McDonnell TC; Nowicki NA. 2006. Assessment of the extent to which
intensively studied lakes are representative of the Adirondack Mountain
region. (Final Report no 06-17).Corvallis, OR; prepared by Environmental
Chemistry, Inc. for: Albany, NY; Environmental Monitoring Evaluation and
Protection Program of the New York State Energy Research and Development
Authority (NYSERDA).

US EPA, 1973. “Effects of Sulfur Oxide in the Atmosphere on
Vegetation”. Revised Chapter 5 of Air Quality Criteria For Sulfur
Oxides. U.S. Environmental Protection Agency. Research Triangle Park,
N.C. EPA-R3-73-030.

US EPA. 1982. Review of the National Ambient Air Quality Standards for
Sulfur Oxides: Assessment of Scientific and Technical Information. OAQPS
Staff Paper. EPA-450/5-82-007. U.S. Environmental Protection Agency,
Office of Air Quality Planning and Standards, Research Triangle Park,
NC.

US EPA, 1984a. The Acidic Deposition Phenomenon and Its Effects:
Critical Assessment Review Papers. Volume I Atmospheric Sciences.
EPA-600/8-83-016AF. Office of Research and Development, Washington, DC

US EPA, 1984b. The Acidic Deposition Phenomenon and Its Effects:
Critical Assessment Review Papers. Volume II Effects Sciences.
EPA-600/8-83-016BF. Office of Research and Development, Washington, DC

US EPA, 1985. The Acidic Deposition Phenomenon and Its Effects: Critical
Assessment Document. EPA-600/8-85/001. Office of Research and
Development, Washington, DC

US EPA. 1995a. Review of the National Ambient Air Quality Standards for
Nitrogen Dioxide: Assessment of Scientific and Technical Information.
OAQPS Staff Paper. EPA-452/R-95-005. U.S. Environmental Protection
Agency, Office of Air Quality Planning and Standards, Research Triangle
Park, NC. September.

US EPA. 1995b. Acid Deposition Standard Feasibility Study Report to
Congress. U.S. Environmental Protection Agency, Washington, DC.
EPA-430/R-95-001a.

US EPA 2007. Integrated Review Plan for the Secondary National Ambient
Air Quality Standards for Nitrogen Dioxide and Sulfur Dioxide. U.S.
Environmental Protection Agency, Research Triangle Park, NC,
EPA-452/R-08-006.

US EPA 2008. Integrated Science Assessment (ISA) for Oxides of Nitrogen
and Sulfur Ecological Criteria (Final Report). U.S. Environmental
Protection Agency, Washington, D.C., EPA/600/R-08/082F, 2008.

US EPA 2009. Risk and Exposure Assessment for Review of the Secondary
National Ambient Air Quality Standards for Oxides of Nitrogen and Oxides
of Sulfur-Main Content - Final Report. U.S. Environmental Protection
Agency, Washington, D.C., EPA-452/R-09-008a

US EPA, 2010a. CASTNET Quality Assurance Project Plan, Revision 7.0,
October 2010,  HYPERLINK "http://java.epa.gov/castnet/"
http://java.epa.gov/castnet/

US EPA, 2010b.  CASTNET Annual Reports, 2004 - 2009,  HYPERLINK
"http://java.epa.gov/castnet/" http://java.epa.gov/castnet/

US EPA 2011. Policy Assessment for the Review of the Secondary National
Ambient Air Quality Standards for Oxides of Nitrogen and Oxides of
Sulfur. U.S. Environmental Protection Agency, Washington, D.C.,
EPA-452/R-11-005a.

US EPA, 2011b.  Federal Reference Methods for NOy and p-SO4 for the New
Combined NOx and SOx Secondary NAAQS Research Plan, EPA/600/1-11/002
January 20, 2011.

Wolff, G. T. 1993. CASAC closure letter for the 1993 Criteria Document
for Oxides of Nitrogen addressed to U.S. EPA Administrator Carol M.
Browner dated September 30, 1993.

Wolff, G. T. 1995. CASAC closure letter for the 1995 OAQPS Staff Paper
addressed to U.S. EPA Administrator Carol M. Browner dated August 22,
1995.

List of Subjects in 40 CFR Part 50

	Environmental protection, Air pollution control, Carbon monoxide, Lead,
Nitrogen dioxide, Ozone, Particulater matter, Sulfur oxides.

________________________________

Dated:  July 12, 2011

Lisa P. Jackson,

Administrator

	For the reasons set forth in the preamble, part 50 of chapter 1 of
title 40 of the code of Federal regulations is proposed to be amended as
follows:

PART 50-NATIONAL PRIMARY AND SECONDARY AMBIENT AIR QUALITY STANDARDS

1.  The authority citation for part 50 continues to read as follows:

Authority: 42 U.S.C. 7401, et seq.

2.  Section 50.5 is amended by revising paragraphs (b) and (c) and by
adding paragraphs (d) and (e)  to read as follows:

§50.5   National secondary ambient air quality standards for sulfur
oxides (sulfur dioxide).

*     *     *     *     *

(b)  The level of the national secondary 1-hour ambient air quality
standard for oxides of sulfur is 75 parts per billion (ppb, which is 1
part in 1,000,000,000), measured in the ambient air as sulfur dioxide
(SO2).

(c)  The levels of the standards shall be measured by a reference method
based on Appendix A-1 or A-2 of this part, or by a Federal Equivalent
Method (FEM) designated in accordance with part 53 of this chapter.

(d)  To demonstrate attainment with the 3-hour secondary standard, the
second-highest 3-hour average must be based upon hourly data that are at
least 75 percent complete in each calendar quarter.  A 3-hour block
average shall be considered valid only if all three hourly averages for
the 3-hour period are available.  If only one or two hourly averages are
available, but the 3-hour average would exceed the level of the standard
when zeros are substituted for the missing values, subject to the
rounding rule of paragraph (a) of this section, then this shall be
considered a valid 3-hour average.  In all cases, the 3-hour block
average shall be computed as the sum of the hourly averages divided by
3.

(e)  The 1-hour secondary standard is met at an ambient air quality
monitoring site when the three-year average of the annual 99th
percentile of the daily maximum 1-hour average concentrations is less
than or equal to 75 ppb, as determined in accordance with Appendix T of
this part.

3.  Section 50.11 is amended by deleting paragraphs (f) and (g) and
revising paragraphs (a) through (e) to read as follows:

§50.11   National primary and secondary ambient air quality
standards for oxides of nitrogen (with nitrogen dioxide as the
indicator).

  (a) The level of the national primary and secondary annual ambient air
quality standards for oxides of nitrogen is 53 parts per billion (ppb,
which is 1 part in 1,000,000,000), annual average concentration,
measured in the ambient air as nitrogen dioxide.

(b) The level of the national primary and secondary 1-hour ambient air
quality standards for oxides of nitrogen is 100 ppb, 1-hour average
concentration, measured in the ambient air as nitrogen dioxide.

(c) The levels of the standards shall be measured by:

(1) a reference method based on appendix F to this part; or

(2) a Federal equivalent method (FEM) designated in accordance with part
53 of this chapter.

(d) The annual primary and secondary standards are met when the annual
average concentration in a calendar year is less than or equal to 53
ppb, as determined in accordance with Appendix S of this part for the
annual standard.

(e) The 1-hour primary and secondary standards are met when the
three-year average of the annual 98th percentile of the daily maximum
1-hour average concentration is less than or equal to 100 ppb, as
determined in accordance with Appendix S of this part for the 1-hour
standard.

4. Appendix S is amended as follows:

a. by revising paragraph 1.(a),

b. by revising the definition of “Design values” under paragraph
1.(c),

c. by  revising paragraph 2.(b),

d. by revising paragraphs 3.1(a) through (d),

e. by revising paragraphs 3.2(a) through (e),

f. by revising paragraph 4.1(b),

g. by revising paragraph 4.2 (c),

h. by revising paragraph 5.1(b), and

i. by revising paragraph 5.2(b) to read as follows:

Appendix S to Part 50—Interpretation of the Primary and Secondary
National Ambient Air Quality Standards for Oxides of Nitrogen (Nitrogen
Dioxide)

 1. General.

(a) This appendix explains the data handling conventions and
computations necessary for determining when the primary and secondary
national ambient air quality standards for oxides of nitrogen as
measured by nitrogen dioxide (“NO2 NAAQS”) specified in §50.11 are
met.  Nitrogen dioxide (NO2) is measured in the ambient air by a Federal
reference method (FRM) based on appendix F to this part or by a Federal
equivalent method (FEM) designated in accordance with part 53 of this
chapter. Data handling and computation procedures to be used in making
comparisons between reported NO2 concentrations and the levels of the
NO2 NAAQS are specified in the following sections.

 *     *     *     *     *

(c) The terms used in this appendix are defined as follows:

*     *     *     *     *

Design values are the metrics (i.e., statistics) that are compared to
the NAAQS levels to determine compliance, calculated as specified in
section 5 of this appendix.  The design values for the primary and
secondary NAAQS are:

 (1) The annual mean value for a monitoring site for one year (referred
to as the “annual primary or secondary standard design value”).

(2) The 3-year average of annual 98th percentile daily maximum 1-hour
values for a monitoring site (referred to as the “1-hour primary or
secondary standard design value”).

*     *     *     *     *

2. Requirements for Data Used for Comparisons with the NO2 NAAQS and
Data

Reporting Considerations.

 *     *     *     *     *

(b) When two or more NO2 monitors are operated at a site, the state may
in advance designate one of them as the primary monitor.  If the state
has not made this designation, the Administrator will make the
designation, either in advance or retrospectively.  Design values will
be developed using only the data from the primary monitor, if this
results in a valid design value.  If data from the primary monitor do
not allow the development of a valid design value, data solely from the
other monitor(s) will be used in turn to develop a valid design value,
if this results in a valid design value.  If there are three or more
monitors, the order for such comparison of the other monitors will be
determined by the Administrator.  The Administrator may combine data
from different monitors in different years for the purpose of developing
a valid 1-hour primary or secondary standard design value, if a valid
design value cannot be developed solely with the data from a single
monitor.  However, data from two or more monitors in the same year at
the same site will not be combined in an attempt to meet data
completeness requirements, except if one monitor has physically replaced
another instrument permanently, in which case the two instruments will
be considered to be the same monitor, or if the state has switched the
designation of the primary monitor from one instrument to another during
the year.

*     *     *     *     *

3. Comparisons with the NO2 NAAQS.

3.1 The Annual Primary and Secondary NO2 NAAQS.

(a) The annual primary and secondary NO2 NAAQS are met at a site when
the valid annual primary standard design value is less than or equal to
53 parts per billion (ppb).

(b) An annual primary or secondary standard design value is valid when
at least 75 percent of the hours in the year are reported.

(c) An annual primary or secondary standard design value based on data
that do not meet the completeness criteria stated in section 3.1(b) may
also be considered valid with the approval of, or at the initiative of,
the Administrator, who may consider factors such as monitoring site
closures/moves, monitoring diligence, the consistency and levels of the
valid concentration measurements that are available, and nearby
concentrations in determining whether to use such data.

(d) The procedures for calculating the annual primary and secondary
standard design values are given in section 5.1 of this appendix.

3.2 The 1-hour Primary and Secondary NO2 NAAQS.

(a) The 1-hour primary or secondary NO2 NAAQS is met at a site when the
valid 1-hour primary or secondary standard design value is less than or
equal to 100 parts per billion (ppb).

(b) An NO2 1-hour primary or secondary standard design value is valid if
it encompasses three consecutive calendar years of complete data.  A
year meets data completeness requirements when all 4 quarters are
complete.  A quarter is complete when at least 75 percent of the
sampling days for each quarter have complete data. A sampling day has
complete data if 75 percent of the hourly concentration values,
including state-flagged data affected by exceptional events which have
been approved for exclusion by the Administrator, are reported.

 (c) In the case of one, two, or three years that do not meet the
completeness requirements of section 3.2(b) of this appendix and thus
would normally not be useable for the calculation of a valid 3-year
1-hour primary or secondary standard design value, the 3-year 1-hour
primary or secondary standard design value shall nevertheless be
considered valid if one of the following conditions is true.

(i) At least 75 percent of the days in each quarter of each of three
consecutive years have at least one reported hourly value, and the
design value calculated according to the procedures specified in section
5.2 is above the level of the primary or secondary 1-hour standard.

(ii) (A) A 1-hour primary or secondary standard design value that is
below the level of the NAAQS can be validated if the substitution test
in section 3.2(c)(ii)(B) results in a “test design value” that is
below the level of the NAAQS.  The test substitutes actual
‘‘high’’ reported daily maximum 1-hour values from the same site
at about the same time of the year (specifically, in the same calendar
quarter) for unknown values that were not successfully measured.  Note
that the test is merely diagnostic in nature, intended to confirm that
there is a very high likelihood that the original design value (the one
with less than 75 percent data capture of hours by day and of days by
quarter) reflects the true under-NAAQS-level status for that 3-year
period; the result of this data substitution test (the ‘‘test design
value”, as defined in section 3.2(c)(ii)(B)) is not considered the
actual design value. For this test, substitution is permitted only if
there are at least 200 days across the three matching quarters of the
three years under consideration (which is about 75 percent of all
possible daily values in those three quarters) for which 75 percent of
the hours in the day, including state-flagged data affected by
exceptional events which have been approved for exclusion by the
Administrator, have reported concentrations. However, maximum 1-hour
values from days with less than 75 percent of the hours reported shall
also be considered in identifying the high value to be used for
substitution.

(B) The substitution test is as follows: Data substitution will be
performed in all quarter periods that have less than 75 percent data
capture but at least 50 percent data capture, including state-flagged
data affected by exceptional events which have been approved for
exclusion by the Administrator; if any quarter has less than 50 percent
data capture then this substitution test cannot be used.  Identify for
each quarter (e.g., January-March) the highest reported daily maximum
1-hour value for that quarter, excluding state-flagged data affected by
exceptional events which have been approved for exclusion by the
Administrator, looking across those three months of all three years
under consideration.  All daily maximum 1-hour values from all days in
the quarter period shall be considered when identifying this highest
value, including days with less than 75 percent data capture.  If after
substituting the highest non-excluded reported daily maximum 1-hour
value for a quarter for as much of the missing daily data in the
matching deficient quarter(s) as is needed to make them 100 percent
complete, the procedure in section 5.2 yields a recalculated 3-year
1-hour standard “test design value” below the level of the standard,
then the 1-hour primary or secondary standard design value is deemed to
have passed the diagnostic test and is valid, and the level of the
standard is deemed to have been met in that 3-year period. As noted in
section 3.2(c)(i), in such a case, the 3-year design value based on the
data actually reported, not the ‘‘test design value’’, shall be
used as the valid design value.

(iii) (A) A 1-hour primary or secondary standard design value that is
above the level of the NAAQS can be validated if the substitution test
in section 3.2(c)(iii)(B) results in a “test design value” that is
above the level of the NAAQS.  The test substitutes actual ‘‘low”
reported daily maximum 1-hour values from the same site at about the
same time of the year (specifically, in the same three months of the
calendar) for unknown values that were not successfully measured.  Note
that the test is merely diagnostic in nature, intended to confirm that
there is a very high likelihood that the original design value (the one
with less than 75 percent data capture of hours by day and of days by
quarter) reflects the true above-NAAQS-level status for that 3-year
period; the result of this data substitution test (the ‘‘test design
value”, as defined in section 3.2(c)(iii)(B)) is not considered the
actual design value. For this test, substitution is permitted only if
there are a minimum number of available daily data points from which to
identify the low quarter-specific daily maximum 1-hour values,
specifically if there are at least 200 days across the three matching
quarters of the three years under consideration (which is about 75
percent of all possible daily values in those three quarters) for which
75 percent of the hours in the day have reported concentrations. Only
days with at least 75 percent of the hours reported shall be considered
in identifying the low value to be used for substitution.

(B) The substitution test is as follows: Data substitution will be
performed in all quarter periods that have less than 75 percent data
capture.  Identify for each quarter (e.g., January-March) the lowest
reported daily maximum 1-hour value for that quarter, looking across
those three months of all three years under consideration.  All daily
maximum 1-hour values from all days with at least 75 percent capture in
the quarter period shall be considered when identifying this lowest
value. If after substituting the lowest reported daily maximum 1-hour
value for a quarter for as much of the missing daily data in the
matching deficient quarter(s) as is needed to make them 75 percent
complete, the procedure in section 5.2 yields a recalculated 3-year
1-hour standard “test design value” above the level of the standard,
then the 1-hour primary or secondary standard design value is deemed to
have passed the diagnostic test and is valid, and the level of the
standard is deemed to have been exceeded in that 3-year period. As noted
in section 3.2(c)(i), in such a case, the 3-year design value based on
the data actually reported, not the ‘‘test design value’’, shall
be used as the valid design value.

 (d) A 1-hour primary or secondary  standard design value based on data
that do not meet the completeness criteria stated in 3.2(b) and also do
not satisfy section 3.2(c), may also be considered valid with the
approval of, or at the initiative of, the Administrator, who may
consider factors such as monitoring site closures/moves, monitoring
diligence, the consistency and levels of the valid concentration
measurements that are available, and nearby concentrations in
determining whether to use such data.

(e) The procedures for calculating the 1-hour primary and secondary
standard design values are given in section 5.2 of this appendix.

4. Rounding Conventions.

4.1 Rounding Conventions for the Annual Primary and Secondary NO2 NAAQS.

*     *     *     *     *

 (b) The annual primary or secondary standard design value is calculated
pursuant to section 5.1 and then rounded to the nearest whole number or
1 ppb (decimals 0.5 and greater are rounded up to the nearest whole
number, and any decimal lower than 0.5 is rounded down to the nearest
whole number).

4.2 Rounding Conventions for the 1-hour Primary and Secondary NO2 NAAQS.

*     *     *     *     *

(c) The 1-hour primary or secondary standard design value is calculated
pursuant to section 5.2 and then  rounded to the nearest whole number or
1 ppb (decimals 0.5 and greater are rounded up to the nearest whole
number, and any decimal lower than 0.5 is rounded down to the nearest
whole number).

5. Calculation Procedures for the Primary and Secondary NO2 NAAQS.

5.1 Procedures for the Annual Primary and Secondary NO2 NAAQS

*     *     *     *     *

 (b) The annual primary or secondary standard design value for a site is
the valid annual mean rounded according to the conventions in section
4.1.

5.2 Calculation Procedures for the 1-hour Primary and Secondary NO2
NAAQS.

*     *     *     *     *

(b) The 1-hour primary or secondary standard design value for a site is
the mean of the three annual 98th percentile values, rounded according
to the conventions in section 4.

*     *     *     *     *

5.  Appendix T is amended as follows:

a. by revising paragraph 1.(a),

b. by revising the definition of “Design values” under paragraph
1.(c),

c. by  revising paragraph 2.(b),

d. by revising paragraphs 3.(a) through (e),

e. by revising paragraph 4.(c), and

f. by revising paragraph 5.(b) to read as follows:

Appendix T to Part 50—Interpretation of the Primary and Secondary
National Ambient Air Quality Standards for Oxides of Sulfur (Sulfur
Dioxide)

1. General.

(a) This appendix explains the data handling conventions and
computations necessary for determining when the primary and secondary
national ambient air quality standards for Oxides of Sulfur as measured
by Sulfur Dioxide (“SO2 NAAQS”) specified in § 50.17 and §50.5
(b), respectively, are met at an ambient air quality monitoring site.
Sulfur Dioxide (SO2) is measured in the ambient air by a Federal
reference method (FRM) based on appendix A-1 or A-2 to this part or by a
Federal equivalent method (FEM) designated in accordance with part 53 of
this chapter. Data handling and computation procedures to be used in
making comparisons between reported SO2 concentrations and the levels of
the SO2 NAAQS are specified in the following sections.

*     *     *     *     *

(c) The terms used in this appendix are defined as follows:

*     *     *     *     *

Design values are the metrics (i.e., statistics) that are compared to
the NAAQS levels to determine compliance, calculated as specified in
section 5 of this appendix.  The design value for the primary and
secondary 1-hour NAAQS is the 3-year average of annual 99th percentile
daily maximum 1-hour values for a monitoring site (referred to as the
“1-hour primary standard design value”).

*     *     *     *     *

2. Requirements for Data Used for Comparisons with the SO2 NAAQS and
Data

Reporting Considerations.

*     *     *     *     *

(b) Data from two or more monitors from the same year at the same site
reported to EPA under distinct Pollutant Occurrence Codes shall not be
combined in an attempt to meet data completeness requirements.  The
Administrator will combine annual 99th percentile daily maximum
concentration values from different monitors in different years,
selected as described here, for the purpose of developing a valid 1-hour
primary or secondary standard design value.  If more than one of the
monitors meets the completeness requirement for all four quarters of a
year, the steps specified in section 5(a) of this appendix shall be
applied to the data from the monitor with the highest average of the
four quarterly completeness values to derive a valid annual 99th
percentile daily maximum concentration.  If no monitor is complete for
all four quarters in a year, the steps specified in section 3(c) and
5(a) of this appendix shall be applied to the data from the monitor with
the highest average of the four quarterly completeness values in an
attempt to derive a valid annual 99th percentile daily maximum
concentration.  This paragraph does not prohibit a monitoring agency
from making a local designation of one physical monitor as the primary
monitor for a Pollutant Occurrence Code and substituting the 1-hour data
from a second physical monitor whenever a valid concentration value is
not obtained from the primary monitor; if a monitoring agency
substitutes data in this manner, each substituted value must be
accompanied by an AQS qualifier code indicating that substitution with a
value from a second physical monitor has taken place.

*     *     *     *     *

3. Comparisons with the 1-hour Primary and Secondary SO2 NAAQS.

 (a) The 1-hour primary or secondary SO2 NAAQS is met at an ambient air
quality monitoring site when the valid 1-hour primary or secondary
standard design value is less than or equal to 75 parts per billion
(ppb).

(b) An SO2 1-hour primary or secondary standard design value is valid if
it encompasses three consecutive calendar years of complete data.  A
year meets data completeness requirements when all 4 quarters are
complete.  A quarter is complete when at least 75 percent of the
sampling days for each quarter have complete data. A sampling day has
complete data if 75 percent of the hourly concentration values,
including State-flagged data affected by exceptional events which have
been approved for exclusion by the Administrator, are reported.

 (c) In the case of one, two, or three years that do not meet the
completeness requirements of section 3(b) of this appendix and thus
would normally not be useable for the calculation of a valid 3-year
1-hour primary or secondary standard design value, the 3-year 1-hour
primary or secondary standard design value shall nevertheless be
considered valid if one of the following conditions is true.

(i) At least 75 percent of the days in each quarter of each of three
consecutive years have at least one reported hourly value, and the
design value calculated according to the procedures specified in section
5 is above the level of the primary or secondary 1-hour standard.

(ii) (A) A 1-hour primary or secondary standard design value that is
equal to or below the level of the NAAQS can be validated if the
substitution test in section 3(c)(ii)(B) results in a “test design
value” that is below the level of the NAAQS.  The test substitutes
actual ‘‘high’’ reported daily maximum 1-hour values from the
same site at about the same time of the year (specifically, in the same
calendar quarter) for unknown values that were not successfully
measured.  Note that the test is merely diagnostic in nature, intended
to confirm that there is a very high likelihood that the original design
value (the one with less than 75 percent data capture of hours by day
and of days by quarter) reflects the true under-NAAQS-level status for
that 3-year period; the result of this data substitution test (the
‘‘test design value”, as defined in section 3(c)(ii)(B)) is not
considered the actual design value. For this test, substitution is
permitted only if there are at least 200 days across the three matching
quarters of the three years under consideration (which is about 75
percent of all possible daily values in those three quarters) for which
75 percent of the hours in the day, including State-flagged data
affected by exceptional events which have been approved for exclusion by
the Administrator, have reported concentrations. However, maximum 1-hour
values from days with less than 75 percent of the hours reported shall
also be considered in identifying the high value to be used for
substitution.

(B) The substitution test is as follows: Data substitution will be
performed in all quarter periods that have less than 75 percent data
capture but at least 50 percent data capture, including State-flagged
data affected by exceptional events which have been approved for
exclusion by the Administrator; if any quarter has less than 50 percent
data capture then this substitution test cannot be used.  Identify for
each quarter (e.g., January-March) the highest reported daily maximum
1-hour value for that quarter, excluding State-flagged data affected by
exceptional events which have been approved for exclusion by the
Administrator, looking across those three months of all three years
under consideration.  All daily maximum 1-hour values from all days in
the quarter period shall be considered when identifying this highest
value, including days with less than 75 percent data capture. If after
substituting the highest reported daily maximum 1-hour value for a
quarter for as much of the missing daily data in the matching deficient
quarter(s) as is needed to make them 100 percent complete, the procedure
in section 5 yields a recalculated 3-year 1-hour standard “test design
value” less than or equal to the level of the standard, then the
1-hour primary or secondary standard design value is deemed to have
passed the diagnostic test and is valid, and the level of the standard
is deemed to have been met in that 3-year period. As noted in section
3(c)(i), in such a case, the 3-year design value based on the data
actually reported, not the ‘‘test design value’’, shall be used
as the valid design value.

(iii) (A) A 1-hour primary or secondary standard design value that is
above the level of the NAAQS can be validated if the substitution test
in section 3(c)(iii)(B) results in a “test design value” that is
above the level of the NAAQS.  The test substitutes actual ‘‘low”
reported daily maximum 1-hour values from the same site at about the
same time of the year (specifically, in the same three months of the
calendar) for unknown hourly values that were not successfully measured.
 Note that the test is merely diagnostic in nature, intended to confirm
that there is a very high likelihood that the original design value (the
one with less than 75 percent data capture of hours by day and of days
by quarter) reflects the true above-NAAQS-level status for that 3-year
period; the result of this data substitution test (the ‘‘test design
value”, as defined in section 3(c)(iii)(B)) is not considered the
actual design value. For this test, substitution is permitted only if
there are a minimum number of available daily data points from which to
identify the low quarter-specific daily maximum 1-hour values,
specifically if there are at least 200 days across the three matching
quarters of the three years under consideration (which is about 75
percent of all possible daily values in those three quarters) for which
75 percent of the hours in the day have reported concentrations. Only
days with at least 75 percent of the hours reported shall be considered
in identifying the low value to be used for substitution.

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 test is as follows: Data substitution will be performed in all quarter
periods that have less than 75 percent data capture.  Identify for each
quarter (e.g., January-March) the lowest reported daily maximum 1-hour
value for that quarter, looking across those three months of all three
years under consideration.  All daily maximum 1-hour values from all
days with at least 75 percent capture in the quarter period shall be
considered when identifying this lowest value. If after substituting the
lowest reported daily maximum 1-hour value for a quarter for as much of
the missing daily data in the matching deficient quarter(s) as is needed
to make them 75 percent complete, the procedure in section 5 yields a
recalculated 3-year 1-hour standard “test design value” above the
level of the standard, then the 1-hour primary or secondary standard
design value is deemed to have passed the diagnostic test and is valid,
and the level of the standard is deemed to have been exceeded in that
3-year period. As noted in section 3(c)(i), in such a case, the 3-year
design value based on the data actually reported, not the ‘‘test
design value’’, shall be used as the valid design value.

 (d) A 1-hour primary or secondary standard design value based on data
that do not meet the completeness criteria stated in 3(b) and also do
not satisfy section 3(c), may also be considered valid with the approval
of, or at the initiative of, the Administrator, who may consider factors
such as monitoring site closures/moves, monitoring diligence, the
consistency and levels of the valid concentration measurements that are
available, and nearby concentrations in determining whether to use such
data.

(e) The procedures for calculating the 1-hour primary or secondary
standard design values are given in section 5 of this appendix.

4. Rounding Conventions for the 1-hour Primary and Secondary SO2 NAAQS.

*     *     *     *     *

(c) The 1-hour primary or secondary standard design value is calculated
pursuant to section 5 and then  rounded to the nearest whole number or 1
ppb (decimals 0.5 and greater are rounded up to the nearest whole
number, and any decimal lower than 0.5 is rounded down to the nearest
whole number).

5. Calculation Procedures for the 1-hour Primary and Secondary SO2
NAAQS.

*     *     *     *     *

(b) The 1-hour primary or secondary standard design value for an ambient
air quality monitoring site is the mean of the three annual 99th
percentile values, rounded according to the conventions in section 4.

 The legislative history of section 109 indicates that a primary
standard is to be set at “the maximum permissible ambient air level .
. . which will protect the health of any [sensitive] group of the
population,” and that for this purpose “reference should be made to
a representative sample of persons comprising the sensitive group rather
than to a single person in such a group” S. Rep. No. 91-1196, 91st
Cong., 2d Sess. 10 (1970).

  Center for Biological Diversity, et al. v. Johnson, No. 05–1814
(D.D.C.)

 The current primary NO2 standard has recently been changed to the 3
year average of the 98th percentile of the annual distribution of the 1
hour daily maximum of the concentration of NO2.  The current secondary
standard remains as it was set in 1971.

 The annual secondary standard for oxides of nitrogen is being specified
in units of ppb to conform to the current version of the annual primary
standard, as specified in the final rule for the most recent review of
the NO2 primary NAAQS (75 FR 6531; February 9, 2010).

 As discussed in chapter 2 of the Policy Assessment, SO2 and particulate
SO4 are routinely measured in ambient air monitoring networks, although
only CASTNET filter packs do not intentionally exclude particle size
fractions.  The CMAQ treatment of SOx is the simple addition of both
species, which are treated explicitly in the model formulation.   All
particle size fractions are included in the CMAQ SOx estimates.

 The Policy Assessment also notes that NOY is a useful measurement for
model evaluation purposes, which is especially important, recognizing
the unique role that CMAQ plays in the development of this standard, as
described below in section III.B.

  This section discusses the linkages between deposition of nitrogen and
sulfur and ANC.  Section III.B.3 then discusses the linkages between
atmospheric concentrations of NOy and SOx and deposition of nitrogen and
sulfur.

 Because Neco is only relevant to nitrogen deposition, in rare cases
where Neco is greater than the total nitrogen deposition, the critical
load would be defined only in terms of acidifying deposition of sulfur
and the Neco term in equation III-1 would be set to zero.

 We note that an 85th area within Omernik’s Ecoregion Level III is
currently being developed for California.

 The distribution of critical loads was based on CL values calculated
with Neco at the lake level.  Consideration could also be given to using
a distribution of CLs without Neco and adding the ecoregion average Neco
value to the nth percentile critical load.  This would avoid cases where
the lake-level Neco value potentially could be greater than total
nitrogen deposition.  The CL at the lake level represents the CL for the
lake to achieve the specified national target ANC value.

 The Policy Assessment judged the data to be sufficient for this purpose
if data are available from more than 10 water bodies in an ecoregion.

 Unlike other NAAQS, where the standard is met when the relevant value
is at or below the level of the standard since a lower standard level is
more protective, in this case a higher standard level is more
protective.

 Tables 7-1a-d and 7-2 in the Policy Assessment present assessment
results for 29 ecoregions that had been initially characterized as acid
sensitive.  Subsequently, based on a broader set of criteria used to
characterize ecoregions as acid sensitive, as discussed above in section
III.B.5.a, the set of ecoregions characterized as acid sensitive was
narrowed to include 22 ecoregions.

Interagency Working Comments on Draft Language under EO12866 and 13563
Interagency Review.  Subject to Further Policy Review.

  PAGE   \* MERGEFORMAT  1

Clarify that you are also keeping the current secondary standards.

I routinely suggest editing this out of boilerplate for water rules.  I
think it sounds unprofessional to say this to the public.  OW has not
had any problem accommodating this suggestion.

There seem to be two closed quotes for a single open quote.  Is this two
quotes or one?  Please fix.

Please clarify what original complaint was amended.

Are these defined terms of art or are you just using these distinctions
casually?  If the former, might be helpful to explain the technical
distinction among the three levels of confidence causality in a
footnote.

Not sure if there is a typo here or if phototoxic and phytotoxic are two
different terms that are being used deliberately.

In t he previous sentence, you say that fish fitness begins to decline
at 100.  Here you say that fitness of sensitive species begins to
decline between 100 and 50.  Not sure if this is redundant or what
distinction you are trying to make.

Would be helpful to add a footnote explaining how ANC is measured
(conceptually, not physically) and what it means to have an ANC < 0.

Wouldn’t the ecological effect result from the interaction of ANC and
load?  That is, if you had low ANC but also very low loadings, you would
not necessarily see the effects cited here, or do I misunderstand?
Would help to clarify this someplace.

This notation may be confusing to some readers.  Suggest you use
eq/ha/yr consistently throughout (as you do elsewhere).

Not clear what this means.  What is “pre-acidification?”  What
“difference” are you referring to here?

Not sure what this means.

I thought the exact quantification of this function was one of the areas
in which there was substantial uncertainty, which is part of your basis
for deferring setting of the ecologically relevant standard.  Please
clarify.

I don’t understand what you are saying here.  Do you mean that
empirically N and S are linked so that neither can be zero.  Or do you
mean that the model constrains both, or the combination of the two, to
be non-zero.  Please clarify.

Not clear from this sentence what was compared to what to get this 20%
decrease.

Unless you have a basis for believing that controls on atmospheric
deposition would be less costly per unit of nitrogen than controls on
other sources (no such evidence is presented here), suggest deleting
this speculative statement.  Does not fit with the generally rigorous
scientific tone of this discussion.

Not sure what you are saying here.  Do you mean that these 65% of
estuaries had the greatest loads relative to other estuaries, relative
to other types of water bodies, or are you saying something about
relative contribution from different source types?

What are non-ambient loadings?

This partial statistic is not very informative.  Would be useful to know
what happens to the entire range of concern (presumably elevated to
acute) collectively, as well as how this overall change breaks down
between the three categories elevated, severe, and acute.

Doesn’t the lowest critical load go with the highest level of
protection?  If so, I would say, “…ranged from 6,008 to 107
eq/ha/yr…” If I understand how this works, a low critical load gives
you a high Bc/Al level.

See prev comment.

This is confusing.  I thought critical load was tied to a specific
target ANC level.  If that is now how you defined critical load here,
would be helpful to clarify.

This is a pretty vague statement. Do you mean greater in some areas and
close in others.  Also I assume that this depends on the critical load
chosen.  Since the loads studies vary by 1.5 orders of magnitude, I
assume the relationships to actual deposition will vary a lot depending
on which load you are using.  It would be helpful to make this statement
more specific.

Do you have any reason to think that deposition levels will rise?
Don’t you have regs recently enacted or in the pipeline that are
likely to significantly reduce NOx/Sox emissions.  Suggest sticking to
the model results and not speculating about what might happen in the
future.

Aren’t these both estuaries where N deposition is known to contribute
significantly to total loadings?  Suggest deleting this speculative
sentence.

Not clear what this means.  Do you mean a slim chance that it would be
enough, or a slim chance that this much would be needed.  Also, if this
comes from a quantified estimate, suggest replacing “slim” with a
more precise statement (preferably quantitative).

I note that the Neuse has a higher share of N coming from deposition
than the Potomac, but that eliminating 78% of deposition could improve
the Potomac from Bad to Poor, while decreasing deposition by any amount
apparently could not produce this result in the Neuse.  It would be
helpful to provide additional explanation for this apparent anomaly.

How do you know this.  This statement appears to be undercut by the next
two sentences.  Please clarify.

It is confusing to have a range of inputs associated with a single point
estimate for emissions changes.  Please clarify what exactly was modeled
and what it showed.

Suggest breaking number one into two as noted below and saying five
issues.  Bullet one here addresses two apparently unrelated issues,
averaging time and appropriate indicators.

Suggest beginning bullet 2 here.  From here to the end of the para
treats a separate issue.

This issue is not unique to NOx/SOx.  Suggest requesting comment on
potential implementation challenges associated with a standard that
varies by region, since a single emissions source may impact multiple
regions.  Modeling to figure out necessary reductions will be
complicated and could become intractable.

Are these levels lower than in the past?  If so, this pattern could also
suggest that there are long lag times in recovery.

This info is distracting and not needed here, also these statistic are
about absolute levels of deposition, not proportions as mentioned
earlier in the sentence.  Suggest deleting.

This insert is suggested so as not to imply that the earlier standards
were not important.

Is this equivalent to saying that 44 percent had an ANC below 50 and 28%
had an ANC below 20?  If so, wouldn’t this be a simpler way to say it,
and also more consistent with preceding and following sentences?  If
not, is the distinction between being below a specified ANC level, and
exceeding the critical load for an ANC level significant?  May be
helpful to clarify.

These two sentences seem inconsistent, unless exceeding the critical
load for an ANC of 50 is not equivalent to having an ANC below 50 (see
previous comment).  Please clarify.

Para above suggests that 0.6 is the relevant ratio for sugar maple.

Again, para above identifies a critical load of 1.2 for red spruce.

Not much context for this statement.  Critical loads based on what ANC
level.  Is 250 a lot?  What would the impact on ANC be of an exceedence
of this magnitude?

This does not seem like a very strong basis for concluding that the
current standards are inadequate, but I’m not sure if this is your
purpose here or not.  Again, do you have any reason to believe that N
and S emission levels will rise in the future.  I would have thought the
opposite.

N/ha/yr

This only shows that these ecosystems are receiving N above the level
necessary for healthy plant growth.  How does it follow that deposition
above this level is adverse?  If N is not limiting above this point,
wouldn’t addtl N deposits have no effect, either positive or negative?
 Please clarify.

Are such change significant.  If so, why does the index only have six
levels?

Statement as worded seems strong for the evidence provided.  How about
suggested edits?

My toxicologist suggests that it is more scientifically neutral to
simply say “neurotoxic.”  How neurotoxic in any given circumstance
is dose-dependent.  Also, she notes that mercury vapor is much more
neurtoxic.

Is this preamble the first place where you have formally articulated
this conclusion:?  Is this a policy or a scientific conclusion?

Why only oxides of N?  Why is NOy separated out from other sources of N
that can also lead to acid deposition?  Wouldn’t a standard that
reflected all such sources of N make more sense?

Why is this not included in the list in the previous sentence?

Do you mean “despite”?

Given that the different components of NOy have different deposition
velocities, what single velocity would you use to represent NOy globally
in calculating the specific standard?

Is this a word? Neither I nor spell check recognize it.  What does it
mean?

Why is there no T coefficient for this term?

I spent a long time puzzling over this equation.  I think this sentence
would help explain what you are doing here.

These seem like very stringent criteria for identifying acid sensitive
regions, given that the table II-1 identifies any ANC level above 100 as
being of “low concern.”  (200 is not even identified as a threshold
of concern in the table.) You are saying that if even 1% of water bodies
exceed this low concern threshold, the region is “acid sensitive.”
What is the basis for these cut points?  They do not seem to fit well
with the info in Table II-1.

Would be helpful to clarify that when you say 70th to 90th percentile,
you are looking at the CLs arranged from highest to lowest.  If they are
arranged in the more intuitive ascending order, this would actually 10th
to 30th percentile, or do I misunderstand what you are doing?

Lowest = most difficult to achieve, no?

I don’t understand the logic here.  If you set at median, you protect
only 50% of water bodies.  If you set at 90th percentile, you protect 90
percent of water bodies.  What does it matter what share of water bodies
in a region are “acid sensitive.”  This is a continuum, not a bright
line.  In fact, by using a lower percentile in non-acid sensitive
regions, you are actually protecting a far lower share of any acid
sensitive water bodes that happen to be in that region.  Consider the
following thought experiment.  If 50% of the water bodies in a region
are acid sensitive, these will presumably correspond to the upper half
of the distribution, and protecting at the 90th percentile level will
protect 80% of these acid sensitive water bodies (plus all of the
non-acid sensitive ones).  On the other hand, if only 20% of the water
bodies are acid sensitive (a less acid sensitive region) then protecting
at the 90th percentile will protect only half of this smaller number of
acid sensitive water bodies.  This problem is further exacerbated if you
instead select the median.  In this case you would not be protecting any
acid sensitive water bodies in this region.

If you use the same percentile in both cases, you will still
(appropriately) get a more stringent standard in acid sensitive regions
(bc 90th percentile in acid sensitive region is more protective than
90th percentile in non-acid sensitive regions) but you will be
protecting the same share of water bodies in both cases. To me this
makes more sense.

This is only true if there are not enough unimpaired lakes to satisfy
current fishing demand.  If there are, adding more will have little
economic benefit (though still significant ecological benefits).  The
information presented here provides no basis for determining if this is
true or not.

Not clear what you are saying here.  Are you saying that a modeled
increment of improvement from 20 to 50 has $600 million in benefits.
This statement is hard to evaluate if the starting point for all the
lakes is not 20 (presumably there is a wide variation in baseline ANCs).
 Alternately, you could mean that cleaning up all the lakes to somewhere
in the range of 20 to 50 provides these benefits, but then I don’t see
how you get a point estimate for benefits.  Wouldn’t cleaning up to 50
give much higher benefits than cleaning up to 20?  Please explain.

It would be helpful to include in this preamble a table showing the
calculated AAI values for all eco-regions, including both acid sensitive
and non-acid sensitive.

What averaging time are you suggesting using in the standard.  I thought
it was annual, or is it longer?

On p 10 you say “In setting standards that are “requisite” to
protect public health and welfare, as provided in section 109(b),
EPA’s task is to establish standards that are neither more nor less
stringent than necessary for these purposes.” I suggest adapting and
emphasizing this language in this section because it is an important
basis for deciding not to set an ecologically relevant standard now.
Although you are confident in the basic form, you do not have enough
info to set a standard that is “neither more nor less stringent than
necessary.”  It is not good enough under the statute to simply err in
the direction of making the standard overly protective, as some may urge
you to do.  It is exactly this need to “get it right” that prevents
you from setting a standard now.

I think it is important to emphasize that this is more than just a
discretionary policy choice, which some may argue you have no authority
to make, having established that the current standard is insufficient to
protect public welfare.  As I understand it, the reason you are not
setting a standard at this time is that even though you have enough info
to determine the current standard is inadequate, you do not have enough
information to establish one that better complies with the new science.
You are confident in the structure of this better standard, but do not
have the data to establish its specific form and level.  Thus, this is
not just a policy choice.  Rather, it is not feasible at this time to
set a standard that meets the statutory objective of being requisite to
protect public welfare without being either more or less stringent than
necessary.

I would be happy to discuss this further by phone on Monday.

Don’t think you want to say the current secondary standards are
inappropriate.  They are appropriate to address direct effects of
gaseous NOx/SOx.

How do you know this?  Please explain the basis for this statement.

We do not agree with this interpretation, which is not in the EO.  In
this case, it is clear that the rule is not subject to the EO because it
is not an economically significant rule, one prong of the two-pronged
applicability test in the EO itself.

I don’t believe this is accurate.  How about the proposed alternative.