1 2008 LEAD (Pb) NAAQS IMPLEMENTATION Questions and Answers

INFRASTRUCTURE STATE IMPLEMENTATION PLANS (SIP s )

1 Q. Are states required to submit “infrastructure SIPs” for the revised Lead national ambient air quality standards ( NAAQS ) ?

A. Yes. Under section 110 of the Clean Air Act (CAA) , all states (including those without any nonattainment areas) are required to submit infrastructure SIPs within three years of the promulgation of a new or revised NAAQS. Since the Lead NAAQS was signed and wide ly
disseminated o n October 15 , 2008, the infrastructure SIPs are due by October 15, 2011. Among the requirements for an infrastructure SIP is a permit program implementing prevention of significant deterioration (PSD).

PREVENTION OF SIGNIFICANT DETERIORATION (PSD) AND NONATTAINMENT NEW SOURCE REVIEW (NSR)

2 Q

. What are the requirements under the Prevention of Significant Deterioration (PSD) and nonattainment New Source Review (NSR) permitting programs for Lead ?

A. The PSD program and nonattainment NSR programs are often referred to as the major NSR program because these programs regulate only major stationary sources. The PSD program applies when a major stationary source of any pollutant, located in an area designa ted as attainment or unclassifiable for any criteria pollutant, is constructed, or u ndergoes a major
modification. The nonattainment NSR program applies when a major source of a criteria pollutant that is located in an area that is designated as non attainm ent for that pollutant is
constructed or u ndergoes a major modification. The major source threshold under the PSD program is generally either 100 or 250 tons per year (tpy) of any regulated NSR pollutant, depending upon whether the source is included withi n one of the categories of sources listed in the applicable PSD regulations (40 CFR 51.166(b)(1)(i)(a) or 52.21(b)(1)(i)(a)). The major source
threshold for Lead under the nonattainment NSR program is 100 tpy for all source categories. Accordingly, the no nattainment NSR program for Lead applies when any major source of Lead located in an area designated nonattainment for Lead is constructed, or u ndergoes a major
modification. Under both programs, a major modification is a project at a major stationary

sour ce that results in a significant emissions increase and a significant net emissions increase, where “significant” for Lead emiss ions is defined as 0.6 tpy

.

The PSD requirements include but are not limited to the following:2 • Installation of Best Available Control Technology (BACT); • Air quality monitoring and modeling analyses to ensure that a project’s emissions will not cause or contribute to a violation of any NAAQS ; • Notification of Federal Land Manager of nearby Class I areas; and
• Public comment on a permit.

Nonattainment NSR requirements include but are not limited to: • Installation of Lowest Achievable Emissions Rate (LAER) control technology; • Offsetting new emissions with creditable emissions reductions;
• A certification that all m ajor sources owned and operated in the state by the same owner are in compliance with all applicable requirements under the CAA; • An alternatives analysis demonstrating that the benefits of the proposed source significantly outweigh the environmental and social costs imposed as a result of its location, construction, or modification; and
• Public comment on a permit.

SIP DEVELOPMENT

3 Q

. When are Lead attainment demonstration SIP s due?

A. Attainment demonstration SIPs are due eighteen months after the effective date of an
area’s designation. For the first round of designations the attainme nt SIPs are due June 30,

2012. For the second round of designation s, the attainment SIP s are expected to be due June 30, 2013.

4 Q. When is the attainment date?

A. Areas are required to attain the revised Lead standard as expeditiously as practicable, but no later than 5 years from the date the nonattainment designation became effective. The attainment date for the first round is December 31, 2015, and the attainment date for the second round is expected to be December 31, 2016.

5 Q

. How do you measure reasonable further progress (RFP) for Lead ?

A. Demonstrating reasonable further progress requires adherence to an ambitious compliance
schedule. The schedule is expected to provide for periodic yields in significant emissions
reductions or line ar progress when appropriate. The U. S. Environmental Protection Agency ( EPA ) recommends that SIPs for Lead nonattainment areas provide a detailed schedule for compliance of reasonably available control measures ( RACM ), including reasonably available control technology ( RACT)

, and accurately indicate the corresponding annual emissi on reductions to be achieved. Expeditious implementation of RACM and RACT by the sources in the nonattainment areas helps to ensure attainment of the standard by the attainment date.3 6 Q

. How do you calculate the amount of emission s reduction necessary for contingency
measures?

A. EPA thinks a reasonable guide to the amount of emissions reduction that a single measure or group of measures should achieve for contingency purposes would be equal to the amount represented by annual average RFP i n the attainment plan. For example, if the attainment plan provides for 1 tpy of Lead reductions over a 5

- year attainment horizon, the recommended target for contingency measures would be at least 0 .2 tpy. Contingency measures should generally go into effect, when necessary, without significant action on the part of the state or

EPA.

EPA recommends using the year of designation (either 2010 or 2011) as the base year for the contingency measure calculation

. States may use an other year if they show anot her year is more appropriate. For example, if complete emissions data for 2010 are not available, a state

may wish to use emissions data from the 2008 periodic inventory. The b asic f ormula is :

Annual average RFP = ( Attainment level emissions

– base year emissions (2010 or 2011) ) ÷ 5

,

where 5 is t he n umber of years between the base year and attainment year (2015 or 2016)

.

T raditionally the amount of reductions required for contingency measures has bee n m e asured
in terms of tpy reductions at a source. However

, where a single source is responsible for

nonattainment

, it may be possible to identify the amount of reductions required by reference to reductions in ambient air concentrations (e.g., measures sufficient to reduce ambient air

concentratio ns by 0

. 02 μg/m 3 ). EPA would need to evaluate the approvability of such an approach on a case

- by

- case basis based on the sources within the nonattainment area, the modeling used, and available control measures.

7 Q. Will the EPA approve a Lead SIP that contains triggers for early implementation of contingency measures?

A. Yes. If an attainment SIP relies on a specific set of control measures to demonstrate timely attainment of the NAAQS, then those control measures are considered necessary for

attainm ent and are not contingency measures. A SIP must also contain additional control measures that must be implemented if an area fails to attai n or fails to demonstrate RFP. (See General Preamble for the Implementation of Title I of the Clean Air Act Amendmen t of 1990,

57 FR 13498

, April 16, 1992 ). If a state elects to implement contingency measures earlier than would be triggered by such a failure, EPA does not believe that the state needs to adopt additional contingency measures to backfill for the early activation of those contingency measures. Of course, if an area fails to attain or fails to demonstrate RFP then addition al contingency measures are needed and must be adopted in accordance with previous guidance. (See ” Early Implementation of Contingency Measures for Ozone and Carbon Mo noxide (CO)

Nonattainment Areas

, ” G.T. Helms, August 1 3, 1993, available at http://www.epa.gov/ttn/oarpg/t1pgm.html

.4 8 Q

. Are Lead nonattainment areas eligible for one
- year attainment date extensions?

A. No. CAA, Subpart 1, Section 172(a)(2)(D) precludes the Administrator from granting
attainment date extensions where the statute separately establishes a specific attainment date,
such as the 5

- year deadline established in section 192(a).

9 Q

. In order to demonstrate attainment, w hen do control measures need to be operational ?

A. Control measures for the 2008 NAAQS need to be in place as expeditiously as practicable. In
order for control measures to result in three years of monitored clean data by the attainment date, areas designated in the first round of designations ( effective December 31, 2010, and requiring attainment demonstrations that show that the area will attain the standard as expeditiously as p racticable, but no later than December 31, 2015) would need to have all

necessary controls in place no later than November 1, 2012 , and the corresponding date for areas designated in the second round of designations is expected to be November 1, 2013.

EPA will consider on a case

- by

- case basis the approvability of attainment demonstration SIPs
where control measures are scheduled to be operational after November 1, 2012 / November 1, 2013. An attainment SIP may be approvable even if the state does no t anticipate having 3 full years of clean data by the attainment date. See EDF v. EPA , 369 F.3d 193 (2d Cir. 2004); Sierra Club v. EPA

, 356 F3d 296 (D.C. Cir. 2004) amended 2004 WL 877850 (D.C. Cir. 2004) ; available at:

2d C ircuit case

-- http://www.ca2.uscourts.gov

DC Cir cuit case

-- http://www.cadc.uscourts.gov

EMISSIONS INVENTORY

10 Q. For reporting emissions to the National Emissions Inventory (NEI) , what are EPA’s plans for the reporting threshold for Lead ?

A. EPA recognizes the discr epancy between the 0.5 tpy Lead threshold for the Lead Monitoring
Rule and the NEI re porting threshold of 5 tpy

. To resolve this inconsistency, EPA is considering proposing changes to align the thresholds by changing the Air Emissions Reporting Rule (AERR)
that governs the repor ting requirements for the NEI. Given the long rule making timeline , which can last more from 1 to 2 years, EPA does not expect that any revision to the rule (if made) would occur in time to require the new threshold for th e 2011 NEI (reporting for 2011 NEI is required by the end of 2012). However, given the discrepancy in the rules that currently exists, states are encouraged to voluntarily collect data on smaller Lead sources and report the data to5 EPA for the 2011 NEI. N ote 40 CFR 51.117(e) states: “The point source inventory on which the summary of the baseline for Lead emission inventory is based must contain all sources that emit 0.5 or more tons of Lead per year.”

MODELING

1 1 Q. What is the appropriate emissions rate (peak seasonal, monthly, or annual rate) to
use for the three

- month rolling average?

A. Modeling analyses should conform with EPA’s guidelines on air quality models contained in Appendix W to 40 CFR part 51. http://www.epa.gov/ttn/scram/guidance/guide/appw_05.pdf

. Modeling input data, including emission rates, are addressed in Section 8.0 of Appendix W. The averaging period for the 2008 Lead NAAQS is a rolling 3

- month average e valuated over a 3

- year period. Accordingly, emissions limits should be based on concentration estimates for this same period (3

- month average) as described in Section 10.2.3 of Appendix W. The emissions rate to input into AERMOD for attain ment demonstrations is based on the maximum allowable or permit limit e missions, often 1

- hour limits. Table 8

- 1 of Appendix W (see below) gives the calculation methodology to use to calculate the emissi ons rate to input into AERMOD. The input emissions rate for a source subject to SIP limits is a product of the maximum allowable or permit limit emissions, operating level (actual or design capacity, whichever is greater, or federally enforceable permit co ndition) and operating factor. This same calculatio n is also used for nearby sources. For “other” sources, the operating level is the annual level when actually operating averaged o ver the most recent two years. For definitions of nearby and other sources, see Section 8.2.3 of Appendix W.6 For the purp ose of deriving permit limits for Lead based on modeling, we interpret th e above procedures as follows. In general, the maximum hourly emission rate (PTE) should be used as the basis for establishing emissi on limits and for model input. This approach is ap propriately
conservative for emissions units that: 1) could be operated at a relatively high capacity factor (% of available capacity) over the applicable averaging period, 2) are associated with non

continuous compliance monitoring methods (e.g., periodi c source testing), and 3) have emissions that are not well correlated with production or other measureable su rrogate monitoring parameters. Additionally, where significant uncertainty exists with respect to estimated emissions, modeling peak hourly rates m ay be necessary to account for this uncertainty.

In certain cases, longer term average emission rates or emissions representative of actual operating schedules may be approved for use in modeling demonstrations and cor responding permit limitations. Consistent with Appendix W, where a source is willing to accept an enforceable limitation on operating schedule, emissions need only be modeled during

a llowable periods of operation. Longer

- term average emission limits (e.g., monthly average,

3

- month average, or 3

- month total) may be approved for qualifying emissions units. To be7 approvable, such limitations must be enf orceable as a practical matter. We emphasize that approval of model input data and proposed emissions limits must be granted by the r eviewing authority on a case

- by

- case basis, taking into account source and e missions unit

- specific
factors. Modeled emission rates, including any proposed limitations on emissions or source operation, should be documented in the modeling protocol

, and any associated permit application materials submitted to the reviewing agency for approval.

12 Q. What is the required for modeling for attainment demonstrations? When should
allowable emissions be used and when should permits be used?

A. Modeling for attainment demonstrations is used to show that a nonattainment area will be

in atta inment by the attainment date. The modeling is used to show the effectiveness of c ontrol
measures on the sources. For attainment modeling, maximum allowable or federally
enf orceable permit limits should be the basis of the model input emissions, as described in
Section 8.1 and Table 8

- 1 of Appendix W and the Guideline for Air Quality Models

. http://www.epa.g ov/scram001/guidance/guide/appw_05.pdf

13 Q. What is EPA’s policy on conductin g model evaluations to avoid under or over predictions compared to monitoring results?

A. As part of the model promulgation process, AERMOD has been evaluated in several studies
and showed excellent performance. For details about the AERMOD evaluation results see the AERMOD Evaluation Paper at http://www.epa.gov/ttn/scram/7thconf/aermod/aermod_mep.pdf

. Any potential bias in modeled results versus monitored concentrations would most likely be introduced by the user (inaccurate characterization of emissions or use of non

- representative meteorological data in the modeling) and if found should be explaine d by the user.

Depending on the level of emission s used (allowable versus actual ) and the number of monitors being used in the evaluation

, it may be possible to conduct a model evaluation for t he specific case being modeled. In terms of the number of moni tors, comparison to a single monitor is not
considered suffic ient to indicate a model bias. If maximum allowable emissions or permitted emissions are used as the model input emissions (either for the SIP modeling or use in designations modeling), it would be expected that modeled concentrations would not be comparable to monitored concentrations because of the nature of the emissions level.

For designations modeling using actual emissions, if emissions have been characterized accurately and input meteorological data is representative of the area being modeled, one way to measure the performance of the modeled results against monitored values is to use quantile

- quantile plots (QQ plots) by plotting the observed and modeled values in ranked order, i.e. highest monitored value paired with highest modeled value at monitor receptor locations.
This c reates concentration pairs of monitored and modeled concentrations that are no longer paired in time space and is considered a pragmatic procedure to evaluate model performance as noted in the AERMOD Evaluation Paper.8 1 4 Q . What is EPA’s policy on modelin g for contingency measures?

A. It is not necessary to model the effect of impl ementing contingency measures. However, modeling is one way to help gauge the potential effectiveness of backstop measures and may demonstrate that any contingency measures tha t are adopted in the SIP are suf ficient to be approved by EPA. Modeling of contingency measures should follow the guidelines in Appendix

W.

1 5 Q. When will the new AERMOD, AERMET, and AERMINUTE updates be released ?

A. The latest updates to AERMET, and AERMINUTE, version 11059, were released on March 8

, 2011. The latest updates to AERMOD and AERMAP were released on April 14, 2011 (version 11103).

1 6 Q. Will AERMOD calculate the Lead NAAQS design value?

A. AERMOD does not calculate the Lead NAAQS desig n value. A post

- processor called
LEADPOST will calculate the Lead NAAQS design valu es from monthly modeled output.
LEADPOST is available on EPA’s SCRAM website at: http://www.epa.gov/ttn/scram/models/aermod/leadpost.zip

1 7 Q. If the modeling uses 5 years of N ational W eather S ervice data do all years have to be modeled in one run or can individual years be modeled?

A. The modeled design value is calculated as the rolling 3

- month average concentration at each

r eceptor across the five years. AERMOD does not calculate the design value, s o post

- processing is required. The EPA post

- processor, LEADPOST, can be used to calcu late the design values. The five years of model output do no t have to be in one AERMOD run. Each individual year can be run separately and the output for each ye ar can be input into LEADPOST. LEADPOST will read the individual files and calculate the design values across the five years provided that each year’s runs have the same receptors and source group contributions

.