Methods for Measurement of Filterable PM10, 80118-80172 [2010-30847]

Agencies

• ENVIRONMENTAL PROTECTION AGENCY

[Federal Register Volume 75, Number 244 (Tuesday, December 21, 2010)]
[Rules and Regulations]
[Pages 80118-80172]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2010-30847]



[[Page 80117]]

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Part II





Environmental Protection Agency





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40 CFR Part 51



Methods for Measurement of Filterable PM10 and 
PM2.5 and Measurement of Condensable PM Emissions From 
Stationary Sources; Final Rule

Federal Register / Vol. 75 , No. 244 / Tuesday, December 21, 2010 / 
Rules and Regulations

[[Page 80118]]


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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 51

[EPA-HQ-OAR-2008-0348; FRL-9236-2]
RIN 2060-AO58


Methods for Measurement of Filterable PM10 and 
PM2.5 and Measurement of Condensable PM Emissions From 
Stationary Sources

AGENCY: Environmental Protection Agency (EPA).

ACTION: Final rule.

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SUMMARY: This action promulgates amendments to Methods 201A and 202. 
The final amendments to Method 201A add a particle-sizing device to 
allow for sampling of particulate matter with mean aerodynamic 
diameters less than or equal to 2.5 micrometers (PM2.5 or 
fine particulate matter). The final amendments to Method 202 revise the 
sample collection and recovery procedures of the method to reduce the 
formation of reaction artifacts that could lead to inaccurate 
measurements of condensable particulate matter. Additionally, the final 
amendments to Method 202 eliminate most of the hardware and analytical 
options in the existing method, thereby increasing the precision of the 
method and improving the consistency in the measurements obtained 
between source tests performed under different regulatory authorities.
    This action also announces that EPA is taking no action to affect 
the already established January 1, 2011 sunset date for the New Source 
Review (NSR) transition period, during which EPA is not requiring that 
State NSR programs address condensable particulate matter emissions.

DATES: This final action is effective on January 1, 2011.

ADDRESSES: EPA has established a docket for this action under Docket ID 
No. EPA-HQ-OAR-2008-0348. All documents are listed in the https://www.regulations.gov index. Although listed in the index, some 
information is not publicly available, e.g., confidential business 
information (CBI) or other information whose disclosure is restricted 
by statute. Certain other material, such as copyrighted material, will 
be publicly available only in hard copy form. Publicly available docket 
materials are available either electronically at https://www.regulations.gov or in hard copy at the EPA Docket Center EPA/DC, 
EPA West, Room 3334, 1301 Constitution Ave., NW., Washington, DC. The 
Public Reading Room is open from 8:30 a.m. to 4:30 p.m., Monday through 
Friday, excluding legal holidays. The telephone number for the Public 
Reading Room is (202) 566-1744, and the telephone number for the Air 
Docket Center is (202) 566-1742.

FOR FURTHER INFORMATION CONTACT: For general information, contact Ms. 
Candace Sorrell, U.S. EPA, Office of Air Quality Planning and 
Standards, Air Quality Assessment Division, Measurement Technology 
Group (E143-02), Research Triangle Park, NC 27711; telephone number: 
(919) 541-1064; fax number; (919) 541-0516; e-mail address: 
sorrell.candace@epa.gov. For technical questions, contact Mr. Ron 
Myers, U.S. EPA, Office of Air Quality Planning and Standards, Sector 
Policies and Programs Division, Measurement Policy Group (D243-05), 
Research Triangle Park, NC 27711; telephone number: (919) 541-5407; fax 
number: (919) 541-1039; e-mail address: myers.ron@epa.gov.

SUPPLEMENTARY INFORMATION:
    Acronyms and Abbreviations. The following acronyms and 
abbreviations are used in this document.

[Delta]pmax maximum velocity pressure
[Delta]pmin minimum velocity pressure
[mu]m micrometers
ASTM American Society for Testing and Materials
AWMA Air and Waste Management Association
CAA Clean Air Act
CBI confidential business information
CCM Controlled Condensation Method
CPM condensable PM
DOP dioctyl phthalate
DOT Department of Transportation
DQO data quality objective
MSHA Mine Safety and Health Administration
NAAQS National Ambient Air Quality Standards
NSR New Source Review
NTTAA National Technology Transfer and Advancement Act of 1995
OSHA Occupational Safety and Health Administration
PCB polychlorinated biphenyl
PM particulate matter
PM10 particulate matter less than or equal to 10 
micrometers
PM2.5 particulate matter less than or equal to 2.5 
micrometers
ppmw parts per million by weight
PTFE polytetrafluoropolymer
RCRA Resource Conservation and Recovery Act
RFA Regulatory Flexibility Act
SBA Small Business Administration
SIP State Implementation Plan
SO2 sulfur dioxide
TDS total dissolved solids
TTN Technology Transfer Network
UMRA Unfunded Mandates Reform Act
www World Wide Web

    The information in this preamble is organized as follows:

I. General Information
    A. Does this action apply to me?
    B. Where can I obtain a copy of this action and other related 
information?
    C. What is the effective date?
    D. Judicial Review
II. Background
    A. Why is EPA issuing this final action?
    B. Particulate Matter National Ambient Air Quality Standards
    C. Measuring PM Emissions
    1. Method 201A
    2. Method 202
III. Summary of Changes Since Proposal
    A. Method 201A
    B. Method 202
    C. How will the final amendments to methods 201A and 202 affect 
existing emission inventories, emission standards, and permit 
programs?
IV. Summary of Final Methods
    A. Method 201A
    B. Method 202
V. Summary of Public Comments and Responses
    A. Method 201A
    B. Method 202
    C. Conditional Test Method 039 (Dilution Method)
VI. Statutory and Executive Order Reviews
    A. Executive Order 12866: Regulatory Planning and Review
    B. Paperwork Reduction Act
    C. Regulatory Flexibility Act
    D. Unfunded Mandates Reform Act
    E. Executive Order 13132: Federalism
    F. Executive Order 13175: Consultation and Coordination With 
Indian Tribal Governments
    G. Executive Order 13045: Protection of Children From 
Environmental Health and Safety Risks
    H. Executive Order 13211: Actions Concerning Regulations That 
Significantly Affect Energy Supply, Distribution, or Use
    I. National Technology Transfer and Advancement Act
    J. Executive Order 12898: Federal Actions To Address 
Environmental Justice in Minority Populations and Low-Income 
Populations
    K. Congressional Review Act

I. General Information

A. Does this action apply to me?

    This action applies to you if you operate a stationary source that 
is subject to applicable requirements to control or measure total 
particulate matter (PM), total PM with mean aerodynamic diameters less 
than or equal to 10 micrometers ([mu]m) (PM10), or total 
PM2.5, where EPA Method 202 is incorporated as a component 
of the applicable test method.
    In addition, this action applies to you if federal, State, or local 
agencies take certain additional independent actions. For example, this 
action applies to sources through actions by State and local agencies 
that implement condensable PM (CPM) control measures to attain the 
National Ambient

[[Page 80119]]

Air Quality Standards (NAAQS) for PM2.5 and specify the use 
of Method 202 to demonstrate compliance with the control measures. 
State and local agencies that specify the use of Method 201A or 202 
would have to implement the following: (1) Adopt this method in rules 
or permits (either by incorporation by reference or by duplicating the 
method in its entirety), and (2) promulgate an emissions limit 
requiring the use of Method 201A or 202 (or an incorporated method 
based upon Method 201A or 202). This action also applies to stationary 
sources that are required to meet new applicable CPM requirements 
established through federal or State permits or rules, such as New 
Source Performance Standards and New Source Review (NSR), which specify 
the use of Method 201A or 202 to demonstrate compliance with the 
control measures.
    The source categories and entities potentially affected include, 
but are not limited to, the following:

------------------------------------------------------------------------
                                                   Examples of regulated
           Category                 NAICS \a\             entities
------------------------------------------------------------------------
Industry......................  332410...........  Fossil fuel steam
                                                    generators.
                                332410...........  Industrial,
                                                    commercial,
                                                    institutional steam
                                                    generating units.
                                332410...........  Electricity
                                                    generating units.
                                324110...........  Petroleum refineries.
                                562213...........  Municipal waste
                                                    combustors.
                                322110...........  Pulp and paper mills.
                                325188...........  Sulfuric acid plants.
                                327310...........  Portland cement
                                                    plants.
                                327410...........  Lime manufacturing
                                                    plants.
                                211111, 212111,    Coal preparation
                                 212112, 212113.    plants.
                                331312, 331314...  Primary and secondary
                                                    aluminum plants.
                                331111, 331513...  Iron and steel
                                                    plants.
                                321219, 321211,    Plywood and
                                 321212.            reconstituted
                                                    products plants.
------------------------------------------------------------------------
\a\ North American Industrial Classification System.

B. Where can I obtain a copy of this action and other related 
information?

    In addition to being available in the docket, an electronic copy of 
these final rules are also available on the World Wide Web (https://www.epa.gov/ttn/) through the Technology Transfer Network (TTN). 
Following the Administrator's signature, a copy of these final rules 
will be posted on the TTN's policy and guidance page for newly proposed 
or promulgated rules at https://www.epa.gov/ttn/oarpg. The TTN provides 
information and technology exchange in various areas of air pollution 
control.

C. What is the effective date?

    The final rule amendments are effective on January 1, 2011. Section 
553(d) of the Administrative Procedure Act (APA), 5 U.S.C. Chapter 5, 
generally provides that rules may not take effect earlier than 30 days 
after they are published in the Federal Register. EPA is issuing this 
final rule under section 307(d)(1) of the Clean Air Act, which states: 
``The provisions of section 553 through 557 * * * of Title 5 shall not, 
except as expressly provided in this section, apply to actions to which 
this subsection applies.'' Thus, section 553(d) of the APA does not 
apply to this rule. EPA is nevertheless acting consistently with the 
purposes underlying APA section 553(d) in making this rule effective on 
January 1, 2011. Section 5 U.S.C. 553(d)(3) allows an effective date 
less than 30 days after publication ``as otherwise provided by the 
agency for good cause found and published with the rule.'' As explained 
below, EPA finds that there is good cause for these rules to become 
effective on or before January 1, 2011, even if this date is not 30 
days from date of publication in the Federal Register.
    While this action is being signed prior to December 1, 2010, there 
may be a delay in the publication of this rule as it contains many 
complex diagrams, equations, and charts, and is relatively long in 
length. The purpose of the 30-day waiting period prescribed in 5 U.S.C. 
553(d) is to give affected parties a reasonable time to adjust their 
behavior and prepare before the final rule takes effect. Where, as 
here, the final rule will be signed and made available on the EPA 
website more than 30 days before the effective date, but where the 
publication may be delayed due to the complexity and length of the 
rule, that purpose is still met. Moreover, since permitting authorities 
and regulated entities may need to rely on the methods described in 
these rules to carry out requirements of the SIP and NSR implementation 
rules that become effective on January 1, 2011 (see section III.C, 
infra), there would be unnecessary regulatory confusion if a 
publication delay caused this rule to become effective after January 1, 
2011. Accordingly, we find good cause exists to make this rule 
effective on or before January 1, 2011, consistent with the purposes of 
5 U.S.C. 553(d)(3).\1\
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    \1\ We recognize that this rule could be published at least 30 
days before January 1, 2011, which would negate the need for this 
good cause finding, and we plan to request expedited publication of 
this rule in order to decrease the likelihood of a publication 
delay. However, as we cannot know the date of publication in advance 
of signing this rule, we are proceeding with this good cause finding 
for an effective date on or before January 1, 2011, in an abundance 
of caution in order to avoid the unnecessary regulatory confusion 
noted above.
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D. Judicial Review

    Under section 307(b)(1) of the Clean Air Act (CAA), judicial review 
of this final action is available only by filing a petition for review 
in the United States Court of Appeals for the District of Columbia 
Circuit by February 22, 2011. Under CAA section 307(b)(2), the 
requirements established by this action may not be challenged 
separately in any civil or criminal proceedings brought by EPA to 
enforce these requirements.
    Section 307(d)(7)(B) of the CAA further provides that ``[o]nly an 
objection to a rule or procedure which was raised with reasonable 
specificity during the period for public comment (including any public 
hearing) may be raised during judicial review.'' This section also 
provides a mechanism for EPA to convene a proceeding for 
reconsideration, ``[i]f the person raising an objection can demonstrate 
to EPA that it was impracticable to raise such objection within [the 
period for public comment] or if the grounds for such objection arose 
after the period for public comment (but within the time specified for 
judicial review) and if such objection is of central relevance to the 
outcome of the rule.'' Any person seeking to make such a demonstration 
to us should submit a Petition for Reconsideration to the Office of the 
Administrator, U.S. EPA, Room 3000,

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Ariel Rios Building, 1200 Pennsylvania Ave., NW., Washington, DC 20460, 
with a copy to both the person(s) listed in the preceding FOR FURTHER 
INFORMATION CONTACT section, and the Associate General Counsel for the 
Air and Radiation Law Office, Office of General Counsel (Mail Code 
2344A), U.S. EPA, 1200 Pennsylvania Ave., NW., Washington, DC 20460.

II. Background

A. Why is EPA issuing this final action?

    Section 110 of the CAA, as amended (42 U.S.C. 7410), requires State 
and local air pollution control agencies to develop, and submit for EPA 
approval, State Implementation Plans (SIP) that provide for the 
attainment, maintenance, and enforcement of the NAAQS in each air 
quality control region (or portion thereof) within each State. The 
emissions inventories and analyses used in the State's attainment 
demonstrations must consider PM10 and PM2.5 
emissions from stationary sources that are significant contributors of 
primary PM10 and PM2.5 emissions. Primary or 
direct emissions are the solid particles or liquid droplets emitted 
directly from an air emissions source or activity, and the gaseous 
emissions or liquid droplets from an air emissions source or activity 
that condense to form PM or liquid droplets at ambient temperatures.
    Appendix A to subpart A of 40 CFR part 51 (Requirements for 
Preparation, Adoption, and Submittal of Implementation Plans) defines 
primary PM10 and PM2.5 as including both the 
filterable and condensable fractions of PM. Filterable PM consists of 
those particles that are directly emitted by a source as a solid or 
liquid at the stack (or similar release conditions) and captured on the 
filter of a stack test train. Condensable PM is the material that is in 
vapor phase at stack conditions but condenses and/or reacts upon 
cooling and dilution in the ambient air to form solid or liquid PM 
immediately after discharge from the stack. In response to the need to 
quantify primary PM10 and PM2.5 emissions from 
stationary sources, EPA previously developed and promulgated Method 
201A (Determination of PM10 Emissions (Constant Sampling 
Rate Procedure)) and Method 202 (Determination of Condensable 
Particulate Emissions from Stationary Sources) in 40 CFR part 51, 
appendix M (Recommended Test Methods for State Implementation Plans).
    On April 17, 1990 (56 FR 65433), EPA promulgated Method 201A in 
appendix M of 40 CFR part 51 to provide a test method for measuring 
filterable PM10 emissions from stationary sources. In EPA 
Method 201A, a gas sample is extracted at a constant flow rate through 
an in-stack sizing device that directs particles with aerodynamic 
diameters less than or equal to 10 [mu]m to a filter. The particulate 
mass collected on the filter is determined gravimetrically after 
removal of uncombined water.
    On December 17, 1991 (56 FR 65433), EPA promulgated Method 202 in 
appendix M of 40 CFR part 51 to provide a test method for measuring CPM 
from stationary sources. Method 202 uses water-filled impingers to 
cool, condense, and collect materials that are vaporous at stack 
conditions and become solid or liquid PM at ambient air temperatures. 
Method 202, as promulgated in 1991, contains several optional 
procedures that were intended to accommodate the various test methods 
used by State and local regulatory entities at the time Method 202 was 
being developed.
    In this action, we are finalizing amendments to Methods 201A and 
202 to improve the measurement of fine PM emissions. For Method 201A, 
the final amendments add a particle-sizing device to allow for sampling 
of PM2.5 emissions. For Method 202, the final amendments 
will (1) revise the sample collection and recovery procedures of the 
method to reduce the potential for formation of reaction artifacts that 
are not related to the primary emission of CPM from the source but may 
be counted erroneously as CPM when using Method 202, and (2) eliminate 
most of the hardware and analytical options in the existing method. 
These changes increase the precision of Method 202 and improve the 
consistency in the measurements obtained between source tests performed 
under different regulatory authorities.

B. Particulate Matter National Ambient Air Quality Standards

    Section 108 and 109 of the CAA govern the establishment and 
revision of the NAAQS. Section 108 of the CAA (42 U.S.C. 7408) directs 
the Administrator to identify and list ``air pollutants'' that ``in his 
judgment, may reasonably be anticipated to endanger public health and 
welfare'' and whose ``presence * * * in the ambient air results from 
numerous or diverse mobile or stationary sources'' and to issue air 
quality criteria for those that are listed. Air quality criteria are 
intended to ``accurately reflect the latest scientific knowledge useful 
in indicating the kind and extent of identifiable effects on public 
health or welfare which may be expected from the presence of [a] 
pollutant in ambient air * * *.'' Section 109 of the CAA (42 U.S.C. 
7409) directs the Administrator to propose and promulgate primary and 
secondary NAAQS for pollutants listed under CAA section 108 to protect 
public health and welfare, respectively. Section 109 of the CAA also 
requires review of the NAAQS at 5-year intervals and that an 
independent scientific review committee ``shall complete a review of 
the criteria * * * and the national primary and secondary ambient air 
quality standards * * * and shall recommend to the Administrator any 
new * * * standards and revisions of existing criteria and standards as 
may be appropriate * * *.'' Since the early 1980s, this independent 
review function has been performed by the Clean Air Scientific Advisory 
Committee.
    Initially, EPA established the PM NAAQS on April 30, 1971 (36 FR 
8186), based on the original criteria document (Department of Health, 
Education, and Welfare, 1969). The reference method specified for 
determining attainment of the original standards was the high-volume 
sampler, which collects PM up to a nominal size of 25 to 45 [mu]m 
(referred to as total suspended particulates or TSP). On October 2, 
1979 (44 FR 56730), EPA announced the first periodic review of the air 
quality criteria and PM NAAQS, and significant revisions to the 
original standards were promulgated on July 1, 1987 (52 FR 24634). In 
that decision, EPA changed the indicator for particles from TSP to 
PM10. When that rule was challenged, the court upheld 
revised standards in all respects. Natural Resources Defense Council v. 
Administrator, 902 F. 2d 962 (D.C. Cir. 1990, cert. denied, 498 U.S. 
1082 (1991).
    In April 1994, EPA announced its plans for the second periodic 
review of the air quality criteria and PM NAAQS, and the Agency 
promulgated significant revisions to the NAAQS on July 18, 1997 (62 FR 
38652). In that decision, EPA revised the PM NAAQS in several respects. 
While EPA determined that the PM NAAQS should continue to focus on 
particles less than or equal to 10 [mu]m in diameter (PM10), 
EPA also determined that the fine and coarse fractions of 
PM10 should be considered separately. EPA added new 
standards, using PM2.5 as the indicator for fine particles 
(with PM2.5 referring to particles with a nominal mean 
aerodynamic diameter less than or equal to 2.5 [mu]m), and using 
PM10 as the indicator for purposes of regulating the coarse 
fraction of PM10.
    Following promulgation of the 1997 PM NAAQS, petitions for review 
were filed by a large number of parties

[[Page 80121]]

addressing a broad range of issues. In May 1999, a three-judge panel of 
the U.S. Court of Appeals for the District of Columbia Circuit issued 
an initial decision that upheld EPA's decision to establish fine 
particle standards. American Trucking Associations v. EPA, 175 F.3d 
1027, 1055 (D.C. Cir. 1999), reversed in part on other grounds in 
Whitman v. American Trucking Associations, 531 U.S. 457 (2001). The 
panel also found ``ample support'' for EPA's decision to regulate 
coarse particle pollution, but vacated the 1997 PM10 
standards concluding that EPA had not provided a reasonable explanation 
justifying use of PM10 as an indicator for coarse particles. 
(Id. at 1054-55.) Pursuant to the court's decision, EPA removed the 
vacated 1997 PM10 standards but retained the pre-existing 
1987 PM10 standards (65 FR 80776, December 22, 2000).
    On October 23, 1997, EPA published its plans for the third periodic 
review of the air quality criteria and PM NAAQS (62 FR 55201), 
including the 1997 PM2.5 standards and the 1987 
PM10 standards. On October 17, 2006, EPA issued its final 
decision to revise the primary and secondary PM NAAQS to provide 
increased protection of public health and welfare respectively (71 FR 
61144). With regard to the primary and secondary standards for fine 
particles, EPA revised the level of the 24-hour PM2.5 
standard to 35 [mu]g per cubic meter ([mu]g/m\3\), retained the level 
of the annual PM2.5 annual standard at 15 [mu]g/m\3\, and 
revised the form of the annual PM2.5 standard by narrowing 
the constraints on the optional use of spatial averaging. With regard 
to the primary and secondary standards for PM10, EPA 
retained the 24-hour PM10 standard (150 [mu]g/m\3\) and 
revoked the annual standard because available evidence generally did 
not suggest a link between long-term exposure to current ambient levels 
of coarse particles and health or welfare effects.

C. Measuring PM Emissions

    Section 110 of the CAA, as amended (42 U.S.C. 7410), requires State 
and local air pollution control agencies to develop and submit plans 
(SIP) for EPA approval that provide for the attainment, maintenance, 
and enforcement of the NAAQS in each air quality control region (or 
portion thereof) within such State. 40 CFR part 51 (Requirements for 
Preparation, Adoption, and Submittal of Implementation Plans) specifies 
the requirements for SIP. Appendix A to subpart A of 40 CFR part 51, 
defines primary PM10 and PM2.5 as including both 
the filterable and condensable fractions of PM. Filterable PM consists 
of those particles directly emitted by a source as a solid or liquid at 
the stack (or similar release conditions) and captured on the filter of 
a stack test train. Condensable PM is the material that is in vapor 
phase at stack conditions but which condenses and/or reacts upon 
cooling and dilution in the ambient air to form solid or liquid PM 
immediately after discharge from the stack.
    Promulgation of the 1987 NAAQS created the need for methods to 
quantify PM10 emissions from stationary sources. In 
response, EPA developed and promulgated the following test methods:
     Method 201A--Determination of PM10 Emissions 
(Constant Sampling Rate Procedure), and
     Method 202--Determination of Condensable Particulate 
Emissions from Stationary Sources.
1. Method 201A
    Method 201A is a test method for measuring filterable 
PM10 emissions from stationary sources. With the exception 
of the PM10-sizing device, the current Method 201A sampling 
train is the same as the sampling train used for EPA Method 17 of 
appendix A-3 to 40 CFR part 60.
    Method 201A cannot be used to measure emissions from stacks that 
have entrained moisture droplets (e.g., from a wet scrubber stack) 
since these stacks may have water droplets that are larger than the cut 
size of the PM10 sizing device. The presence of moisture 
would prevent an accurate measurement of total PM10 since 
any PM10 dissolved in larger water droplets would not be 
collected by the sizing device and would consequently be excluded in 
determining total PM10 mass. To measure PM10 in 
stacks where water droplets are known to exist, EPA's Technical 
Information Document 09 (Methods 201 and 201A in Presence of Water 
Droplets) recommends use of Method 5 of appendix A-3 to 40 CFR part 60 
(or a comparable method) and consideration of the total particulate 
catch as PM10 emissions.
    Method 201A is also not applicable for stacks with small diameters 
(i.e., 18 inches or less). The presence of the in-stack nozzle/cyclones 
and filter assembly in a small duct will cause significant cross-
sectional area interference and blockage leading to incorrect flow 
calculation and particle size separation. Additionally, the type of 
metal used to construct the Method 201A cyclone may limit the 
applicability of the method when sampling at high stack temperatures 
(e.g., stainless steel cyclones are reported to gall and seize at 
temperatures greater than 260 [deg]C).
2. Method 202
    Method 202 measures CPM from stationary sources. Method 202 
contains several optional procedures that were intended to accommodate 
the various test methods used by State and local regulatory entities at 
the time Method 202 was being developed.
    When conducted consistently and carefully, Method 202 provides 
acceptable precision for most emission sources. Method 202 has been 
used successfully in regulatory programs where the emission limits and 
compliance demonstrations are established based on a consistent 
application of the method and its associated options. However, when the 
same emission source is tested using different combinations of the 
optional procedures, there appears to be large variations in the 
measured CPM emissions. Additionally, during validation of the 
promulgated method, we determined that sulfur dioxide (SO2) 
gas (a typical component of emissions from several types of stationary 
sources) can be absorbed partially in the impinger solutions and can 
react chemically to form sulfuric acid. This sulfuric acid ``artifact'' 
is not related to the primary emission of CPM from the source, but may 
be counted erroneously as CPM when using Method 202. We consistently 
maintain that the artifact formation can be reduced by at least 90 
percent if a one-hour nitrogen purge of the impinger water is used to 
remove SO2 before it can form sulfuric acid (this is our 
preferred application of the Method 202 optional procedures). 
Inappropriate use or omission of the preferred or optional procedures 
in Method 202 can increase the potential for artifact formation.
    Considering the potential for variations in measured CPM emissions, 
we believe that further verification and refinement of Method 202 is 
appropriate to minimize the potential for artifact formation. We 
performed several studies to assess artifact formation when using 
Method 202. The results of our 1998 laboratory study and field 
evaluation commissioned to evaluate the impinger approach can be found 
in ``Laboratory and Field Evaluation of EPA's Method 5 Impinger Catch 
for Measuring Condensible Matter from Stationary Sources'' at https://www.epa.gov/ttn/emc/methods/m202doc1.pdf.
    The 1998 study verified the need for a nitrogen purge when 
SO2 is present in stack gas and provided guidance for 
analyzing the collected samples. In 2005, an EPA contractor conducted a

[[Page 80122]]

second study, ``Laboratory Evaluation of Method 202 to Determine Fate 
of SO2 in Impinger Water,'' that replicated some of the 
earlier EPA work and addressed some additional issues. The report of 
that work is available at https://www.epa.gov/ttn/emc/methods/m202doc2.pdf. This report also verified the need for a nitrogen purge 
and identified the primary factors that affect artifact formation.
    Also in 2005, a private testing contractor presented a possible 
minor modification to Method 202 at the Air and Waste Management 
Association (AWMA) specialty conference. The proposed modification, as 
described in their presentation titled ``Optimized Method 202 Sampling 
Train to Minimize the Biases Associated with Method 202 Measurement of 
Condensable Particulate Matter Emissions,'' involved the elimination of 
water from the first impingers. The presentation (available at https://www.epa.gov/ttn/emc/methods/m202doc3.pdf) concluded that modification 
of the promulgated method to use dry impingers resulted in a 
significant additional reduction in the sulfate artifact.
    In 2006, we began to conduct laboratory studies in collaboration 
with several stakeholders to characterize the artifact formation and 
other uncertainties associated with conducting Method 202 and to 
identify procedures that would minimize uncertainties when using Method 
202. Since August 2006, we conducted two workshops in Research Triangle 
Park, NC to present and request comments on our plan for evaluating 
potential modifications to Method 202 that would reduce artifact 
formation, and also to discuss (1) Our progress in characterizing the 
performance of the modified method, (2) issues that require additional 
investigation, (3) the results of our laboratory studies, and (4) our 
commitments to extend the investigation through stakeholders external 
to EPA. Another meeting was held with experienced stack testers and 
vendors of emissions monitoring equipment to discuss hardware issues 
associated with modifications of the sampling equipment and the 
glassware for the proposed CPM test method. Summaries of the method 
evaluations, as well as meeting minutes from our workshops, can be 
found at https://www.epa.gov/ttn/emc/methods/method202.html.
    The laboratory studies that were performed fulfill a commitment in 
the preamble to the Clean Air Fine Particle Implementation Rule (72 FR 
20586, April 25, 2007) to examine the relationship between several 
critical CPM sampling and analysis parameters and, to the extent 
necessary, promulgate revisions to incorporate improvements in the 
method. While these improvements in the stationary source test method 
for CPM will provide for more accurate and precise measurement of all 
PM, the addition of PM2.5 as an indicator of health and 
welfare effects by the 1997 NAAQS revisions generates the need to 
quantify PM2.5 emissions from stationary sources. To respond 
to this need, we are promulgating revisions to incorporate this 
capability into the test method for filterable PM10.

III. Summary of Changes Since Proposal

    The methods in this final action contain several changes that were 
made as a result of public comments. The following sections present a 
summary of the changes to the methods. We explain the reasons for these 
changes in detail in the Summary of Public Comments and Responses 
section of this preamble.

A. Method 201A

    Method 201A contains the following changes and clarifications:
     Revised Section 1.5 to clarify that Method 201A cannot be 
used to measure emissions from stacks that have entrained moisture 
droplets (e.g., from a wet scrubber stack).
     Removed the language in proposed Section 1.5 regarding 
ambient air contributions to PM. The decision to correct results for 
ambient air contributions is up to the permitting or regulatory 
authority.
     Added definitions of Primary PM, Filterable PM, Primary 
PM2.5, Primary PM10, and CPM to Section 3.0.
     Added a requirement to Sections 6.1.3 and 8.6.3 stating 
that the filter must not be compressed between the gasket and the 
filter housing.
     Clarified the sample recovery and analysis equipment in 
Section 6.2, including acceptable materials of construction, analytical 
balance, and fluoropolymer (polytetrafluoroethylene) beaker liners.
     Revised Section 6.2 to add performance-based, residual 
mass contribution specifications for containers rather than specifying 
the type of container that must be used (storage containers must not 
contribute more than 0.1 mg of residual mass to the CPM measurements).
     Revised Section 8.3.1 (regarding sampling ports) to state 
that a 4-inch port should be adequate for the single PM2.5 
(or single PM10) sampling apparatus. However, testers will 
not be able to use conventional 4-inch ports if the combined dimension 
of the PM10 cyclone and the nozzle extending from the 
cyclone exceeds the internal diameter of the port.
     Clarified the sampling procedures in Section 8.3.1 for 
cases where the PM2.5 cyclone is used without the 
PM10 cyclone. In these cases, samples are collected using 
the procedures specified in Section 11.3.2.2 of EPA Method 1, and the 
sampling time is extended at the replacement sampling point to include 
the duration of the unreachable traverse points.
     Revised Section 8.3.2.2 to clarify that Method 201A is not 
applicable for stack diameters less than 26.5 inches when the combined 
PM10/PM2.5 cyclone is used. The in-stack nozzle/
cyclones and filter assembly in stacks less than 26.5 inches in 
diameter would cause significant cross-sectional area interference and 
blockage, leading to incorrect flow calculation and particle size 
separation.
     Revised Section 8.5.5 to express the maximum failure rate 
of values outside the minimum-maximum velocity pressure range in terms 
of percent of values outside the range instead of the number of 
traverse points outside the range.
     Revised section 8.6.1 to clarify that alternative designs 
are acceptable for fastening caps or covers to cyclones to avoid 
galling of the cyclone component threads in hot stacks. The method may 
be used at temperatures up to 1,000[deg]F using stainless steel 
cyclones that are bolted together, rather than screwed together. Using 
``break-away'' stainless steel bolts facilitates disassembly and 
circumvents the problem of thread galling.
     Clarified sampling procedures in Section 8.7.3.3 to 
maintain the temperature of the cyclone sampling head within  10 [deg]C of the stack temperature and to maintain flow until 
after removing and before inserting the sampling head.
     Revised Section 11.2.7 to allow the use of tared 
fluoropolymer beaker liners for the acetone field reagent blank.

B. Method 202

    Method 202 contains the following changes and clarifications:
     Clarified the terminology used to refer to laboratory and 
field blanks throughout the method.
     For health and safety reasons, replaced the use of 
methylene chloride with hexane throughout the method.
     Clarified Section 1.2 by moving the discussion of 
filterable PM methods used in conjunction with Method 202 to Section 
1.5.

[[Page 80123]]

     Clarified Section 1.6 to specify that Method 202 can be 
used for measuring CPM in stacks that contain entrained moisture if the 
sampling temperature is sufficiently high to keep the moisture in the 
vapor phase.
     Moved the recommendation to develop a health and safety 
plan from Section 9.4 to Section 5.0.
     Added amber glass bottles to the list of sample recovery 
equipment in Section 6.2.
     Added alternatives (fluoropolymer beaker liners or 
fluoropolymer baggies) to weighing tins to the list of analytical 
equipment in Section 6.2.2 (Section 6.3 of the proposed method).
     Added specifications for sample drying equipment in 
Section 6.2.2 (Section 6.3 of the proposed method).
     Clarified Section 6.3.7 regarding the use of an analytical 
balance with sensitivity to 0.00001 g (0.01 milligram).
     Added an option to use a colorimetric pH indicator instead 
of a pH meter in Section 6.2.2 (Section 6.3 of the proposed method).
     Added a sonication device to the list of analytical 
equipment in Section 6.2.2 (Section 6.3 of the proposed method).
     Added performance-based, residual mass contribution 
specifications for containers and wash bottles in Section 6.2.2 
(Section 6.3 of the proposed method) rather than specifying the type of 
container that must be used.
     Replaced the prescriptive language regarding filter 
materials in Section 7.1.1 with performance-based requirements limiting 
the residual mass contribution.
     Replaced the prescriptive language regarding water quality 
in Section 7.1.3 with performance-based requirements for residual mass 
content.
     Clarified Section 8.2 to specify that cleaned glassware 
must be used at the start of each new source category tested at a 
single facility.
     Added a performance-based option to Section 8.4 to conduct 
a field train proof blank rather than meeting the glassware baking 
requirements in Section 8.2.
     Clarified the sampling train configuration for the 
nitrogen purge procedures in Section 8.5.3.2 regarding pressurized 
purges.

C. How will the final amendments to methods 201A and 202 affect 
existing emission inventories, emission standards, and permit programs?

    We anticipate that over time the changes in the test methods 
finalized in this action will result in, among other positive outcomes, 
more accurate emissions inventories of direct PM emissions and 
emissions standards that are more indicative of the actual impact of 
the source on the ambient air quality.
    Accurate emission inventories are critical for regulatory agencies 
to develop the control strategies and demonstrations necessary to 
attain air quality standards. When implemented, the test method 
revisions should improve our understanding of PM emissions due to the 
increased availability of more accurate emission tests and eventually 
through the incorporation of less biased test data into existing 
emissions factors. For CPM, the use of the revised method could reveal 
a reduced level of CPM emissions from a source compared to the 
emissions that would have been measured using Method 202 as typically 
performed. However, there may be some cases where the revised test 
method would reveal an increased level of CPM emissions from a source, 
depending on the relative emissions of filterable and CPM emissions 
from the source. For example, the existing Method 202 allows complete 
evaporation of the water containing inorganic PM at 105 [deg]C (221 
[deg]F), where the revised method requires the last 10 ml of the water 
to be evaporated at room temperature (not to exceed 30 [deg]C (85 
[deg]F)), thereby retaining the CPM that would evaporate at the 
increased temperature.
    Prior to our adoption of the 1997 PM2.5 NAAQS, several 
State and local air pollution control agencies had developed emission 
inventories that included CPM. Additionally, some agencies established 
enforceable CPM emissions limits or otherwise required that PM 
emissions testing include measurement of CPM. While this approach was 
viable in cases where the same test method was used to develop the CPM 
regulatory limits and to demonstrate facility compliance, there are 
substantial inconsistencies within and between States regarding the 
completeness and accuracy of CPM emission inventories and the test 
methods used to measure CPM emissions and demonstrate facility 
compliance.
    These amendments would serve to mitigate the potential difficulties 
that can arise when EPA and other regulatory entities attempt to use 
the test data from State and local agencies with inconsistent CPM test 
methods to develop emission factors, determine program applicability, 
or to establish emissions limits for CPM emission sources within a 
particular jurisdiction. For example, problems can arise when the test 
method used to develop a CPM emission limit is not the same as the test 
method specified in the rule for demonstrating compliance because the 
different test methods may quantify different components of PM (e.g., 
filterable versus condensable). Also, when emissions from State 
inventories are modeled to assess compliance with the NAAQS, the 
determination of direct PM emissions may be biased high or low, 
depending on the test methods used to estimate PM emissions, and the 
atmospheric conversion of SO2 to sulfates (or sulfur 
trioxide, SO3) may be inaccurate or double-counted. 
Additionally, some State and local regulatory authorities have assumed 
that EPA Method 5 of appendix A-3 to 40 CFR part 60 (Determination of 
Particulate Matter Emissions from Stationary Sources) provides a 
reasonable estimate of PM10 emissions. This assumption is 
incorrect because Method 5 does not provide particle sizing of the 
filterable component and does not quantify particulate caught in the 
impinger portion of the sampling train. Similar assumptions for 
measurements of PM2.5 will result in greater inaccuracies.
    With regard to State permitting programs, we recognize that, in 
some cases, existing best available control technology, lowest 
achievable emission rate, or reasonably available control technology 
limits have been based on an identified control technology, and that 
the data used to determine the performance of that technology and to 
establish the limits may have focused on filterable PM and, thus, did 
not completely characterize PM emissions to the ambient air. While the 
source test methods used by State programs that developed the 
applicable permit limit may not have fully characterized the PM 
emissions, we have no information that would indicate that the test 
methods are inappropriate indicators of the control technologies' 
performance for the portion of PM emissions that was addressed by the 
applicable requirement. As promulgated in the Clean Air Fine Particle 
Implementation Rule, after January 1, 2011, States are required to 
consider inclusion of CPM emissions in new or revised emissions limits 
that they establish. We will defer to the individual State's judgment 
as to whether, and at what time it is appropriate to revise existing 
facility emission limits or operating permits to incorporate 
information from the revised CPM test method when it is promulgated.
    With regard to operating permits, the title V permit program does 
not generally impose new substantive air quality control requirements. 
In general, after emissions limits are established as CAA requirements 
under the SIP or a

[[Page 80124]]

SIP-approved pre-construction review permit, they are included in the 
title V permits. Obviously, title V permits should be updated to 
reflect any revision of existing emission limits or new emission limits 
created in the context of the underlying applicable requirements. Also, 
if a permit contains previously promulgated test methods, it is not a 
given that the permit would always have to be revised should these test 
method changes be finalized (e.g., where test methods are incorporated 
into existing permits through incorporation by reference, no permit 
terms or conditions would necessarily have to change to reflect changes 
to those test methods). In any event, the need for action related to 
emissions source permitting, due to these changes to the test methods, 
would be determined based upon several factors such as the exact 
wording of the existing operating permit, the requirements of the EPA-
approved SIP, and any changes that may need to be made to pre-
construction review permits with respect to CPM measurement (e.g., 
emissions estimates may be based upon a source test method that did not 
measure CPM or upon a set of Method 202 procedures that underestimated 
CPM emissions).
    In recognition of these issues, the Clean Air Fine Particle 
Implementation Rule contains provisions establishing a transition 
period for developing emission limits for condensable direct 
PM2.5 that are needed to demonstrate attainment of the 
PM2.5 NAAQS. The transition period for CPM is the time 
period during which the new rules and NSR permits issued to stationary 
sources are not required to address the condensable fraction of the 
sources' PM emissions. The end date of the transition period (January 
1, 2011) was adopted in the final Clean Air Fine Particle 
Implementation Rule (72 FR 20586, April 25, 2007) and in the final 
Implementation of the New Source Review Program for Particulate Matter 
Less Than 2.5 Micrometers (PM2.5) rule (73 FR 28321, May 16, 
2008). As discussed in these two rules, the intent of the transition 
period (which ends January 1, 2011) was to allow time for EPA to issue 
a CPM test method through notice and comment rulemaking, and for 
sources and States to collect additional total primary (filterable and 
condensable) PM2.5 emissions data to improve emissions 
information to the extent possible. In the PM2.5 NSR 
Implementation Rule, we stated that as part of this test methods 
rulemaking, we would ``take comment on an earlier closing date for the 
transition period in the NSR program if we are on track to meet our 
expectation to complete the test method rule much earlier than January 
1, 2011'' (73 FR 28344). In the notice of proposed rulemaking for this 
final rule on amendments to Method 201A and 202, EPA sought comment on 
whether to end the NSR transition period for CPM early (74 FR 12976). 
In this final rule, EPA is taking no action to affect the already 
established January 1, 2011 sunset date for the NSR transition period.
    Source test data collected with the use of this updated test method 
will be incorporated into the tools (e.g., emission factors, emission 
inventories, air quality modeling) used to demonstrate the attainment 
of air quality standards. Areas that are designated nonattainment for 
the 1997 PM2.5 NAAQS, and that have approved attainment 
dates of 2014 or 2015, are required to develop a mid-course review in 
2011. If it is determined that additional control measures are needed 
to ensure the area will be on track to attain the standard by the 
attainment date, any new direct PM2.5 emission limits 
adopted by the State must address the condensable fraction and the 
filterable fraction of PM2.5. Additionally, the new test 
data could be used to improve the applicability and performance 
evaluations of various control technologies.

IV. Summary of Final Methods

A. Method 201A

    Method 201A measures PM emissions from stationary sources. The 
amendments to Method 201A add a PM2.5 measurement device 
(PM2.5 cyclone) that allows the method to measure filterable 
PM2.5, filterable PM10, or both filterable 
PM2.5 and filterable PM10. The method can also be 
used to measure coarse particles (i.e., the difference between measured 
PM10 concentration and the measured PM2.5 
concentration).
    The amendments also add a PM2.5 cyclone to create a 
sampling train that includes a total of two cyclones (one cyclone to 
segregate particles with aerodynamic diameters greater than 10 [mu]m 
and one cyclone to segregate particles with aerodynamic diameters 
greater than 2.5 [mu]m) and a final filter to collect particles with 
aerodynamic diameters less than or equal to 2.5 [mu]m. The 
PM2.5 cyclone is inserted between the PM10 
cyclone and the filter of the Method 201A sampling train.
    The revised method has several limitations. The method cannot be 
used to measure emissions from stacks that have entrained moisture 
droplets (e.g., from a wet scrubber stack) because size separation of 
the water droplets is not representative of the dry particle size 
released into the air. In addition, the method is not applicable for 
stacks with diameters less than 25.7 inches when the combined 
PM10/PM2.5 cyclone is used. Also, the method may 
not be suitable for sources with stack gas temperatures exceeding 260 
[deg]C (500 [deg]F) when cyclones with screw-together caps are used 
because the threads of the cyclone components may gall or seize, thus 
preventing the recovery of the collected PM. However, the method may be 
used at temperatures up to 1,000 [deg]F when using stainless steel 
cyclones that are bolted together rather than screwed together. Using 
``break-away'' stainless steel bolts facilitates disassembly and 
circumvents the problem of thread galling. The method may also be used 
at temperatures up to 2,500 [deg]F when using specialty high-
temperature alloys.

B. Method 202

    Method 202 measures concentrations of CPM in stationary source 
sample gas after the filterable PM has been removed using another test 
method such as Method 5, 17, or 201A. The CPM sampling train begins at 
the back half of the filterable PM filter holder and consists of a 
condenser, two dry impingers (temperatures maintained to less than 30 
[deg]C (85 [deg]F)), and a CPM filter (temperature maintained between 
20 [deg]C (65 [deg]F) and 30 [deg]C (85 [deg]F)). During the test, 
sample gases are cooled and CPM is collected in the dry impingers and 
on the CPM filter. As soon as possible after the post-test leak check 
has been conducted, any water collected in the dry impingers is purged 
with nitrogen gas for at least one hour to remove dissolved 
SO2 gas.
    After the nitrogen purge, the sampling train components downstream 
of the filterable PM filter (i.e., the probe extension (if any), 
condenser, impingers, front half of CPM filter holder, and the CPM 
filter) are rinsed with water to recover the inorganic CPM. The water 
rinse is followed by an acetone rinse and a hexane rinse to recover the 
organic CPM. The CPM filter is extracted using water to recover the 
inorganic components and hexane to recover the organic portion. The 
inorganic and organic fractions are then dried and the residues 
weighed. The sum of both fractions represents the total CPM collected 
by Method 202.

V. Summary of Public Comments and Responses

    In response to the March 25, 2009 proposed revisions to EPA Methods 
201A and 202, EPA received public

[[Page 80125]]

comment letters from industry representatives, trade associations, 
State agencies, and environmental organizations. The public comments 
submitted to EPA addressed the proposed revisions to Methods 201A and 
202 and our request for comments on whether to end the transition 
period for CPM in the NSR program on a date earlier than the current 
end date of January 1, 2011.
    This section provides responses to the more significant public 
comments received on the proposed revisions to Methods 201A and 202. 
Summaries and responses for all comments related to the proposed 
revisions to Methods 201A and 202, including those addressed in this 
preamble, are contained in the response to comments document located in 
the docket for this final action (Docket ID No. EPA-HQ-OAR-2008-0348).

A. Method 201A

1. Speciation
    Comment: One commenter stated that EPA should include guidance in 
Method 201A concerning speciation of the constituents present in the 
PM10, PM10-PM2.5, and PM2.5 
size fractions. The commenter believes this information should be 
provided to support the use of speciated PM10, 
PM10-PM2.5, and PM2.5 data in source 
apportionment studies.
    Response: EPA did not revise the method to provide guidance for 
speciation of various particle fractions for source apportionment 
because Method 201A is not a speciation method. However, with judicious 
selection of filter media, sources may use this method for speciating 
the less volatile metals and use these data in source apportionment 
studies. Including details to adapt this method for speciation analysis 
would unduly increase the complexity of the method without increasing 
the precision of the mass measurements.
2. Catch Weight and Sampling Times
    Comment: Several commenters requested that EPA specify the minimum 
solids catch weights needed in the PM10 and PM2.5 
size fractions to help testing organizations determine the necessary 
sampling times, especially for sources with low PM concentrations. 
Other commenters expressed concern about extended sampling times that 
would be necessary to obtain enough sample to weigh accurately. One 
commenter stated that a reasonable limit must be put on sampling volume 
to limit potentially unnecessary sampling time and exorbitant stack 
testing costs that could quickly escalate with such a requirement.
    Response: We agree with the commenters that collecting sufficient 
weighable mass is important for the method to be precise. We also 
understand that the sampling rate used to attain the cyclone cut-points 
is typically less than the rate used during Method 5 sampling. However, 
EPA did not revise the method to dictate a minimum sampling volume or 
minimum catch weight that would be necessary to obtain a valid sample. 
One reason for not specifying a minimum sampling volume or minimum 
catch weight is that different regulatory authorities and testing 
programs have differing measurement goals. For example, some regulatory 
authorities will accept less precision if results are well below 
compliance limits. State agencies or individual regulated facilities 
may develop data quality objectives (DQO) for the test program, which 
may specify minimum detection limits, and/or minimum sample volume, 
and/or catch weight that would demonstrate that DQO can be met. Stack 
samplers should take into consideration the compliance limits set by 
their regulatory authority and determine the minimum amount of stack 
gas needed to show compliance if the mass of particulate is below the 
detection limit.
    Stack testers can use the minimum detection limit to determine the 
minimum stack gas volume. The stack tester may be able to estimate the 
necessary stack gas volume based on how much PM the source or source 
category is expected to emit (which could be determined from a previous 
test or from knowledge of the emissions for that source category).
    Alternatively, the minimum detection limit for a source can be 
determined by calculating the percent relative standard deviation for a 
series of field train recovery blanks. You will not be able to measure 
below the average train recovery blank level, and EPA recommends 
calculating a tester-specific detection limit by multiplying the 
standard deviation of field recovery train blanks by the appropriate 
``Student's t value'' (e.g., for seven field train recovery blanks, the 
standard deviation of the results would be multiplied by three). Short 
of having Method 201A field recovery train blanks for cyclone and 
filter components of the sampling train, you may use the detection 
limit determined from EPA field tests.
    An estimated detection limit was determined from an EPA field 
evaluation of proposed Method 201A (see ``Field Evaluation of an 
Improved Method for Sampling and Analysis of Filterable and Condensable 
PM,'' Docket ID No. EPA-HQ-OAR-2008-0348). The estimated detection 
limit was calculated from the standard deviation of the differences 
from 10 quadruplicate sampling runs multiplied by the appropriate 
``Student's t value'' (n-1 = 9). Detection limits determined in this 
manner were (1) Total filterable PM: 2.54 mg; (2) PM10: 1.44 
mg; and (3) PM2.5: 1.35. These test runs showed more 
filterable particulate in the PM2.5 fraction, and total 
filterable particulate detection limits may be biased high due to the 
small particulate mass collected in the fraction greater than 
PM10.
    Comment: Two commenters questioned the use of reference methods to 
correct for ambient air in Section 1.5 of the proposed Method 201A. One 
commenter believed that the statement would be used as a means to blame 
non-compliance on ambient contributions and would result in legal 
challenges and disputes of test results. The other commenter questioned 
whether it was the intent of EPA to not allow the use of the CPM test 
method for low-temperature sources.
    Response: We agree with the commenters that Section 1.5 of the 
proposed method was unclear. Thus, Section 1.5 (Additional Methods) has 
been removed from the final method. For sources that have very low PM 
emissions, such as processes that burn clean fuels (e.g., natural gas) 
and/or use large volumes of dilution air (e.g., gas turbines and 
thermal oxidizers), any ambient air particulate introduced into the 
process operation could be a large component of total outlet PM 
emissions. However, the decision to correct results for fine PM 
measurements to account for ambient air contributions is up to the 
permitting or regulatory authority. It is likely that these adjustments 
would be limited to gas turbines and possibly sources fired with clean 
natural gas.
    Comment: Commenters expressed concern about the lack of a test 
method to measure PM2.5 in stacks with entrained moisture. 
Another commenter urged EPA to continue work to identify or develop a 
method for measuring filterable (or total) PM at sources with entrained 
moisture droplets in the stack (e.g., units with wet stacks due to wet 
flue gas desulfurization or wet scrubbers). Commenters requested that 
EPA provide guidance or identify a viable alternative for high-moisture 
stacks as soon as possible. One commenter stated that when conducting 
emission testing at facilities with similar wet stack conditions as 
described in the proposal preamble (74 FR 12973), that they support 
EPA's position on the

[[Page 80126]]

limitations of the proposed Method 201A.
    One commenter was not satisfied with the use of Method 5 as the 
only acceptable method for sources with entrained water droplets. To 
provide more accurate emissions data for sources with ``wet'' stacks, 
the commenter is sponsoring the development of an advanced manual 
sampling technique that can accurately measure filterable 
PM2.5 in stacks with entrained water droplets. The commenter 
expects to complete field tests of this method in the near future. The 
commenter will share laboratory and field test evaluations of this new 
method. The commenter believes that this new method for filterable 
PM2.5 emissions in ``wet'' stacks will be highly compatible 
with proposed Method 201A for filterable PM2.5 emission 
testing in ``dry'' stacks.
    Response: We are currently developing a method to measure PM in 
stacks with saturated water vapors and laboratory testing is ongoing. 
EPA has committed a significant budget and personnel to developing an 
acceptable method for sources with wet stacks and we plan to offer the 
method and protocol as soon as possible. EPA's method development and 
evaluation is focused on the ``Dried Particle Method'' (See ``Lab Work 
to Evaluate PM2.5 Collection with a Dilution Monitoring 
Device for Data Gathering for Emission Factor Development (Final 
Report)'' in Docket ID No. EPA-HQ-OAR-2008-0348) that directly measures 
the mass emission rate of particles with specified aerodynamic size. In 
the meantime, the promulgated amendments to Methods 201A and 202 
improve their performance and reduce known artifacts. Testers should 
use these final, amended methods until a PM2.5 method for 
stack gases containing water droplets is promulgated.
    Regarding the advanced manual sampling technique that the commenter 
is currently developing for use in ``wet'' stacks, EPA acknowledges the 
sampling evaluations being conducted by the commenter. When the data 
become available, we will review the data to determine if the 
consistency and performance achieved by the advanced manual sampling 
technique referenced by the commenter are comparable to EPA's wet-stack 
sampling method currently under development. If the data are 
comparable, we will consider whether the commenter's sampling technique 
should be addressed (e.g., as an alternative method) when we propose an 
EPA wet-stack, particle-sizing method in the future.
    Comment: Several commenters disagreed with EPA's recommendation to 
use Method 5 on stacks with entrained moisture and to consider all the 
collected mass to be PM2.5. Commenters stated that the 
categorization of all PM measured by Method 5 as PM2.5 
overstates the true emissions. One commenter supported EPA's 
recommendation to use Method 5 to determine PM10/
PM2.5 filterable mass when measuring emissions following a 
wet scrubber. Another commenter stated that when conducting emissions 
testing at facilities with similar wet stack conditions, as described 
in the proposal preamble (74 FR 12973), they