RESPONSE TO QUESTIONS REGARDING
STATE IMPLEMENTATION PLAN (SIP) DEVELOPMENT
OFFICE OF AIR QUALITY PLANNING AND STANDARDS
RESEARCH TRIANGLE PARK, NORTH CAROLINA 27711
JUNE 1988
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The following are questions regarding implementation that have been
raised since the United States Environmental Protection Agency (EPA)
promulgated national ambient air quality standards (NAAQS) for particles
with an aerodynamic diameter less than or equal to a nominal 10 micrometers
(PMlo), July 31, 1987. The questions are arranged by subject and the
responses were prepared by the Air Quality Management and Technical
Support Divisions of the Office of Air Quality Planning and Standards
(OAQPS).
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RECEPTOR MODELING AND RECONCILING MODELING RESULTS
1. Why should States use dispersion models rather than receptor models?
Dispersion models are the preferred analytical tool for control
strategy development because they estimate concentrations at locations
other than the monitoring site. Also, they can more easily analyze
for attainment in future years. Receptor models should be primarily
viewed as an additional method which will improve confidence in the
dispersion model results.
2. Clarify the use of uncertainty of ambient measurements.
The ambient uncertainty referred to in receptor modeling is the
analytical uncertainty of the method which is used to determine the
elemental or toxic concentrations. Generally, x-ray fluorescence is
used for elemental analysis and this method is more accurate for
some elements than others. This difference in accuracy should be
reflected in the uncertainties for each element.
3. Are receptor models useful if you .are looking at 24-hour samples?
Multivariate analysis and dispersion models are better suited for
annual averaging times. The chemical mass balance and microscopic
methods are well suited for 24-hour samples. .
4. If we take 15 samples, should we use all of them in a receptor
analysis'?
Generally, analyze as many samples as time and budget permit.
Priority should be given to analysis of samples that are collected
when concentrations are the highest. (Refer to page 7 of Protocol
for Reconciling Differences Among Receptor and Dispersion Models.)
5. How does a State reconcile the differences between dispersion and
receptor models if they are based upon different years (time periods)?
Combine the model results into groups which represent similar
meteorological conditions. Refer to page 7 of Protocol for Reconciling
Differences Among Receptor and Dispersion Models IEPA-450/4-87-008).
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6. Clarify the PMio SIP Development Guideline section 6.4 "Determining
Emission Limits" regarding the use of actual versus allowable emissions.
The emissions used should be the same as those used in the base year
and design year in accordance with the guidance in section 7.4
of the supplement to the PMio SIP Development Guideline (SIP guideline).
The "Source Category Contributions to Ambient Concentrations" (AC-j )
would be representative of actual base year conditions. If the
control strategy development is to be based on receptor modeling
(i.e., no dispersion model is applicable), then special attention
must be given to the use of the following equation contained in
section 6.4:
RI, - ISR.. (ug/m3)
AC (ug/m3)
If the emissions change between the base and design years, the AC-j
must be adjusted to reflect the design year conditions. This is
accomplished by assuming that the change in the ambient concentrations
resulting from source category i is proportional to changes in
emissions from that category between the base and design years. The
equation depicted below may be used to derive the appropriate AC-j
for the design year.
ACj = ACi x design year emissions-j
(design . (base .base year emissions-j
year) year)
The emissions-j must be estimated consistently with Table 9-1 in the
Guideline for Air Quality Models (Revised). EPA-450/2-78-027R, and
with the discussion in section 7.4 of the supplement to the SIP
guideline. If the preceding adjustment is made, the percent RI-j
applies to design year emissions-j.
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DISPERSION MODELING
1. Is EPA working on a model to handle secondary particle formation in
a manner suitable for SIP control strategy demonstrations?
No model recommended for regulatory use at this time handles secondary
particle formation in a manner suitable for SIP control strategy
demonstration. However, EPA has completed work on two models, PEM-2
(an urban model) and MESOPUFF-II (a medium scale transport model),
that can provide a supporting analysis (see page 4-8 of the SIP
guideline).
2. Is an exercise to evaluate dispersion model accuracy necessary before
utilizing the model for control strategy demonstrations?
Use of the dispersion models contained in Appendix A of the Guidelines
on Air Quality Models (Revised) and listed in Table 4-3 on page 4-9
of the SIP guideline do not require the evaluation of model accuracy
before utilization for control strategy demonstration. These models
have already been evaluated for a number of situations and have been
found to perform well. However, the evaluation of model performance
for an individual situation is strongly encouraged where appropriate
data bases are available. This evaluation can be used to identify
deficiencies in the emission inventory and source characterizations
. for the area .[see Example Modeling to Illustrate SIP Development for
the PMio NAAQSJ.
3. How should PMio fugitive dust sources be modeled?
fugitive dust sources can be modeled as area, line, or volume
sources with the Industrial Source Complex (ISC) model, depending on
which is most appropriate for the individual fugitive dust source
type. For urban area analysis, fugitive dust sources can be modeled
as area sources with either the Gaussian-Plume Multiple Source Air
Quality Algorithm (RAM) or Cl imatological Dispersion Model (COM 2.0)
as well as with the ISC model.
4. Does a modeled violation in a Group II or Group III area trigger the
need for a SIP revision?
Yes, a modeled violation will result in the State being required to
revise the SIP to correct the deficiency. For Group II areas, the
same timetable triggered by a monitored violation must be followed
(i.e., immediately notify the appropriate Regional Office of the
violation, within 30 days evaluate the existing SIP, and within
6 months submit a PMio control strategy that has been revised as
necessary to maintain the standards). For Group III areas, EPA will
call for a SIP revision under section 110(a)(2)(H) of the Clean Air
Act (Act).
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EMISSION INVENTORIES/EMISSION FACTORS
1. What are the emission inventory requirements for Group II and III
areas?
These requirements are specified in the supplement to the SIP
guideline, section 5.
2. Does Mobile 4 calculate PMio emissions?
No. A separate program is available to calculate PMio emissions.
Contact Jon Adler, EPA Office of Mobile Sources, Ann Arbor, Michigan,
at (313) 688-4260 or FTS 374-8260.
3. Must an emission inventory be prepared for an entire county?
Not necessarily, unless the entire county is included in the designated
attainment demonstration area. The area to be included is determined
based on various considerations discussed in the SIP development
guidance. Often, inventories are compiled for entire counties
because some of the key data used to estimate emissions, particularly
for area and mobile sources, is most readily available on a countywide
basis. However, such data can be apportioned to subcounty areas, if
so needed.
4. How far out does the emission inventory go?
See response to question #3 concerning the area to be inventoried.
The distance out should be based primarily on the characteristics of
the sources in the area. All sources that would cause a significant
concentration gradient in the area of concern should be modeled.
5. The EPA does not have emission factors for 40-50 percent of the PMm
sources in Wisconsin. What is EPA doing to develop new emission
factors for these sources?
The EPA has been in contact with Wisconsin regarding their "gaps."
The estimate of 40-50 percent mentioned at the workshop was based on
a preliminary State PMio inventory. The EPA's initial review indicated
that some of the identified gaps could be filled and many sources needed
to be better defined. Wisconsin plans to refine its inventory, but
until it does, the extent of their gaps cannot be ascertained. The
EPA has anticipated that Wisconsin and others will encounter gaps
and has efforts underway to assist in filling gaps identified by
State and local agencies. In addition, EPA is establishing a clearing-
house to handle gap filling requests and proposals from State/local
agencies.
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6. The EPA needs to provide more information on control efficiencies.
Should a State use the control efficiency or equation if no information
on PMio emissions is available?:
We agree that better information is needed on control efficiencies
for PMio. Unless better information is available elsewhere, States
may use the table and procedure described in Appendix C-2 of AP-42
to estimate PMio control efficiency for the types of control equipment
listed in the table.
7. How does a State handle a range of control efficiencies in AP-42?
AP-42 does not give ranges of control efficiencies for PMiQ. The
table of control efficiencies in Appendix C-2 of AP-42 presents
single values of percent efficiency for each of various segments of
particle size. How these are used individually or how they are
combined is explained with an example in Appendix C-2.
8. The EPA needs to clarify which inventories are based on actual versus
allowable emissions for the three groups of areas.
The requirements in Attachment 1 specify which are based on actual
versus allowables for the three groups of areas.
9. What is the difference between the base year and attainment year
emission inventory?
For Group I areas, the base year is a recent year for which adequate
air quality data are available to evaluate a model's applicability
to an area. This is an optional step that may be performed before a
model is used in the SIP control strategy development. There may be
cases where a particular model has already been sufficiently evaluated
in other similar areas. In such instances, an evaluation for the
area in question may not be necessary. Nevertheless, a base year
emission inventory is a useful starting point for the control strategy
analysis.
An inventory for the projected year of attainment, before the control
strategy is applied, is the basis for the model application to
determine the target percent reduction in PMio emissions needed to
attain the standard. This inventory should consider any permanent
source changes between the base and attainment year, including
projected new sources, modifications, shutdowns, new or discontinued
controls, growth, and banked emissions. In addition, source emissions
should be based on allowables, as specified in Table 9-1 of the EPA
modeling guideline document.
For Group II and III areas, inventory data are only applicable to a
recent "base" year and should reflect actual emissions. In addition,
for Group II areas, an allowables inventory is required for the base
year. In Group M- and III areas, the base year may change as the
data are updated for a more recent year.
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10. If the Aerometric Information Retrieval System (AIRS) program limits
" sources to those greater than 100 tons per year (tpy). does this
limit size of the source to be considered in the plan?
Annual reporting of source emissions to EPA are limited to 100 tpy,
sources, but neither the National Emissions Data System (NEDS) nor
AIRS limit entry of point source data for sources of less emissions,
if desired for some other purpose (e.g., SIP's). For SIP purposes,
EPA is requiring no higher cutpoint than 50 tpy (uncontrolled or
uncontrolled potential) for inventorying and submitting data for
point sources in Group I areas. Detailed data may be necessary for
even smaller sources if they are likely to cause a significant PMiQ
concentration gradient in the area of concern.
11. Is the suggested PMip point source form (revised 9/87) compatible
with the Emissions Information System (EIS)?
Not presently. Some software or guidance may be developed to enhance
compatability but since EIS is likely to be replaced by AIRS based
State systems, the current thinking is to try to build the compatability
into AIRS. This feature is not in the initial design plans for
AIRS, but is being considered as part of an add-on module.
12. Regarding submittal requirements for Group I areas in 9 months,
a) What year do you use as the baseline inventory:
The latest year for which adequate air quality data are available
for model evaluation. The selection should be made with concurrence-
of the appropriate EPA Regional Office.
b) How do you determine the attainment year ahead of time?
A projection needs to be made based on an estimate of how long EPA
will take to approve the SIP and the best information available as
to when all the measures in-the control strategy can be effected.
c) Why is EPA using the old definition of uncontrollable potential
emissions? Is EPA including controls on the source, or are
potential emissions totally uncontrollable? (Person asking
question referred to a court decision of a few years ago.)
The requirements specify that the cutpoint for inventorying emissions
as point sources is for source emissions if totally uncontrolled or
the potential emissions of a controlled source if it were to operate
uncontrolled. This is only to determine if separate records as a
point source are necessary, not to consider in this manner for
control purposes. The purpose is to have a separate record for
verification if a source's impact does not or does not fully reflect
its reported emissions based on an assumed level of control.
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d) If you use a 24-hour standard, do you have to submit annual and
dally inventory?
Generally, no. In many instances, a State (or designated local
agency) may have to run a model for daily and annual periods to
assure that both standards will be protected, even if air quality
measurements show exceedances for only one of the periods. In such
instances, only the annual inventory data needs to be submitted to
EPA, although the 24-hour period inventory data should be available
for review, if needed. There are some exceptions. Some areas may
experience seasonal rises in emissions which largely cause their
nonattainment problem. If the problem involves more than one season
(e.g., summer wind blown dust and winter wood burning), then only
that seasonal inventory should be submitted. In the dual season
situations, a model analysis should be done for each season separately,
and the results combined for the annual standard analysis. For the
daily standard analysis, the model would have to be run for a 24-hour
period for each season. For the single season problem, only a
24-hour modeling analysis for the appropriate season is appropriate.
e) In areas with significant secondary aerosol emissions potential,
does EPA require inventories for secondary pollutants that may form
in the atmosphere?
Generally, only inventories of primarily emitted particulates (or
condensible aerosols at ambient, temperatures) are required. However,
if the control strategy develpped to attain the PMig NAAQS includes
measures to reduce locally emitted precursors of secondarily formed
particles, then the precursor pollutants should be inventoried.
This assumes that EPA and the State have agreed upon a dispersion
model to use in demonstrating the adequacy of such a control strategy.
13. Regarding Group II areas submittal (within 37 months) requirements:
a) How do you determine allowable emissions?
For the selected base year, use the criteria in Table 9-1 of EPA's
modeling duideline document. There may be a need to consult with
the appropriate EPA Regional Office in determining which sources in
an area should be treated as point sources, other contributing
sources, and background sources.
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b) What is the object of the allowable emission inventory for
Group II areas? (It was suggested that this be reevaluated.)
The object is for the State to evaluate the extent to which allowable
emissions may exceed actual emissions. This gap poses a potential
for future exceedances should economic or other factors become
conducive for sources to emit up to their allowables. If a wide gap
exists for any major source in the area (large enough to cause a
violation of the NAAQS), the State must either modify source permits
or emission limitations to bring these closer in line with actual
emissions and, thereby, minimize the potential for future exceedances
or submit a demonstration that the NAAQS will be maintained with
emissions at allowable levels. This objective is in accord with the
stated intent in the Act to "attain and maintain the standards"
(emphasis added).
14. Regarding Group III areas:
a) Is annual reporting (referred to in the second slide at the PMip
Implementation Workshops) required in addition to NEDS reporting.
No. This is the same as the present NEDS reporting. The NEDS is
the current system for handling these data, but in the near future
it will be changed to AIRS. Therefore, we referred to this in
generic terms (in preceding slides) as annual "national" reporting
of emissions....
b) Is the NEDS report due next year, or when?
The NEDS report continues to be due every year. However, through
calendar year (CY) 1987 data due in CY 1988, States will still
report total particulate emissions data. Beginning with CY 1988
data due in CY 1989, States will be required to report PMiQ emissions
data.
15. Regarding PMiQ controlled and uncontrolled emissions factors, why is
the penetration factor included in the calculation of PMiQ emissions
ITsing an uncontrolled PMiQ emission factor? Shouldn't it instead be
used in the calculation using a controlled emission factor?
No. The penetration factor is used to account for the efficiency of
the control device if a source is controlled and an uncontrolled
emission factor is used to calculate emissions. If the source is
controlled and an appropriate controlled emission factor is used to
calculate emissions, the controlled emission factor already takes
into account the control efficiency of the source; hence, a penetration
factor is not needed in the calculation.
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16. New emission factors are needed for:
a) Fugitive dust sources.
The EPA has developed gap filling factors for open sources for
several fugitive dust sources which are not covered in AP-42. These
are default factors based on technology transfer, engineering judgment,
etc. It will cover about 10-15 such sources. The report should be
distributed to State/local agencies in February 1988.
b) Fugitive emission sources, especially.construction activities.
Open fugitive dust sources are covered in the preceding response.
Few PMio factors exist for industrial operations because of a dearth
of test information for such sources. The EPA will continue to try to
develop stop gap factors for such sources. For construction activities,
there is no overall factor for such activities because of their
diversity. PMjQ are presently available for some but not all distinct
construction operations. Some of the construction activities for which
PMio factors exist are road dust emissions, batch or continuous drop
(loading or unloading), and storage (sand or dirt) piles. A clearing-
house has been established by EPA to facilitate the filling of gaps
as they occur in inventory development.
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AIR QUALITY MONITORING NETWORK DESIGN
1. For monitoring purposes, how large is a neighborhood?
Neighborhood, in this context, refers to the spatial scale of
representativeness in Appendix D of 40 CFR 58. A neighborhood scale
defines concentrations within some extended area of the city that
has relatively uniform land use with dimensions in the range of 0.5 to
4.0 kilometers.
2. In the Group I areas, one must sample every day at one site. What
Sampling frequency is required for other samplers in the monitoring
area?
Section 58.13(i) requires everyday PMio sampling for at least one
site in Group I areas during the first year of sampling and it must be
located in the area of expected maximum concentration. The remaining
sites in the Group I area require a minimum of every sixth-day sampling.
This does not preclude operating one or more of the remaining sites
more frequently than every sixth day.
3. How long must total suspended particulate (TSP) samplers continue to
operate?
Appendix C, section 2.2, 40 CFR 58 specifies, that the high-volume
sampler may be used as a PMio surrogate State/Local Air Monitoring
System (SLAMS) as long as the measured concentrations are below the
PMio NAAQS. This applies only to the those samplers which are not a
part of the National Air Monitoring System (NAMS) network.
No TSP samplers may be a part of the official PMio NAMS network.
However, Appendix C also specifies that if a PMio NAMS site is
designated at a site which was previously a TSP NAMS site, then the
TSP and PMio samplers must be concurrently operated for a 1-year
period. The purpose of this is to maintain historical continuity
for trends purposes. All or part of the 1-year period could have
been before the July 1 promulgation or before the official approval
of the NAMS PM network.
A subset of the NAMS TSP sites are being requested to continue operation
to provide filters for the National Particulate Network (NPN). These
filters are being analyzed for trace metals and the data are used for
long-term trends. Studies are being planned to test the possibility
of switching these analyses to the PMio filters. However, until
these studies and analyses are complete, the TSP sampler will continue
to be used for the NPN.
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The officially designated NAMS TSP samplers may be discontinued (except
as'discussed above) only after the PMio network description has been
approved and all the PMio samplers so designated are fully operational
at the required frequency. A reduction of some of the TSP samplers
from the currently approved NAMS/SLAMS network may be considered on
a case-by-case basis before the above conditions are met. Except for
the cases noted above and situations where TSP samplers are used to
collect particulates for lead analyses and where there is a State
standard for TSP, agencies are encouraged to discontinue the use of
TSP samplers.
4. How soon are collocated PMip required?
Part of the requirements in an approved PMio network is for all the
PMio samplers to meet the quality assurance (QA) procedures as set
forth in Appendix A. The collocation of PMig samplers is a part of
the QA plan as specified in Appendix A, section 3. Therefore, the
collocated PMio samplers must be designated and operating before the
NAMS PMio network can be approved.
5. Must TSP monitoring be continued for lead?
Yes. At the current time, the reference methods for lead as specified
in the regulations call for the collection of ambient lead by the
high-volume sampler collection method. Until such time EPA changes
the lead standard and/or reference method, the continued use of the
high-volume sampler for monitoring ambient lead levels is required.
6. When does NAMS. SLAMS PMio monitoring start?
The regulations require the NAMS and SLAMS network description to be
submitted within 6 months after the effective date of the regulation.
The NAMS network, and the SLAMS network in Group I and II areas, must
be operational within 1 year after the effective date of the regulation.
The remaining SLAMS network (i.e., Group III areas) must be operational
within 2 years after the effective date of the regulation. There is
nothing, however, to preclude an agency from submitting their network
descriptions early and, upon approval, implementing their NAMS and/or
SLAMS networks early.
7. If a State has PMip dichotomous and PMio size-selective samplers.
considering the potential for higher values from the size-selective,
which data set should the State us1??
All data must be used at face value after promulgation for attainment/
nonattainment purposes, design value development and monitoring frequency
determination.
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8. How does one incorporate PMm into the Pollutant Standard Index (PSI )
and what are the breakpoints?
One incorporates PMio into the PSI by discontinuing TSP monitoring and
substituting PMio monitors and following the procedure described in the
Part 58 Appendix 6 regulation, which identifies the PSI breakpoints,
and in the guideline entitled Guidance for PMio Episode Monitoring
Methods. EPA 450/4-83-005, February 1983.
9. Are mass flow controllers affected by atmospheric changes?
Yes, they are. Although the mass flow remains constant, the actual
volumetric flow rate through the inlet fluctuates as the ambient
temperature and barometric pressure change at the sampling site.
Normally, the range of the fluctuations is within the tolerance limits
of the inlet. However, the flow rate set point of the mass flow
controller must be correctly adjusted so that the deviations are
centered with respect to the seasonal average temperature and barometric
pressure at the site. Detailed procedures for calculating the set
point and adjusting a mass flow controller are contained in Volume II
of EPA's Quality Assurance Handbook for Air Pollution Measurement
System, section 2.11, EPA report 600/4-77-027a.
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EXCEPTIONAL EVENTS GUIDANCE
1. What is the purpose of flagging described in the Exceptional Events
Guldel in?? ~
The basic purpose of the flagging system is to identify those air
quality measurements that are influenced by exceptional events.
These are events which, if unidentified, could lead to possible
misinterpretation or misuse of the data. Because the flagging
system relies heavily on the identification and understanding of
events that may have influenced a particular air quality measurement,
its major thrust is information exchange. The criteria for identifi-
cation of "exceptional events" are designed to be expansive enough
to encompass most good faith claims by State and local agencies of
when data should be considered for special treatment. It is not
intended to reflect EPA's views on the validity of these claims.
The flagging of data is merely a way for a State or local agency to
state that it regards the data as influenced by exceptional events,
and may later claim that the data should be discounted for certain
purposes.
2. Who flags data?
Under the flagging system, State and local air pollution control
agencies will be responsible for initially identifying and documenting
data influenced by exceptional events. These agencies also must
develop the appropriate background information used to support the
decision to flag an individual piece of data; they must submit the
information to EPA for concurrence and make it available for the
public's review upon request.
3. Does flagging imply use or nonuse of data?
The guideline's general policy is to allow consideration of excluding
flagged da'ta from use in regulatory actions. The actual exclusion
of the use of flagged data would only be allowed if, as a result of
a public review process, the responsible government agency, e.g.,
the State air agency during the State regulatory process, and the U.S.
EPA during the Federal review/approval process, determines that the
data are inappropriate for use in a specific regulatory activity.
This consideration for exclusion of flagged data carries with it no
prior presumption towards use or nonuse of flagged data. The exclusion
of flagged air quality data for SIP regulatory activities (areawide
or local control strategy development, SIP design values, attainment
/nonattainment status, enforcement actions, etc.) shall be considered
on a case-by-case basis and discussed during the public review
process. Exclusion of the flagged data would only be allowed if the
responsible control agency determines in conjunction with a public
review that the flagged data are inappropriate for use.
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4. Is there consistency in the definition of exceptional events nationally?
This guideline provides general definitions for these events and general
criteria for their use in flagging air quality data. The application
of a definition may vary from area to area because of differing air
quality and control situations. For example, salting and sanding of
streets for snow and ice control may be an exceptional event in the
southern sections of the country, whereas they may be routine,
controllable events in the northern sections. Therefore, definitions
in the Exceptional Events Guideline are only a national guide and
are not meant to replace reasonable judgment on the part of the
Regional, State, and local air pollution control agency officials in
defining and identifying exceptional events for the purpose of'
flagging data.
5. How is exceptional defined for exceptional events?
Webster defines "exceptional" as forming an exception, rare, uncommon,
extraordinary, deviating from the norm. With respect to air quality
considerations in this guideline, an exceptional event is defined as
an event that is not expected to recur routinely at a given location,
or that is possibly uncontrollable or unrealistic to control through
the SIP process. As noted previously, what is exceptional in one area
of the country may not be exceptional in another. Therefore, some
judgment is needed in identifying whether an event is exceptional in
the area of the country where it has occurred.
6. How frequently does an event have to occur before it is considered
not an exceptional event?
During the 4-year development of the guidance, which was reviewed
three times by State and local agencies and numerous times by Regional
Offices, no concensus was arrived at concerning frequency of occurence
or how rare should be defined. Therefore, no absolute definition or
numerical quantity has been assigned to rare or unusal. An attempt
has been made to leave some room for interpretation because, what
may be unusual or exceptional for one part of the country may be
typical for another and this variability requires flexibility in
national definitions and criteria.
7. If data are flagged as an exceptional event and the level is greater
than the 24-hour NAAQS U50 ug/m3), is the flagged value counted as
an exceedance?
Yes. A 24-hour value greater than the level of the 24-hour NAAQS,
after rounding to the nearest 10 ug/m3, is defined as an exceedance
of the 24-hour standard. All data, flagged or unflagged, should be
available to the public for comparison to the NAAQS to determine if
24-hour exceedances and, in turn, if violations of the 24-hour or
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annual NAAQS have occurred. However, in section 2.4 of Appendix K,
EPA has authorized special treatment of air quality data affected by
uncontrollable events caused by natural sources or unusual events
that are not expected to recur at a given location. These events
may be discounted or weighted-according to the likelihood of their
recurrence, subject to the approval of the Regional Administrator in
accordance with EPA guidelines.
Moreover, the use or nonuse of flagged exceedances for SIP purposes
will be determined on a case-by-case basis. For example, a flagged
exceedance caused by a volcanic eruption would not require modification
to an approved SIP.
3. Mill flagged data be used to determine monitoring frequency requirements
as specified in 58.13?
Yes. However, if the exceptional event has received regional concurrence
prior to the time in which revisions to existing sampling frequency
would be required to have occurred, a request for relief from accelerated
sampling schedule can be submitted to the Regional Administrator for
SLAMS or the Administrator for NAMS sites.
9. Under what circumstances will prescribed burning not be considered
as an exceptional event?
In those areas of the country where prescribed burning is. used regularly
and extensively for agricultural and/or forestry land management, pre-
scribed burning may not be considered an exceptional event for the
purposes of flagging air quality data. Prescribed burning in these
areas is usually subject to rules and regulations, including smoke
management plans, under which a regulatory agency permits burning
after deciding where, and to what extent, the smoke will be allowed
to impact air quality.
10. Why do we call "agricultural tilling" an exceptional event?
This event was included along with highway construction, salting, and
sanding of streets and others, which are not exceptional; however,
they may be difficult or impractical to control through the SIP
process. There are some conditions attached to the agricultural
tilling; such as, it must occur within a reasonable distance (500
meters) of the monitor and the data in question must have been
collected during or immediately after the day of tilling.
11. What type of documentation is required for an exceptional event?
The type and extent of documentation for an exceptional event will
vary depending on type and nature of the event on a case-by-case
basis. A discussion of documentation is provided in section 4.4 of
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the Exceptional Events Guideline. It could be as simple as a newspaper
article concerning a severe windstorm or as complex as a chemical or
microscopic filter analysis.
12. After EPA has completed the grouping process, can data be flagged?
The Exceptional Events Guideline was developed independently from the
PMio SIP grouping process and it concerns all criteria pollutants. If
data are entered into AIRS, they can be flagged at entry. If the AIRS
system is not used, flagged data should be submitted along with the
SLAMS annual report or its cover letter.
13. Is there a procedure for public comment on'exceptional event data?
It was not the intention of the Exceptional Events Guideline to create
or prescribe a procedure for public comment.Public review only
becomes necessary when a decision is made to use or not to use data
for particular regulatory purposes. All of these regulatory purposes
require some form of public input. It is the intention of the
guideline to utilize those public review processes already in place.
14. When is the last date data may be flagged and documentation submitted?
Requests for flagging data including the documentations should be
submitted prior to, or together with, the submission of the SLAMS
annual report covering the timeframe for which the data was generated.
15. Can only ambient PMio values greater than the NAAQS be flagged?
The exceptional events policy applies to any concentration, regardless
of magnitude, affected by the infrequent activities included in the
policy. Otherwise, the annual arithmetic mean concentration for an
area may be overestimated due to a few high 24-hour concentrations
(but not exceeding the NAAQS) caused by exceptional events.
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AIR QUALITY DATA ANALYSIS AND USEAGE
1. Uith the statistical form of the standard, when does the 3-year
timeframe start for evaluating compliance with the standard*?
The 3-year timeframe for evaluating attainment (compliance) started
on or before promulgation with the initial deployment of PMio samplers.
According to Appendix K to Part 50, the 3 years must be calendar years,
although 3 running years may be used for the initial period of PMio
data collection to allow for midyear startup.
Data collected both before and after the July 1, 1987 promulgation
can be used to satisfy the 3-year data requirement. However, in order
for data to be considered "valid," the data must be consistent with
the short-term and long-term sampling requirements described in
Part 58.13 as well as the data capture requirements of Appendix K.
Once the short-term requirements are satisfied, 2 additional years
of data satisfying the long-term sampling requirement would then be
needed.
The data used to satisfy the short- and long-term sampling requirements
can be data collected prior to the July 1, 1987 promulgation.
2. How is the gray zone data interpreted now that the regulations are
promulgated?:
Prior to promulgation, PMio data were used in combination with TSP
data to place areas into one of three groups for SIP development
purposes. PMio data from the Sierra Anderson 321A instruments that
were within 20 percent of the standard (0 to +20 percent) were not
used to place an area in Group I. Other data or SIP conditions
would be required for that classification. The EPA has determined
that a potential bias in PMio measurements exists in some situations.
This was demonstrated in Phoenix where the particulate matter contained
a large percentage of coarse particles. Since there was limited
time to evaluate the potential for coarse particle influence on
existing PMio monitoring programs, the concept of the gray zone was
developed where areas were placed in Group II, so that more time
would be provided to determine the correct status with respect to
the standards.
A series of meetings are ongoing among EPA staff to resolve issues
related to instrument modification and the recording of observations
in the "gray zone" since the promulgation of the NAAQS for PMiQ. A
policy statement is expected by mid-1988.
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3. If an area has a lot of exceedances, does EPA care what procedures
are used to characterize these exceedances? What procedures are
available to the States?
The estimated number of 24-hour exceedances is needed for several
applications. The foremost application is the determination of
attainment or nonattainment with the 24-hour standard. For this
application, the estimate of the expected number of exceedances is
derived according to the formulas specified in Appendix K to Part 50.
If this estimate is less than or equal to 1.0, the site passes the
attainment test for the 24-hour standard. If this estimate exceeds
1.0, then the site fails the attainment test. When the observed number
of exceedances in the'last 3 years is greater than or equal to 4,
however, the computation for the estimated number of exceedances is not
necessary—the 24-hour standard is automatically violated.
If the observed number of exceedances is greater than 3 (or the
site is otherwise determined to be in nonattainment with the 24-hour
standards), procedures other than those specified in Appendix K may be
used to estimate the number of exceedances per year. This may be of
interest, for example, in the evaluation of dispersion models and
design value estimation. For these applications, the use of a
statistical distribution fitted to observed PMio concentrations may be
considered.
4. How much data capture per site is required before a site can be
used in an attainment demonstration?
Three years of PMio data are needed which are sampled in accordance
with Part 58.13 monitoring frequency requirements and produces
75 percent data capture in each calendar quarter.
5. Can you use more than 3 years of data?
Yes, more than 3 years of data may be used. This is permitted by
the regulation provided that the additional years of data are repre-
sensitive of current conditions and that all additional years are
used. This is stated in Appendix K to Part 50.
6. What would happen if one of the attainment evaluation years does not
have 75 percent data capture?
The test for attainment requires 3 calendar years of data. If one
of the most recent 3 years of monitoring data does not satisfy the
minimum 75 percent data capture for at least one calendar quarter,
then this year cannot be used to test for attainment with the standards.
If an attainment demonstration is desired, then (a) make use of the
guideline on exceptions to minimum data completeness to "fix" the
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incomplete year, or (b) use additional prior calendar years of
data to come up with the required 3 complete calendar years. Appendix K
permits the use of more than 3 years provided that they are representative
and that all such years of data are utilized.
If one of the last 3 years which does not satisfy the 75 percent data
capture requirement has exceedances of the 24-hour standard, however,
these exceedances cannot be ignored in the estimate of the expected
number of exceedances. At an absolute minimum, the observed number of
exceedances for the calendar quarter would be considered in the
computation of the estimate of the expected number of exceedances.
Adjustment for incomplete sampling could still be considered, but must
be considered cautiously in this situation, because the annual number
of estimated exceedances could be overestimated with insufficient data.
Adjustment for incomplete sampling must be permitted even without
75 percent data capture so that there is no incentive to terminate
sampling in a quarter with an observed exceedance to avoid a large
number of estimated exceedances.
Similarly, the average for a calendar quarter which does not satisfy
the 75 percent data capture requirement could also be considered in
the computation of the 3-year annual arithmetic mean. In this way,
a quarter with high PMio concentrations and less than 75 percent
data capture is not necessarily ignored. The use of averages based
on incomplete data must also be used very cautiously because of the
potential for biased estimates. Appendix K indicates that one-half
the minimum detectable concentration' (one-half ug/m3) .can be substi-
tuted for the missing values in order to judge nonattainment. Other
"reasonable" approaches could also be considered. For example, if
the temporal distribution of available observations within the
quarter is balanced and at least 12 observations are available, then
a quarterly mean can be computed from the available data for attainment
or nonattainment purposes. The observations can be considered
temporally balanced if no less than 20 percent of the total number
of quarterly observations are in any single month.
7. Can data from incomplete years be ignored in the attainment determination?
Data from incomplete years can only be ignored if the PMio concentrations
from those incomplete quarters or years indicate attainment. Those
incomplete periods cannot be ignored if they indicate potential
nonattainment.
8. How will a variable monitoring frequency affect the attainment
determination?
The variable monitoring frequency can affect the minimum data
completeness requirements specified in Appendix K. Those requirements
indicate that the site must produce 75 percent data capture and must be
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sampled according to the frequency specified in Part 58.13 of the
monitoring regulations. This may be once in 6 days, every other day
or every day. If the site is sampling at a frequency less than that
required by Part 58.13, then the site does not satisfy the minimum data
completeness requirements and cannot be used to measure attainment with
the standards.
If a site does sample at the correct frequency and produces the
required 75 percent data capture, the missing data periods among the
scheduled samples may not be intentional. It would not be acceptable,
for example, to only sample on weekdays in order to capture 75 percent
of the possible samples.
9. In adjusting for trends in particulate matter emission and air
quality data, would we differentiate between: (2, 2, 0). (2, 2',
2), (0, 1, 2) exceedances per year over the last 3 years?
The adjustment for trends is only permitted if the most current year
indicates attainment with the standards. Therefore, only the first
example cited (2, 2, 0), would qualify for consideration for trends
adjustment. In addition, the justification for trends adjustment is
not merely the appearance of a trend .in observed air quality during the
last 3 years. Rather, it is based on a documented trend in the
underlying emissions during this period.
The adjustment for trends is not intended for situations in which .
emissions have increased and the average of the last 3 years of
monitoring data do not indicate nonattainment. Thus, the case (0, 1,
2) with a corresponding increase of emissions during this period could
not be adjusted for the emission trend to indicate nonattainment.
10. Can data be combined among sampling sites?
In general, you cannot mix data from more than one monitoring site
for attainment/nonattainment demonstration or estimation of design
values, regardless of the similarity of the sources that are affecting
the sites. However, there may be special situations where this may be
justified and data can be combined among consecutive time periods
(e.g., because of a minor movement of ah instrument). Such instances
would have to be clearly documented to justify this special treatment
of these data.
In a situation in which a number of districts are suffering from
similar emission problems, the data from monitors in these districts
cannot generally be combined. However, a single monitoring area can be
defined which includes all such districts. In this way, one site can
be designated as the worst site in the multidistrict area and only
this site would be required to monitor at a frequency greater than once
every 6 days.
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11. If you exceed the 24-hour and annual standards, which one is controlling?
By definition, the "controlling" standard is the standard which
requires more emission control in order to be attained. Furthermore,
when this standard is attained, then the other standard will also be
attained. In the simplest case, where emission reductions are directly
proportional to air quality improvement and the background is assumed
to be zero (or negligible), the standard with the highest ratio of its
design value to the level of the corresponding standard is the
controlling standard. This is the case that is assumed in Part 58.13
where the 24-hour standard is said to be controlling if it has the
largest ratio.
Normally, the annual and 24-hour design values would be reevaluated
from current air quality data for each site in the monitoring area
during the annual network review and used to define sampling require-
ments. However, dispersion modeling may be used to reassess PMjo
design values and corresponding sampling requirements.
If it is determined by modeling that emission reductions are not
directly proportional to air quality improvement, then modeling derived
estimates could indicate a different controlling standard. For
example, the annual standard may be the "controlling" standard even
though the 24-hour standard at monitoring locations has the larger
ratio of its design value to the standard level.
If the modeling results regarding a controlling annual standard and
the corresponding control strategy are deemed valid for the current
year during the annual network review, then 1 in 6-day sampling may
be utilized at the designated worst site; selective sampling require-
ments for 24-hour controlling standards based on observed monitoring
data may be waived. Nevertheless, the occurrence of high 24-hour
design values estimated from monitoring data should be considered in
the SIP tracking and the reassessment of the existing control
strategy to make sure that the SIP strategy is still valid and that
underlying conditions have not shifted towards a controlling 24-hour
standard.
12. How do you use a 24-hour design value that was extrapolated from
observed data?
A 24-hour design value is extrapolated from observed data when less
than 1 complete year of data are available (i.e., 365 observations).
The extrapolated design value must be used to determine whether the
24-hour or the annual standard is controlling, for the purposes of
defining monitoring requirements. The extrapolated design value is
also used in the development of the control strategy.
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If a dispersion model is used in the control strategy development,
the model derived design value is the preferred design value. In this
case, the extrapolated 24-hour design value from ambient data would
be used in the model evaluation. The model should be compared to
statistically extrapolated values as well as observed data if the
number of 24-hour observations represent less than 1 complete year
of data.
Receptor models make use of the chemical composition of actual
samples. If a receptor model is used, then obviously, the receptor
model cannot make comparisons to a hypothetical sampling day which was
not observed. The receptor model would focus on the highest day(s) to
determine the emission contributions to the peak PMio values. The
extrapolated design value in this case would be used to determine the
extent of emission reduction that may be needed for these sources. The
extrapolated design value indicates the PMio concentration that might
have been observed if sampling was performed every day. An assumption
is made that the same sources would contribute to the PMio
concentration predicted by the statistical extrapolation.
If dispersion or receptor models are not applicable, then the design
value derived from ambient air quality data must be used to define
emission reductions. If the data are incomplete (i.e., < 365
observations), then a design value based on observed data must be viewed
as tentative and subject to revision. The extrapolated design value
can be used to estimate emission reductions that may be needed.
13. Do you have to extrapolate to get your design value when you have
less than everyday sampling?
The SIP guideline describes several methods for estimating design
values. One of these is table look-up which does not involve extra-
polation. Since the regulation does not specify the design value
estimation procedure and only provides references for consideration,
extrapolation is not required. However, the SIP guideline does
state that for the purposes of determining the controlling standard
(annual or 24-hour), extrapolation must be considered.
14. Why did you use the upper 10 percent of data to estimate the 24-hour
design value?
Procedures described in the SIP guideline for estimating the 24-hour
design value only depend on the highest values in an air quality
data set. The table look-up procedure may only utilize the highest
value observed in the last 3 years. The procedures that involve the
use of statistical distributions or graphical estimation only utilize
the upper tail of the data. The highest values could be caused by a
different set of source receptor relationships and meteorological
conditions. Common practice is to consider the top 5-10 percent of
the data.
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MONITORING SCHEDULES AND TREATMENT OF EXCEEDANCES
1. How do you handle a change of sampling schedule in the middle of a
quarter?
If the sampling schedule changes in the middle of a calendar
quarter, the calculations for the quarterly mean and the estimated
number of exceedances are performed on the basis of the total number of
observations recorded for the quarter, regardless of the sampling
schedule(s) involved. In Appendix K to Part 50, the calculation of the
annual mean and the adjustment for incompleteness of sampling do not
consider the month in which the samples were recorded.
The change in sampling schedule may be important, however, for
determining if the site is sampling at the correct sampling frequency
in accordance with Part 58.13. The monitoring requirements are always
described in terms of calendar quarters. Therefore, the minimum
frequency reported for the quarter is the frequency with which the
monitoring requirements are compared.
2. What site should be selected to sample on an accelerated schedule
within a monitoring areaT"
The regulations specify that for some areas at least one site must
monitor every day or every other day and that this site must be located
in the "area of expected maximum" concentration." A variety of
considerations for site selection are discussed in Part 58.13 of the
new monitoring regulations including: the magnitude of the high value
observed in the most current year, changes in PM^Q emission sources and
the use of the last 3 years of data for network stability. Ideally,
when the selected site is in attainment with the PM standards, the
entire monitoring area will also be in attainment. The selected site
will be called the "designated worst site."
3. If a site is in the long-term monitoring plan, when does it adjust
its sampling frequency?
At the time of the annual network review, the annual and 24-hour
design values are recomputed. One site is designated the worst site
and its sampling frequency is determined in accordance with the
selective sampling requirements. The new sampling frequency must be
initiated on or before the beginning of the next calendar year. It is
advantageous, however, to track air quality data on a real-time basis
and not wait for the midyear network review. This can keep sampling
schedules more consistent with current air quality status.
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Air quality data, reported to EPA, is summarized by calendar quarter
and calendar year. The sampling frequency used to produce the data
must also be reported, as well as the dates of any changes in sampling
frequency. The minimum reported frequency will define the frequency
for the quarter. This value will be used to judge if minimum sampling
frequency requirements have been satisfied. Since Part 58 requirements
are stated in terms of calendar quarters, and Appendix formulas are
computed in terms of calendar quarters, it is desirable to start
new schedules at the beginning of a calendar quarter.
4. When is the short-term sampling period completed?
The short-term sampling requirements of Part 58 define the first
year of monitoring for the site designated as the worst site in the
monitoring area. In Group I and Group II areas, the sampling frequency
at the designated worst monitor for the first year of monitoring shall
be every day and every other day, respectively. In addition, everyday
sampling for 4 consecutive calendar quarters is required in Group II
and Group III areas that observe a single exceedance of the 24-hour
standard. Acceleration to everyday sampling following an observed
first exceedance is part of the short-term plan.
A definition of an equivalent year is also provided, whereby 2 or
3 years of data produced at lower sampling frequencies could satisfy
the first year requirement. If more than 1 year of data are used
to satisfy the short-term.sampling requirement, these data shall
only count as 1 year towards the required 3 years of "valid" data.
When the designated worst site satisfies the short-term requirements,
the entire monitoring area satisfies the short-term, "first year"
requirement.
5. How are data collected prior to promulgation judged to be consistent
with the short-term and long-term sampling requirements?
If more than 1 year of PMio data were collected prior to promulgation,
then some of these data could be used to satisfy the short-term,
"first year" requirement and the remaining data could be used to
satisfy 1 or more years of long-term monitoring. The short-term
requirements depend on the area grouping and the occurrence of any
exceedances of the 24-hour standard for Group II and Group III areas.
Once the short-term requirement is satisfied, the long-term sampling
requirement depends on the controlling standard and the relative
level to the 24-hour standard if it is controlling. If the annual
standard is judged to be controlling in a Group II or Group III
area, then 1 or more prior years of data collected every sixth day
would be sufficient to satisfy the long-term sampling requirements.
However, if it is determined that the 24-hour standard is controlling,
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then the adequacy of the frequency of the prior sampling depends on the
relative level to the 24-hour standard. This only applies to the
designated worst site in the monitoring area. In principle, this
determination should be made for the year in which the data were
collected, but due to practical constraints, this determination can be
made on the basis of the current assessment of PMjo air quality status.
If, for example it is determined that the 24-hour standard is
controlling and the designated worst site is 30 percent above the level
of this standard, i.e., design value equals 195 ug/m3, then every other
day sampling would be required according to Part 58.13.
6. Short-term monitoring plan; Is more than one monitoring site required
to increase its sampling to everyday for 1 year if an exceedance is
igj
3Mi
observed at multiple sites during the same calendar quarter?
Only one site is required to increase its sampling to everyday
following the first observed exceedance. If several sites observe a
single exceedance in the same calendar quarter, one site is designated
the worst site and this site would be expected to increase to everyday
sampling within 90 days following the end of this calendar quarter.
The selection of the worst site will be based on observed concentrations
as well as other considerations regarding knowledge about emissions
and meteorology.
7. Short-term monitoring plan: How is the first exceedance treated at
a site, if another site in the monitoring area is already sampling"
everyday (or planning to) in accordance to Part 58.13?
By policy, EPA shall exempt the first observed exceedance at all
sites in a monitoring area from adjustment for incomplete sampling in
the exceedance calculations, if one site, the designated worst site,
goes to everyday sampling for 1 year. The monitoring agency may
choose to increase the sampling at additional sites if it feels that
these sites are potential nonattainment sites, reflecting different
emission sources or source receptor relationships.
8. Short-term monitoring plan: How is the second observed exceedance
treated in a monitoring area, prior to the initiation of everyday
sampling at the designated worst site?•
When a second exceedance occurs at the designated worst site or if a
second exceedance occurs at any other site prior to the initiation of
everyday sampling in the monitoring area, then this exceedance (and
subsequent exceedances) would be adjusted for incompleteness of
sampling.
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Exceedances are adjusted for incompleteness of sampling on a
quarterly basis, using the total number of samples in the quarter. The
second exceedance is estimated using the total number of observations
(minus one observed sample for the first observed exceedance).
9. Short-term monitoring plan: During the period of everyday sampling
following the first observed exceedance. how are exceedances'
interpreted which are observed at sites sampling less than everyday?
When the designated worst site is sampling everyday, other sites
sampling less frequently may measure exceedances of the 24-hour
standard. Except for the first observed exceedance, all exceedances at
all sites are adjusted for incompleteness of sampling. If a site which
is sampling less than everyday observes an exceedance, then the
exceedance will be adjusted for incompleteness of sampling. However,
if the designated worst site observes a higher value on the same day,
then designated worst site will continue to be used to assess
attainment/nonattainment, regardless of the estimated number of
exceedances at the other sites. If the designated worst site records a
lower value on the same exceedance day, then the site recording a
higher value must go to everyday sampling to avoid adjustment for
incomplete sampling. The designated worst site would be expected to
continue its current sampling schedule until the time of the next
annual network review. At this point, one or more of these sites could
be identified for accelerated sampling.
10. Long-term monitoring piar>: How are exceedances interpreted at
"sTtes which are sampling less than the designated worst site?
As described above, the designated worst site will be used to assess
attainment/nonattainment if it observes higher concentrations on days
with exceedances at other sites.
11. Long-term monitoring plan: How is the first exceedance interpreted?
If the first exceedance occurs in the long-term plan (even if
another site in the monitoring area previously observed an exceedance
and increased its sampling to everyday) then an increase to everyday
sampling must be initiated. This is not necessary if the designated
worst site previously recorded an exceedance and currently records a
higher concentration on the same sampling day. If multiple sites
record an exceedance on this day, then only one site is required to
accelerate its sampling. The acceleration to everyday sampling will
avoid the adjustment for incompleteness of sampling in the exceedance
calculations for this first exceedance and help to determine if this
site should be the new designated worst site. Since the monitoring is
in the long-term phase, however, the evaluation of revised sampling
frequencies would take place during the annual network review and the
change in sampling frequency can commence at the beginning of the
following calendar year.
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Everyday sampling must be followed for 1 year, even if it is
determined that the selective sampling requirements do not require it
on the basis of the estimated design value.
12. If an area designated Group II or Group III observed its first
exceedance and wants that exceedancte to count as one in future
^xceedance calculations, does it have to initiate everyday sampling
in its first year of monitoring?
If the exceedanee occurred after promulgation, the area must satisfy
the Part 58.13 requirements for 4 calendar quarters of everyday
sampling following the first observed exceedance, in order to permit
the first exceedance to count as one in the exceedance calculations.
If the first exceedance at the site occurred prior to the promulgation
date, however, the site will be exempt from the additional everyday
sampling requirement. This is consistent with the policy used for
the area grouping process, where the first observed exceedance was
not adjusted for incompleteness of sampling at all sites.
If an area observes its first exceedance after the promulgation and
does not initiate the required everyday sampling, the exceedance
shall be adjusted for incompleteness of sampling. On this basis,
the site could fail the attainment test for the 24-hour standard.
If this site is in a Group III area, then EPA could call for a SIP
revision.
13. Is there a problem with having more than one monitor in a given
source area?
In single (or multiple) source situations, multiple high concentration
areas are likely. The number of monitors needed to cover all such
areas, and to provide sufficient spatial resolution within each
area, will depend on professional judgment and the available resources.
It should be recognized that difference in sample frequency (and
subsequent adjustment for incomplete sampling) may complete the
attainment/nonattainment status. Thus, in a case where more than
one site is placed in areas of expected maximum concentration,
either all sites should be sampling at the accelerated schedule, or
only one site should be part of the SLAMS with the others designated
special purpose monitors. If it is determined that each such site
is affected by different emissions or meteorology, then it may be
appropriate to designate each site as the maximum concentration site
in its own monitoring area.
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MONITORING DEADLINES
1. How do the monitoring deadlines relate to the attainment dates for
Group II areas?
Technically, the SLAMS networks do not have to be in place and
operational unti1 August 1, 1988. Therefore these areas are not
required to have any PMio data prior to this point. On this basis,
3 years of PMio data might not be available until July 31, 1991.
According to the SIP guideline, however, Group II areas are required
to determine if they are attainment or nonattainment by September 1,
1990 (37 months from the effective date of the regulation). Thus,
if a Group II area wants to be considered to be in attainment with
the standards, it must have its worst monitoring site to be producing
data by August 1, 1987. This provides 3 years for data collection
and 1 month for analysis. If monitoring was not initiated by August 1,
then 3 years of data will not be available by the required date. In
order for attainment to be demonstrated in this situation, a Regional
Administrator waiver for not satisfying the minimum data completeness
requirements must be granted (in accordance with the EPA Guideline
on Exceptions to Data Requirements for Determining Attainment of the
Particulate Matter Standards, April 1987) or dispersion modeling
must be performed. Otherwise, the area cannot be considered to be
in attainment with the standards.
Since nonattainment can be determined in less than 3 years, this
determination can be made at any time. PMio data collected prior to
promulgation shall be used to judge nonattainment with the standards.
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DEVELOPMENT PLANS/SIP PROCESSING
1. What is EPA's timeframe for SIP processing?
The EPA's policy is to publish a notice of proposed rulemaking within
7 months after a complete SIP or SIP revision is submitted. A notice
of final rulemaking would be published within 7 more months.
2. What is the outside attainment date?
Three years from SIP approval, unless a 2-year extension is justified.
We know that some areas may not be able to attain in that timeframe.
See question 7 on page 42.
3. How does a State set a compliance date when EPA approval date is
indeterminant?
Source compliance dates must be within 3 years of SIP approval. The
SIP could be approved within 14 months of its submission to EPA.
The time between State adoption of the SIP and EPA approval may be
reduced by parallel processing during the period of public review
and comment.
4. Can States expect feedback from EPA when they complete the milestones
in their development plans (i.e.. emission inventory draft control
strategies, etc.)"? : '. '•
The States are encouraged to work closely with their EPA Regional
Offices and submit drafts of emission inventories, emission factors,
model protocol, regulations for review. The EPA will give as much
feedback as time permits; the State is not to stop progress while
waiting for comments, however.
5. Do all SIP actions require a public hearing?
Yes, since each State must revise their SIP for Group III areas
and since the Group II commitments will be incorporated into the
SIP, all such revisions and additions should be included in a public
hearing.
6. (a) Why is August 1990 the deadline for PMio determinations of
attainment status?
The EPA is allowing up to 37 months to determine attainment status.
(b) Does a State have to wait 37 months before it declares an area
to be nonattainment if a violation of the PMm standard is observed?
No, see the SIP guideline, section 7.3.2.(3).
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7. What is the attainment date for Group II areas which observe violations?
Three years from approval of the committal SIP.
8. What demonstration of need is necessary for a 2-year extension of the
attainment deadline"?
See SIP guideline supplement, section 7.3.6.
9. Is it possible to request a 2-year extension after you submit the
initial SIP ^Including committal SIP's) to EPA?
No, see SIP guideline supplement, section 7.3.6.
10. Uhose resources will be used to analyze the ambient air sampling
filters?
The State's resources which are supplemented by EPA grant funds.
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ATTAINMENT DEMONSTRATION
1. Why must an area demonstrate attainment based upon allowable
emissions'?
A SIP is to protect the NAAQS at all times. Therefore, it is
necessary to demonstrate that the SIP will protect the NAAQS when
sources are emitting PMig at the maximum rates allowed. See SIP
guideline, section 7.4.1.
2. What type of demonstration is required for a Group II or III area?
See SIP guideline, section 7.3.2. No demonstration is required for
Group III areas.
3. If a facility emits more than 50 tpy, must it be considered in the plan?
See SIP guideline supplement, section 5.
4. Are sul fates fair game for controls?
Yes, if a State needs to reduce the precursors of sul fate formation
in the atmosphere, they have that prerogative. The State must work
with EPA to develop a procedure for projecting the ambient effect of
this control strategy.
5. How many years are required in extending projections?
The SIP's should take into account the effect on PM^o emissions of future
growth for 10 to 20 years into the future [see 40 CFR 51.110(h) and
00(4)].
6. Will EPA consider a several year control strategy for secondary
aerosol problems'?
If an area cannot attain the PM^o standards because of secondary
particle formation, the area may be able to justify an extension
under section 110(e). In addition, EPA is evaluating a policy on
long-term nonattainment.
Maximum allowable emission modeling will never show attainment and
"does not reflect reality and it may be impossible to adopt control
measures. Actual emissions are significantly less than maximum
TTlowable emissions. (Example: natural gas versus oil in power
plants.)
If boilers actually emit 0.001 Ib PMio/mmBtu but are allowed to emit
0.3 Ib PMio/mroBtu by permit, the SIP must be designed to protect the NAAQS
when boilers are emitting 0.3 Ib/mmBtu. If boilers do not need to
emit 0.3 Ib/mmBtu allowable in the future, then the limit should be
lowered. See SIP guideline supplement 7.4.1.
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8. Comment: In some States, there are a large number of sources with old
permits. It is not reasonable to use allowable limits.
See section 7.4.1. A screening model should be used to identify
significant point sources for which allowable emission limits must be
used. Areas sources do not really have allowable emission limits that
are above the controlled level.
9. Are seasonal controls legal, e.g., burn natural gas in winter and
coal in summer?
Generally, control measures must be applied year-round (especially
those applicable to combustion sources) to continually meet the
applicable emission limit. However, it may be necessary for a State
to develop separate control strategies to solve different seasonal
PMio problems. In such cases, the seasonal control strategies must
have seasonally enforceable emission limits and separate demonstrations
of attainment of the 24-hour NAAQS. The abilities of the seasonal
control strategies to attain the annual PMio NAAQS must also be
demonstrated using the highest seasonal allowable emission rates or
an average annual rate (see SIP guideline supplement, section 7.4.1).
10. What are the general SIP requirements for Group III areas?
See SIP guideline, section 7.3 and supplement, section 7.4.3.
11. How does one define the boundary of a.Group I or II area?
See SIP guideline, section 2.5.
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TRANSITION POLICY
1. Uhen can redesignation of TSP nonattainment area request be submitted?
States can request area redesignation from TSP nonattainment to
attainment if the area has sufficient data to make the demonstration
under EPA's previous policy. Otherwise, a State can request redesig-
nation to unclassifiable when it submits its PM^o SIP for the area
(see 52 FR 24682).
2. Will EPA permit a State to relax its emissions from reasonably
Iwailable control technology (RACT) to actual emission levels?
Yes, consistent with SIP guideline supplement, section 7.5.
3. Uhat is to be done about States with TSP SIP's which are disapproved
under section 110?
The State should focus on developing approvable PMio SIP's. However,
it is likely that the elements of the TSP SIP that were disapproved
will be needed for the PMio SIP.
4. To what extent should enforcement actions during the transition period
be focused on for control of PMi"o?'
See SIP guideline supplement, section 7.5.
5. What happens to SIP's in process?
See SIP guideline supplement, section 7.5.
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STACK TEST
1. Does EPA plan to promulgate an emission test method. for
What is EPA' s plan for test methods for condensibles and secondary
participate?
An advance notice of proposed rulemaking for the reference method was
published April 8, 1988 (see 53 FR 11683).
3. The EPA uses a modified Method 5 to test wood stoves. It collects
the back half of the train (condensibles). Why can't this be used
for PMio condensibles?
The modified Method 5 is designed to measure volatile materials
generated from combustion of wood. It does not necessarily represent
PM at atmospheric conditions.
4. How can the exhaust gas recirculation (EGR) probe be placed in the
stack—too big for the port?
The EGR probe requires a minimum 4-inch port.
5. If you do not have good PMio emission factors, can a State use a
Method 5 emission test and assume the emissions are all PMio?
The EPA would suggest following the test procedure described in
Appendix C of the SIP guideline to determine the PMio portion of the
emission gas stream. Use of Method 5 emission test method will provide
an overestimate of the emissions.
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EMISSION LIMITS/CONTROL STRATEGIES
1. How does a State quantify the emissions during startup/shutdown/
malfunctions?
The point of the provisions for addressing startups, etc., was not
that the State must quantify emissions from these periods, rather
that the State regulations be designed as discussed in section 7.4.
2. If emissions are mostly (e.g.. 70 percent) PMio, do the the PM
limits have to be revised to be PMio limits?
No, not if the SIP can attain the NAAQS without doing so.
3. Will a State in the next 5 years have PMio, TSP, and visible emission
(V.E.) limits for a source?
V.E. limits are required by 40 CFR 51.212(b), and TSP or PM10 limits
will be necessary to restrict the mass emission rate from a source.
The combination of these emission limits must protect the PMio NAAQS
and restrict consumption of TSP increments under the program to prevent
significant deterioration.
4. What is the most effective way of cleaning streets? The Midwest
Research Institute report was inconclusive!
The most effective way is to prevent material from depositing on
street surfaces. Additional guidance is forthcoming in a project
being conducted by EPA.
5. Does EPA have a list of RACT that can be used to evaluate the control
strategies?
No. However, EPA can help in providing references on available control
measures.
6. How current is the MRI report on control of fugitive emissions?
The report includes references through spring, 1984. Some update will
be provided through the above mentioned EPA fugitive dust project.
7. The EPA needs a clearinghouse on control strategies.
The EPA has a clearinghouse on control techniques and will act as a
focal point for control strategies.
8. When must the State start enforcing the new emission limits? .
As soon as possible so attainment can be as expeditious as possible.
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MISCELLANEOUS ISSUES
1. How do we handle violations of the PMio standards caused by emissions
from a foreign country?
These situations are investigated and resolved case-by-case.
2. What is the interrelationship between air toxic and PMio controls?
See supplement to SIP guideline, section 9. In general, PMio control
strategies should attempt to maximize control of air toxics.
3. If a violation in a Group II or III area is modeled (e.g., as part
of an NSR analysis), does the area have to develop a full demonstration
SIP?
SIP revisions have not been required for Group II and III areas because
EPA does not have evidence that the NAAQS is being violated or that
the SIP is inadequate. If modeling for any reason shows that the SIP
is inadequate to protect the PMio NAAQS, a SIP revision and demonstration
of attainment is required.
4. The EPA should correlate opacity limits for roadways with emission
reductions needed for high, medium, and low silt loadings.
The EPA Region Vis attempting to develop this in studies in Ohio
and Indiana.
5. Is there a general requirement that Group III areas must meet RACT?
No, it is being assumed that the existing emission limits are adequate
until EPA receives evidence to the contrary.
6. Does EPA expect more sources to be controlled as a result of PMio
implementation? Will there be an improvement in air quality?
Most of the areas not meeting the PMio NAAQS were also not meeting the
TSP NAAQS. Therefore, sources must be controlled and the ambient PM
concentration reduced to attain the PMio NAAQS.
7. What is an adequate demonstration for maintenance?
The SIP should show that the standard will be maintained for the next
10 to 20 years. [51.42, 51.110(h), 51.110(K) (4)] .
8. Are Part D transportation control measures (TCM's) applicable to
section 110 requirements'?
TCM's implemented to attain the TSP NAAQS must continue to be enforced
until it is demonstrated that they are not necessary to attain and
maintain PMio NAAQS. If TCM's have not been adopted, they are optional.
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Does EPA have discretion to revise the SIP once the State submits it?
The EPA cannot and will not revise a SIP as long as it is approvable
and will attain the NAAQS. If the State fails to submit an approvable
SIP, EPA may have to promulgate a Federal plan.
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INTERIM RURAL FUGITIVE DUST POLICY
1. If an area is impacted by seasonal fugitive dust and Is not attaining
the PMio standard in other seasons due to other sources, does the
source have to reduce emissions from those other sources?
Yes, see SIP guideline supplement section 7.4.
2. Is EPA developing a rural fugitive dust (RFD) policy?
Yes, the policy was proposed in 52 FR 24716. In the interim, the
policy for TSP is being used. See SIP guideline, section 7.11. An area
designated under the interim policy must comply with the final policy
if an when it is revised.
3. If a Group I area meets the definition of a rural fugitive dust area
(RFDA). why is it in Group H
Areas are only considered RFDA's if there is evidence that RFD is the
primary cause of violations and the area has low population and little
impact from industrial sources or wood smoke.
4. If the violations are caused by wood burning, is that rural fugitive
dust?
No, see the answer to question 3.
5. If offsets are required in an RFDA. do they have to be fugitive or
stack emissions? '
Either.
6. How is wood smoke considered when determining if an area is RFDA?
Currently, it is being addressed on a case-by-case basis. It will
be addressed in the final RFD policy.
7. What is normal background?
The average PMio concentration measured at a remote regional scale
monitoring site. See Appendix D of the SIP guideline.
8. Uhere are the rural fugitive dust areas presently designated under
WnT
New Mexico, Kansas, and Nebraska.
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9. What are the requirements for RFDA?
Those areas that meet the requirements of an RFD area are placed in
Group III and are subject to Group III SIP requirements.
10. Can additional areas be classified as RFDA's and if so when?
Yes, if a State requests at any time that the area be classified as
RFDA and can show that it meets the requirements for an RFDA. The
area must also comply with the final policy if and when it is revised.
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ENFORCEMENT OF PMio RULES
1. Can you use V.E. regulations to control emissions from storage piles?
Yes, to enforce control measures such as wet suppression or wind
screens.
2. Does a State have to enforce new emission limits before the attainment
date?
Yes, see SIP guideline supplement section 7.4.
3. Can EPA provide guidance on enforcement of nontraditional controls in
the SIP's?
Additional guidance on fugitive dust controls is being prepared by
EPA. Compliance methodology must be specified in the SIP's.
4. What is required in a Group III area if the SIP is unenforceable?
If EPA knows a PM regulation is unenforceable, the State will be
required to revise the regulation to make it enforceable.
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SIP DISAPPROVAL/SANCTION POLICY
1. Can withheld State Grant Funds be used to pay EPA salaries or contractors?
Withheld funds can be used to pay for contractor (not EPA salaries) to
prepare El, modeling, etc.
2. How can EPA use section 176(b) as a sanction if Part D no longer applies?
Section 176(b) states that "[if the State] is not implementing any
requirement . . . under section 110 . . . the Administrator shall not
make any grants under this Act."
3. Hill sanctions result from only a State failure to submit a plan or
wTll EPA sanction a State for missing development plan milestones'?"
What authority does EPA have to impose sanctions before 9 months?
The EPA's policy on failure to attain is being developed. However,
EPA does not intend to impose sanctions for failing to meet a milestone
in a schedule to develop and implement a SIP, but the State's record
in meeting milestones will be a factor in determining when sanctions
will be imposed.
4. Can EPA use sewage facility sanctions under section 316 of the Act?
.The EPA can condition or withhold grants for construction of new
treatment works if new sewage treatment capacity would be created •
that may cause or contribute to an increase in PMio emissions in
excess of those planned for the SIP. However, under a separate policy,
EPA has limited construction grants only to address existing needs.
Thus, these sanctions have little value.
5. If there is a State/local consolidated grant and the local submits a
proper SIP but the State is recalcitrant, can the sanctions be applied
against the State part and not the local part of this grant?
If Federal grant funds are given directly to the local agency, this
will continue if the agency is meeting EPA requirements. Sanctions on
funds that are passed through the State agency depend on regulations
between the State and local agency.
6.
uciwccu CMC oiaie aiiu iui~ai aycut^y.
Are specific funds being set aside in the grants for PMio SIP
development?
The EPA identified $2 million of its section 105 grant funds in 1986
and 1987 for use in development of PMio SIP's. In 1988, between $1
million and $2 million were again designated for use in preparing PM
.SIP's.
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7. If PMio SIP Is nonapprovable and cannot demonstrate attainment in
3 to 5 years, what do they do? Do sanctions apply only for failure
to submit a SIP?
The EPA's policy on failure to attain is being developed.
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EMERGENCY EPISODE PLANS
1. Regarding priority classifications, is it true that we do not look at
annual geometric mean for PMio? Are classifications revised from
those of TSP?
The EPA has not revised the criteria for classification of Regions
for emergency episode plans with regard to particulate matter under
40 CFR 51.150. States would be wise to reevaluate their priority
classifications as required by 40 CFR 51.153 to determine if Group I
and Group II areas for PMio should have emergency episode plans.
2. Can you use emergency episode strategy as part of your control
strategy?
No, the emergency episode strategy is designed to achieve extra
temporary emission reductions beyond those needed under normal
meteorological conditions.
3. What emergency powers do States have to shut down industries during
harmful episodes"?
The State, in adopting an emergency episode plan, is giving the State
agency authority to order emission reductions for the purpose of
avoiding PM concentrations at significant harnr levels.
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NEW SOURCE REVIEW
1. Will the full TSP increment be available after a TSP nonattainment
area is redesignated to unclasslfiable?
The applicable baseline date would be established on the date of the
first complete prevention of significant deterioration (PSD) application
(for participate matter emissions) which is submitted on or after
the date when the area is designated as unclassifiable for TSP. The
full increment may not be available, however, in cases where actual
emission increases in the baseline area have occurred from major
stationary sources on which construction commenced after January 6,
1975. Conversely, expansion of the allowable TSP increment may have
to be taken into account if actual emission reductions (from major
sources) occur prior to the baseline date. Actual emission decreases
involving construction at a major stationary source occurring since
January 6, 1975 will expand the increment if such decreases are
included in a federally enforceable permit or SIP.
2. What is the rationale for maintaining the section 107 area designations
for TSP when there are no longer TSP NAAQS?
The TSP area designations have been retained because of their direct
relationship to the applicability of the statutory Class II (and III)
increments for particulate matter. . (The EPA intends to keep the
existing TSP increments in force until States have adopted new PMio
increments in their SIP's.) Under section 162(b) of the Act, areas
designated as attainment or unclassifiable are defined as Class II
areas (unless otherwise established as Class I areas or redesignated
under section 164). The EPA believes that this provision applies on
a pollutant basis so that the Class II TSP increments under
section 163(b)(2) apply only in Class II TSP areas, i.e., TSP
attainment or unclassifiable areas.
It should be noted that EPA intends to allow States to redesignate
any existing TSP nonattainment areas to unclassifiable once a revised
implementation plan providing for adequate protection of the
NAAQS is approved by EPA.
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3. Why are there increments in an area that Is nonattainment for
The reason that EPA has required a PSD increment analysis in an area
that is "nonattainment" for .PMio is because the existing increments
for particulate matter, defined under section 163 of the Act, are based
on ambient concentrations of TSP. The significance of this is that
EPA, in accordance with its interpretation of applicable portions of the
Act, has ruled that the Class II and III TSP increments must continue
to apply in areas designated as either attainment or unclassifiable
for TSP. As explained in the previous response (to Question 2), the
Class II (TSP) increments are to apply in areas designated as attainment
or unclassifiable for TSP.
While the TSP increments will continue to apply for several years
(approximately September 1991), PSD sources which would not cause
violations of the TSP increments, but would cause or contribute to
violations of the PMio NAAQS, would not be allowed to proceed with their
construction plans, unless the appropriate PMio emission offsets were
acquired and approved by the permit granting authority.
4. Uhat triggers new source review (NSR) — TSP or PMio?
Either TSP or PMio may trigger NSR. Generally speaking, however, it
would be more accurate to think of NSR being triggered by either .
particulate matter emissions or PMio emissions. TSP and PMio are
ambient indicators of the pollutant particulate matter. .NSR require-
ments are generally triggered by significant amounts of a pollutant
which potentially could be emitted by a new or modified source. In
the case of particulate matter, significant amounts of either particulate
matter emissions or PMio emissions, or both, would require that certain
NSR requirements must be addressed. For example, if a major source
would emit significant amounts of particulate matter emissions, best
available control technology (BACT) and an increment analysis for TSP
would be required. If, however, particulate matter emissions would
not be emitted in significant amounts, but PMio emissions would (as in
the case of a source that could take credit for contemporaneous
emission decreases of particulate matter emissions but still finds
that its potential emissions of PMio are significant), then the source
would be required to apply BACT and comply with the PMio NAAQS. If both
forms of particulate matter would be emitted in significant amounts,
then, of course, all of the above mentioned requirements would apply.
5. If a PMio NAAQS violation is found in a Group III area, would a
PSD review be required for
Yes, since the PSD requirements for PMio aPP^y everywhere (from a
geographic applicability standpoint), PSD review would be required
regardless of the PMio grouping or air quality status relative to the
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NAAQS. In .such instances, where a proposed major source or major
modification would cause or contribute to a PMio NAAQS violation, the
PSD requirements would have to be augmented by an emission offset
requirement under procedures approved in accordance with 40 CFR 51.166(b)
It should also be noted that, in the event a PMio NAAQS exceedance is
found in a Group III area, EPA intends to require a SIP revision which
must meet the criteria for a Group I area in order to be approvable.
Such revision would have to provide for increased ambient monitoring
activities and a control strategy which provides for attainment of the
PMio NAAQS within 3 years of plan approval. As part of the control
strategy, a State may find it necessary to establish more stringent
NSR requirements than currently exist for such areas. For example, a
State may find it appropriate to establish a requirement that new
major sources in the area meet the lowest achievable emission rates
for their PMig emissions. Similarly, other Part D-based requirements
could be considered as
6. What triggers offsets for PMiQ?
A requirement that a major new or modified source must obtain
emission offsets is triggered by a preconstruction review finding that
such new or modified sources would cause or contribute to a violation
of the PMio NAAQS. States may develop an emission offset program in
accordance with the newly amended requirements under 40. CFR 51.165(b)
for implementing PMio offsets. The EPA has already ruled that the
nonattainment area offset requirements based on Part D of the Act do
not apply to
7. How are PMiQ precursors taken into account for emission offsetting
purposes?
The EPA presently has no policy prescribing allowances for PMio precursors
for emission offsetting purposes. No models are yet available to predict
ground level PMio concentrations that would result from precursors.
As mentioned in the .PMig preamble to the July 1, 1987 Federal Register
notice (see 52 FR 24707), EPA will review on a case-by-case basis any
State requests to incorporate in the SIP a provision allowing precursor
offsets for PMio where a site specific model may be proposed for such
implementation.
8. When does a PMiQ source have to obtain emission offsets which provide
a net air quality benefit rather than just compensate for its own adverse
impact?
This issue was discussed in the July 1, 1987 Federal Register notice
(see 52 FR 24684 footnote 14 and discussion on 52 FR 24699, column 1).
Basically, a net air quality benefit is required when a proposed major
source or major modification would cause or contribute to a violation
of the PMio NAAQS (or any other NAAQS) in an area lacking an approved
attainment strategy for the particular pollutant.
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In the absence of an attainment demonstration, no downward trend in
overall emissions has been established; therefore, the proposed source
must provide some air quality improvement to help remedy the existing
ambient problems. Once a downward trend .in emissions is established
via an approved attainment demonstration, a new source need only
compensate for its adverse emissions so as not to interfere with the
attainment demonstration.
9. What happens if a State does not have an approved NSR SIP in a TSP
nonattainment area after the construction ban has been lifted?
• The EPA considers the provisions of the interpretative rule (Offset Rule)
under 40 CFR Part 51, Appendix S, to apply in the absence of a construction
ban where a State does not have an approved NSR SIP. Permits issued
by States in accordance with the Offset Rule are considered to be
federally enforceable by EPA.
10. If a State does not have a PSD program for PMio, why doesn't EPA assume
such responsibility?
The EPA assumes immediate responsibility for a PSD program for
only in those cases where EPA also has PSD responsibility (i.e., where
the SIP has been disapproved with respect to PSD). Where States have
an approved PSD program under their SIP, the -Act clearly provides
9 months from the promulgation date of regulatory amendments before a
revised plan must be submitted to EPA for approval. This statutory
provision is reflected in the PSD requirements for SIP's under 40 CFR
51.166(a)(6)(i). The EPA has no authority under the Act to promulgate
PSD regulations until a State fails to submit its revised SIP in a
timely manner.
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