[Federal Register Volume 68, Number 3 (Monday, January 6, 2003)]
[Pages 557-560]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 03-176]




Nutrient Criteria Development; Notice of Ecoregional Nutrient 

AGENCY: Environmental Protection Agency (EPA).

ACTION: Notice of ecoregional nutrient criteria for lakes and 
reservoirs, and rivers and streams.


SUMMARY: Pursuant to section 304(a) of the Clean Water Act (CWA), the 
Environmental Protection Agency (EPA) announces two actions: (1) The 
finalization of nine section 304(a) ecoregional nutrient criteria 
documents for lakes and reservoirs, and rivers and streams within 
specific geographic regions (ecoregions) of the United States; and (2) 
a request for significant scientific information on three new section 
304(a) ecoregional nutrient criteria documents. These documents serve 
as recommendations for States, Territories and authorized Tribes \1\ to 
use as they develop nutrient criteria to protect designated uses and 
adopt these criteria into water quality standards.

    \1\ Hereafter, this Federal Register Notice refers to these 
entities as ``States and authorized Tribes.'' Throughout this 
document, reference to States and authorized Tribes is intended to 
include Territories.

For Which New Documents Is EPA Requesting Significant Scientific 
Information From the Public?

    EPA invites the public to provide scientific views on three new 
ecoregional nutrient criteria documents: Lakes and reservoirs in 
ecoregions 1 and 10, and rivers and streams in ecoregion 13. EPA 
requests significant scientific information pertaining to the 
derivation of the draft criteria. EPA will accept significant 
scientific information submitted to the Agency within 90 days of 
publication of this notice in the Federal Register. Written significant 
information to: Robert Cantilli, U.S. EPA, Health and Ecological 
Criteria Division (4304), Office of Science and Technology, Ariel Rios 
Building, 1200 Pennsylvania Ave., NW., Washington DC 20460. You may 
also send comments by e-mail to: [email protected].

What Are the Criteria Recommendations for These Three Ecoregions?

                            Aggregate Ecoregional (Agg. ER) Criteria Recommendations
                            Parameter                                Agg. ER I       Agg. ER X     Agg. ER XIII
TP [mu]g/L......................................................           55.00           60.00           15.00
TN mg/L.........................................................           *0.66            0.57            1.44
Chl a [mu]g/L...................................................            4.88            5.47
Secchi/Turbidity**..............................................            2.55            0.77           1.49
*Calculated--a value for TN was not available, so TN was calculated based on measurements of Total Kjeldahl
  Nitrogen (TKN), and Nitrate + Nitrite (NO2+NO3).
**Secchi depth (m) is applicable to the values in Agg. ER's I and X. Turbidity (FTU) is applicable to Agg. ER

Which Documents Are Final?

    The nine documents being finalized today represent nutrient 
criteria recommendations for lakes and reservoirs in ecoregions 3, 4, 
5, and 14 and nutrient criteria recommendations for rivers and streams 
in ecoregions 1, 4, 5, 8, and 10. EPA announced the availability of 
these documents in the Federal Register on February 28, 2002. These 
documents have undergone external peer review and have been reviewed by 
the public.

What Are the Nutrient Criteria Recommendations for Those Ecoregions?

    The following tables summarize criteria recommendations for lakes 
and reservoirs and rivers and streams, respectively. Table 3 of each 
document also provides values for each of the subecoregion (level III) 
within each Aggregate ecoregion.

                Aggregate Ecoregional (Agg. ER) Criteria Recommendations for Lakes and Reservoirs
                    Parameter                       Agg. ER III     Agg. ER IV       Agg. ER V      Agg. ER XIV
TP [mu]g/L......................................           17.00           20.00           33.00            8.00
TN mg/L.........................................            0.40            0.44            0.56            0.32
Chl a [mu]g/L...................................            3.40        2.00 (S)        2.30 (S)            2.90
Secchi (m)......................................            2.70            2.00            1.30           4.50
Chl a--Chlorophyll a measured by Flourometric method, unless specified. S is for Spectrophotometric.

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                 Aggregate Ecoregional (Agg. ER) Criteria Recommendations for Rivers and Streams
            Parameter                Agg. ER 1      Agg. ER IV       Agg. ER V     Agg. ER VIII      Agg. ER X
TP [mu]g/L......................           47.00           23.00           67.00           10.00            *128
TN mg/L.........................            0.31            0.56            0.88            0.38            0.76
Chl a [mu]g/L...................            1.80            2.40            3.00            0.63         2.10(S)
Turb (FTU)......................            4.25            4.21            7.83            1.30          17.50
* This number appears inordinately high and may either be a statistical anomaly or reflects a unique condition.
  In any case, further regional investigation strongly encouraged to determine the sources, i.e., measurement
  error, notational error, statistical anomaly, natural enriched conditions, or cultural impacts (impacts from
  human activities).
Turb = Turbidity, FTU are nephelometric turbidity units, calibrated with formazin suspension.

    What were the Main Submissions of Significant Scientific 
Information Provided by the Public?
    Many of the concerns raised by the public about EPA's approach for 
developing nutrient criteria were raised earlier during the development 
of EPA's Technical Guidance Manuals. At that time, questions were 
raised about EPA's use of a statistical derivation of a reference 
condition. EPA continues to believe these approaches are reasonable for 
the purpose of making today's criteria recommendations. The Science 
Advisory Board (SAB) endorsed the reference condition approach used by 
EPA. The SAB stated in its review of ``Biological Criteria: Technical 
Guidance for Streams and Small Rivers'' (EPA, 1993) that ``the 
definition of reference condition using reference sites is appropriate 
when used in conjunction with historical data, empirical models, and 
expert opinion/consensus.'' EPA's Nutrient Criteria Program later 
adopted the reference condition approach and continues to recommend it 
in all of its nutrient criteria guidance manuals. Additionally, the 
statistical derivation approach to developing nutrient criteria was 
favorably reviewed by peer reviewers as well. Consequently, EPA did not 
change its fundamental approach to nutrient criteria development or 
change the documents significantly beyond responding to comments of 
peer reviewers. Following is a summary of the most significant 
scientific information submitted by the public. The issues are grouped 
by topic, and then followed by EPA's response:

Percentile Approach

    (1) The criteria are based on a statistical analysis of current 
nutrient levels in the Nation's waters rather than on the latest 
scientific knowledge and therefore are inconsistent with section 304(a) 
of the Clean Water Act.
    (2) The use of the 25th percentile of all data or the 75th 
percentile of all reference data as criteria by States is undocumented, 
not scientifically valid, and results in meaningless numerical criteria 
    (3) Many data gaps exist in the nutrient database (for example a 
lake with only one reading for a parameter in a given year). Some 
screening techniques should have been done so that only those 
waterbodies were included for which there are sufficient representative 
    (4) The statistical approach used to develop the nutrient criteria 
is statistically flawed because it ignores the relationship between 
nutrient levels and in-stream/in-lake effects. As a result, there is no 
way of knowing the environmental benefit or the level of protection of 
designated uses gained by attaining the nutrient criteria levels set 
forth in the documents. As a result, EPA's statistical derivation of 
numerical nutrient criteria are meaningless to real world situations 
and are not helpful in making watershed management decisions, TMDL 
allocations, or in developing Water Quality Standards for nutrients at 
the State level. Therefore, they should be withdrawn.
    EPA Response: The mean, median and mode are measures of central 
tendency commonly used in science to represent the distribution of a 
population of observations. The frequency distribution approach is not 
used to establish criteria; rather it is used to determine one of the 
components of a criterion, the reference condition. This reference 
condition is one element of a criterion which should be considered 
along with historical background information, possible model 
extrapolations of data, and consideration of possible downstream 
impacts on those waters by a regional panel of experts (Regional 
Technical Assistance Group--RTAG).
    Further, the scientific community uses frequency distributions as a 
common basic interpreter of data with the upper and lower quartiles as 
an admittedly subjective, but traditional, approach to viewing the 
extent of a distribution about a central tendency. It is not mandatory 
or expected that the reference condition so derived be translated 
directly into a criterion. The selection of an upper quartile (or lower 
quartile with mixed water quality samples) is also consistent with the 
EPA policy to set levels protective of the majority of waters and has 
been peer reviewed both by EPA's SAB and external peer reviewers of our 
water body type technical guidance.
    Finally, EPA's technical guidance manuals provide examples of 
alternate approaches to frequency distributions to assess reference 
conditions and determine relationships among causal response variables.

Model Based Approach

    The percentile-based nutrient criteria proposed by EPA are 
acceptable only as a way to initiate a model-based, decision-theoretic 
approach to standard setting (as described in submission) to be 
undertaken by the effected States and Tribes with the assistance of 
    EPA Response: The presumption underlying EPA's use of a reference 
condition approach is that reference conditions reflect conditions 
conducive to the protection of most aquatic life in the given water 
body type and geographic region. The upper quartile of the reference 
data distribution is an accommodation to variability of the reference 
condition, and the lower quartile of a mixed sample is an effort to 
approach this reference condition when insufficient a priori sites 
exist. Therefore, the percentiles serve as recommended starting points 
to be further refined by in the absence of refinements that may be 
employed by the States, authorized Tribes and RTAGs.

Need for Site Specific Criteria

    (1) Establishing a single nutrient criterion for all waters of a 
geographically diverse region based on inadequate data is not an 
appropriate approach. Numeric criteria should be developed at a site-
specific level.
    (2) Regarding the chlorophyll standard: annual cycle of circadian 
photo-periods vary significantly from southern Georgia to southern 
Maine. Hours of daylight affect the growth of the chlorophyll in a 
water body not only in photons activating chlorophyll but in

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water temperature. It is difficult to understand how a single standard 
for chlorophyll or Secchi depth could be set over this geographic 
    (3) The recommended criteria are lower than concentrations that may 
be needed to support fisheries and may result in a reduction of fish 
    EPA Response: EPA is using an ecoregion approach as an initial 
attempt to assess nutrient conditions in a broad geographic context. 
The Agency encourages RTAGs, including member States and authorized 
Tribes, to refine and further subdivide the initial ecoregions. If time 
and resources permit, States and authorized Tribes should also consider 
adopting nutrient criteria that are tailored to specific sites. EPA 
believes that recommending nutrient criteria on an ecoregion basis, 
with the use of ecoregional reference conditions, is a reasonable 
alternative to recommending a single nation-wide criterion that may 
fail to account for regional variability or to recommending criteria on 
an individual water body basis, which would be very resource-intensive. 
The EPA SAB has endorsed this region and water body-type specificity 
for biological criteria, and nutrient criteria share a similar 
ecological orientation.
    One of the concerns expressed to EPA was that if the recommended 
nutrient criteria were met, there would not be sufficient nutrients to 
support fisheries. Generally, however, cultural eutrophication has been 
identified by States' section 303 (d) reports as one of the top 
national water quality problems. Where enrichment is documented as 
beneficial by regional specialists, EPA recommends that nutrient 
criteria be developed to promote the removal of that amount of ambient 
total nitrogen and phosphorus in excess of optimal fish production as 
determined by consultation of the RTAG with State and Federal fisheries 
biologists and water resource managers.

Total Nitrogen Criteria

    Total Nitrogen criteria are not necessary and should not be 
required unless EPA can show site-specific reasoning for applying 
nitrogen criteria to all water bodies.
    EPA Response: As a threshold matter, it should be noted that EPA's 
choice of parameters and criteria values are recommendations. The 
documents announced today impose no requirements. States and authorized 
Tribes have considerable flexibility in adopting nutrient criteria, 
provided that the criteria meet the requirements of the CWA and EPA's 
regulations (that is, they are based on sound scientific rationale and 
contain sufficient parameters to protect the designated uses).
    With respect to EPA's recommendation that States and authorized 
Tribes adopt nutrient criteria for nitrogen, EPA notes that while 
phosphorus is often considered the limiting nutrient determining the 
extent of vegetative growth in fresh waters, nitrogen is often 
considered to be the limiting nutrient in the lower reaches of 
estuaries and in coastal marine waters. However, there are cases where 
phosphorus limits algal growth in estuaries and nitrogen performs a 
similar role in some freshwater systems. While nitrogen itself will not 
usually cause water quality impairments in the near-field in 
phosphorus-limited systems, if phosphorus supplies are reduced to 
attenuate symptoms of eutrophication within freshwater segments of a 
given river system, corresponding reductions in freshwater algal blooms 
will allow the highly soluble dissolved forms of nitrogen to be 
transported downstream. This downstream nitrogen transportation to 
estuaries or costal waters may support larger algal blooms resulting in 
water quality impairments. The practice of setting criteria for only 
nitrogen or phosphorus in a given region could displace the 
responsibility for nutrient abatement from the area of the source to a 
downstream jurisdiction. This places an undue burden on the recipient 
of this imported material and increases the abatement costs because 
source control is lost as a management option. EPA suggests, therefore, 
that where downstream effects take place, States and Tribes describe 
technologies or best management practices in their plans to begin 
nitrogen control.

Grouping of Reservoirs and Lakes

    The final document should clarify whether Reservoir means impounded 
stream or river. If impoundments were sampled with natural lakes, the 
75th percentile number may be too high as a standard for historic 
conditions in natural lakes.
    EPA Response: EPA agrees that, if possible, reservoirs should not 
be grouped with lakes and recommends in the Technical Guidance Manual 
that, wherever feasible, criteria for reservoirs and lakes should be 
developed separately. Using the National Nutrient Database, one can 
separate data by lake or reservoir and determine reference conditions 
for each.

How Can I Get Copies of These Documents?

    You can get copies of the set of three new criteria documents or 
any nutrient criteria document from the U.S. National Service Center 
for Environmental Publications (NSCEP), 11029 Kenwood Road, Cincinnati, 
OH 45242; (513) 489-8190 or toll free (800) 490-9198. The documents are 
also available electronically at http://www.epa.gov/waterscience/standards/nutrient.html. The waterbody-specific technical guidance 
manuals are also available from EPA's nutrient Web site. EPA's Office 
of Water, Office of Science and Technology prepared this document. 
Mention of trade names or commercial products does not constitute 
endorsement or recommendation for use.

Can the Public Continue To Provide Input After the Documents Are 

    EPA encourages the public to provide additional scientific 
information that could help States and or authorized Tribes refine 
these recommended nutrient water quality criteria. EPA identified 
specific sections within each document where the public could greatly 
assist States and authorized Tribes in the task of augmenting the 
database for deriving ecoregional nutrient water quality criteria. For 
example, the public can provide information about the historical 
conditions and trends of the water resources within an ecoregion 
related to eutrophication resulting from human activities. EPA will 
forward all comments received on a particular ecoregional criterion or 
set of criteria to the appropriate State or authorized Tribe to help 
foster water quality criteria refinement.


What Are Water Quality Criteria?

    Section 304(a) of the Clean Water Act (CWA) requires the EPA to 
develop and publish and, from time to time, revise criteria for water 
quality accurately reflecting the latest scientific knowledge. Water 
quality criteria recommendations developed under section 304(a) are 
based solely on data and scientific judgments. They do not consider 
economic impacts or the technological feasibility of meeting the 
criteria in ambient water.

What Is the Purpose of These Documents?

    These documents give State and Tribal decision makers and others 
information to support the development

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of numeric nutrient criteria for lakes and reservoirs and rivers and 
streams within several different nutrient ecoregions. An ecoregion is a 
geographic area with assumed relative homogeneity of ecological 
characteristics. EPA's section 304(a) criteria recommendations for 
phosphorous, total nitrogen, chlorophyll a and some form of water 
clarity, i.e. Secchi depth or turbidity represent reference conditions 
of surface waters that are minimally affected by human activities and 
provide for the protection and propagation of aquatic life and 
    These recommendations do not substitute for the CWA or EPA's 
regulations; nor are the documents themselves regulations. Thus, they 
cannot impose legally binding requirements on EPA, States, Indian 
tribes or the regulated community. Indeed, there may be other 
approaches that would be appropriate in particular situations or 
circumstances. When EPA reviews a new or revised nutrient water quality 
criterion submitted by a State or authorized Tribe under CWA section 
303(c), EPA will decide to approve or disapprove that submission on a 
case-by-case basis and will be guided by the applicable requirements of 
the Clean Water Act and implementing regulations, taking into account 
comments and information presented at that time by interested persons 
regarding the appropriateness of applying these recommendations to the 
particular situation.

Why Does EPA Develop Ecoregional Nutrient Criteria?

    States and authorized Tribes consistently identify excessive levels 
of nutrients as a major reason why as much as half of the surface 
waters surveyed in this country do not meet water quality objectives, 
such as full support of aquatic life. In 2000, EPA published nutrient 
criteria technical guidance manuals for lakes and reservoirs and for 
rivers and streams. In 2001, EPA published a draft guidance manual for 
estuarine and coastal marine waters. These manuals provide techniques 
for assessing nutrient conditions as well as methods for developing 
nutrient criteria for specific water body types. These and related 
documents are also available from EPA's nutrient Web site: http://www.epa.gov/waterscience/standards/nutrient.html. EPA is developing a 
guidance manual for wetlands.

What Is the Total Set of Ecoregional Nutrient Criteria That EPA Has 

    On January 9, 2001, EPA announced the availability of ecoregional 
nutrient criteria documents for lakes and reservoirs in eight 
ecoregions, for rivers and streams in eight ecoregions (several of 
which overlap with the eight ecoregions for lakes and reservoirs), and 
for wetlands in one ecoregion. Those ecoregions were chosen based on 
the availability of nutrient data within each ecoregion. On February 
28, 2002, EPA announced the availability of nine ecoregional nutrient 
criteria documents for lakes and reservoirs, and rivers and streams. 
Today, EPA announces the availability of three additional ecoregional 
nutrient criteria documents for lakes and reservoirs, and rivers and 
streams. This brings the total number of ecoregional nutrient criteria 
documents to 29 and results in nutrient criteria covering almost 100% 
of the freshwater waterbodies of the U.S. (excluding wetlands).
    EPA also provided guidance on development and adoption of nutrient 
criteria into water quality standards. More recently, on November 14, 
2001, Geoffrey H. Grubbs, Director of the Office of Science and 
Technology, in EPA's Office of Water provided this guidance to EPA, and 
State and Interstate Water Program Directors. This memorandum can be 
viewed electronically at: http://www.epa.gov/waterscience/standards/nutrient.html.

    Dated: December 20, 2002.
Geoffrey H. Grubbs,
Director, Office of Science and Technology.
[FR Doc. 03-176 Filed 1-3-03; 8:45 am]