[Federal Register Volume 80, Number 148 (Monday, August 3, 2015)]
[Notices]
[Pages 46086-46091]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2015-18823]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

[Docket No. FAA-2014-0510]


Implementation of Legislative Categorical Exclusion for 
Environmental Review of Performance Based Navigation Procedures

AGENCY: Federal Aviation Administration, Transportation.

ACTION: Final Notice to Announce Implementation of Section 213(c)(2) 
CATEX and Disposition of Public Comments.

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SUMMARY: On August 19, 2014, the Federal Aviation Administration (FAA) 
published in the Federal Register [79 FR 49141-49144] a notice 
regarding the FAA's consideration of how to implement Section 213(c)(2) 
of the FAA Modernization and Reform Act of 2012. Section 213(c)(2) 
directs the FAA to issue and file a categorical exclusion for any 
navigation performance or other performance based navigation procedure 
that would result in measureable reductions in fuel consumption, carbon 
dioxide emissions, and noise on a per flight basis as compared to 
aircraft operations that follow existing instrument flight rule 
procedures in the same airspace. To inform the FAA's consideration of 
interpretative guidance regarding Section 213(c)(2), the FAA's August 
19 notice requested public comment on a Net Noise Reduction Method 
recommended by the NextGen Advisory Committee (NAC) and possible 
variations on this method. The FAA has reviewed and considered all 
comments and has decided to issue interpretative guidance to implement 
Section 213(c)(2) using the Net Noise Reduction Method with two 
variations to the NAC's recommendation, as described in this final 
notice.

DATES: The effective date of this implementation will be the date the 
FAA issues the interpretative guidance.

FOR FURTHER INFORMATION CONTACT: Lynne S. Pickard, Senior Advisor for 
Environmental Policy, Office of Environment and Energy (AEE-6), Federal 
Aviation Administration, 800 Independence Avenue SW., Washington, DC 
20591; telephone (202) 267-3577; email [email protected]

SUPPLEMENTARY INFORMATION:

Background

    The National Environmental Policy Act (NEPA) establishes a broad 
national policy to protect the quality of the human environment and to 
ensure that environmental considerations are given careful attention 
and appropriate weight in decisions of the Federal Government. 
Regulations promulgated by the Council on Environmental Quality (CEQ) 
(40 CFR parts 1500-1508) to implement NEPA establish three levels of 
environmental review for federal actions. An environmental impact 
statement (EIS) is the detailed written statement as required by 
section 102(2)(C) of NEPA, and is prepared for those actions when one 
or more environmental impacts are potentially significant and 
mitigation measures cannot reduce the impact(s) below significant 
levels. 40 CFR 1508.11. An environmental assessment (EA) is a more 
concise document that provides a basis for determining whether to 
prepare an environmental impact statement or a finding of no 
significant impact. 40 CFR 1508.9. A categorical exclusion (CATEX) is 
used for actions which do not individually or cumulatively have a 
significant effect on the human environment. 40 CFR 1508.4. A CATEX is 
not an exemption or waiver of NEPA review; it is a level of NEPA 
review.
    CEQ regulations require agency procedures to identify classes of 
actions which normally require an EIS or an EA, as well as those 
actions which normally do not require either an EIS or an EA (i.e., a 
CATEX). 40 CFR 1507.3(b). In addition to identifying actions that 
normally are CATEXed, an agency's procedures must also provide for 
extraordinary circumstances in which a normally excluded action may 
have a significant environmental effect which would preclude the use of 
a CATEX. 40 CFR 1508.4.
    The FAA has adopted policy and procedures for compliance with NEPA 
and CEQ's implementing regulations in Order 1050.1F, Environmental 
Impacts: Policies and Procedures, dated July 16, 2015 [80 Federal 
Register 44207, July 24, 2015]. Order 1050.1F lists FAA actions subject 
to a CATEX in accordance with CEQ regulations, including CATEXs for FAA 
actions involving establishment, modification, or application of 
airspace and air traffic procedures.

[[Page 46087]]

    In the FAA Modernization and Reform Act of 2012 (Pub. L. 112-95), 
Congress created two additional legislative CATEXs for certain air 
traffic procedures being implemented as part of the Next Generation Air 
Transportation System (NextGen).\1\ Section 213(c) of this Act 
provides:
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    \1\ The Next Generation Air Transportation System, referred to 
as NextGen, is a term used to describe the ongoing transformation of 
the National Airspace System (NAS). At its most basic level, NextGen 
represents an evolution from a ground-based system of air traffic 
control to a satellite-based system of air traffic management.

    (c) COORDINATED AND EXPEDITED REVIEW.
    (1) In General.--Navigation performance and area navigation 
procedures developed, certified, published, or implemented under 
this section shall be presumed to be covered by a categorical 
exclusion (as defined in section 1508.4 of title 40, Code of Federal 
Regulations) under chapter 3 of FAA Order 1050.1E unless the 
Administrator determines that extraordinary circumstances exist with 
respect to the procedure.
    (2) NextGen Procedures.--Any navigation performance or other 
performance based navigation procedure developed, certified, 
published, or implemented that, in the determination of the 
Administrator, would result in measurable reductions in fuel 
consumption, carbon dioxide emissions, and noise, on a per flight 
basis, as compared to aircraft operations that follow existing 
instrument flight rules procedures in the same airspace, shall be 
presumed to have no significant affect [sic] on the quality of the 
human environment and the Administrator shall issue and file a 
categorical exclusion for the new procedure.

    These two new legislative CATEXs have been included in Order 
1050.1F. The FAA issued implementing guidance on the CATEX described in 
Section 213(c)(1) on December 6, 2012. Technical and legal issues have 
hindered implementing guidance on the CATEX in Section 213(c)(2) 
because none of the current noise methodologies measure noise on a per 
flight basis as contemplated by the statute.
    The CATEX in Section 213(c)(2) has some unique characteristics. It 
presumes no significant effect on the quality of the human environment 
based on a review of three factors--fuel consumption, carbon dioxide 
emissions, and noise. To apply this CATEX, the FAA is directed to 
determine that all three factors would be measurably reduced when 
compared to what is generated by existing instrument flight rules 
procedures, instead of determining that there would be no potential for 
significant impacts. It bases the determination of measurable 
reductions on a per flight basis. It does not provide for extraordinary 
circumstances to override the CATEX.
    Section 213(c)(2) states that this CATEX applies to ``any 
navigation performance or other performance based navigation procedure. 
. . .'' The FAA interprets this to mean NextGen performance based 
navigation (PBN) procedures based on the terminology and because the 
provision is entitled ``NextGen Procedures'' and is within a more 
comprehensive Section 213 that is entitled ``Acceleration of NextGen 
Technologies''. PBN procedures are flight procedures that rely on 
satellite-based navigation, i.e. Area Navigation (RNAV) and Required 
Navigation Performance (RNP). Accordingly, the FAA finds that the use 
of this CATEX is limited to PBN procedures. The CATEX cannot be used 
for conventional procedures (flight procedures that rely on ground-
based navigational aids) or for projects involving a mix of 
conventional and PBN procedures, which is commonly the case for 
sizeable projects such as an Optimization of the Airspace and 
Procedures in the Metroplex (Metroplex). In addition, for projects 
involving only PBN procedures, 95 percent or more already meet the 
conditions of existing FAA CATEXs. Under these circumstances, the 
Section 213(c)(2) CATEX would be expected to be used infrequently. It 
could expedite review of a PBN-only project that would otherwise be 
subject to an EA or possibly an EIS due to a high level of 
environmental controversy or potential environmental impacts that would 
preclude the use of another existing CATEX.
    The statutory language of Section 213(c)(2) states that the CATEX 
cannot be implemented unless the FAA can determine that there are 
measurable reductions of fuel consumption, carbon dioxide emissions, 
and noise on a per flight basis. While measurable reductions in fuel 
consumption and carbon dioxide emissions can be determined on a per 
flight basis using current methodologies, aircraft noise poses unique 
challenges for such a determination. Noise depends not only on the 
varying noise levels of an aircraft as it flies, but also on the 
position of the aircraft in relation to noise sensitive receivers on 
the ground. Noise tends to increase at some locations and decrease at 
other locations as PBN procedures shift and concentrate flight tracks. 
Total noise in an area of airspace cannot be calculated by adding up 
the noise levels at various locations on the ground, and noise levels 
cannot be divided by the number of aircraft to produce noise per 
flight. The FAA could not find a technically sound way to make the 
noise determination required by the statute based on an analysis of 
methodologies currently in use.
    In September 2012, the FAA tasked the NextGen Advisory Committee 
(NAC) for assistance in further exploring how to make use of this 
legislative CATEX. The NAC, established September 23, 2010, is a 28-
member Federal advisory committee formed to provide advice on policy-
level issues facing the aviation community in developing and 
implementing NextGen. In response to FAA's request, the NAC created a 
Task Group of diverse stakeholders representing airlines, airports, 
manufacturers, aviation associations, consultants, and community 
interests. The Task Group agreed with the FAA's technical analysis of 
current methodologies and went on to develop a Net Noise Reduction 
Method. The Net Noise Reduction Method received unanimous support from 
Task Group members and was recommended to FAA by the NAC on June 4, 
2013.\2\
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    \2\ http://www.rtca.org/Files/Miscellaneous%20Files/CatEx2%20Report%20NAC%20June%202013final.pdf.
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    Following extensive evaluation of the NAC's recommended Net Noise 
Reduction Method, the FAA decided to solicit public comment to further 
inform the FAA's consideration of interpretive guidance to implement 
Section 213(c)(2) using the Net Noise Reduction Method and possible 
variations on it. The FAA noted several reasons for seeking public 
review in addition to the NAC's public forum. One reason is that this 
CATEX has some unique statutory requirements that have presented 
challenges to the FAA in determining how to implement the CATEX. In 
addition, the Net Noise Reduction Method would introduce a new method 
for assessing noise for certain proposed PBN procedures under NEPA that 
is different in a number of respects from current noise analysis 
methodologies. The NAC also suggested an additional test, at the FAA's 
discretion, involving a determination of significant noise impact; and 
the FAA wanted input from the public on the use of such a test. 
Finally, there appears to be substantial public interest and concern 
regarding this CATEX, as reflected in numerous comments submitted on 
the inclusion of this CATEX in Order 1050.1F.

FAA's Decision To Implement the Noise Determination in Section 
213(c)(2)

    The FAA will determine that there is a measurable reduction in 
noise on a per flight basis under Section 213(c)(2) if proposed PBN 
procedures, when compared to existing procedures they replace in the 
same airspace, would

[[Page 46088]]

result in a net noise reduction within that area of airspace and would 
not significantly increase noise. The FAA will use the Day-Night 
Average Sound Level (DNL) \3\ to determine average changes in noise and 
whether there is a net noise reduction within an area exposed to noise 
levels of DNL 45 decibels (dB) and higher.\4\ The FAA interprets 
``measurable reductions in . . . noise'' to preclude situations where 
there would be significant increases in noise. Therefore, the FAA will 
not use this CATEX when proposed PBN procedures would result in a noise 
increase of DNL 1.5 dB or more over noise sensitive areas at levels of 
DNL 65 dB and higher, which would constitute a significant noise impact 
under FAA's long-standing NEPA criterion.\5\
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    \3\ DNL, the Day-Night Average Sound Level, is the FAA's primary 
metric for assessing aircraft noise. DNL accounts for the noise 
levels of individual aircraft events, the number of times those 
events occur, and the period of day/night in which they occur.
    \4\ For NEPA purposes, FAA normally performs noise screening to 
determine DNL changes at noise levels of DNL 45 dB and higher for 
air traffic airspace and procedure actions.
    \5\ The FAA's criterion for a significant noise impact under 
NEPA is an increase of DNL 1.5 dB or more for a noise sensitive area 
(e.g. homes, schools) that is exposed to noise at or above the DNL 
65 dB noise exposure level, or that will be exposed at or above this 
level due to a 1.5 dB or greater increase, when compared to the no 
action alternative for the same timeframe. FAA Order 1050.1F.
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    This interpretation uses the NAC's recommended Net Noise Reduction 
Method with two modifications: (1) FAA will base the determination of 
measurable reductions in noise on net changes in noise, instead of net 
changes in the affected population, to be more consistent with the 
statute; and (2) FAA interprets measurable reductions in noise to 
preclude use of the CATEX in situations where noise increases would be 
significant.
    The application of the FAA's interpretation is illustrated below in 
Table 1. Using the same source data used by the NAC in one of its 
examples,\6\ the FAA calculated the average change in the DNL resulting 
from PBN procedures versus existing procedures at thousands of 
locations within an area of airspace. The total average change in noise 
is a decrease, and absent significant noise increases, the required 
noise reduction determination could be made, enabling the CATEX to be 
used for the PBN procedures if fuel consumption and carbon dioxide 
emissions would also be reduced. If there are significant increases in 
noise, the FAA would not use the CATEX irrespective of the average 
change in noise.
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    \6\ This example uses noise and population data from an EA for 
procedural changes at Chicago Midway International Airport. This 
example was also in the FAA's August 19, 2014 notice.

    Table 1--Average Changes in DNL Level PBN Procedures vs Existing
                               Procedures
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                                                          Average change
                 DNL noise exposure band                      in DNL
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45-60...................................................        -0.3 DNL
60-65...................................................               0
Above 65................................................               0
                                                         ---------------
Total...................................................        -0.3 DNL
Change..................................................
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    In the August 19, 2014 notice, the FAA calculated net changes in 
noise in two ways--(1) a straight average of all locations as in Table 
1 of this notice and (2) a population weighted average. The FAA decided 
to use the straight average because it is more consistent with the 
statutory text as well as easier to understand. In both calculations 
shown in the previous notice, the total average change in noise was a 
decrease, which was the same result produced by the NAC method.
    The FAA has determined that its interpretation of the statutory 
language is a reasonable interpretation that enables the agency to 
fulfill its responsibility to implement enacted legislation. It 
provides an additional CATEX that may be used for environmental reviews 
of PBN procedures consistent with legislative intent. It provides a 
method to quantify measurable noise reductions within a sizeable 
geographic area \7\ using the widely-accepted DNL noise metric. It 
supports a determination of measureable noise reductions on a per 
flight basis because, if cumulative noise from multiple flights in a 
geographic area is lower, noise would also be lower per flight if one 
could divide the cumulative noise by the number of flights in the area. 
It is based on a methodology developed by a diverse stakeholder group 
and recommended by a committee that advises the FAA on NextGen (i.e., 
the NAC), and it produces the same CATEX results as the NAC's method 
when applied to the examples used by the NAC.\8\ It precludes the use 
of this CATEX if there are noise increases that would be considered 
significant based on a recognized standard. This final characteristic 
places this CATEX within the normal range of NEPA CATEXs and is 
responsive to community concerns.
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    \7\ FAA will evaluate net changes at DNL 45 dB and higher, 
consistent with FAA's NEPA practice for PBN procedures and also 
consistent with the NAC's recommendation.
    \8\ The NAC used procedural changes at Chicago Midway 
International Airport and Seattle Tacoma International Airport to 
test the results of its method.
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    The FAA is keenly aware of the general negative community response 
to this CATEX. The FAA and the NAC realize that community controversy 
can counterbalance the streamlining effects of any CATEX and result in 
opposition to PBN procedures. These issues are currently receiving more 
attention within FAA and by the NAC.

Discussion of Public Comments

    The FAA initially provided for a 30-day public comment period and 
then, upon request, extended the comment period to 60 days. The FAA 
invited public comment on the entirety of the prospective 
implementation of the CATEX in Section 213(c)(2) of the FAA 
Modernization and Reform Act of 2012, and particularly invited comment 
on the following specific aspects of the Net Noise Reduction Method 
which were under consideration by the FAA as described in the August 
19, 2014 notice:
    1. Extent to which the FAA should rely on the Net Noise Reduction 
Method to determine measurable reductions in noise on a per flight 
basis.
    2. Appropriateness of determining that there is a measurable 
reduction in noise if people receiving a noise decrease outnumber the 
people receiving an increase, but the noise decrease is small compared 
to the noise increase.
    3. Different approaches to a net noise reduction methodology (i.e., 
population change, noise change, population weighted noise change), and 
whether the selection of one approach over another is preferred and 
increases public understanding.
    4. Extent to which a mix of noise increases and decreases could 
support a determination of measurable noise reduction, especially when 
reductions at lower noise levels outweigh increases at higher noise 
levels, and whether an alternative approach that would require 
reductions in all three noise exposure bands to support the use of the 
CATEX should be used.
    5. Whether a significant noise impact threshold test should be 
used; and if so, if it should be used only when there is a net increase 
in people exposed to noise at DNL 65 dB and above, or if it should be 
used when there is any increase in the number of people exposed to 
noise at DNL 65 dB and above--even if there is a net population benefit 
at that level.
    The FAA received 80 comments, including 10 letters of comment from 
parties representing aviation interests;

[[Page 46089]]

18 letters from Federal and state elected representatives, local 
governments, organizations and a law firm on behalf of their 
constituents, members, and community interests; 52 letters from 
individuals, and a neighborhood petition signed by 140 individuals. In 
general, aviation interests supported the FAA's adoption of the NAC's 
recommended Net Noise Reduction Method, while other commenters 
expressed opposition to or reservations about this methodology, 
opposition to this legislated CATEX and to CATEXs in general, and noise 
concerns about the implementation of PBN procedures. The FAA reviewed 
and considered all comments in reaching its decision. Specific issues 
that were commented on and FAA's responses are presented in more detail 
below.
    Comment: Aviation commenters supported NextGen and PBN procedures. 
They viewed the CATEX in Section 213(c)(2) as an advantageous step 
taken by Congress to expedite the environmental review of PBN 
procedures that can reduce fuel burn, emissions, and noise. They 
supported the NAC's recommended Net Noise Reduction Method as 
technically and legally sound. They emphasized that it was developed by 
a diverse group of stakeholders including representatives of airlines, 
airports, manufacturers, aviation associations, consultants, and 
community interests, and that it received unanimous support from the 
NAC. They urged FAA to fulfill its responsibility to carry out a 
legislated mandate by adopting this method without further delay. They 
provided additional details in support of the above points.
    FAA Response: The FAA sought the advice of the NAC and appreciates 
the efforts of the NAC Task Group that resulted in a recommendation 
that was unanimously supported by such a broad diversity of interests. 
Following additional evaluation and consideration of public comments, 
FAA has decided to use the NAC's recommended Net Noise Reduction Method 
with two modifications for greater consistency with the statute, as 
described in this notice.
    Comment: An airport supported the benefits of PBN procedures, while 
noting the importance of local airport operator and community 
involvement in PBN implementation. This commenter expressed the need to 
balance airport operations and impacts with community concerns. The 
commenter asked if a decrease in noise below DNL 65 dB could offset an 
increase in noise above DNL 65 dB using the Net Noise Reduction Method, 
and if the residents that are added to the noise exposure area at DNL 
65 dB and higher would be entitled to mitigation. The commenter 
expressed concern that the Net Noise Reduction Method would not 
adequately account for community annoyance and opposition that can 
occur when flight operations are concentrated over more narrow 
corridors as is common with PBN procedures.
    FAA Response: The FAA agrees with the importance of local airport 
operator involvement and community concerns. The FAA and the NAC are 
currently giving increased attention to improving airport operator and 
community involvement in PBN implementation. Regarding the question 
about whether a decrease in noise below DNL 65 dB could offset an 
increase in noise above DNL 65 dB using the Net Noise Reduction Method, 
the answer is yes. The statutory text provides for comparison of PBN 
procedures versus existing procedures in the same airspace. The FAA 
interprets ``in the same airspace'' to encompass the entire airspace 
study area under review in relation to the proposed PBN procedures. 
With respect to the prospect of adding residents to areas exposed to 
noise at DNL 65 dB and higher, this CATEX will be no different from 
other existing CATEXs. If the additional noise exposure is a 
significant noise increase, this CATEX cannot be used. If it is not a 
significant noise increase, this CATEX may be used with respect to 
noise just as other CATEXs are currently used. Also, as is currently 
the case, residents exposed to aircraft noise of DNL 65 dB and higher 
may be eligible for mitigation such as sound insulation; however, the 
provision of mitigation depends on whether the airport has a noise 
mitigation program, which residents are covered by the program, funding 
availability, and timing. Regarding the commenter's final concern, if 
the concentration of noise from PBN implementation is sufficient to 
increase noise to an extent that it would be considered a significant 
increase, this CATEX would not be used. This same qualification applies 
to other existing CATEXs.
    Comment: A number of elected representatives, local governments, 
organizations representing community and environmental interests, and 
individuals commented that the implementation of PBN procedures should 
require more detailed environmental review than a CATEX and should be 
subject to public disclosure and review. Some commenters regard a CATEX 
as an exemption from environmental review under NEPA. Many objected to 
the use of CATEXs in general for PBN implementation, as well as to the 
Section 213(c)(2) CATEX. A number of commenters said that PBN 
procedures should not be expedited with a CATEX. Some commented that a 
CATEX should not be used if there is any noise increase, as well as 
that the criteria for a CATEX should require noise reductions in all 
areas under flight paths. One commenter asserted that a CATEX should 
not be allowed if newly impacted people are exposed to incompatible 
conditions, i.e., noise exposure of DNL 65 dB and higher. Another 
commenter asserted that PBN procedures do not meet CEQ's standard for a 
CATEX because they have significant negative environmental impacts. 
Additional details were provided by commenters regarding why a CATEX is 
not appropriate.
    FAA Response: The FAA first wants to clarify that a CATEX is not a 
NEPA exemption. A CATEX is a recognized category of NEPA review. CEQ 
regulations define a categorical exclusion, referred to by FAA as a 
CATEX, as ``a category of actions which do not individually or 
cumulatively have a significant effect on the human environment. . 
.'',\9\ and, therefore, for which neither an environmental assessment 
nor an environmental impact statement is required. Each procedure 
subject to the use of a CATEX is individually reviewed for consistency 
with CATEX requirements. PBN procedures may qualify for CATEXs just as 
conventional air navigation procedures have for many years. Most 
procedures--whether PBN or conventional procedures--do not have 
significant environmental impacts, in part because of their altitude 
above ground level. Most CATEXs are established through agency 
administrative procedures that are reviewed and concurred in by CEQ, as 
is the case for FAA's CATEXs in Order 1050.1F, Environmental Impacts: 
Policies and Procedures. The CATEX that is the subject of this notice 
is in enacted legislation, and within this legislative framework, the 
U.S. Congress clearly intended for this CATEX to expedite PBN 
procedures.
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    \9\ 40 CFR 1508.4.
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    CEQ regulations do not require environmental impacts to be reduced 
in order to determine that a CATEX is appropriate, i.e., a CATEX may 
still be the appropriate NEPA review if there are noise increases, 
provided that the noise increases are not significant. In the case of 
the Section 213(c)(2) CATEX, the FAA's interpretation of the statutory

[[Page 46090]]

language is that noise must actually be reduced on a net basis, and the 
CATEX would not be used if any noise increases would be significant.
    Comment: Many commenters who objected to using a CATEX for PBN 
procedures also objected to the Net Noise Reduction Method. Some 
objected to the netting of noise, and said that certain community areas 
would suffer noise increases with PBN implementation that would be 
ignored when noise effects are netted or averaged. A number of 
commenters viewed the Net Noise Reduction Method as a way of masking 
PBN noise focusing effects. A local government commented that the Net 
Noise Reduction Method pits one group of citizens against another. One 
commenter said that the method does not measure adverse effects on 
public health, student learning, a peaceful environment, property 
values, or social community costs; and, therefore, doesn't meet the 
tests for determining the significance of procedural changes. A 
Community Noise Roundtable commented that the Net Noise Reduction 
Method would allow new people to be exposed to incompatible noise of 
DNL 65 dB and higher with no opportunity for mitigation.
    FAA Response: Congress legislated a CATEX that is clearly different 
from other existing CATEXs. Congress used mandatory language in the 
relevant legislation, and the FAA does not have discretion under the 
statute to disregard the legislatively created CATEX. However, the FAA 
cannot directly apply the CATEX as written due to technical challenges 
associated with the language used by Congress in creating the CATEX. As 
a result, the FAA has expended substantial effort evaluating how to 
make the required noise determination and has concluded that the Net 
Noise Reduction Method with two modifications as described in this 
notice provides the best methodology. The FAA has not found a 
methodology that would not involve averaging or netting, as further 
described in response to the comment below. The FAA's methodology 
considers significant impacts and precludes use of this CATEX if noise 
increases would be significant. People newly exposed to noise levels at 
DNL 65 dB and higher would be in the same position with respect to 
eligibility for noise mitigation as they would be absent this CATEX, as 
explained in more detail in response to a previous comment.
    Comment: A number of commenters stated that the Net Noise Reduction 
Method does not measure noise on a per flight basis as the statute 
directs. Some commented favorably on analyzing noise on a per flight 
basis, while others opposed such an approach. A local government 
commented that noise impact cannot be meaningfully measured on a per 
flight basis. Commenters also objected to averaging noise in this 
respect, i.e., that an average is not a per flight basis. One commenter 
said that if ``average'' is read into the statute, it would also apply 
to fuel consumption and carbon dioxide emissions, but that averaging of 
these effects is not proposed. Some commenters criticized DNL and said 
it is inappropriate to use DNL to determine noise on a per flight 
basis. Several commenters offered alternative methodologies, including 
single-event noise metrics.
    FAA Response: The FAA has been unable to identify a methodology 
that would not involve averaging for calculating reductions in noise, 
fuel consumption, or carbon dioxide emissions on a per flight basis for 
PBN procedures ``as compared to aircraft operations that follow 
existing instrument flight rules procedures in the same airspace. . .'' 
as the statute requires. Multiple operations in a sizeable geographic 
area of airspace involving multiple aircraft having different noise, 
fuel, and emission characteristics must be evaluated to support the 
determinations required for this CATEX. For fuel consumption and carbon 
dioxide emissions, FAA will arithmetically total all fuel consumed and 
all carbon dioxide emitted from aircraft in the area of airspace that 
comprises the project study area and divide by the number of aircraft 
in that area to calculate reductions on a per flight basis. However, 
total noise in an area of airspace cannot be calculated by adding noise 
levels at various locations on the ground, and noise levels that are 
expressed in logarithmic decibels cannot arithmetically be divided by 
the number of aircraft to produce a meaningful calculation of noise per 
flight. The FAA's methodology announced in this notice supports a 
determination of measureable noise reductions on a per flight basis 
because, if cumulative noise from all flights in a geographic area is 
lower, it is reasonable to conclude that noise would also be lower per 
flight if one could divide the cumulative noise by the number of 
flights in the area.
    All known noise metrics, including single-event metrics, were 
examined by FAA experts and by expert consultants advising the NAC Task 
Group. The single-event noise metrics that were examined in detail were 
the maximum A-weighted sound level (LAMAX) \10\ and the sound exposure 
level (SEL).\11\ LAMAX was determined not to be a good metric for 
purposes of complying with Section 213(c)(2) because LAMAX is the 
maximum noise level of an event (i.e., aircraft overflight). LAMAX does 
not include the total noise of a flight and does not appear to respond 
to the legislative mandate to determine noise reduction on a per flight 
basis. SEL was also rejected. SEL does not account for the temporal 
aspects of noise exposure (e.g., more annoying nighttime noise), and it 
has drawbacks in accounting for the spatial aspect of noise exposure 
(i.e., a measurable reduction in SEL for any particular flight does not 
ensure that community noise would be reduced within the area of 
airspace being reviewed for potential application of the CATEX). 
Experts agreed that DNL is the best metric to calculate noise from 
multiple flights in a geographic area of airspace. The FAA has decided 
to use reductions in noise (DNL), instead of the NAC's recommended 
reductions in the number of people at DNL exposure levels, to be more 
consistent with the statute. The FAA' selected methodology produces the 
same results as the NAC's methodology when applied to the examples used 
by the NAC.
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    \10\ LAMAX is the maximum sound level of a particular event.
    \11\ SEL is the energy averaged A-weighted sound level over a 
specified period of time or single event, with reference duration of 
one second.
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    Comment: Several commenters supported an approach that would net 
noise increases and decreases within each noise exposure band, instead 
of across all bands, and that would require noise to be reduced in each 
band in order to use the CATEX. Several commenters noted that a total 
netting of noise across all bands is inconsistent with FAA policy that 
gives greater importance to changes at higher noise levels.
    FAA Response: The FAA considered such an approach and sought 
comment on it in the August 19 Federal Register notice. As indicated 
throughout this notice, there is no existing methodology that can 
produce the precise noise comparison required by the statutory text. As 
a result, the FAA has weighed various approaches and has concluded that 
the approach recommended in these comments is less consistent with the 
statutory text than the FAA's selected methodology because the statute 
requires a comparison of noise, fuel consumption, and carbon dioxide 
emissions of PBN procedures compared to existing procedures ``in the 
same airspace. . . .'' The FAA will calculate

[[Page 46091]]

fuel consumption and carbon dioxide emissions in the entirety of the 
airspace area under study and believes the same should be done for 
noise for statutory consistency. A total netting of noise across all 
noise exposure levels is not current FAA policy or practice; however, 
it is FAA's best interpretation of this new legislated CATEX. The FAA 
continues to give greater importance to changes at higher noise levels 
by precluding the use of this CATEX if increases in noise at DNL 65 dB 
and higher levels would be considered significant.
    Comment: A number of commenters said that the law should be changed 
to either revise or eliminate the Section 213(c)(2) CATEX. Some opined 
that the law conflicts with NEPA.
    FAA Response: In this notice, the FAA is fulfilling its 
responsibility to implement existing law. The FAA does not believe that 
the law conflicts with NEPA; rather, it legislatively establishes a new 
CATEX under NEPA.
    Comment: Some commenters objected to the Net Noise Reduction Method 
on the basis that it would not preclude a CATEX if there are 
significant noise impacts. Several commenters advocated lowering FAA's 
significant noise threshold from DNL 65 dB to DNL 55 dB.
    FAA Response: The NAC's recommendation provided for the FAA to 
exercise discretion not to use this CATEX in certain circumstances, 
even if PBN procedures would result in an overall net noise reduction, 
based on an additional test for significant impacts. The FAA has 
modified this aspect of the NAC's recommendation. The FAA interprets 
the phrase ``measurable reductions in . . . noise'' in the statutory 
text to be inconsistent with noise increases that would be considered 
significant; therefore, the FAA would not use this CATEX if noise 
increases would be significant. The issue of the FAA's NEPA threshold 
of significance for aircraft noise is entirely separate from the 
implementation of this legislated CATEX and is not addressed in this 
Federal Register notice.
    Comment: Multiple commenters and the petition signed by 140 people 
did not comment directly on the CATEX or the Net Noise Reduction 
Method, but commented generally on adverse effects of aircraft noise 
over their homes and requested that the FAA undo objectionable flight 
patterns. Specific objections to the TNNIS procedure in New York and to 
the CATEX for this procedure were raised.
    FAA Response: These comments refer to the implementation of PBN 
procedures that were supported by other existing CATEXs that were 
administratively established following public notice and comment and 
review by CEQ. The FAA understands that these commenters object to 
aircraft noise in their neighborhoods, even when noise is below 
significant levels. As part of NextGen, FAA has a robust research 
program to reduce aircraft noise and is currently giving increased 
attention to improving FAA's community involvement.

    Authority: FAA Modernization and Reform Act of 2012, Sec. 
213(c)(2), Pub. L. 112-95, 126 Stat. 11, 49-50.

    Issued in Washington, DC on July 27, 2015.
Lourdes Q. Maurice,
Executive Director, Office of Environment and Energy, Federal Aviation 
Administration.
[FR Doc. 2015-18823 Filed 7-31-15; 8:45 am]
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