Prevention of Significant Deterioration (PSD) 

NSR Program

Jessica Montañez

U.S. Environmental Protection Agency

Office of Air Quality Planning and Standards

919-541-3407, montanez.jessica@epa.gov
2

Agenda

1. PSD Applicability

2. PSD Requirements

3. NSR Applicability Example
Prevention of Significant Deterioration 

(PSD) NSR Program Basics
Which sources might be subject to the major 

PSD program?

• Sources locating in areas attaining the National Ambient 

Air Quality Standards or areas that are unclassifiable

 New major sources

 Existing major sources making major modifications

 Physical or operational changes at the source

 Change should show significant net emissions increase

4
5

How do you know when PSD applies 

to a source?

1. Determine source’s potential to emit (PTE) 

2. Assess attainment status of source’s geographic area

3. Determine applicable source thresholds

4. Determine if source is major for PSD 
6

1. What is the source’s potential to emit (PTE)?

• The maximum capacity of source to emit a 

pollutant under its physical and operational 

design

 Based on operating 24 hours a day, 365 days a year 

(8760 hours/year)

 Can include effect of emissions controls, if 

enforceable by permit or:

 State Implementation Plan (SIP), 

 Tribal Implementation Plan (TIP) or

 Federal Implementation Plan (FIP) conditions
7

2. What is the attainment status of source’s 

geographic area?

• Determine if area is in attainment for each National 

Ambient Air Quality Standard (NAAQS) emitted by the 

source

 To find this information: 

 Contact the appropriate EPA Regional office or applicable 

permitting authority

 Search an EPA database such as: www.epa.gov/air/data
8

3. What is the applicable PSD threshold?

• 250 tons per year (tpy) for most source categories

• 100 tpy, if part of the 28 listed source categories
9

4. How do you determine if a source is major 

for PSD?

• For each pollutant, compare the source’s PTE 

with applicable threshold

• If PTE is equal to or higher than threshold, 

source is major for PSD

• For example:

 Source PTE for NO2 is 300 tpy

 300 tpy > 250 tpy, source is subject to PSD
10

When might a modification be subject to the 

PSD program?

• Based on significant net emissions increase 

 Determine if proposed source emissions exceeds significant 

emissions rate (SER)

 Determine net emissions increase (NEI) 

 Sum of contemporaneous emissions increases and decreases to 

the proposed modification increase 

 NEI = PMEI + CEI – CED (ERC) where:

 PMEI – Proposed modification emissions increase

 CEI – Creditable emissions increase

 CED – Creditable emissions decreases

 ERC – Emissions reduction credit(s)

 Check if NEI is greater than SER, if so, source is major
11

Why might a new or modified source not be 

subject to PSD?

• PTE less than major 

source thresholds

• Source is “grandfathered”

• Source opted for 

“synthetic minor” permit

Major Source 

Threshold

0

50

100

150

200

250

300

350

Emissions

(tpy)

Actual

PTE

Synthetic Minor Source 

Emissions
12

In what other circumstances can a source 

be subject to PSD?

• Once it is determined that a source is major for PSD, 

source also has to review pollutants that are below the 

thresholds by comparing PTE to Significant Emissions 

Rate (SER)

 Pollutants for which the area is in attainment (NAAQS)

 Other pollutants

• Emissions equal to or higher than SER make pollutant 

also subject to PSD

• Concept known as “Major for one Major for all”
13

What must a major source subject to PSD do?

• Install of Best Available Control Technology (BACT)

• Perform air quality analysis

• Perform class I area analysis 

• Perform additional impacts analysis

• Allow opportunities for public involvement
NSR Applicability Example
15

Which pollutants are subject to PSD, 

NA NSR, and minor NSR permitting?

• New Kraft Pulp Mill

• PTE’s:

 PM-10 – 10 tpy

 VOC – 80 tpy

 SO2 – 185 tpy

• Area:

 In attainment for PM-10 

and VOC

 In moderate 

nonattainment for SO2

Kraft pulp mill’s produce the dark 

colored wood pulp used in the 

manufacture of a variety of paper 

products.

http://esask.uregina.ca
16

Example Solution

1. Evaluate for PSD

• Determine applicable threshold

• Kraft pulp mills part of 28 listed source categories

• Major source threshold is 100 tpy, not 250 tpy

• Determine if the source is major based on the threshold

• 185 tpy of SO2 > 100 tpy threshold

• Mill is a major source for PSD

• Now review all attainment pollutants for PSD applicability

PTE’s: SO2=185 tpy, VOC=80 tpy, PM-10=10 tpy; Area in: NA for SO2, Att. for VOC and PM-10
17

Example Solution (Continued)

• Review the two attainment pollutants based on their SER

 VOC:

 PTE = 80 tpy, VOC not on SER list 

 However, VOC is ozone precursor

 Ozone on list, SER = 40 tpy

 80 tpy of VOC > 40 tpy ozone SER, VOC subject to PSD

 PM-10: 

 PTE = 10 tpy 

 PM-10 SER = 15tpy 

 10 tpy of PM-10 < 15 tpy SER, PM-10 not subject to PSD

PTE’s: SO2=185 tpy, VOC=80 tpy, PM-10=10 tpy; Area in: NA for SO2, Att. for VOC and PM-10
18

Example Solution (Continued)

PTE’s: SO2=185 tpy, VOC=80 tpy, PM-10=10 tpy; Area in: NA for SO2, Att. for VOC and PM-10

2. Evaluate for NA NSR

• Determine applicable threshold

• Major source threshold for moderate NA is 100 tpy

• Determine if the source is major based on the threshold

• Only NA pollutant is SO2

• 185 tpy of SO2 > 100 tpy threshold, SO2 subject to NA NSR

3. Evaluate for Minor NSR

• PM-10 PTE = 10 tpy

• PM-10 may be subject to minor NSR

• Proposed minor Tribal NSR rule, PM-10 Att. threshold = 5 tpy

• 10 tpy of PM-10 > 5 tpy threshold, PM-10 subject to minor NSR
PSD Requirements Details
20

Agenda

1. PSD Requirements Details

2. Refinements of Increment Modeling Procedures Proposal
21

Review: What must a major source subject to 

PSD do?

• Install of Best Available Control Technology (BACT)

• Perform air quality analysis

• Perform class I area analysis 

• Perform additional impacts analysis

• Allow opportunities for public involvement
22

What is Best Available 

Control Technology (BACT)?

• Pollutant specific emissions limit, case-by-case

 Takes into account energy, environmental, or economic impacts

• Limit must be at least as stringent as applicable:

 New Source Performance Standard (NSPS) and/or 

 National Emission Standard for Hazardous Air Pollutants 

(NESHAP)

• Selected by “Top Down” BACT analysis
23

What are the requirements for the 

“Top-down” BACT analysis?

1. Identify all available air pollution control technologies, 

regardless of cost

2. Eliminate technical infeasible control options 

3. Rank remaining control technologies according to 

control effectiveness. For each pollutant, list includes: 

– Control efficiency (percent of pollutant removed)

– Expected emissions reduction (tons/year)

– Economic Impacts

– Environmental Impacts (i.e. significant impact on surface water)

– Energy Impacts

4. Evaluate most effective controls based on all the factors 

in step 3 and document results

5. Select BACT
24

What is an air quality analysis and its purpose?

• Analysis that involves: 

 An assessment of existing air quality

 Modeling estimate of ambient concentrations from proposed 

project and future growth associated with project

• Purpose: 

 Will new plus existing emissions cause or contribute to:

 NAAQS and/or 

 PSD increment violation

• Pollutant specific, noncriteria pollutants are also 

evaluated
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What are the steps of the air quality analysis?

Model Impact of Proposed and Other 

Emission Sources

Ambient 

Concentrations 

Above Air 

Quality 

Significance 

Level

Determine Impact Area

Model Impact of Proposed and Other 

Emission Sources

Develop Emissions Inventories of 

Other Sources 

No Further NAAQS or PSD 

Increment Analysis 

Performed for Pollutant

Demonstration of Compliance

Yes

No

Determine Need for Pre-application 

Monitoring

Source Input Data (Pollutants with 

Significant Emissions)

Meteorological Data

Source Input Data (Pollutants with 

Significant Emissions)

Meteorological Data
26

What do we require for an increment analysis?

• A new source or modification cannot cause or contribute 

to significant deterioration of air quality in attainment 

areas

• Maximum amount of deterioration allowed is called an 

increment

• Change in air quality measured against a certain 

baseline 

• Not all sources consume increment
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What is an increment?

• Increment

 Maximum allowed increase in concentration of a pollutant above 

baseline (concentration as of baseline date) in an area

Increment per Area 

Classification (μg/m3)

Averaging 

Period

Pollutant I II III

Annual PM-10 4 17 34

SO2 2 20 40

NO2 2.5 25 50

24-hr PM-10 8 30 60

SO2 5 91 182

3-hr SO2 25 512 700

• Increments exist for:

• 3 pollutants:

• PM-10, SO2, NO2

• Variety of averaging periods 

• 3-hour, 24-hour, annual

• Variety of area classifications

• Class I - national parks 

and other natural areas 

• Class II - nearly all other 

areas in the US

• Class III - areas targeted 

for industrial development
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How is increment compliance determined?

• By using air quality models

• Preliminary analysis (significant impact analysis)

 Screening type models

 Representative meteorology

 Only proposed source emissions 

 Refined receptor grids

• Full impact analysis (cumulative impact analysis)

 Refined model

 Representative meteorology

 All applicable increment affecting sources

 More refined receptor grids (smaller grid spacing)
29

How is increment compliance determined? 

(cont.)

1. Determine Need for Pre-application Monitoring

 If existing ambient impact is less than the Significant 

Monitoring Concentration (SMC), permitting agency can 

exempt an applicant from monitoring
30

How is increment compliance determined? (cont.)

2. Conduct Significant Impact Analysis

• Acquire meteorological and source emissions data (actual 

emissions)

• Model impact of proposed source

 If source ambient concentrations are:

 Lower than the Significant Impact Levels* (SILs), no 

further analysis needed

 Higher than the SILs, full impact analysis is needed

*EPA’s current PSD regulations do not contain SILs, but they have been widely used as a 

screening tool.
31

How is increment compliance determined? 

(cont.)

3. Determine Baseline Area(s) 

• All portions of the attainment or unclassifiable area in which 

the PSD applicant proposes to locate (See section 107 of the 

Act) and/or

• Any attainment or unclassifiable area in which the PSD 

applicant would have a significant ambient impact (i.e. higher 

than SIL) 

• Limited to intrastate areas

• Baseline areas not triggered across state lines 
32

How is increment compliance determined? (cont.)

4. Determine Baseline Date(s) - when increment 

consumption starts, pollutant specific

Major Source Baseline Date

Trigger Date

Minor Source Baseline Date

SO2 and PM - Jan. 6, 1975 

NOx - Feb. 8, 1988

SO2 and PM – 1977, NOx - 1988 

Date of first complete permit 

application

when actual emission changes from all

sources affect the available increment

when actual emissions associated 

with construction at a major source 

affect increment

when the minor source baseline date may 

be established

Start
33

How is increment compliance determined 

(cont.)?

• Example: Baseline Areas and 

Dates

 New source planned for Iowa 

county, Wisconsin

 Wisconsin lists attainment status 

by counties

 Minor source baseline dates (if 

already established) for Iowa and 

surrounding counties listed below

PM-10 SO2 NO2

County Date Date Date

Dane 09/13/1998 09/13/1998 09/13/1998

Iowa -- -- --

Sauk 09/27/2002 -- --
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How is increment compliance determined? 

(cont.)

• Source:

 Is major for SO2 and PM-10 (area in 

attainment for both pollutants)

 Submits complete PSD application 

on November 30, 2007

• What is the baseline area?

 Dispersion modeling shows impact 

area covers Iowa, Sauk and Dane 

counties (e.g., ambient 

concentrations for SO2 and PM-10 

exceed 1μg/m3 annual SIL)

• What are the baseline dates?

 Iowa – November 30, 2007 for SO2

and PM-10 

 Sauk –November 30, 2007 for SO2: 

September 27, 2002 for PM-10

 Dane –September 13, 1998 for SO2

and PM-10 

Significant Impact Area

PM-10 SO2 NO2

County Date Date Date

Dane 09/13/1998 09/13/1998 09/13/1998

Iowa -- -- --

Sauk 09/27/2002 -- --
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How is increment compliance determined? 

(cont.)

• Conduct Cumulative Impact Analysis

 Determine Impact Area

 Based on impact area determined for preliminary analysis

 Circular area with a radius extending from the source to:

 Largest area for all the pollutants modeled during preliminary analysis 

or

 Receptor distance of 50 km, whichever is less

Proposed Source

County B County A
36

How is increment compliance determined? 

(cont.)

• Conduct Cumulative Impact Analysis

 Develop Emissions Inventory 

 Includes all increment affecting sources within the impact area and 

the annular area extending 50 kilometers beyond the impact area.

 Includes mobile, area and secondary sources

 Based on actual emissions over the 2 years preceding the particular 

date (i.e., baseline or current)

 Other time periods may be used if they are “more representative of 

normal source operations”

Proposed 

Source

County B County A

50 km
37

How is increment compliance determined? (cont.)

5. Conduct Cumulative Impact Analysis

C. Model Impact of Proposed and Existing Sources

 Uses emission inventory data and meteorology to determine the 

change (Δ) in concentration from baseline

D. Determination of Compliance

 If model output for each pollutant and averaging period is higher 

than the increment, the permit:

 Is denied or

 Granted, if emissions are “offset’ by other sources in the area 
38

What do we require for the NAAQS analysis?

• A new source or modification cannot cause or contribute 

to a violation of any NAAQS in any area

• Compliance with any NAAQS is based on proposed 

source and all other sources in baseline area

 No baseline dates exist

 Analysis requirements similar to increment analysis

• NAAQS analysis independent from increment analysis
39

What is an class I area impact analysis?

• Evaluation of NAAQS, PSD increments and Air Quality 

Related Values (AQRVs) when a major source’s 

emissions may affect a Class I area

 AQRVs – feature or property of a Class I Area that may be 

affected by a change in air quality

 Differ for each Class I area

 Defined by the Federal Land Manager (FLM) for Federal lands, or 

by the applicable State or Indian Governing body for nonfederal 

lands

 Generally for sources within 100 km of Class I area, not always

 FLM must be notified of potential impacts

 Determines data and analyses needed
40

What is an additional impact analysis?

• Assesses potential effects of increased pollution from 

new source and associated growth on:

 Soils and Vegetation

 Visibility

• Pollutant specific

• Performed within the impact area of the proposed source

• Depends on:

 existing air quality

 quantity and type of emissions

 sensitivity of local soils and vegetation (especially commercial 

crops)

 general visibility concerns
41

What is done with the PSD information?

• Source submits the analyses in PSD permit application 

to permitting authority

• Permitting authority evaluates analyses/application to 

determine requirements for PSD permit 

• Reviewing authority then prepares or provides:

 Draft permit

 Adequate public notice to affected and general public

 30-day public comment period on draft permit

 Opportunity for public hearing on draft permit

• If all requirements met, permitting authority grants permit
Proposed Refinements to Increment 

Modeling Procedures Rule
43

Refinements of Increment Modeling 

Procedures Proposal

• Purpose:

 Clarifies the status of existing PSD increment guidance

 Addresses how the emissions and meteorology inventory for 

increment purposes can be developed 

 Seeks comment on some of the Western States Air Resources 

Council (WESTAR) recommendations for improving the PSD 

program

 Addresses the issue of Class I Federal Land Manager (FLM) 

variances 

• Proposal:

 Published in Federal Register on June 6, 2007

• Promulgation:

 Scheduled for December 2008
44

What have been some difficulties in 

increment modeling?

• Often don’t have adequate older emissions data

• Don’t have direct emissions data for all averaging 

periods

• Don’t have hourly data for any sources other than utilities

• Don’t have older meteorological data

• Regions and states using different methods
45

Issues Addressed in the Proposal

• What is the effect of the 1990 Draft NSR Workshop 

Manual?

 Manual not a binding regulation, not final agency policy

• How are emissions estimated for increment purposes?

 No prescribed method, reviewing authority discretion allowed

 Requested comment on WESTAR’s recommended approaches: 

 menu of acceptable emissions calculation approaches for both shortterm and annual increments

 set of guiding principles for selecting the most appropriate option from 

the menu

 Mobile sources emissions should be included 

 Other time periods may be used to establish actual emissions if 

they are “more representative of normal source operations”
46

Issues Addressed in the Proposal (cont.)

• How are meteorological data estimated for increment 

purposes?

 Reviewing authorities have discretion for using prognostic 

meteorological models (models that fill gaps in data) 

 Years of Data Needed:

 Observational data: 5 years and at least 1 year for site specific data

 Prognostic data: less than 5, but at least 3 years of data

 If proprietary data or software needed, reviewing authority has 

discretion for: 

 requiring independent review of the proprietary data and conducting 

the review, provided that confidential information is protected 

 determining software acceptability based on the: (1) reproducibility 

of the data or model simulation and (2) quality assurance 

procedures used in its development
47

Issues Addressed in the Proposal (cont.)

• How future sources in the area where a variance has 

been granted treat the emissions from the source who 

received the variance? 

 Variances – approval of permit when increment is exceeded, but 

AQRVs are not impacted

• We proposed:

 Area now has to comply with two increments: the Class I and 

Class II increments. The Class II increment can never be 

exceeded.

 Variance source(s) emissions not counted in future Class I 

increment analyses, counted toward future Class II analyses

 Implementation Plans (SIPs) not amended to correct violation
48

Appendix
49

What are the pollutants regulated by the NSR 

program?

• The National Ambient Air Quality Standards (NAAQS) 

pollutants

• Any NAAQS precursors 

• Any pollutant regulated under the New Source 

Performance Standards (CAA, Section 111)

• Any pollutant otherwise regulated under the Act, 

except the National Emission Standards for 

Hazardous Air Pollutants (CAA Section 112)

• Any Class I or Class II substance regulated by Title VI 

of the Act, Stratospheric Ozone Protection
50

What are the National Ambient Air Quality 

Standards (NAAQS)?

• EPA sets NAAQS for:

 Ozone (smog) 

 Carbon Monoxide (CO)

 Particulate Matter (dust/soot)

• For each of the NAAQS pollutants, every area of the 

U.S. is designated into one of the following categories:

 Attainment - air quality concentrations equal to or lower than 

NAAQS

 Nonattainment - air quality concentrations higher than NAAQS

 Unclassifiable – not enough data on air quality; generally 

treated as attainment

– Nitrogen dioxide (NO2)

– Sulfur dioxide (SO2)

– Lead (Pb)
51

National Ambient Air Quality Standards

Pollutants Primary 

Standards

Averaging Times Secondary 

Standards

Carbon Monoxide 9 ppm (10 mg/m3) 8-hour -------

35 ppm (40 mg/m3) 1-hour -------

Lead 1.5 μg/m3 Quarterly Average Same as Primary

Nitrogen Dioxide 0.053 ppm 

(100 μg/m3) 

Annual (Arithmetic Mean) Same as Primary 

Particulate Matter (PM10) 150 ug/m3 24-hour -------

Particulate Matter (PM2.5) 15 μg/m3 Annual (Arithmetic Mean) Same as Primary 

35 ug/m3 24-hour -------

Ozone 0.08 ppm 8-hour Same as Primary 

0.12 ppm 1-hour

(Only in some areas)

Same as Primary

Sulfur Oxides 0.03 ppm Annual (Arithmetic Mean) -------

0.14 ppm 24-hour -------

------- 3-hour 0.5 ppm (1300 ug/m3) 

As of June 19, 2008; changes have been proposed to the Lead NAAQS
52

PSD 28 Source Categories with 100 tpy thresholds

1. Coal cleaning plants (with thermal dryers) 15. Coke oven batteries

2. Kraft pulp mills 16. Sulfur recovery plants

3. Portland cement plants 17. Carbon black plants (furnace process)

4. Primary zinc smelters 18. Primary lead smelters

5. Iron and steel mills 19. Fuel conversion plants

6. Primary aluminum ore reduction plants 20. Sintering plants

7. Primary copper smelters 21. Secondary metal production plants

8. Municipal incinerators capable of charging 

more than 250 tons of refuse per day

22. Chemical process plants

9. Hydrofluoric acid plants 23. Petroleum storage and transfer units with a total 

storage capacity exceeding 300,000 barrels

10. Sulfuric acid plants 24. Taconite ore processing plants

11. Nitric acid plants 25. Glass fiber processing plants

12. Petroleum refineries 26. Charcoal production plants

13. Lime plants 27. Fossil fuel-fired steam electric plants of more than 250 

million British thermal units (BTU)/hour heat input

14. Phosphate rock processing plants 28. Fossil-fuel boilers (or combination thereof) totaling 

more than 250 million BTU/ hour heat input
53

SER – a rate of emissions that would equal or exceed any of the following rates:

Notwithstanding the above, any emissions rate or any net emissions increase associated with a major 

stationary source or major modification, which could construct within 10 km of a Class I area, and have 

an impact on such area equal to or greater than 1 μg/m3 (24-hour average)

Significant Emission Rates (SERs)

Pollutant SER 

(tpy)

Pollutant SER 

(tpy)

Carbon Monoxide 100 Hydrogen sulfide(H2S) 10

Nitrogen Oxides 40 Total reduced sulfur (including H2S) 10

Sulfur Dioxide 40 Reduced sulfur compounds (includes H2S) 10

Particulate Matter (PM10) 15 Municipal waste combustor organics 3.5 x 10-6

Ozone 40 of VOCs or NOx Municipal waster combustor metals 15

Lead 0.6 Municipal waste combustor acid gases 40

Fluorides 3 Municipal solid waste landfills emissions 50

Sulfuric acid mist 7

As of June 19, 2008; SER has been proposed for PM-2.5
54

Significant Impact Levels (SILs)

Proposed Significant Impact Levels (μg/m3)

61 Fed. Reg. 38250; July 23, 1996

Pollutant Averaging Time Class I Class II Class III

Sulfur Dioxide (SO2) Annual 0.1 1.0 1.0

24- hour 0.2 5.0 5.0

3-hour 1.0 25.0 25.0

Particulate Matter 

(10μm)

Annual 0.2 1.0 1.0

24- hour 0.3 5.0 5.0

Nitrogen Oxides (NO2) Annual 0.1 1.0 1.0

SILs– air quality concentrations below which a full impact analysis may be 

exempted by the permitting authority

As of June 19, 2008; SIL has been proposed for PM-2.5
55

SMCs– air quality concentrations below which monitoring may be exempted by 

the permitting authority

Significant Monitoring Concentrations (SMCs)

Pollutant SMC (μg/m3) and Averaging Time

Carbon Monoxide 575 (8-hour)

Nitrogen Dioxide 14 (Annual)

Sulfur Dioxide 13 (24-hour)

Particulate Matter (PM10) 10 (24-hour)

Lead 0.1 (3-month)

Fluorides 0.25 (24-hour)

Hydrogen sulfide (H2S) 0.2 (1 hour)

Reduced sulfur compounds (includes H2S) 10 (1 hour)

Ozone Applicants with a net emissions increase of 100 

tons/year or more of VOC’s or NOx required to monitor

As of June 19, 2008; SMC has been proposed for PM-2.5
56

Air Quality Models

• Screening Models 

 Used to determine if a more refined air quality model is needed

 Examples: SCREEN3/AERSCREEN

• Preferred/Recommended Models (40 CFR Appendix W)

 Required for NSR permitting and SIPs. These models include:

 AERMOD

 source-oriented dispersion model that characterizes atmospheric processes by 

dispersing a directly emitted pollutant plume to predict concentrations at selected 

downwind locations

 CALPUFF 

 dispersion model that simulates the effects of time- and space-varying 

meteorological conditions on pollution transport, transformation, and removal

 May be applied for long-range transport and for complex terrain on a case-bycase basis

• Alternative Models 

 Not listed in Appendix W, can be used in regulatory applications with 

case-by-case justification (See Section 3.2 in 40 CFR Appendix W)