Document ID: EPA-HQ-OW-2019-0675-0101
Agency: epa
Document Type: Notice
Title: Ambient Water Quality Criteria to Address Nutrient Pollution in Lakes and Reservoirs
Posted Date: 2021-08-13T04:00Z

[Federal Register Volume 86, Number 154 (Friday, August 13, 2021)]
[Notices]
[Pages 44712-44713]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2021-17357]

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ENVIRONMENTAL PROTECTION AGENCY

[EPA-HQ-OW-2019-0675; FRL 5880-03-OW]

Ambient Water Quality Criteria To Address Nutrient Pollution in 
Lakes and Reservoirs

AGENCY: Environmental Protection Agency (EPA).

ACTION: Notice of availability.

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SUMMARY: The Environmental Protection Agency (EPA) is announcing the 
release of Ambient Water Quality Criteria to Address Nutrient Pollution 
in Lakes and Reservoirs. These national recommended criteria are models 
for total nitrogen and total phosphorus concentrations in lakes and 
reservoirs to protect three different designated uses--aquatic life, 
recreation, and drinking water source protection--from the adverse 
effects of nutrient pollution. Nutrient pollution can degrade the 
conditions of water bodies worldwide, and the effects of excess 
nitrogen and phosphorus may be particularly evident in lakes and 
reservoirs. These recommended criteria are based on stressor-response 
models, which link nutrient pollution stressors (nitrogen, phosphorus) 
to responses associated with protection of designated uses. Models and 
associated criteria provided in this document are based on national 
data. States and authorized tribes can also incorporate local data, 
when available, into the national models, helping states and authorized 
tribes to derive numeric nutrient criteria that apply relationships 
estimated from national data while accounting for unique local 
conditions. These recommended criteria replace numeric nutrient 
criteria recommended by EPA in 2000 and 2001 for lakes and reservoirs 
for 12 out of 14 ecoregions of the conterminous United States. This 
document was released for 60-day public comment in the Federal Register 
on May 22, 2020. The comment period was extended 30 days, for a total 
comment period of 90 days. EPA has considered the comments, made minor 
revisions to the draft document in response, and published this final 
document to provide recommendations for states and authorized tribes 
interested in establishing water quality standards under the Clean 
Water Act (CWA) to protect the designated uses of their lakes and 
reservoirs from nutrient pollution.

ADDRESSES: EPA has established a docket for this action under Docket ID 
No. EPA-HQ-OW-2019-0675. All documents in the docket are listed on the 
https://www.regulations.gov website. Although listed in the index, some 
information is not publicly available, e.g. confidential business 
information (CBI) or other information whose disclosure is restricted 
by statute. Certain other material, such as copyrighted material, is 
not placed on the internet and will be publicly available only in hard 
copy form. Publicly available docket materials are available 
electronically through https://www.regulations.gov.

FOR FURTHER INFORMATION CONTACT: Lester Yuan, Health and Ecological 
Criteria Division, Office of Water (Mail Code 4304T), Environmental 
Protection Agency, 1200 Pennsylvania Avenue NW, Washington, DC 20460; 
telephone number: (202) 566-0908; email address: yuan.lester@epa.gov.

SUPPLEMENTARY INFORMATION:

I. What is nutrient pollution, and why is EPA concerned about it?

    Nutrient pollution, or the excess loading of nitrogen and 
phosphorus, can degrade the conditions of water bodies and potentially 
make them unsafe for aquatic life, recreation, or to use as drinking 
water sources. Nutrient pollution stimulates excess growth of algae, 
which can limit the recreational use of lakes and reservoirs. 
Overabundant algae also increase the amount of organic matter in a lake 
or reservoir, which, when decomposed, can depress dissolved oxygen 
concentrations below levels needed to sustain aquatic life. In extreme 
cases, the depletion of dissolved oxygen causes fish kills. Nutrient 
pollution can also stimulate the excess growth of nuisance algae, such 
as cyanobacteria, which can produce cyanotoxins that are toxic to 
animals and humans. Elevated concentrations of these cyanotoxins can 
reduce the suitability of a lake or reservoir for recreation and as a 
source of drinking water.

II. Information on Recommended Ambient Water Quality Criteria for Lakes 
and Reservoirs

    These recommended ambient water quality criteria for lakes and 
reservoirs are part of EPA's ongoing efforts to support states and 
authorized tribes in developing and adopting numeric nutrient criteria. 
Numeric nutrient criteria provide an important tool for managing the 
effects of nutrient pollution by providing nutrient goals that support 
the protection and maintenance of the designated uses of the waters of 
the United States. Recognizing the utility of such criteria, EPA 
published recommended numeric nutrient criteria for lakes and 
reservoirs for 12 out of 14 ecoregions of the conterminous United 
States from 2000 to 2001. These criteria were derived by analyzing 
available data on the concentrations of total nitrogen, total 
phosphorus, chlorophyll a, and Secchi depth. Scientific understanding 
of the relationships between nutrient concentrations and deleterious 
effects in lakes and reservoirs has increased since 2001, and 
standardized, high-quality data collected from lakes and reservoirs 
across the United States have become available. In this document, EPA 
describes analyses of these new data and provides models to derive 
numeric nutrient criteria for lakes and reservoirs

[[Page 44713]]

that replace the recommended numeric nutrient criteria of 2000 and 
2001. These models and associated criteria are provided in accordance 
with the provisions of CWA Section 304(a) for EPA to revise national 
recommended ambient water quality criteria from time to time to reflect 
the latest scientific knowledge. The ecological responses on which 
these models and criteria are based were selected by applying a risk 
assessment approach to explicitly link nutrient concentrations to the 
protection of designated uses.
    The recommended ambient water quality criteria for lakes and 
reservoirs are based on the available data from EPA's National Lakes 
Assessment (NLA) survey. The NLA surveys are carried out under EPA's 
National Aquatic Resource Survey program, which conducts water quality 
and biological surveys of the nation's surface waters in partnerships 
with state and authorized tribal water quality monitoring programs 
(https://www.epa.gov/national-aquatic-resource-surveys). The NLA 
surveys were designed using random sampling of lakes and reservoirs 
across the United States, and as a result, the collected data represent 
the characteristics of the full population of United States lakes and 
reservoirs. The NLA surveys were implemented using standardized field 
sampling and analytical methods, with internal oversight and 
independent quality control surveillance yielding data of high quality 
and statistical rigor.
    The stressor-response models used in generating the recommended 
ambient water quality criteria are based on previously published EPA 
technical guidance (U.S. EPA 2010, Using stressor-response 
relationships to derive numeric nutrient criteria, Office of Water, 
U.S. Environmental Protection Agency, Washington, DC, EPA-820-S-10-
001), as well as scientific peer-reviewed statistical and modeling 
techniques. Models provided in the recommended criteria document are 
based on national data, but states and authorized tribes may have 
additional data collected during routine monitoring. Incorporating 
these local data into the national models can refine and improve the 
precision of the stressor-response relationships on a site-specific 
basis. EPA stands ready to assist states and authorized tribes to add 
their data into the models through the Nutrient Scientific Technical 
Exchange Partnership & Support (N-STEPS) program. In the appendices of 
the criteria document, EPA describes case studies in which state 
monitoring data have been combined with national data, yielding models 
that can be used to derive numeric nutrient criteria that account for 
both unique local conditions and national, large-scale trends.

III. What are CWA Section 304(a) recommended water quality criteria?

    CWA Section 304(a) water quality criteria are non-binding 
recommendations developed by EPA under authority of CWA Section 304(a) 
based on the latest scientific knowledge on the effects that pollutant 
concentrations have on aquatic species, recreation, and/or human 
health.
    CWA Section 304(a)(1) directs EPA to develop, publish, and, from 
time to time, revise criteria for water quality accurately reflecting 
the latest scientific knowledge. Water quality criteria developed under 
CWA Section 304(a) are based on data and scientific judgments on the 
relationship between pollutant concentrations and environmental and 
human health effects. CWA Section 304(a) recommended criteria do not 
reflect consideration of economic impacts or the technological 
feasibility of meeting pollutant concentrations in ambient water.
    CWA Section 304(a) recommended criteria provide non-binding 
guidance to states and authorized tribes in adopting water quality 
standards that ultimately provide a basis for controlling discharges of 
pollutants. Under the CWA and its implementing regulations, states and 
authorized tribes are to adopt water quality criteria to protect 
designated uses (e.g., aquatic life, recreational use). EPA's 
recommended water quality criteria are not regulations and do not 
constitute legally binding requirements. States and authorized tribes 
may adopt other scientifically defensible water quality criteria that 
differ from these recommendations. The CWA and its implementing 
regulations require that any new or revised water quality standards 
adopted by the states and authorized tribes be scientifically 
defensible and protective of the designated uses of the bodies of 
water. States and authorized tribes have the flexibility to do this by 
adopting criteria based on (1) EPA's recommended criteria, (2) EPA's 
criteria modified to reflect site-specific conditions, or (3) other 
scientifically defensible methods.

IV. Use of the Recommended Ambient Water Quality Criteria for Lakes and 
Reservoirs by States and Authorized Tribes

    EPA is publishing the recommended ambient water quality criteria 
for lakes and reservoirs for consideration by states and authorized 
tribes as they adopt numeric nutrient criteria to protect aquatic life, 
recreation, and drinking water sources from nutrient pollution. States 
and authorized tribes could consider using the recommendations as an 
alternative to or as a supplement of other scientifically defensible 
approaches. States and authorized tribes may also modify the criteria 
to reflect site-specific conditions or establish criteria based on 
other scientifically defensible methods (40 CFR 131.11(b)). These 
updated CWA Section 304(a) recommended nutrient criteria for lakes do 
not, as a general matter, compel a state or authorized tribe to revise 
current EPA approved and adopted criteria, Total Maximum Daily Load 
nutrient load targets, or nitrogen or phosphorus numeric values 
established by other scientifically defensible methods. As part of its 
triennial review, if a state or authorized tribe uses its discretion to 
not adopt new or revised nutrient criteria based on these CWA Section 
304(a) recommended criteria, then the state or authorized tribe shall 
provide an explanation when it submits the results of its triennial 
review (40 CFR 131.20(a)).

V. What changed between the draft and final criteria?

    Changes in the final recommended criteria document, compared to the 
May 2020 draft posted for public comment, include technical revisions 
to the models limited to the parameter estimates for the zooplankton 
model, which were updated to reflect a slight change in how the model 
calculates seasonal mean biomasses of phytoplankton and zooplankton. 
Other changes include the addition of an appendix that provides an 
example workflow for identifying appropriately protective numeric 
nutrient criteria using the interactive tools, as well as minor 
editorial revisions that clarify or expand on existing text.

Radhika Fox,
Assistant Administrator.
[FR Doc. 2021-17357 Filed 8-12-21; 8:45 am]
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