts
----------------------------------------------------------------------------------------------------------------
                         Lake Ecoregion                                 TP              TN             Chl-a
----------------------------------------------------------------------------------------------------------------
Plains..........................................................              44             817              14
Ozarks..........................................................              23             500             7.1
----------------------------------------------------------------------------------------------------------------
(1) Lake and reservoir water quality must not exceed nutrient protection values for chlorophyll-a. (2) Lake and
  reservoir water quality must also not exceed nutrient protection values for total nitrogen and total
  phosphorus unless each of the following eutrophication impacts are evaluated and none occur within the same
  three-year rolling average period: (I) Eutrophication-related mortality or morbidity events for fish and other
  aquatic organisms; (II) An excursion from the DO or pH criteria in Missouri water quality standards applicable
  for Clean Water Act purposes; (III) Cyanobacteria counts equal to or greater than 100,000 cells per ml; (IV)
  Observed shifts in aquatic diversity directly attributable to eutrophication; or (V) Excessive levels of
  mineral turbidity that consistently limit algal productivity during the period May 1-September 30, or Secchi
  disk measurements of turbidity equal to or less than EPA's recommended Level III Ecoregions IX (1.53 m) or IX
  (2.86 m).

    Alternative 1 is comprised of nutrient protection values and
eutrophication impacts. Nutrient protection values are defined
similarly as Missouri defines their ``screening values'': maximum
ambient concentrations of TP, TN, and chl-a based on the three-year
rolling average geometric mean of nutrient data collected April through
September. EPA has chosen the term ``protection values,'' rather than
``causal'' or ``screening'' values, to emphasize that in general, lakes
and reservoirs that do not exceed these values may be assumed to meet
designated uses without further assessment of eutrophication impacts.
However, EPA recognizes, consistent with the logic of the combined
criteria approach, that exceedance of such values does not necessarily
mean that a water body is impaired. Alternative 1 uses nutrient
protection values for TN, TP, and chl-a derived using a reference
condition approach for the Plains ecoregion and a combined Ozarks
ecoregion described in detail in the following section. These values
are based on a reference condition approach using the 75th percentile
of a distribution of values from a population of least disturbed lakes
in each of the two ecoregions (Plains and Ozarks). The nutrient
protection values for chl-a in Alternative 1 function as stand-alone
criteria independent from the TN and TP protection values and other
eutrophication impact factors. This approach gives additional weight to
chl-a as a key early response indicator of adverse impact from excess
nitrogen and phosphorus.
    Under Alternative 1, lake and reservoir water quality must not
exceed protection values for TN or TP unless each of the eutrophication
impacts are evaluated and data demonstrate that none occur within the
same three-year rolling average period as a TN or TP exceedance. EPA
included this presumption to address potential for data gaps for
response parameters.\52\ As such, when TN and TP levels are exceeded,
the designated uses would be considered impaired unless sufficient
information exists demonstrating no eutrophication impacts are
occurring. Eutrophication impacts include: (I) Eutrophication-related
mortality or morbidity events for fish and other aquatic organisms;
(II) An excursion from the dissolved oxygen (DO) or pH criteria in
Missouri water quality standards applicable for Clean Water Act
purposes; (III) Cyanobacteria counts equal to or greater than 100,000
cells per ml; (IV) Observed shifts in aquatic diversity directly
attributable to eutrophication; or (V) Excessive levels of mineral
turbidity that consistently limit algal productivity during the period
May 1-September 30, or Secchi disk measurements of turbidity equal to
or less than EPA's recommended Level III Ecoregions IX (1.53 m) or IX
(2.86 m). Alternative 1 does not include a qualifier of ``epilimnetic''
with respect to excursion of DO or pH criteria to reflect that aquatic
habitat extends beyond the surficial layer of lakes and reservoirs, and
to be consistent with the State's currently approved DO and pH
criteria. Alternative 1 includes specific Secchi disk measurement
thresholds as part of the turbidity component to provide a means of
quantifying this eutrophication impact factor.\53\
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    \52\ EPA recognizes that there are differences of opinion on
whether addressing such data gaps is necessary in a combined
criteria approach and that this presumption is not a feature of the
co-proposed Alternative 2.
    \53\ Secchi disk measurement thresholds could be those presented
in in EPA's Level III ecoregional criteria documents (1.53 m for
Ecoregion IX and 2.86 for Ecoregion XI). See USEPA. December 2000.
Ambient Water Quality Criteria Recommendations, Information
Supporting the Development of State and Tribal Nutrient Criteria
Lakes and Reservoirs in Nutrient Ecoregion IX. EPA 822-B-00-011.
https://www.epa.gov/sites/production/files/documents/lakes9.pdf and
USEPA. December 2000. Ambient Water Quality Criteria Recommendations
Information Supporting the Development of State and Tribal Nutrient
Criteria Lakes and Reservoirs in Nutrient Ecoregion XI. EPA 822-B-
00-012. https://www.epa.gov/sites/production/files/documents/lakes11.pdf. An alternative Secchi disk measurement could be 1 meter
based on the hypereutrophic boundary identified in Carlson, R.E. and
J. Simpson. 1996. A Coordinator's Guide to Volunteer Lake Monitoring
Methods. North American Lake Management Society. 96 pp., and further
supported by the data used to derive reference condition values. A
third set of alternatives appears in the Technical Support Document
accompanying this rule describing reference condition values for
Missouri lakes.
---------------------------------------------------------------------------

C. Derivation of Nutrient Protection Values for Alternative 1

    EPA requests comment on a set of nutrient protection values as
derived below. This methodology considered the water quality
characteristics of lakes and reservoirs located in watersheds with
comparatively low levels of human disturbance. This methodology, known
as the reference condition approach, comports with longstanding Agency
guidance \54\ and builds on earlier collaborative efforts in the four-
state region.\55\ This approach could be implemented using the State's
existing water quality dataset \56\ and key geographical concepts and
interpretations supported previously by the State.\57\
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    \54\ USEPA. 2000. Nutrient Criteria Technical Guidance Manual:
Lakes and Reservoirs. EPA-822-B00-001. U.S. Environmental Protection
Agency, Office of Water, Washington DC.
    \55\ RTAG. 2011. Nutrient Reference Condition Identification and
Ambient Water Quality Benchmark Development Process: Freshwater
Lakes and Reservoirs within USEPA Region 7. Regional Technical
Advisory Group. Kansas Biological Survey, University of Kansas,
Lawrence, KS.
    \56\ Obrecht, D. 2015. Statewide Lake Assessment Program.
Quality assurance project plan. School of Natural Resources,
University of Missouri, Columbia, MO.
    Thorpe, A. 2015. The Lakes of Missouri Volunteer Program.
Quality assurance project plan. School of Natural Resources,
University of Missouri, Columbia, MO.
    \57\ Nigh, T.A. and W.A. Schroeder. 2002. Atlas of Missouri
Ecoregions. Missouri Department of Conservation, Jefferson City, MO.
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    Protecting a waterbody at reference conditions should inherently
protect all designated uses, and therefore, should support the most
sensitive use.58 59 EPA

is unaware of compelling scientific evidence that would suggest that
the reference condition approach employed here would not protect
Missouri's aquatic life, recreation, and drinking water designated
uses, though EPA is not suggesting that there are no other approaches
to protect applicable designated uses. EPA believes that the reference
condition approach described here also comports with the State's
regulatory definition for the aquatic life support use. This definition
recognizes three subcategories under the aquatic life support header:
Warm water habitat, cool water habitat, and cold water habitat.\60\
Each subcategory is described as ``waters in which naturally-occurring
water quality and habitat conditions allow [for] the maintenance of a
wide variety of [warm, cool or cold water] biota.'' This description is
explicitly applied to lakes and reservoirs (10 CSR 20-
7.031(1)(C)1.A.VI, B.V and C.V and 10 CSR 20-7.031(2)). Moreover, it
links the aquatic life support use to the naturally occurring water
quality condition, which is approximated by the reference condition. In
the context of ambient nutrient concentrations, the accuracy of this
approximation varies among regions depending on the prevailing extent
of disturbance to natural land cover and other factors.\61\ Given the
prevailing level of disturbance to natural land cover in Missouri, this
approach could use nutrient protection values based on the least
disturbed reference condition, which represents the best remaining
condition in Missouri, rather than the historical or minimally
disturbed reference condition.\62\
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    \58\ USEPA. 2000a. Nutrient Criteria Technical Guidance Manual:
Lakes and Reservoirs. EPA-822-B-00-001. U.S. Environmental
Protection Agency, Office of Water, Washington, DC.
    \59\ Grubbs, Geoffrey. 2001. Development and Adoption of
Nutrient Criteria into Water Quality Standards. WQSP-01-01. Policy
memorandum signed on November 14, 2001, by Geoffrey Grubbs,
Director, Office of Science and Technology, U.S. Environmental
Protection Agency, Washington, DC.
    \60\ The same nutrient criteria apply to all three subcategories
based on the way EPA aggregated data for purposes of deriving
protective criteria using a reference condition approach.
    \61\ EPA Technical Support Document for this rule, Nutrient
Criteria Recommendations for Lakes in Missouri, Section 2.4.
    \62\ Stoddard, J.L., D.P. Larsen, C.P. Hawkins, R.K. Johnson and
R.H. Norris. 2006. Setting expectations for the ecological
conditions of streams: The concept of reference condition.
Ecological Applications 16:1267-1276. Stoddard et al. (2006)
suggested that waters exhibiting comparatively little degradation
could be placed into one of two categories: Minimally disturbed
systems (those little affected by human actions); and least
disturbed systems (those exhibiting the best remaining condition in
a region widely impacted by human actions). The term historical was
used by the same authors to denote a condition occurring at some
specified point in the past (e.g., immediately prior to European
settlement).
---------------------------------------------------------------------------

    In developing this Alternative 1 approach, EPA initially considered
all readily available water quality data (i.e., TN, TP, total
chlorophyll, chlorophyll a, Secchi transparency data) for lakes and
reservoirs in Missouri. These records were accessed using the federal
Water Quality Portal (WQP), which is maintained jointly by the EPA, the
U.S. Geological Survey (USGS), and the National Water Quality
Monitoring Council. The WQP integrates publicly available data from the
EPA Storage and Retrieval Data Warehouse, the USGS National Water
Information System, and the U.S. Department of Agriculture's
Agricultural Research Database System.
    EPA subsequently reviewed sampling and analytical protocols
employed by the various governmental agencies, academic institutions
and private entities (e.g., consulting firms) contributing to the
above-mentioned databases. Based on this review, EPA elected to confine
its analysis to data derived from the Missouri Statewide Lake
Assessment Program (SLAP) and the Lakes of Missouri Volunteer
Monitoring Program (LMVP), both overseen by the University of Missouri-
Columbia Limnology Laboratory. This decision ensured that all water
quality data used in the reference condition analysis were obtained
using comparable field and analytical methods and derived from the same
sampling period, 1989-2015. The dataset was narrowed further by
removing data for all waters smaller than ten acres or located in the
Big River Floodplain Ecoregion, consistent with the scope of waters
covered by this proposal. For consistency, only data from the main body
of these lakes/reservoirs (i.e., from deeper, open water locations)
were used in the reference condition analysis. Overall, this effort
yielded suitable long-term data for 170 lakes/reservoirs in Missouri
(119 located in the Plains Ecoregion and 51 located in the Ozarks
Ecoregion). As explained in the Technical Support Document accompanying
this proposal, EPA combined data obtained from the Ozark Border and the
Ozark Highlands ecoregions identified in the State proposal because
lakes in these two regions exhibited statistically similar
concentrations for chlorophyll, total phosphorus and total nitrogen.
    In identifying candidate (least disturbed) reference sites, EPA
used the following criteria as an initial screen to identify least
disturbed waters, all previously included in the State's 2009 WQS
submittal.
     Cropland and urban land combined accounted for less than
twenty percent of the watershed land use.63 64 This
criterion was applied by EPA in all instances.
---------------------------------------------------------------------------

    \63\ Jones, J.R., M. F. Knowlton, and D.V. Obrecht. 2008. Role
of land cover and hydrology in determining nutrients in mid-
continent reservoirs: implications for nutrient criteria and
management. Lake and Reservoir Management. 24:1, 1-9, DOI:10.1080/
07438140809354045.
    \64\ W. K. Dodds and R. M. Oakes. 2004. A technique for
establishing reference nutrient concentrations across watersheds
affected by humans. Limnology and Oceanography: Methods. 2:333-341.
---------------------------------------------------------------------------

     No point source, to include concentrated animal feeding
operation (CAFO), was located in the watershed. EPA applied this
criterion to CAFOs and major wastewater treatment plants (WWTPs)
permitted under the National Pollutant Discharge Elimination System
(NPDES). Non-discharging facilities and smaller discharging facilities
(e.g., mobile home parks) were evaluated individually based on their
location in the watershed and other factors.
     If located in the Plains, more than fifty percent of the
watershed was covered by grassland.\65\ In applying this threshold, EPA
considered grassland and all other forms of native land cover (e.g.,
forest, marshland).
---------------------------------------------------------------------------

    \65\ J.R. Jones, M.F. Knowlton, D.V. Obrecht, and E.A. Cook.
2004. Importance of landscape variables and morphology on nutrients
in Missouri reservoirs. Canadian Journal of Fisheries and Aquatic
Science. 61:1503-1512.
---------------------------------------------------------------------------

     If located in the Ozark Highlands, more than fifty percent
of the watershed was forested. Forests in the Ozark Highlands are the
equivalent to grasslands in the Plains in terms of native land cover
and associated nutrient delivery. This selection criterion was applied
by EPA to the Ozark Highlands and the adjoining Ozark Border, which
collectively comprise the Ozarks Ecoregion.\66\
---------------------------------------------------------------------------

    \66\ EPA Technical Support Document for this rule, Nutrient
Criteria Recommendations for Lakes in Missouri, Section 6.1.
---------------------------------------------------------------------------

    In order to identify waters meeting this initial screening
criteria, EPA obtained digital watershed polygons from USGS's National
Hydrography Dataset and a separate dataset maintained by the University
of Missouri-Columbia. In about five cases, polygons were not available
in either dataset and had to be digitized in ArcGIS.\67\ NHDPlus-V2
flowlines and medium resolution NHD (1:100,000 scale) elevation-derived
catchments were used to identify the watersheds for each lake/
reservoir. In cases where a watershed was represented by more than one
catchment, the catchments were dissolved into one polygon. For many of
the smaller lakes/reservoirs, watersheds were defined using the Water
Erosion Prediction Project

(WEPP) model.\68\ The Zonal Tabulate Area tool in ArcGIS Spatial
Analyst and the 2014 edition of the 2011 National Land Cover
(www.mrlc.gov) were used to calculate the percentage of each watershed
in specific land cover types. These percentages, along with ArcGIS-
generated maps depicting the locations of permitted point sources and
CAFOs, were used to identify lakes/reservoirs meeting the
aforementioned selection criteria.
---------------------------------------------------------------------------

    \67\ ArcGIS is a digital geographic information system (GIS)
used for creating and using maps, compiling geographic data,
analyzing mapped information, sharing and discovering geographic
information, and managing geographic information in a database form.
    \68\ Flanagan, D.C., J.R. Frankenberger, T.A. Cochrane, C.S.
Renschler & W.J. Elliot. 2011. Geospatial application of the water
erosion prediction (WEPP) model. International Symposium on Erosion
and Landscape Evolution (ISELE), Anchorage, Alaska. September 18-21,
2011. ISELE Paper Number 11084.
    Flanagan, D.C., J.R. Frankenberger, T.A. Cochrane, C.S.
Renschler & W.J. Elliot. 2013. Geospatial application of the water
erosion prediction (WEPP) model. Transactions of the American
Society of Agricultural and Biological Engineers 50(2):591-601.
---------------------------------------------------------------------------

    After this initial screening exercise, EPA then subjected the
identified candidate watersheds/lakes to further evaluation using
aerial imagery, NPDES permit records, Missouri Department of
Conservation (MDC) conservation area reports, and other available
sources of information. EPA removed watersheds and lakes from further
consideration if they (1) received substantial drainage from the Big
River Floodplain Ecoregion (out of scope); (2) exhibited extensive
shoreline residential development; (3) had received historical or
recent manure applications from nearby feedlots; (4) had undergone
deliberate (fisheries oriented) fertilization efforts; and (5) had been
situated in an area of formerly cultivated fields.\69\ The latter four
reasons relate to factors relate to disturbance.
---------------------------------------------------------------------------

    \69\ EPA Technical Support Document for this rule, Nutrient
Criteria Recommendations for Lakes in Missouri, Section 6.1.
---------------------------------------------------------------------------

    Additionally, three isolated waterbodies in the Plains exhibited
median chlorophyll a concentrations exceeding 40 [micro]g/L.\70\ Based
on earlier studies, hypereutrophic waters of this kind are not
representative of the reference condition in the Central Irregular
Plains \71\, a region encompassing much of the Plains Ecoregion in
Missouri.\72\ Therefore, EPA evaluated these waters in greater detail.
In one instance, historical and ongoing confined animal feeding
operations (CAFOs) in an adjacent watershed likely explained the noted
hypereutrophic condition.\73\ The other two instances involved state-
managed fishing lakes, one situated in a formerly cultivated field and
the other situated in a watershed extending into the heavily cultivated
Big River Floodplain. A few other lakes on state-managed lands were
disqualified based on disturbance related to reported sedimentation and
algal bloom issues.\74\ EPA ultimately identified 21 reference lakes
and reservoirs in the Plains and 27 in the Ozarks that met the criteria
discussed above. EPA calculated seasonal geometric mean TN, TP, and
chlorophyll a concentration values for each waterbody, then calculated
the long-term median seasonal geometric means for each parameter/
waterbody combination. These medians were partitioned by ecoregion,
ranked, and used in the calculation of appropriate concentration
percentiles.\75\ EPA invites public comment on the methodology to
select reference lakes and reservoirs for this alternative's
methodology.
---------------------------------------------------------------------------

    \70\ Id.
    \71\ Dodds, W.K., C. Carney and R.T. Angelo. 2006. Determining
ecoregional reference conditions for nutrients, Secchi depth and
chlorophyll a in Kansas lakes and reservoirs. Lake and Reservoir
Management 22(2):151-159.
    \72\ Omernik, J. M. 1987. Ecoregions of the conterminous United
States. Annals of the Association of American Geographers 77:118-
125.
    \73\ The hog CAFO in question generated an amount of waste
equaling a human population of about 19,000. Owing to high
transportation costs, manure from such facilities generally is
applied to surrounding fields and cropland.
    \74\ This is illustrated by the following excerpt from the ten-
year management plan for one of these areas: ``Strategy 1:
Sufficient phytoplankton densities will be maintained through
artificial fertilization to shade and discourage the development of
rooted plant growth. Successful artificial fertilization should
limit the need for the extensive use of grass carp or herbicides
while increasing phytoplankton blooms and zooplankton communities
throughout the summer and into the early fall'' (MDC. 2015. Lake
Girardeau Conservation Area Management Plan. Missouri Department of
Natural Resources, Southeast Region, Poplar Bluff, MO.)
    \75\ USEPA. 2000. Nutrient Criteria Technical Guidance Manual:
Lakes and Reservoirs. EPA-822-B00-001. U.S. Environmental Protection
Agency, Office of Water, Washington DC.
---------------------------------------------------------------------------

    To assist in the identification of appropriate concentration
percentiles, land cover disturbance patterns in the three ecoregions
were compared to patterns reported for the conterminous United States
using ArcGIS. This comparison indicated that cropland and developed
(urban) land collectively comprised 21.1 percent of the cover in the
lower 48 states. This is comparable to the percentage reported for the
Ozark Border (22.2 percent), higher than the percentage reported for
the Ozark Highlands (6.9 percent), and lower than the percentage
reported for the Plains (39.9 percent). Based on its review of the
applicable federal guidance,\76\ EPA interpreted this to mean that
application of the standard 75th percentile nutrient concentration
would be appropriate for the Ozark Border, because this region has
experienced a degree of land cover disturbance typifying that of the
nation as a whole (excluding Alaska and Hawaii). The 75th percentile
also was selected for the Ozark Highlands, and therefore appropriate
for the combined Ozark ecoregion. In choosing this percentile, EPA was
mindful of the limited number of potentially suitable reference waters
in this region, and in turn, the difficulty in accurately estimating a
higher percentile. EPA recognizes that there are higher levels of land
cover disturbance in the Plains region relative to other locations in
Missouri and most of the United States and considered using the 50th
percentile for the Plains. However, EPA concluded that the screening
criteria for reference sites (described above), already appropriately
accounted for these differences by including the allowable percent of
cropland and urban land in the lake watershed, is the same for each
ecoregion. EPA decided to use of the 75th percentile for all
ecoregions. EPA invites public comment on whether the use of the 75th
percentile for these ecoregions was appropriate. EPA notes that using
the 75th percentile of reference lakes to derive protection values
implies that 25 percent of reference lakes would be deemed to exceed
the protection values if assessed using the data used to derive the
criteria. This could be interpreted to mean that 25 percent of the
lakes meeting the reference condition selection criteria described
above would none-the-less be determined to be impaired. This could also
be interpreted as appropriately ensuring that high levels of nutrient
parameters for lakes that, in fact, may or may not meet designated uses
are not identified as protective for the vast majority of lakes that
have much lower levels of nutrient parameters. A higher percentile
value, such as the 90th or 95th percentile, would ensure that, at least
based on the data used to derive the criteria, all or most of the
reference lakes would in fact be found to meet designated uses. EPA
invites public comment on whether the use of a higher percentile would
be appropriate in the context of the selection criteria used by EPA to
identify reference lakes and reservoirs for the purpose of calculating
protective values indicative of meeting designated uses.
---------------------------------------------------------------------------

    \76\ Id.
---------------------------------------------------------------------------

    In this alternative, these concentration percentiles would serve as
nutrient protection values as part of a combined criterion approach for
all classified lakes and reservoirs in Missouri that (1) are listed in
Table G of the State's WQS and the Missouri Use Designation

Dataset (10 CSR 20-7.031(2)(E)) with respect to use designations, (2)
equal or exceed ten acres, (3) are located outside of the Big River
Flood Plain Ecoregion and (4) are not already listed in Table M of the
State's WQS. In all instances, these values are expressed as seasonal
(April through September) geometric mean values and interpreted in the
context of three-year rolling averages.\77\ EPA invites public comment
on the use of moving averages versus fixed averaging periods.
---------------------------------------------------------------------------

    \77\ Use of a seasonal mean and three-year averaging period is
consistent with recommendations set forth in: RTAG. 2011. Nutrient
Reference Condition Identification and Ambient Water Quality
Benchmark Development Process: Freshwater Lakes and Reservoirs
within USEPA Region 7. Regional Technical Advisory Group, U.S.
Environmental Protection Agency Region 7, Lenexa, KS.
---------------------------------------------------------------------------

    As described in the Technical Support Document accompanying this
proposal, the resulting values are comparable in magnitude to those
recommended by the Regional Technical Assistance Group (RTAG) for the
four-state region, to criteria developed or adopted in neighboring
Kansas, Nebraska and Oklahoma, and to TMDL targets adopted previously
in Missouri. As such, EPA is confident that the nutrient protection
values are protective of downstream lakes and reservoirs, though EPA
emphasizes that this is not the only way of developing protective
values. For protection of downstream rivers and streams, lakes often
act as a ``sink'' for nutrients because of the relatively longer water
residence time and associated physical processes and biochemical
cycling. As such, lakes retain nutrients and outflow nutrient
concentrations are generally lower than inflow nutrient concentrations.
In terms of level of protection needed, nutrient criteria for lakes and
reservoirs are generally lower than nutrient criteria for rivers and
streams in the same ecoregion (see, for example, EPA's criteria
published in 2000 for Ecoregion IX). For these reasons, EPA concludes
that the values are protective of downstream waters and their assigned
uses. EPA invites public comment on the derivation of EPA's proposed
nutrient protection values based on least disturbed reference
conditions. EPA specifically requests comments on the use of the 75th
percentile of the reference lake values to establish the TN, TP, and
chl-a nutrient protection values proposed for Alternative 1.

D. Proposed Combined Criterion Alternative 2

    Alternative 2 is presented in Table 4 below.

  Table 4--Alternative 2 Lake Ecoregion Chl-a Criteria, Nutrient Screening Values ([mu]g/L), and Eutrophication
                                                     Impacts
----------------------------------------------------------------------------------------------------------------
                                                                            Screening Values ([mu]g/L)
                 Lake ecoregion                   Chl-a criteria -----------------------------------------------
                                                                        TP              TN             Chl-a
----------------------------------------------------------------------------------------------------------------
Plains..........................................              30              49             843              18
Ozark Border....................................              22              40             733              13
Ozark Highland..................................              15              16             401               6
----------------------------------------------------------------------------------------------------------------
Lakes with water quality that exceed Chl-a Criteria are to be deemed impaired for excess nutrients.
Lakes with water quality that exceed screening values for Chl-a, TN, or TP are to be deemed impaired for excess
  nutrients if any of the following eutrophication impacts are documented for the respective designated uses
  within the same year. Eutrophication impacts for aquatic life uses include:
(I) Occurrence of eutrophication-related mortality or morbidity events for fish and other aquatic organisms;
(II) Epilimnetic excursions from dissolved oxygen or pH criteria;
(III) Cyanobacteria counts in excess of 100,000 cells per milliliter (cells/ml);
(IV) Observed shifts in aquatic diversity attributed to eutrophication; and
(V) Excessive levels of mineral turbidity that consistently limit algal productivity during the period May 1-
  September 30.

    As of the date of this proposal, Missouri has not finalized, and
EPA has not made any determination with respect to, Missouri's proposed
standards. Notwithstanding this, EPA believes it is appropriate to
propose standards for consideration that are essentially identical to
the proposed state standards, and is doing so in Alternative 2.
Alternative 2 includes chl-a criteria for three ecoregions (Plains,
Ozark Border, and Ozark Highland) that determine impairment independent
of the screening values and eutrophication impact factors. Alternative
2, similarly to Alternative 1, includes screening values for TN, TP,
and chl-a (at a lower level than the criteria for chl-a) that operate
in coordination with five eutrophication impact factors to determine
impairment. However, as explained above, one significant distinction is
that Alternative 1 would treat the lower chl-a screening value (called
a ``protection value'' in Alternative 1) as stand-alone criteria and
deem any exceedance of this value as indicative of impairment without
assessment of additional eutrophication impacts. Alternative 2 includes
a qualifier of ``epilimnetic'' with respect to excursion of DO or pH
criteria to mirror the State's proposal. EPA seeks comment on limiting
application of DO and pH criteria to the epilimnion (surface layer) of
lakes.
    The State of Missouri has documented a supporting rationale for the
values proposed in Alternative 2 as part of a combined criterion
structure.\78\ This document includes maps of the three ecoregions
(Plains, Ozark Border, and Ozark Highland). In this document, Missouri
describes how it considered input from a stakeholder group and
``decided on an approach that provided for the most scientifically
defensible protections for the underlying designated uses.'' Missouri
indicates that its approach ``focuses on the biological response,
considers ecoregional differences and existing trophic levels, and
supplements criteria with conservative screening values coupled with
weight of evidence analysis to better support determinations of
impairment''. Missouri indicates that it reviewed several different
sources of information to derive reservoir numeric nutrient criteria,
including recent numeric nutrient criteria development activities in
other states, Missouri-specific reservoir water chemistry data,
literature reviews, and expert opinion.
---------------------------------------------------------------------------

    \78\ Missouri Department of Natural Resources. 2016. Missouri
Lake Numeric Nutrient Criteria Rationale of Nov. 21, 2016.
---------------------------------------------------------------------------

    Missouri indicated the stand-alone independent chl-a criterion for
the Plains ``is conservatively set to support sport fisheries rather
than maximizing

sport fish harvest. Missouri maintains that using sport fishery status
as an indicator of aquatic life use protection is ecologically
justified because sport fish are generally apex predators in reservoir
systems. Therefore, the health of sport fish populations can be
interpreted as an indicator of overall ecosystem health and the
presence a `wide variety' of aquatic biota, as defined in the existing
regulations''.\79\ For the Ozark Highlands, Missouri identified ``a
lower chlorophyll concentration of 15 [mu]g/L, which reflects the
regional pattern of reservoir fertility associated with the different
physiographic regions of the state''.\80\ Because the Ozark Border
section represents a transition zone between the Plains and Ozark
Highlands, Missouri identified a chl-a criterion intermediate to the
other two sections. Missouri proposed chl-a screening values equal to
the 50th percentile of the distribution of growing season chlorophyll
data for each ecoregion, and back calculated TN and TP screening values
using regression relationships with chl-a presented in their rationale
document.
---------------------------------------------------------------------------

    \79\ Id.
    \80\ Id.
---------------------------------------------------------------------------

    EPA is seeking comment on whether the chl-a criteria in Alternative
2 would protect the State's designated uses for these lakes. EPA seeks
comment on whether a different (i.e., more protective) level of chl-a
as a eutrophication impact factor is necessary to protect the
designated uses for these lakes. EPA further seeks comment on whether
or not the hypothetical scenario pursuant to Alternative 2 is
scientifically supportable as protecting the designated use: Not
identifying a lake as impaired when it (1) exceeds a screening value
for TP or TN, (2) exceeds a screening value for chl-a, and (3) there
are no documented eutrophication impacts. In other words, EPA seeks
comment on whether it is sufficient or insufficient to identify
impairment if a water body exceeds a screening value for TN or TP and
also exceeds a screening value for chl-a.
    The combined criterion could function in the manner proposed for
Alternative 1, where a lake with water quality that exceeds protection
values for TN or TP is deemed impaired for excess nutrients unless each
of the eutrophication impacts are evaluated and none occur within the
same evaluation period (or unless the chl-a protection value is
exceeded). In contrast, the combined criterion could function in the
manner proposed for Alternative 2, where a lake with water quality that
exceeds a screening value for TN, TP, or chl-a (at a ``screening''
level) is deemed impaired for excess nutrients only if one or more of
the eutrophication impacts are documented to occur within the same
year. Using this Alternate 2 expression, a lake exceeding screening
values for TN, TP, or chl-a (at a ``screening'' level) would not be
considered to be impaired unless and until additional information is
collected and evaluated to confirm the impairment. EPA has not
separately prepared supporting documentation for Alternative 2 at the
same level of detail as for Alternative 1, because as noted above,
Alternative 2 is intended to closely mirror the State's 2017 proposed
rule. Accordingly, EPA has placed documentation as provided by the
State, in its own docket as an integral part of the supporting
documentation for Alternative 2. EPA is asking for comment on this
approach.
    EPA also has not provided proposed regulatory text for Alternative
2, because the regulatory text for this option would be largely
identical to the regulatory text in the State's 2017 proposed rule.
Rather, the Agency is providing notice of its consideration of
Alternative 2 in the preamble to today's proposed rule. The Agency
recognizes that, if the Agency were to adopt this alternative in the
final rule, there may need to be formatting changes to the State
regulatory text to conform to requirements applicable to codification
in the Code of Federal Regulations.

E. Additional Alternative Approaches Considered

    This federal action fulfills EPA's commitment under the consent
decree with MCE to propose criteria addressing its 2011 disapproval by
December 15, 2017. EPA acknowledges that the alternatives in the
current proposal are not the only possible options that EPA could
promulgate or Missouri could adopt to address the 2011 disapproval
action. When promulgating federal water quality standards for a state,
EPA's preference is to rely on state-specific data, where available, to
derive criteria to protect the state's applicable designated uses. EPA
solicits comment from the public and stakeholders on the Agency's co-
proposals, in addition to other scientifically defensible options, to
support a well-informed and robust final rule that reflects thoughtful
consideration of Missouri's regulatory structure and implementation
mechanisms.
    EPA considered several alternatives to the two alternatives
proposed combined criterion approaches, component nutrient protection
(or screening) values, and eutrophication impacts, and is interested in
public comment on these approaches. First, EPA considered proposing the
reference condition-derived nutrient protection values as stand-alone
nutrient criteria (i.e., in absence of a combined criterion structure).
However, given Missouri's interest in the combined criterion approach
and EPA's position that such an approach can be appropriate and
protective, EPA elected to structure the two alternatives in this
proposal in a similar fashion. Second, EPA considered relying on fewer
response parameters to avoid use of factors that may be onerous to
routinely measure and assess, may be subject to various
interpretations, and may not be necessary to indicate adverse impact.
For example, EPA considered using only chl-a, DO, and pH as
eutrophication impacts. EPA instead elected to include the full set
Missouri identified in recognition that Missouri had concluded each was
an appropriate eutrophication impact to be included in the State's
proposed rule. Lastly, for Alternative 1, EPA considered using the 50th
percentile of the data from reference lakes in the Plains ecoregion for
deriving nutrient protection values; these values are 9.8 [micro]g/L
chl-a, 39 [micro]g/L TP, and 690 [micro]g/L TN. EPA decided to use the
75th percentile for the Plains ecoregion for this proposal because
reference lakes in both ecoregions could have no greater than 20
percent cropland and urban land in their watershed based on EPA's
screening procedure. EPA specifically solicits comment on the use of
the 50th percentile for the Plains. As noted above, EPA is also
requesting comment on using a higher percentile, such as 90th or 95th.

F. Applicability of Combined Criterion When Final

    Unless EPA approves water quality standards addressing EPA's 2011
disapproval, EPA's proposed nutrient combined criterion for Missouri's
lakes and reservoirs would be effective for CWA purposes 60 days after
publication of a final rule. The proposed combined criterion in this
rule, if finalized would be subject to Missouri's general rules of
applicability in the same way and to the same extent as are other
state-adopted criteria.
    EPA's proposed nutrient combined criterion, if finalized, would
serve as a basis for development of new or revised National Pollutant
Discharge Elimination System (NPDES) permit limits in Missouri for
regulated dischargers found to have reasonable potential to cause or
contribute to an

excursion of the proposed nutrient combined criterion. Although EPA
cannot be certain of whether a particular direct or indirect discharger
would change their operations if these proposed criterion were
finalized, EPA acknowledges that point source dischargers would need to
be assessed to determine if they have a reasonable potential for the
discharge to cause or contribute to an excursion of the water quality
standard, and could well be subject to additional water quality-based
effluent limits as a result. Nonpoint dischargers could also be subject
to additional control requirements under Missouri law, perhaps in
conjunction with a TMDL. Missouri has NPDES permitting authority, and
retains discretion in issuing permits consistent with CWA permitting
regulations, which require that permit limits be established such that
permitted sources do not cause or contribute to a violation of water
quality standards, including numeric nutrient criteria.

IV. Tributary Arms

    As part of its efforts to establish its water quality standards,
the State of Missouri established water quality criteria in its 2009
WQS submission to address nutrient-related pollutants for certain
lakes, reservoirs and tributary arms. As mentioned previously, on
August 16, 2011, EPA disapproved most numeric criteria for TN, TP, and
chl-a for Missouri lakes and reservoirs and also disapproved TP
criteria for tributary arms Grand Glaize, Gravois, and Nianga to the
Lake of the Ozarks, and tributary arms James River, Kings River, and
Long Creek to Table Rock Lake. In Missouri's disapproved rule (10 CSR
20-7.0314)(N)(1)(D)) and current proposed rule (10 CSR 20-
7.031(N)(1)(E)), it considers a tributary arm to be a substantial
segment of a Class L2 lake that is primarily recharged by a source or
sources other than the main channel of the lake. EPA requests public
comments on applying Alternative 1, Alternative 2, or any other
appropriate alternative to the respective tributary arms to address
EPA's 2009 disapproval. EPA invites the public to provide any data or
scientific information to inform decision-making towards this option.

V. Endangered Species Act

    Section 7(a)(2) of the Endangered Species Act (ESA) requires the
EPA, in consultation with the U.S. Fish and Wildlife Service (USFWS)
and/or the National Marine Fisheries Service (NMFS), to ensure that any
action authorized by the Agency is not likely to jeopardize the
continued existence of any endangered or threatened species or result
in the destruction or adverse modification of designated critical
habitat for such species.
    Pursuant to this section, EPA intends to initiate consultation with
USFWS regarding the effects that finalizing this rulemaking would have
on federally-listed threatened and endangered species and designated
critical habitat. EPA will subsequently conduct a biological evaluation
to determine whether any federally-listed threatened or endangered
species or their critical habitat are likely to be adversely affected
by the finalization of this rulemaking.

VI. Under what conditions will federal standards be either not
finalized or withdrawn?

    Under the CWA, Congress gave states primary responsibility for
developing and adopting WQS for their navigable waters. See CWA section
303(a)-(c). Although EPA is proposing nutrient criteria for Missouri's
lakes and reservoirs, the State has the option of adopting and
submitting revised nutrient criteria for these waters consistent with
CWA section 303(c) and implementing regulations at 40 CFR part 131.
Consistent with CWA section 303(c)(4) and the consent decree discussed
in Section II, if Missouri adopts water quality criteria to address
EPA's 2011 disapproval, and if EPA approves such criteria prior to the
December 15, 2018 consent decree deadline to publish the final rule,
EPA will not proceed with the final rulemaking.
    Pursuant to 40 CFR 131.21(c), if EPA does promulgate final
criteria, they would be applicable for the purposes of the CWA. EPA
could eventually withdraw any federally promulgated criteria through a
rulemaking. EPA would undertake a withdrawal action if Missouri adopts
and EPA approves water quality criteria to address EPA's 2011
disapproval as meeting CWA requirements.

VII. WQS Regulatory Approaches and Implementation Mechanisms

    The Federal water quality standards regulation at 40 CFR part 131
provides several tools that Missouri has available to use at its
discretion when implementing or deciding how to implement these numeric
nutrient criteria, if finalized. Among other things, EPA's WQS
regulation: (1) Specifies how states and authorized tribes establish,
modify or remove designated uses, (2) specifies the requirements for
establishing criteria to protect designated uses, including criteria
modified to reflect site-specific conditions, (3) authorizes and
provides requirements for states and authorized tribes to adopt WQS
variances that provide time to achieve the underlying WQS, and (4)
allows states and authorized tribes to authorize the use of compliance
schedules in NPDES permits to meet Water Quality Based Effluent Limits
(WQBELs) derived from the applicable criteria. Each of these approaches
is discussed in more detail in the next sections.

A. Designating Uses

    Federal regulations at 40 CFR 131.10 provide regulatory
requirements for establishing, modifying, and removing designated uses.
If Missouri removes or modifies the aquatic life or recreational
designated uses of a lake or reservoir subject to EPA's proposed
nutrient criteria and adopts the highest attainable use,\81\ the state
must also adopt criteria to protect the newly designated highest
attainable use consistent with 40 CFR 131.11. Any designated use change
must meet the requirements of 40 CFR part 131 and obtain EPA approval.
If EPA finds removal or modification of the designated use, the
adoption of the highest attainable use and criteria to protect that use
is consistent with CWA section 303(c) and the implementing regulation
at 40 CFR part 131 and thus approves the revised WQS, then the new or
revised use and criteria would become effective for CWA purposes. As an
additional step, EPA would initiate rulemaking to withdraw its
promulgation of nutrient criteria in Missouri if the criteria to
protect the new use is something other than the federally promulgated
criteria.
---------------------------------------------------------------------------

    \81\ If a state or authorized tribe adopts a new or revised WQS
based on a required use attainability analysis, then it must also
adopt the highest attainable use (40 CFR 131.10(g)). Highest
attainable use is the modified aquatic life, wildlife, or
recreational 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 40 CFR 131.10(g) that preclude(s) attainment of
the use and any other information or analyses that were used to
evaluate attainability. There is no required highest attainable use
where the state demonstrates the relevant use specified in section
101(a)(2) of the Act and sub-categories of such a use are not
attainable (See 40 CFR 131.3(m)).
---------------------------------------------------------------------------

B. Site-Specific Criteria

    The regulation at 40 CFR 131.11 specifies 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 to a federally promulgated nutrient criterion that would
be applied on a watershed, area-wide, or water body-specific basis,

provided this alternative is protective of the designated use, is
scientifically defensible, and provides for the protection and
maintenance of downstream water quality. A SSC may be more or less
stringent than the otherwise applicable federal criterion. A SSC may be
appropriate when further scientific data and analyses more precisely
define the concentration of a pollutant that is protective of the
designated uses of a particular watershed, region, or water body. If
Missouri adopts, and EPA approves, a SSC that fully meets the
requirements of both section 303(c) of the CWA and EPA's implementing
regulation at 40 CFR part 131, EPA would undertake a rulemaking to
withdraw the corresponding federal criterion for the water(s) affected
by the SSC.

C. WQS Variances

    Federal regulations at 40 CFR 131.14 define a WQS variance as a
time-limited designated use and criterion, for a specific pollutant or
water quality parameter, that reflects the highest attainable condition
during the term of the WQS variance. WQS variances adopted in
accordance with 40 CFR 131.14 (including a public hearing consistent
with 40 CFR 25.5) provide a flexible but defined pathway for states and
authorized tribes to meet their NPDES permit obligations by allowing
dischargers the time they need (as demonstrated by the state or
authorized tribe) to make incremental progress toward meeting WQS that
are not immediately attainable but may be in the future. When adopting
a WQS variance, states and authorized tribes specify the interim
requirements of the variance by identifying a quantitative expression
that reflects the highest attainable condition (HAC) during the term of
the variance, defining the term of the variance, and describing the
pollutant control activities to achieve the HAC during the term of the
variance. WQS variances will help states and authorized tribes focus on
improving water quality, rather than pursuing a downgrade of the
underlying water quality goals through modification or removal of a
designated use, as a variance cannot lower currently attained water
quality. As water quality standards, variances are submitted to EPA for
review and approval under CWA section 303(c) which provides legal
avenue by which NPDES permit limits can be written to derive from, and
comply with, the WQS variance rather than the underlying WQS, for the
term of the WQS variance. If dischargers are still unable to meet the
WQBELs derived from the applicable WQS once a variance term is
complete, the regulation allows the state to adopt a subsequent
variance if it is adopted consistent with 131.14.
    EPA's proposed nutrient criterion applies to use designations that
Missouri has already established. Missouri may adopt time-limited
designated uses and criteria to apply for the purposes specified in 40
CFR 131.14(a)(3).

D. NPDES Permit Compliance Schedules

    EPA's regulations at 40 CFR 122.47 and 40 CFR 131.15 address how
states and authorized tribes 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
131.15 require that states and authorized tribes that wish to allow the
use of permit compliance schedules adopt specific provisions
authorizing their use and obtain EPA approval under CWA section 303(c)
to ensure that a decision to allow permit compliance schedules is
transparent and allows for public input (80 FR 51022, August 21, 2015).
On December 11, 2012, Missouri submitted a revised compliance schedule
authorizing provision at 10 CSR 20-7.031(10). This revision was partly
approved by EPA on January 25, 2015. Missouri is authorized to grant
permit compliance schedules, as appropriate, to permitted facilities
impacted by federally promulgated numeric nutrient criteria as long as
such compliance schedules are consistent with EPA's permitting
regulation at 40 CFR 122.47.

VIII. Economic Analysis

    At this time, EPA has prepared only a preliminary economic analysis
specifically for Alternative 1. This analysis will be further refined
and an updated more comprehensive economic review will be put out for
comment in a Notice of Data Availability at a later time. At that time,
to best inform the public of the potential impacts of this rule, EPA
will evaluate the potential benefits and costs associated with
implementation of EPA's proposed criterion.
    The analysis of acres with BMPs to address nonpoint sources of
nutrients was conducted at the HUC-12 level of resolution. Many of the
potentially incrementally impaired lakes in Missouri are small, and
their watersheds are smaller than the HUC-12 watershed in which they
are located; thus, the estimated costs for these watersheds may be
overstated. However, EPA did not initially include any costs for
watersheds for which it does not have data, thus, at least some likely
costs were not included in the preliminary analysis. Due to these and
other limitations, EPA believes that its current draft analysis is too
preliminary to adequately inform public comment on the rule. EPA will
address these issues in the updated analysis provided in the NODA.
    EPA also preliminarily estimated the benefits from water quality
improvements resulting from implementing the nutrient protection values
in Missouri Lakes and reservoirs. However, due to data and resource
limitations and other challenges, EPA believes that this benefits
analysis is also too preliminary to be presented at this time. EPA will
also include an updated analysis of benefits in the NODA.
    EPA seeks public comment to inform EPA's economic analysis. EPA is
interested in public comment regarding how likely it is that lakes
without water quality data may trigger the screening criteria; what
practices the agricultural sector and cities may take to reduce
nonpoint source discharges and the likelihood that such practices are
implemented; what unit costs EPA should consider using in conducting
this analysis; and what assumptions EPA should consider using for
expected nutrient load reductions.
    EPA intends to make the revised analysis, including pre-publication
peer review, available for public comment no later than six months
after the date of publication of this proposed rule. In no
circumstances will EPA issue a final rule without providing an economic
analysis sufficiently in advance of the final rule for public comment
on the analysis to meaningfully inform EPA's development of the rule.

IX. 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 an economically significant regulatory action that
was submitted to the Office of Management and Budget (OMB) for review.
Any changes made in response to OMB recommendations have been
documented in the docket. (Docket Id. No. EPA-HQ-OW-2009-0596) is
available in the docket. A summary of the report can be found in
Section VIII of this preamble.

B. Executive Order 13771: Reducing Regulation and Controlling
Regulatory Costs

    This action is expected to be an Executive Order 13771 regulatory
action. Details on the estimated costs of this proposed rule will be
available for public comment in a subsequent Notice of Data
Availability to be published no later than six months after this
proposed rule (See summary at Section VIII. Economic Analysis, and full
economic analysis report in the docket for this proposed rulemaking).

C. Paperwork Reduction Act

    This action does not impose an information collection burden under
the provisions of the PRA, 44 U.S.C. 3501 et seq. Burden is defined at
5 CFR 1320.3(b). This action does not include any information
collection, reporting, or record-keeping requirements.

D. Regulatory Flexibility Act

    For purposes of assessing the impacts of this action on small
entities, a small entity is defined as: (1) A small business as defined
by the Small Business Administration's (SBA) regulations at 13 CFR
121.201; (2) a small governmental jurisdiction that is a government of
a city, county, town, school district or special district with a
population of less than 50,000; and (3) a small organization that is
any not-for-profit enterprise that is independently owned and operated
and is not dominant in its field.
    Under the CWA, states must adopt WQS for their waters and submit
these standards to EPA for approval. If the Agency disapproves a
submitted standard and the state does not adopt revisions to address
EPA's disapproval, EPA must promulgate standards consistent with the
CWA requirements. State standards (or EPA-promulgated standards) are
implemented through various water quality control programs including
the NPDES program, which limits discharges to navigable waters except
in compliance with an NPDES permit. The CWA requires that all NPDES
permits include any limits on discharges that are necessary to meet
applicable WQS. Thus, under the CWA, EPA's promulgation of WQS
establishes standards that the state implements through the NPDES
permit process. The State has discretion in developing discharge
limits, as needed to meet the standards. This proposed rule, as
explained earlier, does not itself establish any requirements that are
applicable to small entities. As a result of this action, the State of
Missouri will need to ensure that permits it issues include any
limitations on discharges necessary to comply with the standards
established in the final rule. In doing so, the state will have a
number of choices associated with permit writing. While Missouri's
implementation of the rule may ultimately result in new or revised
permit conditions for some dischargers, including small entities, EPA's
action, by itself, does not impose any of these requirements on small
entities; that is, these requirements are not self-implementing. Thus,
I certify that this rule will not have a significant economic impact on
a substantial number of small entities under the RFA.

E. Unfunded Mandates Reform Act

    This proposed rule contains no federal mandates (under the
regulatory provisions of Title II of the UMRA) for state, local, or
tribal governments or the private sector.
    EPA determined that this proposed rule contains no regulatory
requirements that might significantly or uniquely affect small
governments. Moreover, WQS, including those proposed here, apply
broadly to dischargers and are not uniquely applicable to small
governments. Thus, this proposed rule is not subject to the
requirements of section 203 of UMRA.

F. Executive Order 13132 (Federalism)

    This action does not have federalism implications as that term is
used in EO 13132. Although section 6 of Executive Order 13132 does not
apply to this action, EPA had extensive communication with the State of
Missouri to discuss EPA's concerns with the State's previously
submitted and disapproved criteria and the federal rulemaking process.
In the spirit of Executive Order 13132, and consistent with EPA's
policy to promote communications between EPA and state and local
governments, EPA specifically solicits comment on this proposed rule
from state and local officials.

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

    This action does not have any tribal implications as specified by
Executive Order 13175. As there are no federally-recognized tribes in
the State of Missouri, this executive order does not apply. Thus,
Executive Order 13175 does not apply to this action.

H. Executive Order 13045 (Protection of Children from Environmental
Health and Safety Risk)

    Executive Order 13045 (62 FR 19885, April 23, 1997) requires
agencies to identify and assess health and safety risks that may
disproportionately affect children and ensure that activities address
disproportionate risks to children. This action not subject to
Executive Order 13045 because the EPA does not believe the
environmental health risks or safety risks addressed by this action
present a disproportionate risk to children.

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

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

J. National Technology Transfer Advancement Act of 1995

    EPA is not aware of any voluntary consensus standards that address
the numeric nutrient criteria in this proposed rule.

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

    EPA has determined that this proposed rule does not have
disproportionately high and adverse human health or environmental
effects on minority or low-income populations because it would afford a
greater level of protection to both human health and the environment if
these nutrient criteria are promulgated in the State of Missouri.

List of Subjects in 40 CFR Part 131

    Environmental protection, water quality standards, nutrients,
Missouri.

    Dated: December 15, 2017.
E. Scott Pruitt,
Administrator.

    For the reasons set out 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--[Amended]

0
2. Section 131.47 is added as follows:

Sec.  131.47  Missouri.

    (a) Scope. This section promulgates a combined criterion for
designated uses for all lakes and reservoirs in the State of Missouri
that (1) are listed in Table G and the Missouri Use Designation
Dataset) in the State's water quality standards (WQS) (10 CSR 20-
7.031), (2)

equal or exceed ten acres, (3) are located outside of the Big River
Flood Plain Ecoregion and (4) are not listed as having site-specific
criteria in Table M of the State's WQS.
    (b) Combined Criterion for Missouri lakes and reservoirs. In all
instances, nutrient protection values are maximum ambient
concentrations expressed as seasonal (April through September)
geometric mean values on a three-year rolling average basis.

          Table 1--Lake Ecoregion Nutrient Protection Values ([micro]g/L) and Eutrophication Impacts *
----------------------------------------------------------------------------------------------------------------
                         Lake Ecoregion                                 TP              TN             Chl-a
----------------------------------------------------------------------------------------------------------------
Plains..........................................................              44             817              14
Ozarks..........................................................              23             500             7.1
----------------------------------------------------------------------------------------------------------------
* Table 1 also applies to tributary arms Grand Glaize, Gravois, and Nianga to the Lake of the Ozarks, and
  tributary arms James River, Kings River, and Long Creek to Table Rock Lake.

    (1) Lake and reservoir water quality must not exceed nutrient
protection values for chlorophyll a.
    (2) Lake and reservoir water quality must also not exceed nutrient