FRM network, and that are seeing growing use in the PM10 and PM10-2.5
networks.  Finally, the use of a low-volume sampler is consistent with
the comments and recommendations from CASAC and members of CASAC's AAMM
Subcommittee (Henderson 2007a, Henderson 2008a, Russell 2008b).

We proposed XRF as the FRM analysis method because we believe that it
has several advantages which make it a desirable analysis method.  XRF
does not require sample preparation or extraction with acids prior to
analysis.  It is a non-destructive method; therefore, the sample is not
destroyed during analysis and can be archived for future re-analysis if
needed.  XRF analysis is a cost-effective approach that could be used to
simultaneously analyze for many additional metals (e.g., arsenic,
antimony, and iron) which may be useful in source apportionment.  XRF is
also the method used for the urban PM2.5 Chemical Speciation Network
(required under Appendix D to 40 CFR part 58) and for the Interagency
Monitoring of Protected Visual Environments (IMPROVE) rural visibility
monitoring program in Class I visibility areas, and is being considered
by EPA for a role in PM10-2.5 coarse speciation monitoring.  Based on
data from the PM2.5 speciation monitoring program, the XRF analysis
method when coupled with the low-volume PM10c sampler, is expected to
have an adequate method detection limit (MDL, the lowest quantity of a
substance that can be distinguished from the absence of that substance)
and meet the measurement uncertainty goals for precision and bias as
determined through the data quality objective (DQO) analysis (Papp,
2008), as explained later in this preamble.

b.	Comments on the proposed Pb-PM10 FRM

	We received a number of comments on the proposed FRM for Pb-PM10.  In
addition, the CASAC AAMM Subcommittee provided a peer review of the
proposed Pb-PM10 FRM.  The following paragraphs describe the comments
received and our responses.

The CASAC AAMM Subcommittee agreed with our proposed use of the PM10C
sampler. Other comments on our proposed use of the low-volume PM10C
sampler for the Pb-PM10 FRM were in support of the PM10C as an
appropriate sampler for the FRM.  We are promulgating the Pb-PM10 FRM
based on the use of the low-volume PM10C sampler.

We also received comments on our proposed use of XRF as the analysis
method for the Pb-PM10 FRM, including comments from CASAC’s AAMM
Subcommittee during the peer review of the proposed FRM.  Several
commenters agreed with our proposed use of XRF as the analysis method,
citing several of the advantages we identified in the preamble to the
proposed rule.  However, several other commenters suggested that
Inductively-Coupled Plasma-Mass Spectrometry (ICP-MS) would be a more
appropriate analysis method for the FRM.

The AAMM Subcommittee and other commenters raised concerns with the
potential for measurement bias due to non-uniform filter loadings.  They
noted that the analysis beam of the XRF analyzer does not cover the
entire filter collection area; therefore, it is possible for the
measurement to be biased if the Pb particles deposit more (or less) on
the edge of the filter as compared to the center of the filter.  To
address these concerns, EPA’s Office of Research and Development (ORD)
conducted qualitative and quantitative tests of filter deposits
generated in the laboratory under controlled conditions.  Although test
results confirmed prior reports of formation of a deposition band at the
circumference of the PM10C filters, this band comprises only 5 percent
of the filter’s deposition area.  Quantitative analysis of collected
calibration aerosols in the 0.035 micrometer to 12.5 micrometer size
range revealed that use of either a centrally located 10 mm or 20 mm
spot size can accurately represent the filter’s mean mass
concentration within approximately 2 percent.  Similar results were
obtained using a PM2.5 FRM sampler and a “total particulate sampler”
(a PM2.5 sampler with the internal separator removed).  Based on these
results, it can be concluded that any non-uniformity of particle
deposition on PM10C filters will represent a small fraction of the
overall uncertainty in ambient Pb concentration measurement.  As such,
we believe the concerns associated with non-uniform filter loading are
sufficiently addressed to allow XRF as an appropriate analysis method
for the FRM.

The AAMM Subcommittee and other commenters suggested ICP-MS as an
alternative to the XRF analysis method.  Advantages identified with
ICP-MS included the analysis of the entire filter deposit and a higher
sensitivity (i.e., lower MDL.)  We agree that the ICP-MS analysis method
is also an appropriate method for the analysis of Pb.  However, ICP-MS
(and other analysis methods requiring the extraction of Pb prior to
analysis) also has potential bias due to uncertainty in the percentage
of total Pb that is extracted.  While this bias can be minimized by use
of very strong acids (i.e., hydrogen fluoride), many laboratories wish
to avoid these strong acids due to the damage they can do to the
analyzer and due to safety concerns.  In addition, ICP-MS is a
destructive method and samples can not be saved for further analysis.
We agree that the ICP-MS method is more sensitive than the XRF method.
However, the XRF method detection limit provides sufficient sensitivity
for use in determining compliance with the Pb NAAQS being promulgated
today.  As pointed out in our preamble to the proposed rule, we
estimated the method detection limit for XRF and ICP-MS coupled with
low-volume sampling to be 0.001 (g/m3 and 0.00006 (g/m3, respectively.
No commenters disagreed with these estimates.

	Several states requested approval for alternative analysis methods
because their laboratories are already equipped to perform those
analysis methods.  Our decision to use XRF as the FRM analysis method
does not prevent monitoring agencies from using alternative analysis
methods.  However, before these alternative analysis methods can be used
they must be approved as FEMs for the measurement of Pb-PM10.
Monitoring agencies can seek FEM approval for alternative analysis
methods by following the FEM requirements (40 CRF Part 53.33).  In
addition, we plan to approve (after conducting the necessary testing and
developing the necessary applications ourselves) FEMs for ICP-MS and
Graphite Furnace Atomic Absorption (GFAA) to support monitoring agencies
that prefer to use these analysis methods.

We also received comments on the specific details of the proposed XRF
analysis method. The AAMM Subcommittee and one other commenter raised
concerns about the lack of a thin-film XRF National Institute of
Standards and Technology (NIST)-traceable Pb standard.  NIST currently
offers Standard Reference Material (SRM) 2783, “Air Particulate on
Filter Media”, that are a polycarbonate filter that contain a
certified concentration for Pb equivalent to 0.013 ± 0.002 µg/m3.
Calibration materials for XRF are not destroyed during analysis;
therefore, the SRM should be stable over time and can be reused multiple
times if properly handled and protected.

The AAMM Subcommittee raised concerns regarding lot-specific laboratory
blanks, field blanks, and possible contamination of filters.  The
commenters suggested that the laboratory blanks (the results of Pb
analysis of “clean” filters that have not been used in a sampler)
that are used for XRF background measurement and correction be
lot-specific. The addition of lot-specific laboratory blanks will help
minimize contamination that may be due to new filter lots and the
analytical system. A few commenters suggested the addition of field
blanks in order to minimize the Pb contamination of filters in the
field.  Field blanks are filter blanks that are sent to the field and
are placed into the sampler for the sampling duration without ambient
air flow. We agree with the suggestions to make laboratory blanks
lot-specific and to add the collection of field blanks.  A comment to
add annual MDL determinations and filter-lot specific MDL determinations
was received.  We agree that the addition of annual MDL estimates and
lot-specific MDL determinations is an improvement to the proposed FRM
text.  In addition, several editorial comments were received that
related to modifying existing statements to add clarity and help to
ensure consistency across laboratories. We are making changes to the XRF
analysis method to address these editorial comments.

We received one comment related to the need for data quality objectives
(DQOs).   We agree with the commenter on the need for DQOs for the
Pb-PM10 FRM.  Since the time of proposal, we have completed the DQO
analysis to evaluate the acceptable measurement uncertainty for
precision and bias.  The DQO report is in the docket.  As part of that
process, the recommended goals for precision were defined as an upper 90
percent confidence limit for the coefficient of variation of 20 percent
and the goals for bias were defined as an upper 95 percent confidence
limit for the absolute bias of 15 percent.  We have reflected this in
our final regulation.

c.  Decision on Pb-PM10 FRM

We are finalizing the FRM for Pb-PM10 as proposed with the exception of
the following amendments and additions.  Changes to the XRF analysis
method are being made to address comments received during the public
comment period and peer review of the proposed Pb-PM10 FRM.  These
changes include a revision to the Pb-PM10 FRM text to include reference
to the SRM 2783 NIST-traceable calibration standard.  The FRM text was
modified to add a section that requires the collection of field blanks,
and clarify that the laboratory blanks used for background measurement
and correction shall be lot-specific.  We added the requirements for
annual MDL estimates and lot-specific MDL determinations.  Several minor
changes were made to address editorial comments received that related to
modifying existing statements to add clarity and help to ensure
consistency across laboratories.  Examples of these changes include the
addition of other commercial XRF instrumentation vendors; clarification
of the maximum filter loading for Pb analysis which is based on the
maximum mass loading (200 µg/m3) for a PM10C sampler; inclusion of
additional references for spectral processing methods; and clarification
that the FRM applies specifically to Pb.  A reference was included for
additional guidance if multi-elemental analysis is performed.  To ensure
consistency in reporting uncertainties for Pb by XRF across
laboratories, an equation to calculate uncertainties was added and
follows the same procedure used for XRF in the PM2.5 speciation program.
 Based on the DQO process, the FRM precision and bias requirements were
modified to reflect the measurement uncertainty goals of 20 percent and
15 percent, respectively.

FEM Requirements

We are finalizing changes to the FEM requirements for Pb.  These
requirements will apply for both Pb-TSP and Pb-PM10 methods.  This
section discusses the proposed changes to the FEM requirements, comments
received on the proposed changes, and the final FEM requirements being
promulgated with this action.

Proposed FEM Requirements

The current FEM requirements state that the ambient Pb concentration
range at which the FEM comparability testing must be conducted to be
valid is 0.5 to 4.0 (g/m3.  Currently there are few locations in the
United States where FEM testing can be conducted with assurance that the
ambient concentrations during the time of the testing would exceed 0.5
(g/m3.  In addition, the Agency proposed to lower the Pb NAAQS level to
between 0.10 and 0.30 µg/m3.  Consistent with this proposed revision,
we also proposed to revise the Pb concentration requirements for
candidate FEM testing to a range of 30 percent of the revised level to
250 percent of the revised level in µg/m3.  The requirements were
changed from actual concentration values to percentages of the NAAQS
level to allow the FEM requirements to remain appropriate if subsequent
changes to NAAQS levels occur during future NAAQS reviews.

The current FEM does not have a requirement for a maximum MDL.  In order
to ensure that candidate analytical methods have adequate sensitivity or
MDLs, we proposed adding a requirement for testing of a candidate FEM.
The applicant must demonstrate that the MDL of the method is less than 1
percent of the level of Pb NAAQS.

We proposed to modify the FEM requirements for audit samples.  Audit
samples are the known concentration or reference samples provided by EPA
and used to verify the accuracy with which a laboratory conducts the FRM
analytical procedure before it may be compared to the candidate FEM.
The current requirements are that audit samples be analyzed at levels
that are equal to 100, 300, and 750 µg per spiked filter strip
(equivalent to 0.5, 1.5, and 3.75 µg/m3 of sampled air).  We proposed
to revise the levels of the audit concentrations to percentages (30
percent, 100 percent and 250 percent) of the level of the Pb NAAQS to
provide for reduced audit concentrations that are more appropriate for a
reduced level of the revised NAAQS.

The existing FEM requirements are based on the high-volume TSP sampler,
and as such, refer to ¾-inch x 8-inch glass fiber strips.  In order to
also accommodate the use of low-volume sample filters, we proposed to
add references to 46.2 mm filters where appropriate.  For FEM candidates
that differ only from the FRM with respect to the analysis method for
Pb, pairs of these filters will be collected by a pair of FRM samplers.

b.  Comments

We received few comments on the proposed amendments to the FEM
requirements for Pb.  One commenter suggested that the proposed MDL
requirement, 1 percent of the NAAQS, was overly stringent, and that an
MDL of 5 percent would be sufficient. Another commenter suggested that
an MDL at 10 percent would be more achievable.  After reviewing these
comments, we have reconsidered the requirement for the MDL to be 1
percent of the NAAQS or less and now believe that the requirement may be
unduly restrictive.  The MDL represents an estimate of the lowest Pb
concentration that can be reliably distinguished from a blank.  The
concept of the “limit of quantitation” (LOQ), the level at which the
we can reasonably tell the difference between two different values, is
often used to determine the concentration at which we have confidence in
the accuracy of the measurement.  The LOQ is usually estimated at 5 to
10 times the MDL.  At a MDL of 5 percent (i.e., 0.0075 µg/m3), the
maximum LOQ would still be less than one half of the NAAQS (i.e., 0.075
µg/m3).  We believe this is adequate for the purposes of determination
of compliance with the NAAQS.  The three most commonly used Pb-PM10
analysis methods (XRF, ICP-MS, and GFAA) all have estimated method
detection limits below 5 percent of the revised Pb NAAQS.  We note
however, that for areas where concentrations may frequently be well
below the NAAQS such as at nonsource-oriented sites it may be desirable
to use a FEM with a more sensitive analysis method (such as ICP-MS) to
assure fewer non-detect measurements and to provide better accuracy at
concentrations well below the NAAQS.

We received two comments supporting the development and consideration of
the use of continuous Pb monitors. We agree that the FEM testing
requirements should include language regarding FEM testing and approval
of continuous or semi-continuous monitors.

c.  Decisions on FEM Requirements

We are finalizing the FEM requirements for Pb as proposed except for the
addition of language to include FEM testing and approval of continuous
or semi-continuous monitors.

4.  Quality Assurance Requirements

	We are finalizing changes to the quality assurance (QA) requirements
for Pb.  These requirements will apply for both Pb-TSP and Pb-PM10
measurements.  This section discusses the proposed changes to the QA
requirements, comments received on the proposed changes, and the final
QA requirements being promulgated with this action.

a.  Proposed Changes

We proposed modifications to the quality assurance (QA) requirements for
Pb in 40 CFR part 58 Appendix A paragraph 3.3.4 in order to accommodate
Pb-PM10 monitoring.  In addition, we proposed to consolidate several
existing requirements for PM samplers (TSP and PM10 samplers) into
paragraph 3.3.4 to clarify that these requirements also apply to Pb-TSP
and Pb-PM10 samplers.  The following paragraphs detail the QA
requirements we proposed to amend.

The collocation requirement for all TSP samplers (15 percent of a
primary quality assurance originations sites at a 1 in 12 day sampling
frequency, paragraph 3.3.1) applies to TSP samplers used for Pb-TSP
monitoring.  These requirements are the same for PM10 (paragraph 3.3.1);
thus, no changes are needed to accommodate low-volume Pb-PM10 samplers.
However, to clarify that this requirement applies to Pb-PM10 monitoring,
in addition to mass measurements for PM10, we proposed to add a
reference to this requirement in paragraph 3.3.4.  The current
requirement for selecting the collocated site requires that the site be
selected from the sites having annual mean concentrations among the
highest 25 percent of the annual mean concentration for all sites in the
network.

 The sampler flow rate verifications requirement (paragraph 3.3.2) for
low-volume PM10 and for TSP are at different intervals.  To clarify that
this requirement also applies to Pb monitoring (in addition to sample
collection for TSP and PM10 mass measurements) we proposed to add a
reference to this requirement in paragraph 3.3.4.

Paragraph <IP_ADDRESS> has an error in the text that suggests an annual flow
rate audit for Pb, but then includes reference in the text to
semi-annual audits.  The correct flow rate audit frequency is
semi-annual.  We proposed to correct this error.  We also proposed to
change the references to the Pb FRM to include the proposed Pb-PM10 FRM.

Paragraph <IP_ADDRESS> discusses the audit procedures for the Pb analysis
method.  This section assumes the use of a high-volume TSP sampler, and
we proposed edits to account for the proposed Pb-PM10 FRM.

We proposed to require one audit at one site within each primary quality
assurance organization (PQAO) once per year.  We also proposed that, for
each quarter, one filter of a collocated sample filter pair from one
site within each PQAO be sent to an independent laboratory for analysis,
for a total of 5 audits per year.  The independent measurement on one
filter from each pair would be compared to the monitoring agency’s
routine laboratory’s measurement on the other filter of the pair, to
allow estimation of any bias in the routine laboratory’s measurements.

b. Comments

	We received one comment on the proposed QA requirements specifically
addressing the overall sampling and analysis bias.  The commenter was
concerned that the proposal to implement one independent performance
evaluation audit (similar to the PM2.5 Performance Evaluation Program
(PEP)) and then augment that sample with four samples from collocated
precision site would be inadequate.  The commenter suggested that in
order for the audit program to be successful it would require the same
independent laboratory be used by all monitoring agencies across the
country.

We believe it is important to have a measurement of the bias of the
overall method for Pb (including both sampling and analysis aspects).
We proposed five audits per PQAO per year (one independent audit and
four collocated samples all analyzed at an independent lab).  This
proposal was based on data evaluations of PM2.5 bias information, and
the assumption that no PQAO would have more than 5 Pb sites.  However,
we now recognize that some PQAO are likely to have more than 5 sites,
and as part of our consideration of this comment, we are revising the
audit requirements to require 1 additional audit per PQAO and an
additional 2 collocated sample filters for PQAO’s with more than 5
sites.  This sampling frequency would parallel the PM2.5 performance
evaluation.  Based on our review of PM2.5 bias information, five audits
per year for PQAOs with five or fewer monitoring sites provide an
adequate assessment of bias over a 3-year period.  We believe we can
provide an adequate three-year estimate of bias with this approach since
it will yield the same number of audit results as the PM2.5 PEP program.
 In addition, the statistic used to assess bias for PM10-2.5 and the
gaseous pollutants (section 4.1.3) will be used for the Pb bias
assessment and will be referenced in section 4.4.2.  This will eliminate
the need to assess bias by combining data from the flow rate audits and
Pb audit strips as discussed in sections 4.4.2 through 4.4.5, so this
assessment will be removed. The use of the flow rate audits and Pb audit
strips  will be able to be assessed separately using statistics already
available in Appendix A. Sections 4.2.2 and 4.2.3 for flow rate
information  and section 4.1.3 will be used for the Pb strip assessment.

Like the PM2.5 PEP program, we are planning to implement an audit
program for monitoring agencies requesting federal implementation of the
audits, but allow monitoring agencies to implement their own audit
program.  We plan to utilize one laboratory for the analysis of the Pb
audit samples for those monitoring organization requesting federal
implementation of these audits.  However, we expect some states will
elect to implement their own audits.  Independent laboratory services
will be offered to monitoring organizations that are self-implementing
this performance evaluation program, however, they may use other
independent labs.  Based on the current PM2.5 PEP program, we expect the
majority of monitoring agencies will elect to make use of the federally
implemented audit program.

	We also received comments on our proposed precision and bias goals from
individual members of the CASAC AAMM Subcommittee as part of the
consultation on March 25, 2008.  The AAMM Subcommittee members indicated
that we should base the precision and bias goals on the findings of the
ongoing DQO analysis identified in our proposal.  We have completed the
DQO analysis as described in the proposed rule, and a copy of the report
is in the docket for this rule.  Based on the findings from the DQO
analysis, we are finalizing a goal for precision and bias of 20 percent
and 15 percent, respectively.  These values allow for slightly higher
uncertainty than the proposed values and reflect the finding that the
existing high-volume samplers may not routinely be capable of meeting
the proposed precision and bias goals.

c. Decisions on Quality Assurance Requirements

We are finalizing amendments to the QA requirements for Pb measurements
as proposed with the following differences.  Based on the DQO analysis,
the goal for acceptable measurement uncertainty will be defined for
precision as an upper 90 percent confidence limit for the coefficient of
variation (CV) of 20 percent and as an upper 95 percent confidence limit
for the absolute bias of 15 percent.  The evaluation of precision will
also be limited to those data greater than or equal to 0.02 (g/m3.
These goals are included in section 2.3.1 of 40 CFR Part 58 Appendix A.
We are requiring 1 PEP audit per year per PQAO with 5 or fewer sites,
and 2 PEP audits per year per PQAO with more than 5 sites.  Due to the
addition of the Pb performance evaluation, a reference to the
statistical  assessment of bias used for PM10-2.5 and the gaseous
pollutants (section 4.1.3) will be included in section 4.4.2 and the
requirement for the bias calculation using the Pb strips in combination
with the flow rate audits, as discussed in sections 4.4.2 through 4.4.5,
will be removed and  sections 4.2.2 and 4.2.3 will be used to assess
flow rate information  and section 4.1.3 will be used for the Pb strip
laboratory bias assessment.

B.  Network Design

As a result of this Pb NAAQS review and the tightening of the standards,
EPA recognizes that the current network design requirements are
inadequate to assess compliance with the revised NAAQS.  Accordingly, we
are promulgating new network design requirements for the Pb NAAQS
surveillance network.  The following sections provide background,
rationale, and details for the final changes to the Pb network design
requirements.

1.  Proposed changes

We proposed to modify the existing network design requirements for the
Pb surveillance monitoring network to achieve better understanding of
ambient Pb air concentrations near Pb emission sources and to provide
better information on exposure to Pb in large urban areas.  We proposed
that monitoring be presumptively required at sites near sources that
have Pb emissions (as identified in the latest National Emissions
Inventory (NEI) or by other scientifically justifiable methods and data)
that exceed a Pb “emission threshold”.  This monitoring requirement
would apply not only to existing industrial sources of Pb, but also to
fugitive sources of Pb (e.g., mine tailing piles, closed industrial
facilities) and airports where leaded aviation gasoline is used.  In
this context, the “emission threshold” was intended to be the lowest
amount of Pb emissions per year for a source that may reasonable be
expected to result in ambient air concentrations at a nearby monitoring
site in excess of the proposed Pb NAAQS (as discussed later, based on
reasonable worst case scenarios).  We conducted an analysis to estimate
the appropriate emission threshold (Cavender 2008a) which is available
in the docket for this rulemaking.  Using the results from this
analysis, we proposed that the emission threshold be set in the range of
200 kg-600 kg per year total Pb emissions (including point, area, and
fugitive emissions and including Pb in all sizes of PM), corresponding
to the proposed range of levels for the Pb NAAQS, with the final
selection of the threshold to be dependent on the final level for the
NAAQS.

We recognized that a number of factors influence the actual impact a
source of Pb has on ambient Pb concentrations (e.g., local meteorology,
emission release characteristics, and terrain).  Accordingly, we also
proposed to allow monitoring agencies to petition the EPA Regional
Administrator to waive the requirement to monitor near a source that
emits less than 1000 kilograms per year where it can be shown that
ambient air concentrations at that site are not expected to exceed 50
percent of the NAAQS during a three year period (through modeling,
historical monitoring data, or other means).  We proposed that for
facilities identified as emitting more than 1000 kilograms per year in
the NEI, a waiver would only be provided for those sites at which it
could be demonstrated that actual emissions are less than the emission
threshold.

We proposed that source-oriented monitors be located at locations of
maximum impact classified primarily as microscale monitors
representative of small hot-spot areas adjacent or nearly adjacent to
facility fence-lines.  We also indicated that source-oriented monitors
may be located at locations of maximum impact but which are
representative of larger areas and classified as middle scale.
Additionally we sought comments on the appropriateness of requiring
monitors near Pb sources.

We also proposed a small network of non-source oriented monitors in
urban areas in addition to the source-oriented monitors discussed above,
in order to gather additional information on the general population
exposure to Pb in ambient air.  While it is expected that these
non-source oriented monitors will show lower concentrations than source
oriented monitors, data from these non-source oriented monitors will be
helpful in better characterizing population exposures to ambient
air-related Pb and may assist in determining nonattainment boundaries.
We proposed to require one non-source oriented monitor in each Core
Based Statistical Area (CBSA, as defined by the Office of Management and
Budget) with a population of 1,000,000 people or more as determined in
the most recent census estimates.  Based on the most current census
estimates, 52 CBSAs would be required to have non-source oriented
population monitors (see   HYPERLINK
"http://www.census.gov/popest/metro/index.html"
http://www.census.gov/popest/metro/index.html  for the latest census
estimates.)

We noted in our proposal that monitoring agencies would need to install
new Pb monitoring sites as a result of the proposed revisions to the Pb
monitoring requirements.  We estimated that the size of the required Pb
network would range from between approximately 160 and 500 sites,
depending on the level of the final standard.  If the size of the final
network is on the order of 500 sites, we proposed to allow monitoring
agencies to stagger the installation of newly required sites over two
years, with at least half the newly required Pb monitoring sites being
installed and operating by January 1, 2010 and the remaining newly
required monitoring sites installed and operating by January 1, 2011.
As proposed, monitors near the highest Pb emitting sources would need to
be installed in the first year, with monitors near the lower Pb emitting
sources and nonsource-oriented monitors being installed in the second
year.  We also proposed to allow monitoring agencies one year following
the release of updates to the NEI or an update to the census to add new
monitors if these updates would trigger new monitoring requirements.

We also proposed to allow States to use Pb-PM10 monitors to meet the
network design requirements if our proposed use of scaled Pb-PM10 data
was adopted in the final rule.

2.  Comments on Network Design

We received several comments on the proposed network design
requirements.  These comments and our responses are broken down into the
following categories: source-oriented monitoring, non-source oriented
monitoring, roadway monitoring, the use of Pb-PM10 samplers, and the
required timeline for installing newly required monitors.

a.  Source-oriented monitoring

We received several comments supporting the need for monitoring near Pb
sources.  Alternatively, one commenter suggested that near source
monitoring is not necessary because “the EPA and the State already
know where and what the problems are” and “EPA should … develop
control standards to deal with the problem …”   We note individual
sources do not violate a NAAQS but that under the CAA a primary method
to achieve control of emissions at sources contributing to an exceedence
of the NAAQS is the State Implementation Plan (SIP).  We expect the
highest concentrations of Pb to be near sources of Pb due to its
dispersion characteristic.  Monitoring data are important evidence used
to designate areas as non-attainment of the NAAQS.  Thus, monitoring
near Pb sources is needed to properly designate areas that violate or
contribute to air quality in a nearby area that does not meet the Pb
NAAQS.

We received a comment that the methods used in developing the emission
thresholds estimated ambient impacts over different averaging periods,
and that the emission thresholds should be recalculated for all methods
using the final averaging period.  We recognized this issue in our
memorandum documenting the analysis (Cavender, 2008a), and we have
recalculated the estimate of the lowest Pb emission rate that under
reasonable worst-case conditions could lead to Pb concentrations
exceeding the NAAQS, based on the final level and form of the standard
(Cavender, 2008b).

We also received comments on the approach used in developing the
proposed emission thresholds that would trigger consideration of the
placement of a monitoring site near a Pb source.  Commenters expressed
concerns that the approach overestimated the potential impact of Pb
sources, and would result in either unnecessary burden on monitoring
agencies or worse yet, monitoring agencies would install and operate
monitors at sources that had little to no potential to exceed the NAAQS.
 Several commenters suggested various alternative levels, including a
threshold of 1 ton or higher, basing their recommendations on concerns
such as the reliability of data in the NEI.  Other commenters suggested
that EPA was in the best position to determine which sources had the
potential to exceed the NAAQS.

We note that the approach used in developing the emission threshold in
the proposal was intended to represent a reasonable worst case scenario.
 As such, we recognize that many Pb sources which emit at or above the
proposed emission threshold will have Pb impacts that are below the Pb
NAAQS.  To account for this, we proposed to allow monitoring agencies to
request monitoring waivers if they could demonstrate that facilities
would not contribute to a Pb impact of greater than 50 percent of the
NAAQS.  However, upon further consideration, we agree that by basing the
threshold on these worse case condtions we will be placing an
unnecessary burden on monitoring agencies to evaluate or monitor around
sources that may not have a significant potential to exceed the NAAQS.
As a result, we are finalizing changes to our approach for requiring
source-oriented monitors.  We are including a requirement that
monitoring agencies conduct monitoring taking into account sources that
are expected to exceed or shown to have contributed to a maximum
concentration that exceeded the NAAQS, the potential for population
exposure, and logistics.  In addition, specifically we are requiring
monitoring agencies to conduct monitoring at sources which emit Pb at a
rate of 1.0 or more tons per year.  This emissions rate corresponds to
two times the estimate of the lowest Pb emission rate that under
reasonable worst-case conditions could lead to Pb concentrations
exceeding the NAAQS.  This recognizes the thresholds used in the
proposal represented reasonable worst case scenarios, and that a more
appropriate approach to balance the factors important in designing a
network is to use a higher threshold that is more likely to clearly
identify sources that would contribute to exceedences of the NAAQS.   In
addition, the State, and the Agency working together will identify what
additional sources should be taken into account because they are
expected to or have been shown to contribute to maximum concentrations
that contribute to exceedences.

To account for the other sources that may contribute to a maximum Pb
concentration in ambient air in excess of the NAAQS, we are retaining
the authority granted to the EPA Regional Administrator in the existing
monitoring requirements to require monitoring “where the likelihood of
Pb air quality violations is significant or where the emissions density,
topography, or population locations are complex and varied.”  We
believe that these final monitoring requirements are adequate to ensure
that monitoring will be conducted respecting facilities that have the
potential to exceed the NAAQS with out placing undue burden on
monitoring agencies.

We received several comments supporting the need for monitoring waivers,
and one comment that did not support waivers.  Those in favor of the
waivers pointed out that, as discussed above, many Pb sources will
result in much lower Pb impacts than the “worst case” Pb source.
They argued that the states need flexibility in meeting the
source-oriented monitoring requirements, and agreed that it is
appropriate to focus on sites near those Pb sources with the greater
potential to result in Pb concentrations that exceed the Pb NAAQS.   The
commenter who cautioned against the allowance of monitoring waivers
expressed concerns that modeling results are not exact and this
uncertainty could result in waivers being granted when actual Pb
concentrations could exceed the NAAQS.  We took the uncertainty of
modeled results into account when proposing to limit waivers to
situations where the modeled data indicated maximum concentrations would
be 50 percent of the NAAQS, rather than at 100 percent of the NAAQS, and
we believe this provides a sufficiently protective approach to account
for uncertainty in modeling and other assessments estimating a Pb
sources expected impacts.

We received comments questioning the need to restrict the provision of
waivers to sites near sources emitting less than 1000 kg/yr.  We agree
it is possible for sources greater than 1000 kg/yr to have an impact
less than 50 percent of the NAAQS under certain conditions.  We also
acknowledge the need for flexibility in implementing the Pb NAAQS
monitoring network.  As such, we have reconsidered our proposed
restriction limiting waivers to those for sources emitting less than
1000 kg/yr, and we are not finalizing a restriction on the size of
sources near sites eligible for a waiver from the source-oriented
monitoring requirement.

We received comments on relying on the National Emission Inventory (NEI)
to identify Pb sources with emissions greater than the emission
threshold.  In general, several commenters said better data should be
used to identify Pb sources emitting above the proposed emission
threshold.  Several commenters expressed concerns with the accuracy of
the NEI, and recommended allowing states to use “the best available
information” on emissions from Pb sources. Some commenters pointed to
differences in Pb emissions data reported in the Toxics Release
Inventory and the NEI as evidence that the NEI was inaccurate.  One
commenter said current practices to reduce toxic emissions are not
reflected in the NEI and wanted the opportunity to update the
information. Commenters said EPA should correct the errors in the NEI or
allow states to submit revised local data that more accurately reflect
Pb emissions before emissions inventory data are used to determine which
sources exceed the threshold.

We agree that the most current Pb emissions information should be used
when making final decisions about which sources exceed the emission
threshold.  This may include datasets that could include sources not
contained in the NEI.  We acknowledge that many of the NEI emission
estimates likely would be improved with more site specific data (e.g.,
emissions test data).  We have added the phrase “or other
scientifically justifiable methods and data” to the monitoring
requirements to clarify that NEI emissions estimates are not the only
emission estimates that can be used to estimate emissions.

We received comments that the proposed source-oriented monitoring
requirements did not address situations where multiple sources
contribute to Pb concentrations at one location.  Our proposed waiver
requirements do take into account the impacts from multiple sources.
The proposed language stated that waivers could only be granted for
source-oriented sites that did not “contribute to a maximum Pb
concentration in ambient air in excess of 50 percent of the NAAQS”.
We recognize that exceedances of the standard may be caused by emissions
from a number of smaller sources none of which would cause a violation
in isolation, but we expect it is unlikely that violations would occur
when all of the sources in an area are below the emissions threshold due
to the rapid decrease in Pb concentrations with distance from a Pb
source.  However, the purposes of the monitoring network would be
undermined if multiple sources in a single area were able to receive
waivers, with the result that no monitor was required even though Pb
concentrations in the area were in excess of 50 percent of the standard.
 Accordingly, EPA expects that Regional Administrators, in deciding
whether to grant waivers, will take into account whether other waivers
have been granted or sought for sources in the same area, and whether
the cumulative emissions of the sources in the area warrant at least one
monitor being sited.

Several monitoring agencies expressed concern about the need for
flexibility in implementing the source-oriented monitoring requirements.
 We believe that the proposed rule provides significant flexibility to
monitoring agencies for the implementation of the monitoring
requirements.  One area where we believe it is appropriate to provide
additional flexibility is for situations where multiple sources above
the emission threshold contribute to a single maximum impact.  A strict
reading of the proposed source-oriented monitoring requirement could be
that monitoring agencies would be required to monitor each Pb source
separately.  This was not intended, and our existing monitoring guidance
is clear that a single monitor can be used to monitor multiple sources
where the maximum impact is influenced by multiple sources.
Nonetheless, we believe it is appropriate to clarify this point in the
rule language.  As such, we are adding a clause to the source-oriented
monitoring requirement that specifies that a single monitor can be used
to monitor multiple Pb sources where they contribute to a single maximum
impact.

We received two comments that source-oriented monitors should be located
at the location of maximum estimated Pb concentration without
consideration for the potential for population exposure, and six
comments that source-oriented monitors should be located in an area
where population exposure occurs.  In their comments on the proposed
rule, one commenter argued that monitors “should be located in or
around only those Pb point sources with a nearby population base”
because “air Pb concentrations have regulatory importance largely in
those areas where significant groups of children are exposed for
considerable time periods.”  They argue that as an example “a rural
road going by a lead mining facility is an unlikely place that children
will spend considerable amounts of time” and as such “placing a
monitoring site on such a road would have de minimis, if any, value.”
Another commenter suggested that “monitors should be located near
playgrounds, sports fields, long-established highways, and the like.”

Siting of required monitors at the expected maximum concentration in
ambient air is consistent with how all NAAQS pollutants are monitored.
In considering the siting criteria for the required Pb source-oriented
monitors, we recognize that Pb is a persistent, multimedia pollutant,
such that deposited Pb from current emissions can contribute to human
exposures over extended amounts of time.  Also, Pb deposited in one area
can be transported to another area by “tracking” from vehicle and
foot traffic.  In addition, unlike the case for other criteria
pollutants, ingestion of deposited Pb is a major Pb exposure pathway.
Given these complexities, it is appropriate to allow siting agencies to
also consider the potential for population exposure in siting monitors
near sources.

In our proposed rule, we recognized that there are reasons for not
requiring monitoring at the location of expected maximum concentration
such as logistical limitations (i.e., the location of expected maximum
concentration occurs in the middle of a lake).  In consideration of
public comments on this issue and due to the complexities of Pb, we
believe it is appropriate, in the final rule, to also allow states to
consider the potential for population exposure as a factor (in addition
to other factors such as logistical considerations) when siting required
source-oriented monitors.  Thus, we are including the potential for
population exposure as a factor that monitoring agencies can consider
when siting a maximum concentration source-oriented monitoring site
required under part 58.

b.  Non-source oriented monitoring

We received a number of comments on our proposed non-source oriented
monitoring requirement.  One state and several tribes commented that the
proposed population limit would result in no required non-source
oriented monitors in low population states and tribal lands.  One
commenter expressed concerns that the population limit was too high, and
would result in environmental justice concerns since many poor
communities would not be monitored.

As stated in the proposed rule, it is unlikely that exceedences of the
Pb NAAQS will occur at sites distant from Pb sources.  As such, our
non-source-oriented monitoring requirements satisfy monitoring
objectives in addition to ensuring compliance with the Pb NAAQS.  For
the most part, these monitoring sites should be sited to represent
neighborhood scale exposures.  We are requiring non-source oriented Pb
monitors to provide additional information that will be useful in better
characterizing air-related Pb exposures in neighborhoods.  Sources
affecting neighborhoods may include re-entrained dust from roadways,
closed industrial sources which previously were significant sources of
Pb, hazardous waste sites, construction and demolition projects, or
other fugitive sources of Pb.  Non-source sites will also support the
next Pb NAAQS review by providing additional information on the spatial
variations in Pb concentrations between areas that are affected by
sources to a significant degree and those that are not.

We believe it is most appropriate to focus the non-source monitoring
requirements in large urban areas since high population locations are
most used in health and epidemiological studies.  We proposed to require
one non-source oriented monitor in each CBSA with a population of
1,000,000 or more as determined in the most recent census.  That
proposed requirement would have resulted in approximately 50 CBSAs
required to have non-source Pb monitors.  EPA notes the comments that
the proposed population limit of 1,000,000 was too high, and may result
in the lack of non-source oriented monitors in smaller urban
communities.  Accordingly, we have decreased the population limit for
requiring non-source monitors to CBSAs with a population of 500,000
people or more, thereby increasing the number of required non-source Pb
monitors from approximately 50 to approximately 100 (based on 2007
population estimates from the Census Buearu).

We also note that these requirements are minimum monitoring
requirements, and that state and tribal monitoring agencies may operate
additional non-source oriented monitors beyond the minimum number of
required monitors.  Data that meets the quality assurance requirements
that is collected from non-required FRM or FEM monitors will also be
used to determine compliance with the Pb NAAQS, assuming that the data
meets.  Additionally, as described previously, source-oriented
monitoring would be required in rural and small communities if a Pb
source emitting 1 ton per year or more are present.

c.  Roadway Monitoring

The majority of commenters agreed with our finding that the available
data on Pb concentrations near roadways do not indicate the potential
for exceedances of the proposed range of Pb NAAQS levels and
requirements for monitors near roadways were not needed to ensure
compliance with the NAAQS.  However, one commenter argued that our
finding that activity on roadways would not likely contribute to air Pb
concentrations in exceedence of the proposed levels for the standard was
based on data from monitors that did not represent the maximum impact
from roadways.

While some of the monitors used in our analysis of air Pb impacts from
activity on roadways may not represent the site of maximum impact, we
believe they are representative of locations where roadway monitoring
might be conducted.  As we indicated in our proposal, these monitors
indicate that Pb concentrations are slightly elevated near roadways, but
do not occur at levels approaching the Pb NAAQS being finalized today.
Nonetheless, we agree that more information on Pb concentrations near
roadways would be valuable, and we encourage monitoring agencies to
consider placing Pb monitors near population centers heavily impacted by
roadways in some of the CBSAs required to install and operate
nonsource-oriented monitors to provide information for use in future
NAAQS reviews.  In addition, the EPA has research initiatives
investigating Pb concentrations near roadways that will provide
additional information that can be used in future NAAQS reviews.

d. 	Use of Pb-PM10 monitors

Comments were received on the use of Pb-PM10 monitoring in lieu of
required Pb-TSP under certain circumstances.  Several commenters
suggested an approach for the use of Pb-PM10 monitors as an alternative
to the proposed use of scaling factors.  Commenters suggested that
Pb-PM10 monitoring would only be allowed in certain instances.
Specifically, Pb-PM10 monitoring would be allowed where estimated Pb
concentrations were predicted to be less than 50 percent of the NAAQS
and where Pb in ultra-coarse particulate was expected to be low.  That
commenter also suggested that if at some point in the future the monitor
were to show that Pb-PM10 concentrations exceeded an arithmetic 50
percent of the NAAQS, the monitoring agency would be required to replace
the Pb-PM10 monitor with a Pb-TSP monitor.

We support this suggested approach, noting that it allows for the use of
Pb-PM10 in areas where we do not expect Pb concentrations to exceed the
Pb NAAQS without the burden and uncertainty associated with the
development and use of site-specific scaling factors.  As noted in
section II.C.1, use of Pb-PM10 monitors in these locations offers the
advantages of increased monitor precision and decreased spatial
variation of Pb-PM10 concentrations, without raising the same concerns
over a lack of protection against health risks from all particulate Pb
emitted to the ambient air that support retention of Pb-TSP as the
indicator.

However, we feel the combined requirements for allowing use of Pb-PM10
monitors to areas where the concentration is expected to be less than
50% of the NAAQS and where Pb in ultra-coarse particles is expected to
be low  may be too restrictive, especially in light of the fact that a
monitoring agency may request a waiver from monitoring all together if
the expected concentration is less than 50% of the NAAQS.  We believe it
is appropriate to allow Pb-PM10 in lieu of Pb-TSP where the maximum
3-month arithmetic mean Pb concentration is expected to be less than
0.10 µg/m3 (i.e., two thirds of the NAAQS) and where sources are not
expected to emit ultra-coarse Pb.  By limiting the use of Pb-PM10
monitoring to locations where the Pb concentrations are less than 0.10
µg/m3 on a 3-month arithmetic mean and where ultra-coarse Pb is
expected to be low, we believe  that the Pb-TSP concentrations will also
be less than 100% of the NAAQS.  Examples of locations where Pb-PM10
monitoring may be more representative of Pb-TSP levels than others are
urban areas away from Pb sources (i.e., nonsource-oriented monitoring
locations), near airports, combustion sources, and other Pb sources
which are expected to only emit Pb in the fine PM size fraction.
Locations where it would not be appropriate to monitor using Pb-PM10
samplers include near smelters, roadways, and sources with significant
fugitive dust emissions.

We are revising the proposed allowance for the use of Pb-PM10 monitors
to allow Pb-PM10 monitors without the use of scaling factors for
nonsource-oriented monitors (unless existing data indicates maximum
3-month arithmetic mean Pb concentration have exceeded 0.10 µg/m3 in
the last three years) and for source-oriented monitors where maximum
3-month arithmetic mean Pb concentration is expected to be less than
0.10 µg/m3 (based on modeling or historic data) and where ultra-coarse
Pb is expected to be low.  We are also requiring that a Pb-TSP monitor
be required at the site if at some point in the future the Pb-PM10
monitor shows that the maximum 3-month arithmetic mean Pb-PM10
concentration was equal to or greater than 0.10 µg/m3.  Section IV.C of
this preamble discusses how data from Pb-PM10 monitors will be used in
comparison to the Pb NAAQS.

e.	Required timeline for monitor installation and operation

We received several comments from monitoring agencies regarding the
proposed timeline for monitor installation.  Commenters supported the
need for a staggered network deployment, especially if a large number of
new monitors would be required.  Two commenters argued that even the
proposed two-year deployment would not provide enough time for
monitoring agencies to site and install the number of monitors needed.

Based on the network design requirements being finalized with this
action, we estimate that approximately 135 facilities emit Pb at levels
over the “emissions threshold” of 1 ton per year and would result in
required monitoring.  We are also requiring urban areas with populations
over 500,000 to site non-source oriented monitors, thus another 101
monitors are required.  Together the required source oriented and
non-source oriented monitors are expected to total 236 monitors.  Some
of the existing 133 lead monitoring stations will be useful to support
the required network, but other stations may need to move.  We are
estimating that approximately 90 of the existing stations are in
locations that are of benefit to other monitoring objectives, even when
well below the NAAQS (e.g., long-term trends or for use in a health
study) and are not part of the minimum network requirements being
finalized in today’s action.  Once the network is fully operational
the 236 required stations plus an additional 90 stations in existing
locations that are not required results in an expected network of 326
lead monitoring stations to adequately support characterization of lead
across the country.

We believe it would be unrealistic to require monitoring agencies to
site and install the required 240 new monitoring stations within one
year, even if some of these are already in the right locations.
However, we do believe it is reasonable to require monitoring agencies
to site and install half of these stations in one year with the
remaining stations deployed in the following year.  Accordingly, and as
discussed further below, we are finalizing a two-year monitor deployment
schedule for required monitoring.

3.  Decisions on Network Design Requirements

We are finalizing new network design requirements for the Pb NAAQS
monitoring network that differ from those proposed in the following
aspects. The differences from the proposal reflect our consideration of
the comments on the proposed network design requirements and
consideration of the level, form, and averaging time for the final NAAQS
being promulgated today.

We are adding a requirement that monitoring agencies conduct ambient air
Pb monitoring taking into account Pb sources which are expected to or
have been shown to contribute to a maximum Pb concentration in ambient
air in excess of the NAAQS, the potential for population exposure, and
logistics. At a minimum, there must be one source-oriented SLAMS site
located to measure the maximum Pb concentration in ambient air resulting
from each Pb source which emits 1.0 or more tons per year based on
either the most recent NEI or other scientifically justifiable methods
and data (such as improved emissions factors or site-specific data).  We
are maintaining the existing authority for the EPA Regional
Administrator to require additional monitoring where the likelihood of
Pb air quality violations is significant or where the emissions density,
topography, or population locations are complex and varied.  In
addition, we are adding a clause to the source-oriented monitoring
requirement to clarify that a single monitor may be used to monitor
multiple Pb sources when the sources contribute to a single maximum Pb
concentration.

In addition, monitoring agencies may consider the potential for
population exposure when siting source-oriented monitors.  While this
change does not restrict monitoring agencies from monitoring at any
location meeting the definition of ambient air, this provision allows
monitoring agencies to consider the potential for population exposure
when siting the required source-oriented monitors at the maximum Pb
concentration.

We are removing the proposed restriction that waivers may only be
granted for sites near sources emitting less than 1000 kg/yr.  The EPA
Regional Administrator may approve waivers for the source-oriented
monitoring requirement for any site where the monitoring agency
demonstrates that the emissions from the source will not contribute to a
Pb-TSP concentration greater than 50 percent of the final NAAQS (based
on historic data, monitoring data, or other means).

We are requiring one nonsource oriented monitor in every CBSA with a
population of 500,000 people or more.  In addition, we are requiring
these monitors be placed in neighborhoods within urban areas impacted by
re-entrained dust from roadways, closed industrial sources which
previously were significant sources of Pb, hazardous waste sites,
construction and demolition projects, or other fugitive dust sources of
Pb.

Monitoring agencies may use Pb-PM10 monitors to meet the
nonsource-oriented monitoring requirements tied to CBSA population
provided that historical monitoring does not indicate Pb-TSP or Pb-PM10
concentrations greater than an arithmetic 3-month mean of 0.10 µg/m3,
and to meet the source-oriented monitoring requirements where Pb
concentrations are expected (based on historic data, monitoring data, or
other means) to be less than 0.10 µg/m3 on an arithmetic 3-month mean,
and ultra-coarse Pb is expected to be low.  However, monitoring agencies
are required to begin monitoring for Pb-TSP within six months of a
measured Pb-PM10 arithmetic 3-month mean concentration of 0.10 µg/m3 or
more.  For example, if a Pb-PM10 monitoring site measures an arithmetic
3-month mean concentration of 0.10 µg/m3 or more for the period March
– May 2011, the responsible monitoring agency would be required to
install and begin operation of a Pb-TSP monitor at the site no later
than December 1, 2011.

We are allowing monitoring agencies to stagger installation of any newly
required monitors over a two-year period.  Each monitoring agency is
required to install and operate the required source-oriented monitors by
January 1, 2010.  The nonsource-oriented monitors are required to be
installed and operated by January 1, 2011.  The annual monitoring plan
due July 1, 2009 must describe the planned monitoring that will begin by
January 1, 2010, and the plan due July 1, 2010 must describe the planned
monitoring that will begin by January 1, 2011.

C.  Sampling Frequency

	We proposed to maintain the 1-in-6 day sampling frequency if the final
averaging time for the NAAQS standard was based on a quarterly average.
We did not receive any comments on our proposed sampling frequency for a
NAAQS based on a quarterly average.  While the final NAAQS is based on a
moving 3-month average rather than a quarterly average, the statistical
and practical monitoring considerations are the same.  As such, we are
maintaining the current 1-in-6 day minimum sampling frequency as
proposed (i.e., monitoring agencies will be required to collect at least
one 24-hour Pb sample every six days.)

D.  Monitoring for the Secondary Standard

We did not propose any specific additional monitoring requirements for
the secondary standard because based on the available data, we do not
expect exceedences of either the primary or the secondary NAAQS away
from the point sources that will be addressed by the monitoring
requirements already described.  We also noted that the Pb-PM2.5 data
collected as part of the Interagency Monitoring of Protected Visual
Environments (IMPROVE) program provides useful information on Pb
concentrations in rural areas that can be used to track trends in
ambient air Pb concentrations in rural areas including important
ecosystems.  We received one comment supporting our proposed reliance on
the IMPROVE network Pb-PM2.5 data.  We did not receive any other
comments on additional monitoring needs to support the secondary Pb
NAAQS.  Thus, we are not finalizing any additional requirements for Pb
monitoring specifically for the secondary Pb NAAQS.

E.  Other Monitoring Regulation Changes

We are finalizing two other proposed changes to the monitoring
requirements for Pb, and making one editorial revision for ease of
reference.  We are changing the reporting requirements to require the
reporting of average pressure and temperature for each Pb sample
collected.  We are also removing Pb from the list of criteria pollutants
where data from special purpose monitors can be excluded from
consideration for designations.  The proposed changes, comments
received, and final amendments are described in the following
paragraphs.

1.  Reporting of Average Pressure and Temperature

We proposed revisions to 40 CFR 58.16(a) to add a requirement that the
monitoring agency report the average pressure and temperature during the
time of sampling for both Pb-TSP monitoring and Pb-PM10 monitoring.  We
did not receive any comments on this proposed requirement.  As such, we
are finalizing this requirement as proposed.  Monitoring agencies may
use site specific meteorological measurements generated by on-site
equipment (meteorological instruments, or sampler generated), a
representative nearby monitoring station, or measurements from the
nearest airport reporting ambient pressure and temperature.

2.  Special Purpose Monitoring

We proposed to revise 40 CFR Section 58.20(e) by removing the specific
reference to Pb in the rule language.  We proposed to make this change
because the form of the proposed Pb NAAQS would allow a non-attainment
finding to be based on as little as 3-months of data which would have to
be considered during mandatory designations.  We did not receive any
comments on this proposed revision to the special purpose monitoring
requirements.  As such, we are finalizing the revision to 40 CFR Section
58.20(e) as proposed.

VI.	Implementation Considerations

This section of the final rule discusses the specific CAA requirements
related to implementation of the revised Pb NAAQS based on the structure
outlined in the CAA, existing rules, existing guidance, and in some
cases revised guidance.

The CAA assigns important roles to EPA, states, and tribal governments
in implementing NAAQS.  States have the primary responsibility for
developing and implementing State Implementation Plans (SIPs) that
contain state measures necessary to achieve the air quality standards in
each area.  EPA provides assistance to states and tribes by providing
technical tools, assistance, and guidance, including information on the
potential control measures.

A SIP is the compilation of regulations and control programs that a
state uses to carry out its responsibilities under the CAA, including
the attainment, maintenance, and enforcement of the NAAQS.  States use
the SIP development process to identify the emissions sources that
contribute to the nonattainment problem in a particular area, and to
select the emissions reduction measures most appropriate for the
particular area in question.  Under the CAA, SIPs must ensure that areas
reach attainment as expeditiously as practicable, but by no later than
the statutory attainment date that is set for the area.

	The EPA’s analysis of the available Pb monitoring data suggests that
a large percentage of recent Pb ambient air concentrations in excess of
0.15 µg/m3 have occurred in locations with active industrial sources of
lead emissions.  Accordingly, we anticipate that many areas may be able
to attain the revised NAAQS by implementing air pollution control
measures on lead emitting industrial sources only.  These controls could
include measures such as particulate matter fabric filter control
devices and industrial fugitive dust control measures applied in plant
buildings and on plant grounds.  However, it may become necessary in
some areas to also implement controls on non-industrial, or former
industrial, type sources. Based on these considerations, EPA believes
that the regulations and guidance currently being used to implement the
pre-existing Pb NAAQS are still appropriate to implement the revised Pb
NAAQS with modifications in some cases.

The regulations and guidance which address the implementation of the
pre-existing NAAQS for Pb are mainly provided in the following
documents: (1) “State Implementation Plans; General Preamble for the
Implementation of Title I of the Clean Air Act Amendments of 1990”, 57
FR 13549, April 16, 1992, (2) “State Implementation Plans for Lead
Nonattainment Areas; Addendum to the General Preamble for the
Implementation of Title I of the Clean Air Act Amendments of 1990”, 58
FR 67748, December 22, 1993, and (3) regulations listed at 40 CFR
51.117.  These documents address requirements such as designating areas,
setting nonattainment area boundaries, promulgating area
classifications, nonattainment area SIP requirements such as Reasonably
Available Control Measures (RACM), Reasonably Available Control
Technology (RACT), New Source Review (NSR), Prevention of Significant
Deterioration (PSD), and emissions inventory requirements.  The EPA
believes that the existing guidance and regulations are sufficient to
implement the revised Pb NAAQS at this time.  As discussed below, EPA is
finalizing some changes to the existing guidance and regulations, and
EPA will, as appropriate, review, and revise or update these policies,
guidance, and regulations to ensure effective implementation of the Pb
NAAQS.

Several commenters submitted comments stating that the usual agency
practice for revising the NAAQS has been to first promulgate a rule
setting the health and welfare based standards, and then to promulgate a
rule that addresses the numerous implementation issues relating to the
NAAQS.  These commenters stated that the lead NAAQS proposal, however,
combines these two rulemakings into one compressed rule.  Commenters
stated that they theoretically believe that this two-in-one rule
approach could benefit states and localities by preventing the types of
delays that have been encountered with the implementation of other
pollutants.  The commenters, however, stated that they believe that the
lead NAAQS implementation provisions in the proposed rule are
insufficient to give state and local agencies adequate guidance to
implement the revised standard.  Commenters further stated that they
believe that EPA should particularly update lead control strategy and
emissions inventory guidance documents to account for the change to the
level of the standard.

As stated in the proposed rule, EPA believes that the regulations and
guidance currently being used to implement the pre-existing Pb NAAQS are
generally still appropriate to address the issues required to begin
implementing the revised Pb NAAQS. As discussed in the proposal, EPA is
revising the emission inventory requirements of 40 CFR 51.117(e)(1).  In
some areas, as discussed below, EPA is providing additional guidance in
response to comments.  The EPA believes that these policies, guidance
and regulations should be used by states, local, and Tribal governments
as a basis for implementing the revised Pb NAAQS.  Also, as stated in
the proposed rule, EPA will as appropriate, further review and revise or
update these policies, guidance, and regulations in the future to ensure
that states, local, and Tribal governments have the appropriate
information necessary to fully implement the revised Pb NAAQS in a
timely manner.

As discussed below, the EPA is generally finalizing the guidance
concerning the implementation of the revised Pb NAAQS consistent with
the proposed rule.

A.	Designations for the Lead NAAQS

1.	Proposal

As discussed in the proposed rule, after EPA establishes or revises a
primary and/or secondary NAAQS, the CAA requires EPA and the states to
begin taking steps to ensure that the new or revised NAAQS are met.  The
first step is to identify areas of the country that do not meet the new
or revised NAAQS.  The CAA defines EPA’s authority to designate areas
that do not meet a new or revised NAAQS.  Section 107(d)(1) provides
that “By such date as the Administrator may reasonably require, but
not later than 1 year after promulgation of a new or revised NAAQS for
any pollutant under section 109, the Governor of each state shall
…..submit to the Administrator a list of all areas (or portions
thereof) in the state” that designates those areas as nonattainment,
attainment, or unclassifiable.  Section 107(d)(1)(B)(i) further
provides, “Upon promulgation or revision of a NAAQS, the Administrator
shall promulgate the designations of all areas (or portions thereof)
….as expeditiously as practicable, but in no case later than 2 years
from the date of promulgation.  Such period may be extended by up to one
year in the event the Administrator has insufficient information to
promulgate the designations.”  The term “promulgation” has been
interpreted by the courts to mean the signature and dissemination of a
rule.   By no later than 120 days prior to promulgating final
designations, EPA is required to notify states or Tribes of any intended
modifications to their boundaries as EPA may deem necessary.  States and
Tribes then have an opportunity to comment on EPA’s tentative
decision.  It should be noted that, whether or not a state or a Tribe
provides a recommendation, EPA must promulgate the designation that it
deems appropriate.

In the proposal, EPA indicated that Governors and tribal leaders would
be required to submit their initial designation recommendations to EPA
no later than September 2009, and the initial designation of areas for
the new Pb NAAQS would occur no later than September 2010, although that
date may be extended by up to one year under the CAA (or no later than
September 2011) if EPA has insufficient information to promulgate the
designations.  These dates were based on the court-ordered schedule in
effect at the time of proposal, which required a final rule to be signed
no later than September 15, 2008.  The court-ordered schedule was
subsequently amended to require a notice of final rulemaking to be
signed no later than October 15, 2008.

In the proposed rule, EPA also discussed issues related to possible
schedules for designations, and EPA took comment on issues related to
the anticipated designation schedule.  The proposal identified two
“key considerations” in establishing a schedule for designations:
“(1) The advantages of promulgating all designations at the same time;
and (2) the availability of a monitoring network and sufficient
monitoring data to identify areas that may be violating the NAAQS” (73
FR 29267).  The EPA then stated its view that “there are important
advantages to promulgating designations for all areas at the same
time” and expressed its intention to do so.

The proposal also discussed EPA’s belief that the existing Pb
monitoring network is not adequate to evaluate attainment of the revised
Pb NAAQS at locations consistent with EPA’s proposed new monitoring
network siting criteria and data collection requirements.  These new
requirements would result in a more strategically targeted network that
would begin operation by January 1, 2010.   The proposal pointed out
that taking the additional year provided under section 107(d)(1)(B)(i)
of the CAA (which would allow up to 3 years to promulgate initial
designations following the promulgation of a new or revised NAAQS) would
allow the first year of data from the new monitoring network to be
available. The proposal also stated that, due to the updated monitoring
network design requirements, this additional data would be of
significant benefit for designating areas for the new NAAQS.

Accordingly, the proposal identified an initial designation schedule
under which states (and Tribes) would be required to submit designation
recommendations to EPA no later than one year following promulgation of
the new NAAQS.  States would be able to consider ambient data collected
with the existing network FRM and FEM samplers through the end of
calendar year 2008 when formulating their recommendations.  The proposal
further indicated that if, as EPA anticipated, EPA needed an additional
year to make designations due to insufficient information, EPA would
have access to Pb air quality monitoring data from calendar year 2010,
which state monitoring officials have certified as being complete and
accurate, since the deadline for such certification is May 1, 2011.
Under this schedule, EPA would be able to consider data from calendar
years 2008-2010 in formulating its proposed revisions, if any, to the
designations recommended by states and Tribes.  States and Tribes would
then have an opportunity to comment on EPA’s proposed modifications,
if any, prior to the promulgation of designations by Fall 2011. The EPA
solicited comment on whether EPA has the authority to determine in this
final rule that three years would be necessary to make designations.
The EPA also solicited comment on making designations within two years
from promulgation of a revised NAAQS.

2.	Comments and Responses

	Several commenters suggested that EPA should require that states with
current nonattainment or maintenance areas submit designation
recommendations for those counties or Metropolitan Statistical Areas
(MSAs) with nonattainment or maintenance areas within 120 days of
promulgation of the rule.

	Section 107(d)(1)(A) provides that States shall submit recommendations
for areas to be designated attainment, nonattainment, and unclassifiable
“[b]y such date as the Administrator may reasonably require, but not
later than 1 year after promulgation of a  new or revised  national
ambient  air quality standard for  any pollutant under section 109.”
EPA’s consistent practice in revising NAAQS has been to allow states a
year to prepare their lists of designations, and the proposal likewise
indicated EPA’s intent to allow a year for states to prepare their
recommendations.  It is often true that when a standard is made more
stringent there will be existing nonattainment and maintenance areas
that may be expected to be nonattainment for the new standard as well.
Furthermore, EPA notes that the most recent three years of available
monitoring data for East Helena , MT, one of the two current
nonattainment areas, showed no violations of the current standard,
although the monitors were shut down in December 2001 following the
shutdown of the large stationary source of lead emissions there.  The
EPA also notes that preparing designation recommendations is a complex
task, and the magnitude of the reduction in the Pb NAAQS, and the long
interval since the last revision to the standard is likely to add to the
difficulty for states.

Thus, while EPA considers the increased stringency of the standard to be
relevant to the question of when states should submit designation
recommendations, EPA does not believe that under the current
circumstances it would be reasonable to require states to submit a list
of areas to be designated attainment, nonattainment, or unclassifiable
sooner than one year following promulgation year.

Therefore, pursuant to section 107(d)(1)(A), states shall, and Tribes
may, provide area designation recommendations to EPA no later than
October 15, 2009.  In some areas, EPA anticipates that state and Tribal
officials will be able to base their recommendations on existing
monitoring data, and can therefore identify an area as “attainment”
or “nonattainment.”  EPA also anticipates that there will be other
areas where state and Tribal officials will not have sufficient
information to make such a determination.  State and Tribal officials
are advised to identify such areas as “unclassifiable.”  For these
areas EPA may wait until sufficient ambient air quality data from the
newly deployed Pb monitoring network are available to take final action
on the state and Tribal recommendations.

	Several commenters stated that EPA should promulgate designations for
the

revised Pb NAAQS within the 2 year period provided in the CAA.
Commenters further stated that they do not understand why EPA needs to
take an additional year beyond the two years provided under the CAA to
do the designations.  In addition, the commenters stated that they
believe EPA does not have the authority to take the additional year
(i.e., the 3rd year provided under section 107(d)(1)(B)(i) of the CAA)
to do designations for the Pb NAAQS because sufficient monitoring data
is available to do the designations within 2 years of promulgation of
the NAAQS.

	Other commenters stated that they agree with EPA that, given that the
current monitoring network for the Pb NAAQS is insufficient to base
designations on for the new NAAQS, EPA should not promulgate
designations until there is sufficient data from the new monitoring
network.

	Section 107(d)(1)(B)(i) provides that the Administrator shall
promulgate the designations of  all areas as expeditiously as
practicable,  but in no case later than  2 years from the date of
promulgation of  the  new  or  revised  national  ambient  air  quality
standard.  Such period may be extended by up to one year in the event
the   Administrator has insufficient information to promulgate the
designations.

	After considering the comments, and recognizing that in some locations
there may be monitoring data sufficient to determine whether or not the
area is attaining the standard, EPA now believes that the benefits of
identifying nonattainment areas as soon as possible, in some areas as
discussed shortly below, outweigh the potential administrative benefits
of designating all areas at the same time.

	At the same time, EPA continues to believe that the current monitoring
network is inadequate for making designations in many, if not most,
areas of the country, and agrees with those commenters who stated that
it would be preferable to wait until additional monitoring data was
available for those areas than to proceed to designate areas based only
on data from the current insufficient monitoring network.  The EPA notes
that any delay in designations beyond two years would be based on the
lack of monitoring data (and the expectation that additional monitoring
data would be available if designations were delayed) and would not be
based on staffing and other non-data resource issues.

	Accordingly, EPA believes that the most appropriate approach to
designations for the Pb NAAQS is for EPA to complete final designations
as expeditiously as possible, and to recognize that “as expeditiously
as possible” may result in making nonattainment designations at
different times for different areas.  In some areas, EPA expects that it
will be possible to do designations within two years based on currently
available monitoring data.  In other areas, EPA expects that taking the
additional year will prove necessary in order to collect the necessary
monitoring data before making designations.

3.	Final

	After considering the comments and for the reasons discussed above, EPA
no longer plans to make all designations, and particularly all
nonattainment designations, at the same time.  The EPA intends to make
designations as expeditiously as possible in areas where monitoring data
is currently sufficient, or will be sufficient in the immediate future,
to accurately characterize the areas as either not attaining or
attaining the new Pb NAAQS.  In some cases this will be possible  as
expeditiously as practicable, but no later than two years following
promulgation of the final rule. In other cases this will not be possible
until additional data are collected from the newly deployed monitoring
network, and may take up to three years.

B.	Lead Nonattainment Area Boundaries

1.	Proposal

The process for initially designating areas following the promulgation
of a new or revised NAAQS is prescribed in section 107(d)(1) of the CAA.
 This section of the CAA provides each state Governor an opportunity to
recommend initial designations of attainment, nonattainment, or
unclassifiable for each area in the state.  Section 107(d)(1) of the CAA
also directs the state to provide the appropriate boundaries to EPA for
each area of the state, and provides that EPA may make modifications to
the boundaries submitted by the state as it deems necessary. A lead
nonattainment area must consist of that area that does not meet (or
contributes to ambient air quality in a nearby area that does not meet)
the Pb NAAQS.  Thus, a key factor in setting boundaries for
nonattainment areas is determining the geographic extent of nearby
source areas contributing to the nonattainment problem.  For each
monitor or group of monitors that exceed a standard, nonattainment
boundaries must be set that include a sufficiently large enough area to
include both the area judged to be violating the standard as well as the
source areas that are determined to be contributing to these violations.

Historically, Pb NAAQS violations have been the result of lead emissions
from large stationary sources and mobile sources that burn lead-based
fuels.  In some locations, a limited number of area sources have also
been determined to have contributed to violations.  Since lead has been
successfully phased out of motor vehicle gasoline, these sources are no
longer a significant source of ambient lead concentrations. At the
revised standard level, EPA expects stationary sources to be the primary
contributor to violations of the NAAQS.  However, it is possible that
fugitive dust emissions from area sources containing deposited lead will
also contribute to violations of the revised Pb NAAQS.  The location and
dispersion characteristics of these sources of ambient lead
concentrations are important factors in determining nonattainment area
boundaries.

In the proposed rule, EPA proposed to presumptively define the boundary
for designating a nonattainment area as the perimeter of the county
associated with the air quality monitor(s) which records a violation of
the standard.  This presumption was also EPA’s recommendation for
defining the nonattainment boundaries for the 1978 Pb NAAQS, and is
described in the 1992 General Preamble (57 FR 13549).  In the proposed
rule, EPA also requested comment on an option to presumptively define
the nonattainment boundary using the OMB-defined Metropolitan
Statistical Area (MSA) associated with the violating monitor(s).  This
presumption was used historically, by the CAA requirement, for the 1-hr
ozone and CO NAAQS nonattainment boundaries, and was also recommended by
EPA as the appropriate presumption for the 1997 8-hour ozone and PM2.5
NAAQS nonattainment boundaries.  In the proposed rule we stated that
under either option, the state and EPA may conduct additional
area-specific analyses that could lead EPA to depart from the
presumptive boundary. The factors relevant to such an analysis are
described below.

For the proposed Pb NAAQS, EPA recommended that nonattainment area
boundaries that deviate from presumptive county boundaries should be
supported by an assessment of several factors, which are discussed
below. The factors for determining nonattainment area boundaries for the
Pb NAAQS under this recommendation closely resemble the factors
identified in recent EPA guidance for the 1997 8-hour ozone NAAQS, the
1997 PM2.5 NAAQS, and the 2006 PM2.5 NAAQS nonattainment area
boundaries.  For this particular option of the proposal, EPA would
consider the following factors in assessing whether to exclude portions
of a county and whether to include additional nearby areas outside the
county as part of the designated nonattainment area:

(	Emissions in areas potentially included versus excluded from the
nonattainment area

(	Air quality in potentially included versus excluded areas

(	Population density and degree of urbanization including commercial
development in included versus excluded areas

(	Expected growth (including extent, pattern and rate of growth)

(	Meteorology (weather/transport patterns)

(	Geography/topography (mountain ranges or other air basin boundaries)

(	Jurisdictional boundaries (e.g., counties, air districts,
Reservations, etc.)

(	Level of control of emission sources

The proposal indicated that analyses of these factors may suggest
nonattainment area boundaries that are either larger or smaller than the
county boundary.  A demonstration supporting the designation of
boundaries that are less than the full county would be required to show
both that violation(s) are not occurring in the excluded portions of the
county and that the excluded portions are not source areas that
contribute to the observed violations.  Recommendations to designate a
nonattainment area larger than the county should also be based on an
analysis of these factors.  The proposal stated that EPA would consider
these factors as well in evaluating state and Tribal recommendations and
assessing whether any modifications are appropriate.

Under previous Pb implementation guidance, EPA advised that Governors
could choose to recommend lead nonattainment boundaries by using any
one, or a combination of the following techniques, the results of which
EPA would consider when making a decision as to whether and how to
modify the Governors’ recommendations: (1) qualitative analysis, (2)
spatial interpolation of air quality monitoring data, or (3) air quality
simulation by dispersion modeling.  These techniques are more fully
described in “Procedures for Estimating Probability of Nonattainment
of a PM10 NAAQS Using Total Suspended Particulate or  PM10 Data,”
December 1986 (see 57 FR 13549).  In the proposed rule,  EPA solicited
comments on the use of these factors and modeling techniques, and other
approaches, for adjusting county boundaries in designating nonattainment
areas.

2.	Comments and Responses

Several commenters submitted comments stating that the nonattainment
boundaries should be limited to the smallest political boundary that
possesses an ambient monitor-based design value above the standard,
unless subsequent analyses demonstrate that the boundaries should be
larger or smaller.  Commenters also stated that because lead does not
transport over long distances, monitoring data from upwind and downwind
sites illustrate that violations of the lead NAAQS are most commonly
isolated within a specific geographic area in close proximity to a major
source.

The EPA agrees with the commenter that lead emissions do not generally
transport over long distances (as compared, e.g., to fine particulate
matter).  In the proposed rule, EPA proposed to presumptively define the
boundary for designating a nonattainment area as the perimeter of the
county associated with the air quality monitor(s) which records a
violation of the standard.  In the proposed rule, EPA also stated that,
at the revised level of the standard, EPA expects stationary sources to
be the primary contributor to violations of the NAAQS, although we also
believe that nearby area sources may also contribute to concentrations
of lead emissions that may affect a violating monitor.  In light of the
possibility that a number of smaller sources may collectively contribute
to concentrations in excess of the NAAQS, EPA believes that adopting the
county boundary as the presumptive boundaries for lead nonattainment
areas is appropriate.  However, as stated in the proposed rule, a state,
Tribe, or EPA may conduct additional area-specific analyses that could
lead to the boundary for an area either being increased or decreased
from the presumptive county boundary.  In situations where a single
source, rather than multiple sources, is causing a NAAQS violation, the
EPA believes that a state may well be able to use area-specific analyses
to identify whether a nonattainment area that is smaller than the county
boundary is appropriate.

	Several commenters stated that EPA should use the MSA as the
presumptive boundary for designating areas for the Pb NAAQS in order for
a broader range of source emissions to be taken into consideration when
the state develops its SIP for the nonattainment area.

As stated previously, at the revised level of the standard, EPA expects
stationary sources to be the primary contributor to violations of the Pb
NAAQS, although we also expect that in some areas a number of smaller
sources may collectively contribute to concentrations in excess of the
NAAQS.  MSAs are frequently composed of several  counties.  Recognizing
that lead emissions, particularly ultracoarse particles, deposit
relatively short distances from the proximity of their initial source,
EPA believes that adopting the county boundary surrounding a violating
monitor as the presumptive boundary for any given lead nonattainment
area is more appropriate than presuming the larger MSA boundary.
Furthermore, as stated in the proposed rule (and the previous response),
a state, Tribe, or EPA may conduct additional area-specific analyses
that could lead to the boundary for an area either being increased or
decreased from the presumptive boundary.  Thus, where it appears that
emissions from one or more sources are contributing to nonattainment
throughout an MSA, the site-specific analysis may result in the
boundaries of the nonattainment area overlapping with those of the MSA.

3.	Final

The EPA is finalizing the option to presumptively define the boundary
for designating a nonattainment area as the perimeter of the county
associated with the air quality monitor(s) which records a violation of
the standard as proposed.  This presumption was also EPA’s
recommendation for defining the nonattainment boundaries for the
pre-existing Pb NAAQS, and is described in the 1992 General Preamble (57
FR 13549).  As a part of the county boundary presumption for
nonattainment areas, the state and/or EPA may conduct additional
area-specific analyses that could lead EPA to depart from the
presumptive county boundary. The EPA is also finalizing the factors
relevant to such an analysis as described in the proposed rule because
we believe that they will allow for both the State as well as EPA in
some cases to define better the appropriate boundaries for an area.  The
state may, in addition to submitting recommendations for boundaries
based on the factor analysis, also choose to recommend lead
nonattainment boundaries using any one, or a combination of the
following techniques, the results of which EPA would consider when
making a decision as to whether and how to modify the Governors’
recommendations: (1) qualitative analysis, (2) spatial interpolation of
air quality monitoring data, or (3) air quality simulation by dispersion
modeling,  as described more fully in “Procedures for Estimating
Probability of Nonattainment of a  PM10 NAAQS Using Total Suspended
Particulate or  PM10 Data,” December 1986 (see 57 FR 13549).

C.	Classifications

1.	Proposal

Section 172(a)(1)(A) of the CAA authorizes EPA to classify areas
designated as nonattainment for the purpose of applying an attainment
date pursuant to section 172(a)(2), or for other reasons.  In
determining the appropriate classification, EPA may consider such
factors as the severity of the nonattainment problem and the
availability and feasibility of pollution control measures (see section
172(a)(1)(A) of the CAA).  The EPA may classify lead nonattainment
areas, but is not required to do so.

While section 172(a)(1)(A) provides a mechanism to classify
nonattainment areas, section 172(a)(2)(D) provides that the attainment
date extensions described in section 172(a)(2)(A) do not apply to
nonattainment areas having specific attainment dates that are addressed
under other provisions of the part D of the CAA.  Section 192(a), of
part D, specifically provides an attainment date for areas designated as
nonattainment for the Pb NAAQS.  Therefore, EPA has legal authority to
classify lead nonattainment areas, but the 5 year attainment date under
section 192(a) cannot be extended pursuant to section 172(a)(2)(D).
Based on this limitation, EPA proposed not to establish classifications
within the 5 year interval for attaining any new or revised NAAQS.  This
approach is consistent with EPA’s previous classification decision for
Pb in the 1992 General Preamble (See 57 FR 13549, April 16, 1992).

2.	Comments and Responses:

Several commenters stated that they disagreed with EPA’s proposal not
to classify lead nonattainment areas under CAA section 172(a)(1)(A).
The commenters stated that existing nonattainment areas, meaning areas
that have not yet achieved the pre-existing Pb NAAQS, would benefit from
more rigorous SIP requirements associated with classifications.  The
commenters stated that such classifications are appropriate not only for
deadline extensions (not applicable in this case, as EPA notes), but
“for other purposes”.   The commenters state that such purposes
should include lower emissions thresholds for defining major stationary
sources, higher offset ratios, and a more ambitious definition of
reasonable further progress.

EPA stated in the proposed rule, that while section 172(a)(1)(A)
provides a mechanism to classify nonattainment areas, section
172(a)(2)(D) provides that the attainment date extensions described in
section 172(a)(2)(A) do not apply to nonattainment areas having specific
attainment dates that are addressed under other provisions of the part D
of the CAA.  Based on this limitation, EPA proposed not to establish
classifications within the 5 year interval for attaining any new or
revised NAAQS.  This approach is consistent with EPA’s previous
classification decision for Pb in the 1992 General Preamble (See 57 FR
13549, April 16, 1992) notes that subpart 2 of part D of the CAA
specifies mandatory control measures required for areas with different
classifications for the ozone standard, including such items as higher
offset ratios and specific percentage requirements for reasonable
further progress.  Areas with higher classifications are subject to more
stringent controls, but also receive additional time to attain the
standard.  Subpart 5 of part D contains no such provisions, but instead
requires submittal of a SIP within 18 months of designation of an area
as nonattainment, and requires attainment for all areas as expeditiously
as practicable, but no later than 5 years following designation.
Although EPA does have authority to establish classifications for Pb,
EPA continues to believe, taking into consideration these differing
statutory schemes (and particularly the requirement to attain as
expeditiously as practicable, but no later than 5 years from
designation) that it is not appropriate or necessary to establish
classifications for the revised Pb NAAQS.

3.	Final

The EPA is finalizing the guidance for classifications as provided in
the proposed rule.  Therefore, there will be no classifications under
the revised Pb NAAQS.

D.	Section 110(a)(2) Lead NAAQS Infrastructure Requirements

1.	Proposal

	Under section 110(a)(1) and (2) of the CAA, all states are required to
submit plans to provide for the implementation, maintenance, and
enforcement of any new or revised NAAQS.  Section 110(a)(1) and (2)
require states to address basic program elements, including requirements
for emissions inventories, monitoring, and modeling, among other things.
 States are required to submit SIPs to EPA which demonstrates that these
basic program elements have been addressed within 3 years of the
promulgation of any new or revised NAAQS.  Subsections (A) through (M)
of section 110(a)(2) listed below, set forth the elements that a
state’s program must contain in the SIP.  The list of section
110(a)(2) NAAQS implementation requirements are the following:

Ambient air quality monitoring/data system:  Section 110(a)(2)(B)
requires SIPs to provide for setting up and operating ambient air
quality monitors, collecting and analyzing data and making these data
available to EPA upon request.

Program for enforcement of control measures:  Section 110(a)(2)(C)
requires SIPs to include a program providing for enforcement of measures
and regulation and permitting of new/modified sources.

Interstate transport:  Section 110(a)(2)(D) requires SIPs to include
provisions prohibiting any source or other type of emissions activity in
the state from contributing significantly to nonattainment in another
state or from interfering with measures required to prevent significant
deterioration of air quality or to protect visibility.

Adequate resources:  Section 110(a)(2)(E) requires states to provide
assurances of adequate funding, personnel and legal authority for
implementation of their SIPs.

Stationary source monitoring system:  Section 110(a)(2)(F) requires
states to establish a system to monitor emissions from stationary
sources and to submit periodic emissions reports to EPA.

Emergency power:  Section 110(a)(2)(G) requires states to include
contingency plans, and adequate authority to implement them, for
emergency episodes in their SIPs.

Provisions for SIP revision due to NAAQS changes or findings of
inadequacies:  Section 110(a)(2)(H) requires states to provide for
revisions of their SIPs in response to changes in the NAAQS,
availability of improved methods for attaining the NAAQS, or in response
to an EPA finding that the SIP is inadequate.

Section 121 consultation with local and Federal government officials:
Section 110(a)(2)(J) requires states to meet applicable local and
Federal government consultation requirements of section 121.

Section 127 public notification of NAAQS exceedances:  Section
110(a)(2)(J) requires states to meet applicable requirements of section
127 relating to public notification of violating NAAQS.

PSD and visibility protection:  Section 110(a)(2)(J) also requires
states to meet applicable requirements of title I part C related to
prevention of significant deterioration and visibility protection.

Air quality modeling/data:  Section 110(a)(2)(K) requires that SIPs
provide for performing air quality modeling for predicting effects on
air quality of emissions of any NAAQS pollutant and submission of data
to EPA upon request.

Permitting fees:  Section 110(a)(2)(L) requires the SIP to include
requirements for each major stationary source to pay permitting fees to
cover the cost of reviewing, approving, implementing and enforcing a
permit.

Consultation/participation by affected local government:  Section
110(a)(2)(M) requires states to provide for consultation and
participation by local political subdivisions affected by the SIP.

2.	Final

	The EPA is finalizing the guidance related to the submittal of SIPs to
address the infrastructure requirements of section 110(a)(1) and (2) as
stated in the proposed rule.

E. 	Attainment Dates

1.	Proposal

	As discussed in the proposal, the maximum deadline date by which an
area is required to attain the Pb NAAQS is determined by the effective
date of the nonattainment designation for the area.  For areas
designated nonattainment for the revised Pb NAAQS, SIPs must provide for
attainment of the NAAQS as expeditiously as practicable, but no later
than 5 years from the date of the nonattainment designation for the area
(see section 192(a) of the CAA).  In the proposed rule, EPA stated it
would determine whether an area had demonstrated attainment of the Pb
NAAQS by evaluating air quality monitoring data from the one, two, or
three previous years as available.

2. 	Comments and Responses

A commenter stated that the attainment deadline for the current
nonattainment and maintenance areas should be three years.

Under the CAA, states are required to attain as expeditiously as
practicable (but in no case later than five years).  If it is
practicable for a nonattainment area to attain the standard within three
years, then the SIP must provide for attainment within three years.  If,
however, attainment within three years is not practicable, then EPA has
no authority to require attainment by that deadline.

2.	Final

	The EPA is generally finalizing the guidance related to attainment
dates as provided in the proposed rule.  States with nonattainment areas
will be required to attain the standard as expeditiously as practicable,
but in no event later than five years from the effective date of the
nonattainment designation.  EPA wishes to clarify that it will be
considering air quality monitoring data from the three previous years,
as available, in determining whether areas have demonstrated attainment
(i.e., EPA would only consider data for less than the three previous
years in situations where the data for all three years was unavailable).

F.  	Attainment Planning Requirements

	Any state containing an area designated as nonattainment with respect
to the Pb NAAQS must develop for submission, a SIP meeting the
requirements of part D, Title I, of the CAA, providing for attainment by
the applicable deadline (see sections 191(a) and 192(a) of the CAA).  As
indicated in section 191(a) all components of the lead part D SIP must
be submitted within 18 months of the effective date of an area’s
designation as nonattainment.  Additional specific plan requirements for
lead nonattainment areas are outlined in 40 CFR 51.117.

The general part D nonattainment plan requirements are set forth in
section 172 of the CAA. Section 172(c) specifies that SIPs submitted to
meet the part D requirements must, among other things, include
Reasonably Available Control Measures (RACM) (which includes Reasonably
Available Control Technology (RACT)), provide for Reasonable Further
Progress (RFP), include an emissions inventory, require permits for the
construction and operation of major new or modified stationary sources
(see also CAA section 173), contain contingency measures, and meet the
applicable provisions of section 110(a)(2) of the CAA related to the
general implementation of a new or revised NAAQS.  It is important to
note that lead nonattainment SIPs must meet all of the requirements
related to part D of the CAA, including those specified in section
172(c), even if EPA does not provide separate specific guidance for each
provision.

1.	RACM/RACT for Lead Nonattainment Areas

	a.	Proposal

Lead nonattainment area SIPs must contain RACM (including RACT) that
address sources of ambient lead concentrations.  In general, EPA
believes that lead NAAQS violation issues will usually be attributed to
emissions from stationary sources. In EPA’s 2002 National Emissions
Inventory (NEI), there were 12 stationary sources in the country with
lead emissions over 5 tons per year, and 124 sources over 1 ton of lead
emissions per year.

Some emissions that contribute to violations of the Pb NAAQS may also be
attributed to smaller area sources.  At primary lead smelters, the
process of reducing concentrated ore to lead involves a series of steps,
some of which are completed outside of buildings, or inside of buildings
that are not totally enclosed.  Over a period of time, emissions from
these sources have been deposited in neighboring communities (e.g., on
roadways, parking lots, yards, and off-plant property).  This
historically deposited lead, when disturbed, may be re-entrained into
the ambient air and may contribute to violations of the Pb NAAQS in
affected areas.

The first step in addressing RACM for lead is identifying potential
control measures for sources of lead in the nonattainment area.  A
suggested starting point for specifying RACM in lead nonattainment area
SIPs is outlined in appendix 1 of the guidance entitled “State
Implementation Plans for Lead Nonattainment Areas; Addendum to the
General Preamble for the Implementation of Title I of the Clean Air Act
Amendments of 1990”, 58 FR 67752, December 22, 1993.  If a state is
aware of facts, or receives substantive public comments, that
demonstrate through appropriate documentation, that additional control
measures may be reasonably available in a specific area, the measures
should be added to the list of available measures for consideration in
that particular area.

While EPA does not presume that these control measures are reasonably
available in all areas, a reasoned justification for rejection of any
available control measure should be prepared.  If it can be shown that
measures, considered both individually as well as in a group, are
unreasonable because emissions from the affected sources are
insignificant, then the measures may be excluded from further
consideration as they would not be representative of RACM for the
affected area. The resulting control measures should then be evaluated
for reasonableness, considering their technological feasibility and the
cost of control in the area for which the SIP applies.  In the case of
public sector sources and control measures, this evaluation should
consider the impact and reasonableness of the measures on the municipal,
or other governmental entity that must assume the responsibility for
their implementation.  It is important to note that a state should
consider the feasibility of implementing measures in part when full
implementation would be infeasible.  A reasoned justification for
partial or full rejection of any available control measure, including
those considered or presented during the state’s public hearing
process, should be prepared.  The justification should contain a
detailed explanation, with appropriate documentation, as to why each
rejected control measure is deemed infeasible or otherwise unreasonable
for implementation.

	Economic feasibility considers the cost of reducing emissions and the
difference between the cost of the emissions reduction approach at the
particular source in question and the costs of emissions reduction
approaches that have been implemented at other similar sources.  Absent
other indications, EPA as a general matter expects that it is reasonable
for similar sources to bear similar costs of emissions reduction.
Economic feasibility for RACT purposes is largely determined by evidence
that other sources in a particular source category have in fact applied
the control technology or process change in question.  The EPA also
encourages the development of innovative measures not previously
employed which may also be technically and economically feasible.

	The capital costs, annualized costs, and cost effectiveness of an
emissions reduction technology should be considered in determining
whether a potential control measure is reasonable for an area or state.
One available reference for calculating costs is the EPA Air Pollution
Control Cost Manual, which describes the procedures EPA uses for
determining these costs for stationary sources. The above costs should
be determined for all technologically feasible emission reduction
options.  States may give substantial weight to cost effectiveness in
evaluating the economic feasibility of an emission reduction technology.
 The cost effectiveness of a technology is its annualized cost ($/year)
divided by the emissions reduced (i.e., tons/year) which yields a cost
per amount of emission reduction ($/ton).  Cost effectiveness provides a
value for each emission reduction option that is comparable with other
options and other facilities.  With respect to a given pollutant, a
measure is likely to be reasonable if it has a cost per ton similar to
other measures previously employed for that pollutant.  In addition, a
measure is likely to be reasonable from a cost effectiveness standpoint
if it has a cost per ton similar to that of other measures needed to
achieve expeditious attainment in the area within the CAA’s time
frames.

The fact that a measure has been adopted or is in the process of being
adopted by other states is also an indicator (though not a definitive
one) that the measure may be technically and economically feasible for
another state.  We anticipate that states may decide upon RACT and RACM
controls that differ from state to state, based on the state’s
determination of the most effective strategies given the relevant
mixture of sources and potential controls in the relevant nonattainment
areas, and differences in difficulty of attaining expeditiously.
Nevertheless, states should consider and address RACT and RACM measures
developed for other areas, as part of a well reasoned RACT and RACM
analysis.  The EPA’s own evaluation of SIPs for compliance with the
RACT and RACM requirements will include comparison of measures
considered or adopted by other states.

	In considering what level of control is reasonable, EPA is not adopting
a specific dollar per ton cost threshold for RACT. Areas with more
serious air quality problems typically will need to obtain greater
levels of emissions reductions from local sources than areas with less
serious problems, and it would be expected that their residents could
realize greater public health benefits from attaining the standard as
expeditiously as practicable.  For these reasons, we believe that it
will be reasonable and appropriate for areas with more serious air
quality problems and higher design values to impose emission reduction
requirements with generally higher costs per ton of reduced emissions
than the cost of emissions reductions in areas with lower design values.
 In addition, where essential reductions are more difficult to achieve
(e.g., because many sources are already controlled), the cost per ton of
control may necessarily be higher.

The EPA believes that in determining appropriate emission control
levels, the state should consider the collective public health benefits
that can be realized in the area due to projected improvements in air
quality.  Because EPA believes that RACT requirements will be met where
the state demonstrates timely attainment, and areas with more severe air
quality problems typically will need to adopt more stringent controls,
RACT level controls in such areas will require controls at higher cost
effectiveness levels ($/ton) than areas with less severe air quality
problems.

In identifying the range of costs per ton that are reasonable,
information on benefits per ton of emission reduction can be useful as
one factor to consider. It should be noted that such benefits estimates
are subject to significant uncertainty and that benefits per ton vary in
different areas.  Nonetheless this information could be used in a way
that recognizes these uncertainties.  If a per ton cost of implementing
a measure is significantly less than the anticipated benefits per ton,
this would be an indicator that the cost per ton is reasonable. If a
source contends that a source-specific RACT level should be established
because it cannot afford the technology that appears to be RACT for
other sources in its source category, then the source should support its
claim by providing detailed and verified information regarding the
impact of imposing RACT on:

fixed and variable production costs ($/unit),

product supply and demand elasticity,

product prices (cost absorption vs. cost pass-through),

expected costs incurred by competitors,

company profits, and

employment costs.

The technical guidance entitled “Fugitive Dust Background Document and
Technical Information Document for Best Available Control Measures”
(EPA-450/2-92-004, September 1992) provides an example for states on how
to analyze control costs for a given area.

Once the process of determining RACM for an area is completed, the
individual measures should then be converted into a legally enforceable
vehicle (e.g., a regulation or permit program) (see section 172(c)(6)
and section 110(a)(2)(A) of the CAA).  The regulations or other measures
submitted should meet EPA’s criteria regarding the enforceability of
SIPs and SIP revisions. These criteria were stated in a September 23,
1987 memorandum (with attachments) from J. Craig Potter, Assistant
Administrator for Air and Radiation; Thomas L. Adams, Jr. Assistant
Administrator for Enforcement and Compliance Monitoring; and S. Blake,
General Counsel, Office of the General Counsel; entitled “Review of
State Implementation Plans and Revisions of Enforceability and Legal
Sufficiency.” As stated in this memorandum, SIPs and SIP revisions
that fail to satisfy the enforceability criteria should not be forwarded
for approval.  If they are submitted, they will be disapproved if, in
EPA’s judgment, they fail to satisfy applicable statutory and
regulatory requirements.

The EPA’s historic definition of RACT is the lowest emissions
limitation that a particular source is capable of meeting by the
application of control technology that is reasonably available
considering technological and economic feasibility.  RACT applies to the
“existing sources” of lead in an area including stack emissions,
industrial process fugitive emissions, and industrial fugitive dust
emissions (e.g., on-site haul roads, unpaved staging areas at the
facility, etc) (see section 172(c)(1)).  The EPA’s previous guidance
for implementing the pre-existing Pb NAAQS recommends that stationary
sources which emit a total of 5 tpy of lead or lead compounds, measured
as elemental lead, be the minimum starting point for RACT analysis (see
58 FR 67750, December 22, 1993).  Further, EPA’s existing guidance
recommends that available control technology be applied to those
existing sources in the nonattainment area that are reasonable to
control in light of the attainment needs of the area and the feasibility
of such controls.  Thus, under existing guidance, a state’s control
technology analysis may need to include sources which actually emit less
than 5 tpy of  lead or lead compounds in the area, or other sources in
the area that are reasonable to control, in light of the attainment
needs and feasibility of control for the area.

 significantly lower than the current level of 1.5 μg/m3, EPA requested
comment on the appropriate threshold for the minimum starting point for
future Pb RACT analyses for stationary lead sources in nonattainment
areas.  In the proposed rule, EPA requested comment on the emissions
level associated with the minimum network source monitoring
requirements. These source levels range from 200 kg/yr to 600 kg/yr.
The EPA also stated that one possible approach for RACT is to recommend
that RACT analyses for Pb sources be consistent with sources that are
required to monitor such that all stationary sources above 200 kg/yr to
600 kg/yr should undergo a RACT review.  EPA also requested comment on
source monitoring for stationary sources that emit lead emissions in
amounts that have potential to cause ambient levels at least one-half
the selected NAAQS level.  This suggests another potential
recommendation for the starting point for the RACT analysis.  The EPA
sought comment on these ideas as well as any information which
commenters could provide that would help inform EPA’s recommendation
on an appropriate emissions threshold for initiating RACT analyses.

b.	Comments and Responses

μg/m3 and the existing threshold for RACT analysis is 5 tpy.  Since the
standard is being reduced by a factor of ten, from 1.5  μg/m3 to 0.15
μg/m3, it is appropriate to also reduce the threshold for RACT analysis
by a factor of 10, from 5 tpy to 0.5 tpy.  Furthermore, the monitor
siting criteria include a requirement for monitoring agencies to conduct
monitoring taking into account sources that are expected to exceed the
NAAQS, and require monitoring for sources which emit Pb at a rate of one
ton per year.  Although EPA expects that sources emitting less than one
tpy may also contribute to violations of the revised Pb NAAQS, EPA
believes that the one tpy requirement in the monitor siting criteria
provides a benchmark that is more likely to clearly identify sources
that would contribute to exceedances of the NAAQS.  Accordingly, using
50% of that figure (0.5 tpy) as the threshold for RACT analysis is
generally consistent with EPA’s consideration in the proposal of
setting the RACT threshold to include those stationary sources that emit
lead emissions in amounts that have the potential to cause ambient
levels at least one-half the selected NAAQS.

EPA believes that setting the RACT threshold higher (e.g., at 1 tpy)
would not be appropriate because it is likely that in a nonattainment
area sources emitting less than one tpy are contributing to the
nonattainment of the NAAQS.  EPA also does not believe a lower threshold
is warranted as a general matter, but EPA agrees with commenters that
the state’s control technology analysis should also include, as
appropriate, sources which actually emit less than the threshold level
of 0.5 tpy of lead or lead compounds in the area, or other sources in
the area that are reasonable to control, in light of the attainment
needs and feasibility of controls for the affected area.

Several commenters stated that in the proposed rule EPA suggests that
the 1993 guidance document, which lists control measures as a starting
point for state’s consideration, puts the burden on the public to
demonstrate through appropriate documentation that additional control
measures may be reasonably available in a particular circumstance for an
area. The commenters further stated that in light of an anticipated
substantial reduction in the Pb NAAQS, as well as the failure of the
remaining two existing nonattainment areas to achieve attainment of the
pre-existing (1978) NAAQS under the 1993 guidance, that both EPA and the
states should bear the principal responsibility for developing an
updated roster of successful control measures.

As stated in the proposed rule, EPA believes that the regulations,
policies, and guidance currently in place for the implementation of the
pre-existing Pb NAAQS are still appropriate to address the issues
required to implement the revised Pb NAAQS.  The EPA believes that these
guidance, policies, and regulations should be used by states, local, and
Tribal governments as a starting point to begin implementation of the
revised Pb NAAQS.  The EPA expects that as states gain additional
experience with implementing the revised NAAQS, additional information
on successful control measures will become available to states, EPA, and
the public.  The EPA will, as appropriate, review, and revise or update
policies, guidance, and regulations to provide for effective
implementation of the Pb NAAQS.

c.	Final

The EPA is finalizing the guidance related to RACM (including RACT) for
lead nonattainment areas consistent with the proposed rule.  Based upon
the above considerations regarding the scale of the reduction in the
standard, the final monitor siting criteria, and the public comments
received related to the starting point for a RACT analysis, EPA is
recommending a threshold for RACT analysis such that at least all
stationary sources emitting 0.5 tpy or more should undergo a RACT
review.

2.  	Demonstration of Attainment for Lead Nonattainment Areas

a.	Proposal

The SIPs for lead nonattainment areas should provide for the
implementation of control measures for point and area sources of lead
emissions which demonstrate attainment of the Pb NAAQS as expeditiously
as practicable, but no later than the applicable statutory attainment
date for the area (see also 40 CFR 51.117(a) for additional control
strategy requirements).  Therefore, if a state adopts less than all
available measures in an area but demonstrates, adequately, that
reasonable further progress (RFP), and attainment of the Pb NAAQS are
assured, and the application of all such available measures would not
result in attainment any faster, then a plan which requires
implementation of less than all technologically and economically
available measures may be approved (see 44 FR 20375 (April 4, 1979) and
56 FR 5460 (February 11, 1991)).  The EPA believes that it would be
unreasonable to require that a plan which demonstrates attainment
include all technologically and economically available control measures
even though such measures would not expedite attainment.  Thus, for some
sources in areas which demonstrate attainment, it is possible that some
available control measures may not be “reasonably” available because
their implementation would not expedite attainment for the affected
area.

b.	Final

The EPA is finalizing the guidance related to demonstration of
attainment for lead nonattainment areas as stated in the proposed rule.
Further discussion of modeling for attainment and other topics is
presented below.

3.  	Reasonable Further Progress (RFP)

a.	Proposal

	Part D SIPs must provide for RFP (see section 172(c)(2) of the CAA).
Section 171 of the CAA defines RFP as “such annual incremental
reductions in emissions of the relevant air pollution as are required by
part D, or may reasonably be required by the Administrator for the
purpose of ensuring attainment of the applicable NAAQS by the applicable
attainment date.”  Historically, for some pollutants, RFP has been met
by showing annual incremental emission reductions generally sufficient
to maintain linear progress toward attainment by the applicable
attainment date. The EPA believes that RFP for lead nonattainment areas
should be met by “adherence to an ambitious compliance schedule”
which is expected to periodically yield significant emission reductions,
and as appropriate, linear progress.  The EPA recommends that SIPs for
lead nonattainment areas provide a detailed schedule for compliance of
RACM (including RACT) in the affected areas and accurately indicate the
corresponding annual emission reductions to be achieved.  In reviewing
the SIP, EPA believes that it is appropriate to expect early
implementation of less technology-intensive control measures (e.g.,
controlling fugitive dust emissions at the stationary source, as well as
required controls on area sources) while phasing in the more
technology-intensive control measures, such as those involving the
installation of new hardware.  Finally, failure to implement the SIP
provisions required to meet annual incremental reductions in emissions
(i.e., RFP) in a particular area could result in the application of
sanctions as described in section 179(b) of the CAA (pursuant to a
finding under section 179(a)(4)), and the implementation of contingency
measures required by section 172(c)(9) of the CAA.

b.	Comments and Responses

Several commenters stated that EPA’s proposal related to RFP would
allow states to avoid the need to demonstrate linear progress towards
attainment, departing from the typical method used, and statutorily
required in some cases, for other criteria pollutants.  These commenters
further state that the recognition that some nonattainment urban areas
have numerous sources contributing to excessive ambient levels of lead
which undermines the reasoning employed to justify a non-linear approach
in the context of single source nonattainment areas.  If areas with
large sources install key controls early on in the attainment process,
and thus achieve attainment ahead of schedule, that would advance the
goals and requirements of the CAA.

Historically, for some pollutants, RFP has been met by showing annual
incremental emission reductions generally sufficient to maintain linear
progress toward attainment by the applicable attainment date. As EPA has
previously noted, we expect that some nonattainment designations will be
attributable to a single stationary source, and others may be
attributable to a number of smaller sources.  Where a single source is
the cause of nonattainment, EPA would not expect linear progress towards
attainment.  Rather, there may be relatively less progress while the
source adopts non-technological control measures and begins to install
necessary technological controls, and then significant progress towards
attainment in a short period of time once all the controls are
operational.  EPA expects that, since states are required to attain the
standard as expeditiously as practicable, the SIP will require large
sources to install “key controls” as expeditiously as practicable.
At the same time, where a number of sources are contributing to
nonattainment, it is more reasonable to expect that controls (both
technological and non-technological) may be adopted at different times,
making linear progress a more reasonable expectation.  To accommodate
both of these possible situations, EPA concludes it is appropriate that
RFP for lead nonattainment areas should be met by the strict adherence
to an ambitious compliance schedule which is expected to periodically
yield significant emission reductions, and, to the extent appropriate,
linear progress.

c.	Final

The EPA is finalizing the guidance related to reasonable further
progress (RFP) consistent with the proposed rule.  The EPA believes that
RFP for lead nonattainment areas should be met by the strict adherence
to an ambitious compliance schedule which is expected to periodically
yield significant emission reductions, and to the extent appropriate,
linear progress.  The EPA recommends that SIPs for lead nonattainment
areas provide a detailed schedule for compliance of RACM (including
RACT) and accurately indicate the corresponding annual emission
reductions to be achieved.  In reviewing the SIP, EPA believes that it
is appropriate to expect early implementation of less
technology-intensive control measures (e.g., work practices to control
fugitive dust emissions at the stationary sources) while phasing in the
more technology-intensive control measures, such as those involving the
installation of new hardware.  The EPA believes that the expeditious
implementation of RACM/RACT at affected sources within the nonattainment
area is an appropriate approach to assure attainment of the Pb NAAQS in
an expeditious manner.

4.   	Contingency Measures

a.	Proposal

Section 172(c)(9) of the CAA defines contingency measures as measures in
a SIP that are to be implemented if an area fails to achieve and
maintain RFP, or fails to attain the NAAQS by the applicable attainment
date.  Contingency measures must be designed to become effective without
further action by the state or the Administrator, upon determination by
EPA that the area has failed to achieve, or maintain reasonable further
progress (RFP), or attain the Pb NAAQS by the applicable statutory
attainment date.  Contingency measures should consist of available
control measures that are not already included in the primary control
strategy for the affected area.

Contingency measures are important for lead nonattainment areas, which
may violate the NAAQS generally due to emissions from stationary
sources, for several reasons.  First, process and fugitive emissions
from these stationary sources, and the possible re-entrainment of
historically deposited emissions, have historically been difficult to
quantify.  Therefore, the analytical tools for determining the
relationship between reductions in emissions, and resulting air quality
improvements, can be subject to some uncertainties.  Second, emission
estimates and attainment analysis can be influenced by overly-optimistic
assumptions about fugitive emission control efficiency.

Examples of contingency measures for controlling area source fugitive
emissions may include measures such as stabilizing additional storage
piles.  Examples of contingency measures for process-related fugitive
emissions include increasing the enclosure of buildings, increasing air
flow in hoods, modifying operation and maintenance procedures, etc.
Examples of contingency measures for stack sources include reducing
hours of operation, changing the feed material to lower lead content,
and reducing the occurrence of malfunctions by modifying operation and
maintenance procedures, etc.

	Section 172(c)(9) provides that contingency measures should be included