Document ID: EPA-HQ-OAR-2003-0062-0249
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2007-04-25T04:00Z

Final revisions reflected from 3/12/07 draft  

I.  Transportation Conformity

	Transportation conformity is required under CAA section 176(c) (42
U.S.C. 7506(c)) to ensure that Federally supported highway and transit
project activities are consistent with (“conform to”) the purpose of
the SIP.  Conformity currently applies to areas that are designated
nonattainment, and those redesignated to attainment after 1990
(“maintenance areas” with plans developed under CAA section 175A)
for the following transportation-related criteria pollutants:  ozone,
particulate matter (PM2.5 and PM10), carbon monoxide (CO), and nitrogen
dioxide (NO2).  Conformity to the purpose of the SIP means that
transportation activities will not cause new air quality violations,
worsen existing violations, or delay timely attainment of the relevant
NAAQS (or “standards”).

	The final PM2.5 implementation rule does not contain any revisions to
the transportation conformity regulation.  The EPA addressed the
transportation conformity requirements that apply in PM2.5 nonattainment
and maintenance areas in three separate rulemakings as described below.

	First, on July 1, 2004, EPA published a final rule (69 FR 40004) that
addressed the majority of requirements that apply in PM2.5 areas
including: 

regional conformity tests to be used in conformity determinations both
before and after SIPs are submitted and motor vehicle emissions budgets
are found adequate or are approved;

consideration of direct PM2.5 emissions in regional emissions analyses;

consideration of re-entrained road dust in PM2.5 regional emissions
analyses;

consideration of transportation construction-related fugitive dust in
PM2.5 regional emissions analyses; and

compliance with PM2.5 SIP control measures.

	Then on May 6, 2005, EPA promulgated a final rule (70 FR 24280) that
specified the transportation-related PM2.5 precursors and when they
apply in transportation conformity determinations in PM2.5 nonattainment
and maintenance areas.

	Finally, on March 10, 2006, EPA promulgated a final rule (71 FR 12468)
that establishes the criteria for determining which transportation
projects must be analyzed for local particle emissions impacts in PM2.5
and PM10 nonattainment and maintenance areas.  If required, an analysis
of local particle emissions impacts is done as part of a transportation
project’s conformity determination.

Transportation conformity for the PM2.5 standards  began applying in
PM2.5 nonattainment areas on April 5, 2006,  one year after the
effective date of EPA’s PM2.5 nonattainment designations (i.e., April
5, 2005).  CAA section 176(c)(6) and 40 CFR 93.102(d) provide a one-year
grace period before conformity applies in areas newly designated
nonattainment for a new standard.  PM2.5 SIP submissions such as RFP and
attainment demonstrations would identify motor vehicle emissions budgets
(“budgets”) for direct PM2.5 or PM2.5 precursors, as described
below.  These budgets would be used for satisfying transportation
conformity requirements, once the budgets are found adequate or the SIP
containing the budgets is approved by EPA.  For example, state and local
agencies would consider during the development of the PM2.5 SIP whether
on-road mobile source SO2 emissions are a significant contributor to an
area’s PM2.5 air quality problem, and if so, establish a SO2 motor
vehicle emissions budget for transportation conformity purposes.

The EPA has previously addressed its intentions regarding when budgets
must be established in PM2.5 SIPs for transportation conformity
purposes.  RFP plans, attainment demonstrations, and maintenance plans
must include a budget for direct PM2.5 emissions, except for certain
cases as described below.  All PM2.5 SIP budgets would include directly
emitted PM2.5 motor vehicle emissions from tailpipe, brake wear, and
tire wear.  States should also consider whether re-entrained road dust
or highway and transit construction dust are significant contributors
and should be included in the PM2.5 budget.  For further information,
see 40 CFR 93.102(b) and 93.122(f) of the transportation conformity
regulation, as well as Sections VIII-X of the July 1, 2004 conformity
rule preamble at 69 FR 40031-40036.

Under certain circumstances, directly emitted PM2.5 from on-road mobile
sources may be found an insignificant contributor to the air quality
problem and NAAQS.  Section 93.109(k) of the conformity rule states that
“[s]uch a finding would be based on a number of factors, including the
percentage of motor vehicle emissions in the context of the total SIP
inventory, the current state of air quality as determined by monitoring
data for that NAAQS, the absence of SIP motor vehicle control measures,
and historical trends and future projections of the growth of motor
vehicle emissions.”  The EPA discussed its intentions for applying the
insignificance provision in the July 2004 final rule (69 FR
40061-40063).  

In the May 6, 2005 final rule, EPA provided details regarding when
states must establish SIP budgets for any PM2.5 precursor (i.e., NOx,
VOCs, SO2 and ammonia). If through the SIP process a state concludes
that on-road mobile source emissions of one or more precursors are
significant (i.e. need to be addressed in order to attain the PM2.5
standards as expeditiously as practicable), then EPA expects that the
state will include a budget in the SIP for each of the relevant
precursors.  (70 FR 24287)  The EPA also noted in the May 2005
conformity rule that, if inventory and modeling analyses demonstrating
RFP, attainment or maintenance indicate a level of emissions of a
precursor that must be maintained to demonstrate compliance with the
applicable requirement, then that level of emissions should be clearly
identified in the SIP as a budget for transportation conformity
purposes, even if the SIP does not establish particular controls for the
given precursor.  If the state fails to identify such a level of
emissions as a budget, EPA will find the submitted SIP budgets
inadequate because the SIP fails to clearly identify the motor vehicle
emissions budget as required by the conformity rule (40 CFR
93.118(e)(4)(iii)).  (70 FR 24287)  

In determining whether the on-road mobile source emissions of a PM2.5
precursor are significant, state and local agencies would use the
criteria for insignificance findings provided in 40 CFR 93.109(k) of the
transportation conformity regulation.  A further discussion of the
criteria to be considered in establishing PM2.5 precursor budgets is
contained in the May 2005 final transportation conformity rule (70 FR
24282-24288).  If state and local agencies conclude that on-road sources
of a precursor are not a significant contributor to the area’s PM2.5
air quality problem, as described above, motor vehicle emissions budgets
would not be established even though emissions may be addressed in the
area’s RFP plan, attainment demonstration and/or maintenance plan.  

For example, PM2.5 SIPs must address SO2 emissions from applicable
sources, as described in the final rule.  As described above, during the
development of the PM2.5 SIP, state and local agencies would consider
whether on-road mobile source SO2 emissions are a significant
contributor to the area’s PM2.5 air quality problem. If determined to
be a significant contributor, the state would establish an SO2 motor
vehicle emissions budget for transportation conformity purposes.  Any
such budgets would be used in future conformity determinations after
they are found adequate or are approved by EPA.  If the state and local
agencies conclude that on-road mobile sources of SO2 are not a
significant contributor to the area’s PM2.5 air quality problem, motor
vehicle emissions budgets would not be established for SO2 even though
emissions of SO2 would be addressed in the area’s attainment
demonstration and/or RFP plan. 

Finally, PM2.5 areas need to consider when budgets should be established
from SIP inventories for the annual and/or 24-hour PM2.5 standards.  The
Clean Air Act and transportation conformity rule require that conformity
determinations consider both PM2.5 standards in all PM2.5 nonattainment
and maintenance areas.  However, transportation plan and TIP conformity
determinations and regional emissions analyses could address only one
PM2.5 standard if meeting conformity for the controlling standard would
ensure that statutory requirements are met for both standards.  (71 FR
12471, March 10, 2006)  Similarly, if a state determined through the SIP
process that demonstrating attainment for the annual PM2.5 standard will
allow an area to meet both PM2.5 standards, then budgets for conformity
purposes would only be required for the annual PM2.5 standard.  Such a
case would most likely occur in areas that are violating the annual
standard and have air quality data that is significantly below the
24-hour standard. 

Draft 3/12/07 for OMB Submittal