Delaware Redesignation Request and Maintenance Plan 

Under the 2006 Daily PM2.5

National Ambient Air Quality Standard

State Implementation Plan

For the New Castle County Portion of the 

Philadelphia-Wilmington, PA-NJ-DE 

Nonattainment Area for Fine Particles

PROPOSED

October 23, 2012
Delaware Redesignation Request and Maintenance Plan– 2006 Daily PM2.5 NAAQS

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Table of Contents

Acronym List .................................................................................................................................. 4

List of Tables .................................................................................................................................. 5

List of Figures................................................................................................................................. 6

EXECUTIVE SUMMARY ............................................................................................................ 7

1 Introduction............................................................................................................................. 9

1.1 Documentation Organization.......................................................................................... 9

2 Background............................................................................................................................. 9

2.1 Health Effects.................................................................................................................. 9

2.2 Philadelphia-Wilmington, PA-NJ-DE Nonattainment Area Designation .................... 10

3 EPA Requirements for Redesignation .................................................................................. 11

3.1 NAAQS Compliance .................................................................................................... 12

3.1.1 EPA Requirements.................................................................................................... 12

3.1.2 Delaware Approach .................................................................................................. 12

3.2 Demonstration that the NAAQS for daily PM2.5, as published in 40 CFR 50.13, has 

been attained (requirement 1 of 3)................................................................................ 13

3.3 Ambient monitoring data quality assured in accordance with 40 CFR 58.10, recorded 

in the EPA air quality system (AQS) database, and available for public view 

(requirement 2 of 3)....... ............................................................................................. 16

3.4 A commitment that once redesignated, the state will continue to operate an appropriate 

monitoring network to verify the maintenance of the attainment status (requirement 3 

of 3)............................................................................................................................... 19

3.4.1 EPA Requirements.................................................................................................... 19

3.4.2 Delaware Approach .................................................................................................. 19

4 Permanent and Enforceable Emission Reductions ............................................................... 19

4.1 U. S. EPA Requirements............................................................................................... 19

4.2 Delaware Approach ...................................................................................................... 20

4.2.1 Economic Conditions................................................................................................ 20

4.2.2 Meteorology.............................................................................................................. 21

4.2.3 Emission Inventory Improvements from 2007 base year to the 2008 attainment 

year................................................................................................................................... ...23

4.3 Enforceable and Permanent PM2.5, NOx and SO2 Measures that Contributed to 

Improved Air Quality between 2007 and 2008............................................................. 28

4.3.1 Delaware-specific Control Measures........................................................................ 28

4.3.2 Federal Control Measures......................................................................................... 29
Delaware Redesignation Request and Maintenance Plan– 2006 Daily PM2.5 NAAQS

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5 SIP Completeness - Fully Approved SIP, Section 110 and Part D Requirements ............... 33

5.1 EPA Requirements........................................................................................................ 33

5.2 Delaware Approach ...................................................................................................... 34

5.3 Part D Plan Requirements for Nonattainment Areas.................................................... 34

6 Maintenance Plan.................................................................................................................. 36

6.1 EPA Requirements........................................................................................................ 36

6.2 Delaware Approach ...................................................................................................... 37

7 Attainment Inventory............................................................................................................ 38

7.1 EPA Requirements........................................................................................................ 38

7.2 Delaware Approach ...................................................................................................... 39

7.3 2008 Attainment Year Inventory .................................................................................. 42

8 Maintenance Demonstration ................................................................................................. 43

8.1 EPA Requirements........................................................................................................ 43

8.2 Delaware Approach ...................................................................................................... 43

8.2.1 2017 and 2025 Projection Inventories ...................................................................... 44

8.2.2 2017 and 2025 Mobile Source Emissions Budgets................................................... 50

8.2.3 Control Measures for Maintenance of Good Air Quality ......................................... 52

8.2.4 Delaware-specific NOx, PM2.5 or SO2 Control Measures (Effective Post 2008)... 55

8.2.5 Federal Control Measures (Effective or Phased-in Post 2008)................................. 56

8.2.6 Future Point Source Emissions Reductions Programs.............................................. 56

8.2.7 Controls to Remain in Effect .................................................................................... 58

9 Verify Continued Attainment ............................................................................................... 58

9.1 EPA Requirements........................................................................................................ 58

9.2 Delaware Approach ...................................................................................................... 58

10 Contingency Measures.......................................................................................................... 59

10.1 EPA Requirements........................................................................................................ 59

10.2 Delaware Approach ...................................................................................................... 59

11 Other Delaware Commitments ............................................................................................. 63

11.1 Commitment to Revise Plan ......................................................................................... 63

11.2 Public Participation....................................................................................................... 63

12 Conclusions........................................................................................................................... 64
Delaware Redesignation Request and Maintenance Plan– 2006 Daily PM2.5 NAAQS

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Acronym List

AQS - EPA’s Air Quality System

BYR - Base Year

CAA - Federal Clean Air Act

CAAA - Clean Air Act Amendments of 1990 

CFR - Code of Federal Regulations (of the United States)

CSAPR - Cross-State Air Pollution Rule 

DAQ - DNREC Division of Air Quality

DelDOT - Delaware Department of Transportation 

DNREC - Delaware Department of Natural Resources and Environmental 

Control

EGU - Electric Generating Unit

GDP - Gross Domestic Product

EPA - United States Environmental Protection Agency

FYR - Future Year

FHWA - Federal Highway Administration

FR - United States Federal Register

FRM - Federal Reference Method

FTA - Federal Transit Authority

I/M - Inspection and Maintenance Program

MANEVU - Mid-Atlantic and Northeast Visibility Union

MARAMA - Mid-Atlantic Regional Air Management Association

NESCAUM - Northeast States for Coordinated Air Use Management

LRTP - Long Range Transportation Plan 

MLK - Martin Luther King Blvd. monitor in Wilmington, Delaware

MPO - Metropolitan Planning Organization

mmBTU - Million British Thermal Unit

NAA - Non-Attainment Area

NAAQS - National Ambient Air Quality Standard 

NEI - National Emission Inventory

NOx - Oxides of Nitrogen 

NAA - Non-attainment area 

PM2.5 - Particulate Matter with an aerodynamic diameter of 2.5 microns or less

RACM - Reasonably Available Control Measure

RACT - Reasonably Available Control Technology 

RPO - Regional Planning Organization

SIP - State Implementation Plan 

(SAFETEA-LU) - Safe, Accountable, Flexible, Efficient Transportation Equity Act – A 

Legacy for Users 

SO2 - Sulfur Dioxide

TIP - Transportation Improvement Program

tpy - Tons per Year

TSD - Technical Supporting Document

VOC - Volatile Organic Compound 

WILMAPCO - Wilmington Area Planning Council 
Delaware Redesignation Request and Maintenance Plan– 2006 Daily PM2.5 NAAQS

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List of Tables

Table 3-1 Philadelphia NAA 98th percentiles and Design Values (2008-2011)

Table 3-2 PM2.5 Monitoring Site General Information

Table 3-3 PM2.5 Monitor Site Specific Information

Table 4.1 Min, Max and Mean Temperatures and Total Precipitation (2006-

2008 vs. 2008-2010) 

Table 4-2 Philadelphia NAA 2006-2011 daily NAAQS (98th percentiles)

Table 4-3 New Castle County 2007-2008 Emission Changes

Table 7-1 Summer vs. Winter – Regional Consistency

Table 7-2 2006-2010 Seasonal PM2.5 Average Percentages

Table 7-3 2008 New Castle County Emissions (tpy)

Table 8-1 Comparison of emissions for the years 2008, 2017 and 2025

Table 8-2 Reductions and % Change of NOx emissions for the years 2008, 2017 and 2025

Table 8-3 Reductions and % Change of PM2.5 emissions for the years 2008, 2017 and 2025

Table 8-4 Reductions and % Change of SO2 emissions for the years 2008, 2017 and 2025

Table 8-5 New Castle County Mobile Source Emissions Budgets

Table 8-6 Post-2008 Emission Reductions due to Control Measures

Table 10-1 Schedule for Permit Revisions or Rule Revisions for Contingency Measures
Delaware Redesignation Request and Maintenance Plan– 2006 Daily PM2.5 NAAQS

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List of Figures

Figure 2-1 Philadelphia Nonattainment Area Boundaries - 2006 PM2.5 NAAQS

Figure 3-1 Delaware’s PM2.5 Monitoring Site Locations

Figure 4-1 2006- 2011 Delaware Gross Domestic Product – All Industry

Figure 4-2 Philadelphia NAA – 2006 to 2011 daily PM2.5 trends

Figure 4-3 Philadelphia NAA –daily PM2.5 trends (avg. all monitors)

Figure 4-4 Philadelphia NAA – 2006 to 2011 PM2.5 3-Year Rolling Averages

Figure 4.5 Philadelphia NAA – daily PM2.5 trends (avg. all monitors)

Figure 7-1 Number of Winter vs. Summer Exceedances
Delaware Redesignation Request and Maintenance Plan– 2006 Daily PM2.5 NAAQS

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EXECUTIVE SUMMARY

This request for redesignation to attainment and maintenance plan is a State 

Implementation Plan (SIP) revision for the Delaware portion1of the Philadelphia-Wilmington, 

PA-NJ-DE fine particulate matter (PM2.5) nonattainment area (Philadelphia NAA). 

On November 13, 2009, EPA published the area designations for the 2006 24-hour 

standard (74 FR 58688). That action, effective on December 14, 2009, designated the 

Philadelphia NAA as nonattainment for the 2006 24-hour standard, based on 2006-2008 

monitoring data. The Philadelphia NAA includes New Castle County in Delaware; Burlington, 

Camden, and Gloucester Counties in New Jersey; and Bucks, Chester, Delaware, Montgomery, 

and Philadelphia Counties in Pennsylvania. CAA Section 107 establishes specific requirements 

to be met in order for a nonattainment area to be considered for redesignation. This 

redesignation request and maintenance plan SIP revision addresses all of the CAA Section 107 

requirements, and provides technical information that supports a request to redesignate the 

Philadelphia NAA area to attainment of the 2006 daily PM2.5 NAAQS. 

PM2.5 air quality has improved in New Castle County as a result of the implementation of 

State and Federal emissions control measures. The air quality improvement is due to permanent 

and enforceable emissions control measures. The entire Philadelphia NAA has certified and 

quality assured ambient air quality monitoring data for the 3-year periods 2008-2010 and 2009-

2011 that all demonstrates attainment of the 2006 PM2.5 NAAQS. The purpose of this 

redesignation request and maintenance plan is to request that the United States Environmental 

Protection Agency (EPA) redesignate the Delaware portion of the Philadelphia NAA to 

attainment for this standard pursuant to the provisions of Section 107 of the federal Clean Air 

Act (CAA) (42 U.S.C. 7407). In summary, the plan includes:

 A demonstration that attainment of the 2006 PM2.5 air quality standards for the 

Philadelphia NAA will continue through 2025. 

 An attainment emissions inventory that identifies the level of emissions in the area that 

is sufficient to attain the NAAQS and projected future emissions inventories showing 

that future emissions in the area will not exceed the level of the attainment inventory 

over the 10-year maintenance period. 

 Contingency measures to be implemented in the unlikely event of a subsequent violation 

of the air quality standard. The contingency measures listed in the Plan will be triggered 

to expeditiously correct any future exceedances. 

 On-road motor vehicle emissions budgets for 2017 and 2025 for use in transportation 

conformity determinations to assure that any increases in emissions from this sector do 

not jeopardize continued attainment of the 2006 daily PM2.5 standards during the 

maintenance period.

 

1 Pennsylvania and New Jersey Departments of Environmental Protection are responsible for developing similar 

plans for their portion of the Philadelphia NAA.
Delaware Redesignation Request and Maintenance Plan– 2006 Daily PM2.5 NAAQS

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Based on this presentation, New Castle County, Delaware meets the requirements for 

redesignation under the CAA (Section 107(d)(3)) and EPA guidance for fine particles. 

Consistent with the authority granted to EPA, the State of Delaware requests that New Castle 

County, Delaware be redesignated to attainment for the 2006 daily fine particles standard 

simultaneously with EPA approval of this Delaware State redesignation request and PM2.5

Maintenance Plan for the New Castle County portion of the Philadelphia NAA.
Delaware Redesignation Request and Maintenance Plan– 2006 Daily PM2.5 NAAQS

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1 Introduction

The State of Delaware requests that the EPA redesignate the Delaware portion of 

Philadelphia NAA to attainment for the 2006 daily PM2.5 NAAQS pursuant to the provisions 

Section 107 of the CAA (42 U.S.C. 7407).2 Since the designations for the 2006 NAAQS for this 

pollutant were published, the area’s PM2.5 air quality has improved due to permanent and 

enforceable emission reductions. Air quality in the area is significantly better than required by 

this standard. This document demonstrates that PM2.5 air quality in the Philadelphia area will 

remain compliant with the 2006 daily PM2.5 NAAQS, as measured by a monitoring network that 

meets all federal requirements, through 2025. 

Delaware is also requesting that EPA concurrently approve, as a revision to the Delaware 

state implementation plan (SIP), the related Section 175A maintenance plan, as described in 

Sections 6-8 of this document. This plan includes mobile vehicle emissions budgets for the 

interim year of 2017 and the out year of 2025. It also contains contingency measures that will be 

implemented in the unlikely event that the area experiences an exceedance of the 2006 PM2.5

NAAQS. The maintenance plan ensures that good PM2.5 air quality will be maintained through 

2025.

1.1 Documentation Organization

This document presents Delaware’s discussions and analysis of summarized air quality 

data and emission inventories, PM2.5 control measures and applicable CAA and EPA

requirements in support of Delaware’s request for redesignation to attainment under the 2006 

daily PM2.5 NAAQS. Supporting documentation and data, such as Technical Support 

Documents (TSD), calculation spreadsheets, model input and output files, and other related data 

are available on the CD enclosed with this redesignation request and maintenance plan. Much of 

the documentation that is referenced in the report, but not contained on the CD, has been 

compiled in electronic files located at the Division of Air Quality offices in Dover, Delaware and 

are available for review upon request by the public.

2 Background

2.1 Health Effects

PM2.5, also known as fine particulate matter or fine particles, is defined as any airborne 

particle of solid or liquid matter that is less than or equal to 2.5 micrometers in diameter. PM2.5

is not a single pollutant, but is a sum of all pollutants that have diameters less than 2.5 

micrometers. For reference, 2.5 micrometers is about 1/30th the diameter of a human hair. 

Sources of PM2.5 and PM2.5 precursors include, most significantly, coal-fired power 

plants and other combustion sources, fires, emissions from motor vehicles, windblown dust, and 

natural emissions from trees and the oceans. These sources can be divided up into two types of

 

2 After EPA redesignates the Philadelphia nonattainment area to attainment, it will be known as the Philadelphia 

Maintenance Area, or Philadelphia MA
Delaware Redesignation Request and Maintenance Plan– 2006 Daily PM2.5 NAAQS

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sources, primary and secondary. Primary sources directly emit fine particulate matter into the 

atmosphere without any chemical change occurring to the pollutant. Secondary sources are 

sources from which precursor chemical species are released into the atmosphere, which then 

react with other chemical species in the atmosphere to create fine particulate matter. Some 

species which comprise fine particulate matter are sulfates, ammonium nitrate, soot, sea salt, 

organic carbon, elemental carbon and metals (crustal metals, transitional metals, and potassium).

Exposure to high levels of PM2.5 adversely affects human health. The main impacts of 

PM2.5 on human health are on the respiratory system and the cardiovascular system. Children, 

the elderly, and individuals with pre-existing pulmonary or cardiac disease are the most 

susceptible to PM2.5 pollution. Complications that can arise from exposure to PM2.5 include 

decreased lung function, chronic bronchitis; respiratory symptoms such as asthma attacks and 

difficulty breathing, nonfatal heart attacks, irregular heartbeat, and premature death in 

individuals with pulmonary or cardiac disease.

2.2 Philadelphia-Wilmington, PA-NJ-DE Nonattainment Area Designation

Following promulgation of a new or revised NAAQS, EPA is required by the CAA to 

designate areas throughout the United States as attaining or not attaining the NAAQS; this 

designation process is described in Section 107(d)(1) of the CAA. On October 17, 2006, EPA

retained the 1997 annual PM2.5 NAAQS at 15 μg/m3based on a 3-year average of annual mean 

PM2.5 concentrations, and promulgated a 24-hour standard of 35 μg/m3based on a 3-year 

average of the 98th percentile of 24-hour concentrations (71 FR 61144), also known as the 2006 

24-hr NAAQS.

3

On November 13, 2009, EPA published the area designations for the 2006 24-hour 

standard (74 FR 58688). That action, effective on December 14, 2009, designated the same 

Philadelphia Area as nonattainment for the 2006 24-hour standard, based on 2006-2008

monitoring data. The Philadelphia Area includes New Castle County in Delaware; Burlington, 

Camden, and Gloucester Counties in New Jersey; and Bucks, Chester, Delaware, Montgomery, 

and Philadelphia Counties in Pennsylvania (see Figure 2-1). 

CAA Title I, Part D, Subpart 1 sets forth the basic nonattainment requirements applicable 

to all nonattainment areas. For the 2006 PM2.5 daily NAAQS, these requirements are required to 

be met by December 14, 2012. However, as stipulated in 40 CFR 51.1004(c), a “clean data 

determination” (CDD) by the EPA suspends the requirements to submit an attainment 

demonstration and associated reasonably available control measures (RACM) (CAA Section 

172(c)(1) and (c)(6)), reasonable further progress (RFP) requirements (CAA Section 172(c)(2)), 

contingency measures (CAA Section 172(c)(9)), and other planning SIP elements related to 

attainment for so long as the area continues to attain the NAAQS. [EPA proposed the 

determination of attainment or “clean data determination” (CDD) for the 2006 annual 

PM2.5 standard for the Philadelphia-Wilmington, PA-NJ-DE nonattainment area on 

 

3 The terms “24-hr” and daily are used interchangeably throughout this document.
Delaware Redesignation Request and Maintenance Plan– 2006 Daily PM2.5 NAAQS

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October 2, 2012 (77 FR 60089).] [EPA informed Delaware Division of Air Quality (DAQ) 

staff, that they expect the CDD Rulemaking to be proposed in the Federal Register by 

December 14, 2012.4]

Figure 2-1 Philadelphia Nonattainment Area Boundaries - 2006 PM2.5 NAAQS

3 EPA Requirements for Redesignation

Section 107(d)(3)(E) of the CAA allows states to request nonattainment areas to be 

redesignated to attainment provided certain criteria are met. The criteria for redesignating a 

nonattainment area to attainment are as follows:

 EPA has determined that the area attained the NAAQS. For the 2006 PM2.5 NAAQS, the 

areas must show that the 3-year average of the 98th percentile of 24-hour concentrations 

from three (3) consecutive calendar years of quality-assured air quality monitoring data 

is 35 μg/m3, or lower (71 FR 61144).

 The request must contain a showing that the improvement in air quality is due to 

permanent and enforceable reductions in emissions resulting from the implementation of 

the applicable SIP.

 The applicable implementation plan must be fully approved by EPA under Section 110(k) 

of the CAA, and the redesignation request must contain a determination that the state 

 

[

4 M. Pino, EPA Region 3 (August 14, 2012).]
Delaware Redesignation Request and Maintenance Plan– 2006 Daily PM2.5 NAAQS

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meets all applicable requirements for the area under Section 110 and Part D.

 A fully approved maintenance plan, including contingency measures, for the area under 

Section 175A of the Act. Section 175A requires demonstrating that the area will 

maintain (continue to attain) the standard for at least ten years after redesignation to 

attainment, and that contingency measures be implemented if a violation is monitored at 

any time during the ten-year maintenance period. 

This document addresses each of these requirements. EPA has published applicable 

guidance in a memorandum from John Calcagni, Director, Air Quality Management Division, 

entitled Procedures for Processing Requests to Redesignate Areas to Attainment (redesignation 

guidance), issued September 4, 1992, to Regional Air Directors. 40 CFR Part 51, Subpart Z, 

entitled Provisions for Implementation of PM2.5 National Ambient Air Quality Standards

(implementation rule) provides additional information. The State of Delaware has based this 

redesignation request and maintenance plan on the redesignation guidance and the 

implementation rule, supplemented with additional guidance received through coordination with

EPA Region 3 staff.

3.1 NAAQS Compliance

3.1.1 EPA Requirements

CAA Section 107(d)(3)(E)(i) addresses attaining the standard. This Section states that 

the demonstration should rely upon ambient air quality data. The data that are used to 

demonstrate attainment should be the product of ambient monitoring that is representative of the 

area of highest concentration. Additionally, the data should be collected and quality-assured in 

accordance with 40 CFR Part 58 and recorded in the Air Quality System (AQS) in order for it to 

be available to the public for review. 

3.1.2 Delaware Approach

EPA’s published guidance document, Procedures for Processing Requests to Redesignate 

Areas to Attainment (September 4, 1992), which details specific requirements regarding the 

collection and use of ambient air monitoring data needed to support a redesignation request. 

Before the Philadelphia NAA can be redesignated to attainment for the 2006 daily PM2.5

NAAQS, the City of Philadelphia, Delaware Department of Natural Resources and 

Environmental Control (DNREC), Division of Air Quality (DAQ), the New Jersey Department 

of Environmental Protection and the Pennsylvania Department of Environmental Quality must 

each demonstrate that the daily PM2.5 NAAQS has been attained in their respective jurisdictions 

of the Philadelphia NAA. PM2.5 monitoring data must show that violations of the NAAQS are 

no longer occurring within the NAA.

This showing must rely on three complete, consecutive calendar years of quality assured 

data. Further, the air monitoring data must be quality assured in accordance with 40 CFR 58.10, 

recorded in EPA’s Air Quality System (AQS) database, and made available to the public. 

Finally, Delaware DAQ must commit to continue to operate an appropriate monitoring network 
Delaware Redesignation Request and Maintenance Plan– 2006 Daily PM2.5 NAAQS

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to verify the maintenance of the attainment status, once the area has been redesignated to 

attainment. Taken together there are three primary requirements: 

1) A demonstration that the NAAQS for daily PM2.5, as published in 40 CFR 50.13, has 

been attained.

2) Ambient monitoring data quality assured in accordance with 40 CFR 58.10, recorded in 

the EPA air quality system (AQS) database, and available for public view.

3) A commitment that once redesignated, the state will continue to operate an appropriate 

monitoring network to verify the maintenance of the attainment status.

3.2 Demonstration that the NAAQS for daily PM2.5, as published in 40 CFR 50.13, has 

been attained (requirement 1 of 3)

The City of Philadelphia, and the States of Delaware and New Jersey, and the 

Commonwealth of Pennsylvania, (‘‘the States’’) submitted quality assured air quality monitoring 

data into the EPA Air Quality System (AQS) database for the 2008–2010 and 2009-2011 

monitoring periods. The States then certified that data. The criteria for determining if an area is 

attaining the 2006 daily PM2.5 NAAQS are set out in 40 CFR 50 and appendix N. The 24-hour 

primary and secondary PM2.5 standards are met when the 98th percentile 24-hour concentration is 

less than or equal to 35 μg/m3. Three years of valid daily means are required to produce a valid 

daily standard design value. A year meets data completeness requirements when at least 75 

percent of the scheduled sampling days for each quarter have valid data. The use of less than 

complete data is subject to the approval of EPA, which may consider factors such as monitoring 

site closures/moves, monitoring diligence, and nearby concentrations in determining whether to 

use such data. 

While most of the monitoring data submitted by the States was complete, several 

monitors in the Philadelphia NAA had less than four quarters of complete data for one or more 

years during the 2008–2010 and 2009-2011 monitoring periods. For these monitors, EPA 

applied the data substitution test set out in the April 1999 EPA guidance document ‘‘Guideline 

on Data Handling Conventions for the PM NAAQS”. The ‘‘maximum quarter’’ substitution test 

(Max-Q) identified in the guidance document is used for monitors with missing data. Maximum 

recorded values are substituted for the missing data. The resulting design value is compared to 

the standard. The monitor passes if the design value with maximum values substituted meets the 

standard. If the monitor does not pass using the Max-Q Sub test, then another statistical method 

was required. The statistical method used to determine whether an incomplete monitor would 

have met the NAAQS, is to first establish a linear regression relationship between the target 

monitor and another monitor in or close to the nonattainment area. The linear regression would 

then be used to fill in the missing data for the target monitor. The results are checked with an 

additional statistical procedure (“bootstrapping”) to give a “diagnostic” design value verifying if 

the conclusion of attainment is correct. 

2008-2010 data
Delaware Redesignation Request and Maintenance Plan– 2006 Daily PM2.5 NAAQS

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The Max-Q test could not be used to show attainment, considering 2008–2010 data, for 

one monitor located in Chester County, Pennsylvania (“New Garden” monitor: ID 420290100). 

For this monitor, EPA performed a linear regression between the site with incomplete data and a 

nearby site (“Newark” monitor: ID 100031012), which has more complete data in the period in 

which the incomplete site is missing data. The equation developed from the relationship 

between the monitors was used to fill in missing data for the New Garden monitor, so that the 

normal data completeness requirement of 75 percent of data in each quarter of the three years 

was met. After the missing data for the site was filled in, the results were verified through 

bootstrapping. The results of EPA’s statistical analysis indicated that while the Chester County, 

Pennsylvania monitor had less than complete data, the data is sufficient to demonstrate that the 

NAAQS has been met for 2008-2010 design values. Therefore, all monitors in the Philadelphia 

NAA meet the 2006 daily PM2.5 NAAQS based on certified, quality assured and complete 2008-

2010 monitoring data.

2009-2011 data

Although the Philadelphia NAA initially came into attainment considering 2008-2010, 

this redesignation request is being submitted in late 2012. Therefore, more recent monitoring 

data is available (e.g., 2011 and preliminary 2012). However, the Philadelphia Area had three

incomplete monitors for 2009-2011.5 Monitoring site 42-101-0024 was shutdown on Jan 2011, 

and site 42-101-1002 started operating in January 2011. EPA applied linear regression analysis, 

followed by bootstrap runs for the third incomplete monitor: the New Garden monitor at site 42-

029-0100 located in Chester, PA, which had missing data due to power failures in 2011. The 

results of EPA’s analysis show that the "diagnostic design value” computed from EPA's 

statistical procedure is 33 μg/m3for the New Garden monitor.

6

,7 EPA’s analysis may be found 

in this Plan’s supporting documentation, “B2- Statistical Results for 2009-2011 Design Values”.

Summary

As shown in Table 3-1, the highest 3-year design value for the daily NAAQS, based on 

2008-2010 and 2009-2011 data is 33 μg/m3, which is less than the level of the daily PM2.5

NAAQS of 35 μg/m3. In addition, preliminary 2012 data from AQS, the 1st quarter values 

continue to show attainment with the highest value of 35 μg/m3(“Bucks County”: monitor ID 

420170012). Therefore, certified and quality-assured ambient air quality monitoring data 

demonstrates that the air quality has met the 2006 NAAQS for daily PM2.5 in the Philadelphia 

NAA for the 2008-2010, and 2009-2011 timeframes. The 2006 daily PM2.5 NAAQS attainment, 

accompanied by decreases in emission levels discussed in Section 3.3.1, supports a redesignation 

to attainment for the New Castle County, Delaware portion of the Philadelphia NAA based on 

the requirements in Section 107(d)(3)(E) of the CAA as amended.

 

5 As of July, 2012 the 2011 AQS monitoring data showed one quarter of missing data for each of the following 

monitor sites: Newark, ID 100031012, Bellefonte, ID 100031003 and New Garden, ID 420290100. Delaware’s 

incomplete 2011 data has since been deemed valid because it passed the Max Q test.

6 E. V. Rosa, EPA Region 3 (August 27, 2012).

7 Chester County PA monitor had incomplete data in 2011. However, the EPA " Statistical Results for Computation 

of 2009-2011 Diagnostic 24-hour PM2.5 Design Values of Monitoring Site 42-029-0100 in the PhiladelphiaWilmington Nonattainment Area” demonstrates 2009-2011 “Clean Data” for the Philadelphia NAA. 
Delaware Redesignation Request and Maintenance Plan– 2006 Daily PM2.5 NAAQS

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Table 3-1 Philadelphia NAA 98th percentiles and Design Values (2008-2011)

98th Percentile Value1

2008-

2010 

Design 

Value

2008-

2010

Status 2

2009-

2011 

Design 

Value

2009-

2011 

Status 2

State County Monitor 

ID 2008 2009 2010 2011

PreLim. 

20126

DE Bellefonte 100031003 28.0 23.2 24.3 22.4* 17.5 25 C 23 Max-Q

Lums 100031007 23.9 20.6* 27.5 21.0 21.8 22 C 23 Max-Q

Newark 100031012 31.6 23.4 24.9 22.2* 20.2 26 Max-Q 24 Max-Q

MLK 100032004 28.1 28.4 27.9 24.7 22.7 25 Max-Q 27 C

NJ Camden 340071007 28.6 25.0 23.4 24.3 22.0 26 C 24 C

Gloucester 340150004 34.8 21.9 21.6* 22.2 23.9 30 C 22 Max-Q

PA Bucks 420170012 30.9 25.8 28.3 29.7 34.9 28 C 28 C

Chester 420290100 32.0 31.1 35.1 33.8* 21.0 33 Bootstrap 33 Inc. (3)

Delaware 420450002 28.6 27.9 32.8 28.6 23.9 30 C 30 C

Montgomery 420910013 23.7 27.2 25.9 27.6 21.1 26 C 27 C

Philadelphia 421010004 34.5 25.9 27.6 29.6 27.9 29 C 28 C

Philadelphia 421010024 30.5 25.5 25.2 - - 27 C 25 Inc. (4)

Philadelphia 421010047 32.8 27.2 27.6 27.5 20.0 29 C 27 C

Philadelphia 421010055 34.5 28.6 28.9 30.6 19.6 31 C 29 C

Philadelphia 421010057 32.8 28.3 27.9 30.5 20.6 30 C 29 C

Philadelphia 421011002 - - - 27.5 23.4 NA NA 27 Inc. (5)

NAA Avg. (all monitors) 30.4 26.0 27.3 26.8 22.7 27.8 26.6 30.4

NOTES:

2009-2011 data source: E. V. Rosa, EPA Region 3 (August 27, 2012).

2008 data source: EPA AQS (as of July, 2012).

1. Yearly 98th percentile values initially not meeting the completeness criteria are marked with an asterisk (*). 

The dash (-) indicates that no data was collected during this time.

2. This column indicates whether the monitoring data from the monitor meet the completeness requirement (C) or 

not (Inc.) for each quarter of the 3-year period. “Max-Q” denotes that the monitor has incomplete data, but 

passed the maximum quarter substitution test.

3. “EPA only applied its statistical procedure (a.k.a. bootstrapping) for the 2011 third incomplete monitor for: the 

New Garden monitor (420290100 located in Chester, PA, which had missing data due to power failures 

in 2011. The "diagnostic" design value computed from EPA's procedure was 33 μg/m3”, (see footnote 6).

4. Monitoring site was shut down on January 1, 2011.

5. Monitoring site commenced operation on June 1, 2010.

6. Preliminary 2012 data is 1st quarter only, obtained from AQS in July, 2012.
Delaware Redesignation Request and Maintenance Plan– 2006 Daily PM2.5 NAAQS

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3.3 Ambient monitoring data quality assured in accordance with 40 CFR 58.10, 

recorded in the EPA air quality system (AQS) database, and available for public 

view (requirement 2 of 3)

Delaware DAQ has quality assured all data in accordance with 40 CFR 58.10 and all 

other federal requirements. Delaware DAQ has recorded the data in the AQS database and, 

therefore, the data are available to the public.

Delaware began official PM2.5 monitoring in 1999. Delaware’s PM2.5 network consists of 

seven (7) monitoring sites, one of which employs a collocated monitor. There are four (4) sites 

in New Castle County, two (2) in Kent County and one (1) in Sussex County. Table 3-2 lists the 

PM2.5 sites in New Castle County (the only nonattainment county), including the nature of the 

area, and general site descriptions. Table 3-3 contains more specific information for each PM2.5

monitoring site in New Castle County.

Table 3-2 PM2.5 Monitoring Site General Information

Site Name & AQS ID Land Use Setting Metropolitan Statistical Area

Bellefonte

10-003-1003 Residential Suburban Philadelphia - Wilmington

MLK

10-003-2004 Commercial Urban Philadelphia - Wilmington

Newark

10-003-1012 Residential Suburban Philadelphia - Wilmington

Lums Pond

10-003-1007 Agricultural Rural Philadelphia - Wilmington

Table 3-3 PM2.5 Monitor Site Specific Information

Site Name & AQS ID Parameter Start Date Objective

Bellefonte

10-003-1003 PM2.5 1/1/1999 Population Exposure,Attainment Status

MLK

10-003-2004

PM2.5 1/1/1999 Maximum concentration,

Attainment Status

PM2.5 speciation 6/1/2001 PM2.5 Characterization

Black Carbon 1/1/2001 Diesel PM2.5 Indicator

Newark

10-003-1012 PM2.5 12/15/1999 Population Exposure,Attainment Status

Lums Pond

10-003-1007 PM2.5 1/1/1999 Transport/Background,Attainment Status
Delaware Redesignation Request and Maintenance Plan– 2006 Daily PM2.5 NAAQS

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The primary goal of the PM2.5 monitoring network in Delaware is to determine the status 

of the ambient air with respect to the 24-hour and annual average PM2.5 NAAQS. In accordance 

with federal regulations, state agencies must operate at least the minimum number of required 

PM2.5 sites listed in 40 CFR Part 58 Appendix D Table D-5. These required monitoring stations 

or sites must be sited to represent community-wide air quality. In addition, the following 

specific criteria also apply:

1) At least one monitoring station is to be sited in a population-oriented area of expected 

maximum concentration. 

2) For areas with more than one required station, a monitoring station is to be sited in an 

area of poor air quality.

3) Each State shall install and operate at least one PM2.5 site to monitor for regional 

background and at least one PM2.5 site to monitor regional transport. 

Figure 3-1 shows the locations of Delaware’s PM2.5 monitors. All data from these 

monitors are measured using EPA approved federal reference methods (FRM). All PM2.5

monitoring sites are located appropriately and are eligible for comparison to the annual and daily 

PM2.5 NAAQS. 

The standard monitoring schedule is one in three days, with one site (MLK-Wilmington) 

monitoring every day. MLK is also the designated collocated site, with the collocated monitor 

designated as MLK-b operating on a one in six day schedule. All data were submitted to EPA’s 

Air Quality System (AQS) in a timely manner in accordance with the schedule prescribed by 

EPA.

Chemical speciation is encouraged at sites where the chemically resolved data would be 

useful in developing SIPs and supporting atmospheric or health effects related studies. Chemical 

speciation is conducted at MLK in Wilmington and Dover in Kent County. The PM2.5 chemical 

speciation sites include analysis for elements, selected anions and cations, and carbon. 
Delaware Redesignation Request and Maintenance Plan– 2006 Daily PM2.5 NAAQS

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Figure 3-1 Delaware’s PM2.5 Monitoring Site Locations

Delaware’s original PM2.5 monitoring network design and monitor siting were completed 

in accordance with EPA requirements and guidance as stated in 40 CFR Part 58 Appendices D 

and E, and the EPA Office of Air Quality Planning & Standards (OAQPS) document “Guidance 

for Network Design and Optimum Site Exposure for PM2.5 and PM10” (EPA 1997a). Final 

network documents were submitted to EPA Region 3 in June 1998, and EPA approved 

Delaware’s PM2.5 monitoring network. 

Delaware Annual Ambient Air Monitoring Network Reviews, including PM2.5, have been 

completed each year in accordance with 40 CFR Part 58 Appendix D and subsequently 

submitted to EPA Region 3 for approval.

In fulfillment of the federal 103 grant requirements, Delaware submits annual Delaware 

Data Quality Assessments for PM2.5 speciation data and PM2.5 FRM data to EPA Region 3. All 

data comply with appropriate federal and state requirements, including 40 CFR Part 50 

Appendices L and N, and 40 CFR Part 58 Appendix A.

In fulfillment of the federal 103 grant requirements, Delaware also submits annual PM2.5

Speciation Monitoring Network Review and Monitoring Strategy reports to EPA Region 3. The 

PM2.5 speciation network design and monitor siting follows EPA requirements and guidance as 

stated in 40 CFR Part 58 Appendices D and E, and the documents “Guidance for Network 

Design and Optimum Site Exposure for PM2.5 and PM10" (EPA 1997a), “Particulate Matter 
Delaware Redesignation Request and Maintenance Plan– 2006 Daily PM2.5 NAAQS

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(PM2.5) Speciation Guidance” (EPA 1999), and “Guideline on Speciated Particulate 

Monitoring” (EPA 1999a).

3.4 A commitment that once redesignated, the state will continue to operate an 

appropriate monitoring network to verify the maintenance of the attainment status 

(requirement 3 of 3)

3.4.1 EPA Requirements

Once an area has been redesignated, the states must continue to operate an appropriate air 

quality monitoring network in accordance with 40 CFR Part 58, to verify the area's attainment 

status. In cases where measured mobile source parameters (for example, vehicle miles traveled) 

have changed over time, a state may also need to perform a saturation monitoring study to 

determine the need for, and location of, additional permanent monitors.

3.4.2 Delaware Approach 

The State of Delaware operates a monitoring network that is significantly more robust 

than required by federal regulation. New Castle County is nonattainment for the 1997 PM2.5

annual standard and the 2006 daily PM2.5 standard. Accordingly, Delaware is required to 

maintain its current monitoring network. 

As mentioned in above, states must continue to operate an appropriate air quality 

monitoring network in accordance with 40 CFR Part 58, to verify the area's attainment status. 

Information on Delaware’s monitoring network was discussed in Section 3.3.

The State of Delaware commits to operating and maintaining an air quality network for 

PM2.5 monitoring that meets all federal requirements. However, should changes become 

necessary in the future Delaware DAQ will consult with EPA Region 3 prior to making changes 

to the existing monitoring network. Delaware DAQ will continue to quality assure the 

monitoring data to meet the requirements of 40 CFR 58 and all other federal requirements. 

Delaware DAQ will enter all data into AQS on a timely basis in accordance with federal 

guidelines.

4 Permanent and Enforceable Emission Reductions

4.1 U. S. EPA Requirements

As noted in Section 107(d)(3)(E)(iii) and in the redesignation guidance, states must be 

able to reasonably attribute its air quality improvements to emission reductions of precursors or 

direct PM2.5 that are permanent and enforceable. Attainment resulting from temporary reductions 

in emission rates (such as reduced production or shutdown due to temporary adverse economic 

conditions) or unusually favorable meteorological conditions does not qualify.
Delaware Redesignation Request and Maintenance Plan– 2006 Daily PM2.5 NAAQS

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4.2 Delaware Approach

Delaware will demonstrate the improvement in air quality described in 3.2 of this 

document was not a result of temporary adverse economic conditions (4.2.1) or unusually 

favorable meteorology (4.2.2). Delaware then demonstrates that the improvements in air quality 

described in 3.2 of this document are reasonably attributable to permanent and enforceable 

emission reductions of direct PM2.5 and PM2.5 precursors (4.2.3 and 4.3). 

4.2.1 Economic Conditions

Delaware evaluated the role economic conditions may have played in the improvement

in air quality described in 3.2 of this document by evaluating the Gross Domestic Product 

(GDP) growth rate. The GDP growth rate is an indicator of economic health. If the GDP 

growth rate is increasing, it is an indication that the activity of emitting sources are increasing. 

Conversely, if the GDP is declining it is an indication that the activity of emitting sources may 

be reduced because of economic conditions. 

Delaware specific GDP for all industries, obtained from the U.S. Bureau of Economic 

Analysis (BEA), is presented in Figure 4-1. 

Figure 4-1 2006 – 2011 Delaware Gross Domestic Product – All Industry

Figure 4-1 shows that except for a decline between 2007 and 2008,8 all industries 

increased GDP in every year from 2006 through 2011. Of specific relevance to air quality is the 

comparison between the time when Delaware’s air quality did not meet the PM2.5 daily NAAQS 

(2006-2008 design value) and the time when it did meet the NAAQS (2008-2010 and 2009-2011 

 

8 According to the Delaware Department of Labor the reason for the decline between 2007 and 2008 was an 

economic recession that began in Delaware in December 2007.
Delaware Redesignation Request and Maintenance Plan– 2006 Daily PM2.5 NAAQS

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design values). The GDP in every year between 200[9][8] and 2011 is greater than every year 

between 2006 and 2008. This analysis of GDP indicates that economic conditions did not 

contribute to the improvement in air quality.

4.2.2 Meteorology 

Delaware evaluated the role meteorology may have played in the improvement in air

quality described in 3.2 of this document by evaluating temperature and precipitation data. 

Temperature and precipitation are the primary meteorological variables that impact the 

formation of PM2.5. Temperature and precipitation impact both the emission from sources 

(e.g., power plant emissions are highest during very hot and cold weather), and ambient PM2.5

concentrations (e.g., precipitation removes PM2.5 from the air through deposition).

Delaware analyzed historical meteorological data for Wilmington, Delaware, which is the 

location where Delaware’s highest PM2.5 concentrations are recorded (monitor ID = 100032004).

Table 4-1 shows 3-year monthly averages for: minimum, maximum and means temperatures (in 

degrees Fahrenheit), as well as total precipitation by monthly average and for the entire 3-year 

periods 2006-2008 and 2008-2010.

9

 

9 Recall that 2006-2008 average PM2.5 concentration was used to calculate the final Philadelphia NAA design 

values causing nonattainment, and the 2008-2010 average PM2.5 concentration was when the Philadelphia NAA 

initially came into attainment. Therefore, by comparing the meteorology between these two 3-year periods we can 

evaluate the effect that meteorology had on PM2.5 concentrations during a time when the air quality was 

nonattainment and a time when it was attainment.
Delaware Redesignation Request and Maintenance Plan– 2006 Daily PM2.5 NAAQS

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Table 4-1 Min, Max and Mean Temperatures and Total Precipitation (2006-

2008 vs. 2008-2010) 

2006-

2008

2008-

2010

2006-

2008

2008-

2010

2006-

2008

2008-

2010

2006-

2008

2008-

2010

3-yr 

AVG 

Min. 

Temp

(

o F)

3-yr 

AVG 

Min. 

Temp

(

oF)

3-yr 

AVG 

Max. 

Temp

(

oF)

3-yr 

AVG 

Max. 

Temp

(

oF)

3-yr 

Mean 

Temp

(

oF)

3-yr 

Mean 

Temp

(

oF)

Total 

Precip

(in)

Total 

Precip 

(in)

Jan 29.6 24.7 46.2 39.6 37.9 32.2 9.2 7.0

Feb 25.0 26.4 41.6 43.1 33.3 34.8 8.6 10.5

Mar 33.9 35.4 54.2 54.4 44.1 44.9 8.9 11.3

Apr 43.4 44.8 63.8 65.5 53.6 55.2 14.9 8.4

May 51.3 52.9 73.7 73.1 62.5 63.0 8.4 11.3

Jun 63.7 64.4 82.6 83.7 73.2 74.1 14.8 11.2

Jul 67.9 67.0 87.2 87.0 77.6 77.1 13.9 14.8

Aug 65.9 66.4 85.0 84.9 75.4 75.6 7.1 9.2

Sep 58.9 59.6 78.2 78.4 68.5 69.0 11.9 16.1

Oct 47.8 46.1 68.2 65.9 58.0 56.0 13.3 13.2

Nov 38.7 38.9 54.8 55.4 46.8 47.1 9.5 8.1

Dec 31.0 27.5 47.3 42.6 39.1 35.0 11.1 15.4

Annual average 3-Yr 

Average Temp., and 3-

Yr Total

Precipitation

46.4 46.2 65.2 64.5 55.8 55.3 131.7 136.5

From Table 4-1, we see that the annual average 3-year monthly averages for minimum, 

maximum, and mean temperatures for 2006-2008 are slightly higher than those temperatures 

during the years 2008-2010 (e.g., the 2006-2008 annual average mean temperature was 55.8 

degrees while the 2008-2010 annual average mean temperature was 55.3 degrees). Because

temperatures were only slightly lower during the years showing attainment (2008-2010), 

decreased temperatures did not likely contribute to the improved air quality.

From Table 4-1, we see that 3-year total precipitation was about 3.5% higher in 2008-

2010 compared to 2006-2010 (136.5 in. and 131.7 in. respectively). Increased precipitation 

disfavors PM2.5 formation, because it results in deposition of existing ambient PM2.5 and 

precursors. Because total precipitation was only slightly higher during the years showing 

attainment (2008-2010), increased precipitation did not likely contribute to the improved air 

quality. 
Delaware Redesignation Request and Maintenance Plan– 2006 Daily PM2.5 NAAQS

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In summary, 1) the annual average 3-year monthly min, max, and mean temperatures are 

very similar between the nonattainment timeframe (2006-2008) and the attainment timeframe 

(2008-2010), and 2) the total precipitation is also very similar between those two periods. 

Therefore, although Meteorology will always play a role in the formation of PM2.5, DAQ 

concludes that meteorology did not play a significant role in air quality improvements for 

redesignation purposes under the 2006 daily PM2.5 NAAQS. 

4.2.3 Emission Inventory Improvements from 2007 base year to the 2008 attainment year

It was demonstrated in 4.2.1 and 4.2.2 that neither economic conditions nor meteorology 

significantly contributed to the improved air quality. Given this, it follows that permanent and 

enforceable reductions of PM2.5, NOX and SO2,

10 from a variety of state and federal measures 

are the primary reason for the improved air quality and attainment of the standard for fine 

particles. 

As discussed previously, in November, 2009 (effective December 14, 2009), EPA

published its air quality designations for the 2006 PM2.5 NAAQS based upon air quality 

monitoring data for calendar years 2006–2008 (74 FR 8688). Since 2007, permanent and 

enforceable reductions of primary PM2.5 and secondary PM2.5 precursor emissions have 

contributed to improvements in PM2.5 air quality and to the attainment of the daily PM2.5

NAAQS. To help demonstrate how emission reductions have improved air quality, we evaluate 

air quality trends, which can be seen in Table 4-2 and Figures 4-2 and 4-3, and discuss emission 

reductions due to permanent and enforceable control measures.

The Table values represent the daily average concentrations as calculated from the four 

calendar quarterly averages at each monitoring site, and the 3-year design values from 2006-

2011. As Table 4-2 shows, the highest annual value in the Philadelphia NAA nonattainment 

area has decreased from 39.0 μg/m3in 2006 (monitor ID 421010047) to 34.0 μg/m3in 2011

(monitor ID 420290100), or 5.0 μg/m3, which represents a 12.8% drop. This daily average is 

the basic statistic used in determining trends and compliance with the daily average NAAQS. 

 

10 Ammonia and volatile organic compounds (VOC) are contributors to PM2.5 formation; however, they are not 

considered significant overall contributors in the Philadelphia NAA. Therefore, this demonstration of air quality

improvements due to permanent and enforceable emission reductions of precursors or direct PM2.5 focuses on SO2, 

PM2.5, and NOX.
Delaware Redesignation Request and Maintenance Plan– 2006 Daily PM2.5 NAAQS

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Table 4-2 Philadelphia NAA 2006-2011 daily NAAQS (98th percentiles)

State County and DE sites Monitor ID 2006 2007 2008 2009 2010 2011

DE New Castle (Bellefonte) 100031003 31 32 36 23 24 22

New Castle (Lums) 100031007 28 30 28 21 28 21

New Castle (Newark) 100031012 31 31 29 23 25 22

New Castle (MLK) 100032004 38 34 35 28 28 25

NJ Camden 340071007 38 35 28 25 23 24

Gloucester 340150004 - 31 24 22 22 22

PA Bucks 420170012 34 35 31 26 28 30

Chester 420290100 38 38 32 31 35 34

Delaware 420450002 37 34 29 28 33 29

Montgomery 420910013 36 30 24 27 26 28

Philadelphia 421010004 38 35 35 26 28 30

Philadelphia 421010024 35 33 31 26 25 -

Philadelphia 421010047 39 35 33 27 28 28

Philadelphia 421010055* - - 35 29 29 31

Philadelphia 421010057 - - 33 28 28 31

Philadelphia 421011002 - - - - - 28

Philadelphia NAA Average μg/m3 (all monitors) 35 33 31 26 27 27

 Camden 340070003 was shutdown in 2008; therefore not included for this 2006-2010 trend analysis

 Gibbstown (Gloucester) monitor: On February 2, 2007, a PM2.5 monitor (0004) began sampling at the 

Gibbstown site which was the replacement for a site discontinued in 2006 (5001) in a different area of 

Gibbstown.

 Monitor 421010055 in Philadelphia County, Pennsylvania, started operating in 2008.

 Monitor 4210010057 started operating in the 3rd Quarter, 2007.

 Monitor 421011002 started operating in January, 2011.

 ND = monitor did not operate or was not in existence in that year.

As Table 4-2 shows, the daily mean for the Philadelphia NAA decreased from a high of 

39 μg/m3in 2006, to 34 μg/m3in 2011, or 5 μg/m3, this equates to a 13% drop in the daily mean 

value. Figure 4-2 illustrates the trends of the yearly 98th percentile PM2.5 concentrations of each 

NAA monitor since 2006, which are generally decreasing. Figure 4-3 also shows 2006-2011 

yearly 98th percentiles, but instead of showing a trend for each monitor, all the monitors in the 

Philadelphia NAA were averaged. This helped eliminate some variability between monitors in 

order to get a NAA-wide overall trend. Figure 4-4 shows the downward trends since 2006 using 

3-year rolling-averages, which smoothes out inter-monitor variability yet uses actual design 

values for each monitor. Figure 4-5 is a variation on Figure 4-4 by plotting the average design 

values per year, calculated from all monitors in the Philadelphia NAA. 
Delaware Redesignation Request and Maintenance Plan– 2006 Daily PM2.5 NAAQS

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Figure 4-2 Philadelphia NAA – 2006 to 2011 daily PM2.5 trends

Figure 4-3 Philadelphia NAA – daily PM2.5 trends (avg. all monitors)
Delaware Redesignation Request and Maintenance Plan– 2006 Daily PM2.5 NAAQS

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Figure 4 Philadelphia NAA – 2006 to 2011 PM2.5 3-Year Rolling Averages

Figure 4.5 Philadelphia NAA – daily PM2.5 trends (avg. all monitors)

Some of these air quality improvements were a result of emissions reductions which were 

due to the application of tighter federal emission standards on motor vehicles and fuels, and 

some due to the requirements of the federal NOx SIP Call. Others were due to Delaware-
Delaware Redesignation Request and Maintenance Plan– 2006 Daily PM2.5 NAAQS

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specific control measures. Section 4 of this plan describes these reductions in more detail, along 

with an explanation of their regulatory status. 

One of the ways states have demonstrated how controls have contributed to reductions is 

by comparing a base year emission inventory to the attainment year emission inventory. The 

EPA’s PM2.5 Emissions Inventory Guidance required that states with PM2.5 NAAQS 

nonattainment areas prepare and submit a base year inventory of anthropogenic sources of direct 

PM2.5 and precursors of secondary PM2.5 emissions, namely NOx and SO2. The 2007 base year 

inventory included emissions from point, non-point, on-road mobile and non-road mobile 

emissions. It was picked as the base year for the daily redesignation request and maintenance 

plan because it reflects one of the years in which Delaware was designated nonattainment (e.g., 

2006-2008). 

The 2007 inventory was developed through the MARAMA regional planning process.

Documentation of how the 2007 attainment year was developed can be found in Technical 

Support Document for the Development of the 2007 Emission Inventory for Regional Air Quality 

Modeling in the Northeast / Mid-Atlantic Region Version 3.3 January 23, 2012. The MARAMA 

2007 TSD includes annual emissions for carbon monoxide (CO), ammonia (NH3), oxides of 

nitrogen (NOx), particulate matter (PM), sulfur dioxide (SO2), and volatile organic compounds 

(VOC). The PM species in the inventory are categorized as: filterable and condensable particles 

with an aerodynamic diameter less than or equal to a nominal 10 and 2.5 micrometers (i.e., 

PM10-PRI and PM25-PRI); filterable particles with an aerodynamic diameter less than or equal 

to a nominal 10 and 2.5 micrometers (i.e., PM10-FIL and PM25-FIL); and condensable particles 

(PM-CON). Note that PM10-PRI equals the sum of PM10-FIL and PM-CON, and PM25-PRI 

equals the sum of PM25-FIL and PM-CON. 

The Philadelphia NAA first came into attainment for the 2006 daily PM2.5 NAAQS based 

on 2008-2010 data. Delaware is using 2008 as the attainment year (e.g., one of the three years 

during which the area attained the standard as the attainment year inventory), from which future 

inventories are projected in the maintenance plan. Documentation of how the 2008 attainment 

year was developed can be found in the 2008 Attainment Year State Implementation Plan 

Emissions Inventory for PM2.5, SO2, and NOx.
Delaware Redesignation Request and Maintenance Plan– 2006 Daily PM2.5 NAAQS

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Table 4-3 summarizes 2007 and 2008 emissions by major source category and by 

pollutant for New Castle County, as well as the change in terms of tons per year (tpy) and 

percent decrease/increase.

Table 4-3 New Castle County 2007-2008 Emission Changes

Source 

Sector

NOx PM2.5 SO2

2007 2008 Δ 

(tpy)

Δ 

(%) 2007 2008 Δ (tpy)

Δ 

(%)

2007 2008 Δ 

(tpy)

Δ 

(%)

Point 6,635 5,589 1,046 16% 1,335 1,109 226 17% 13,380 10,576 2,805 21%

Non-point 1,293 1,287 6 0% 1,207 1,191 16 1% 630 402 228 36%

On-road 10,577 9,311 1,266 12% 324 283 42 13% 100 94 6 6%

Non-road 4,580 4,317 263 6% 327 312 15 5% 1,118 1,067 51 5%

All Sectors 23,084 20,504 2,580 11% 3,193 2,894 300 9% 15,228 12,139 3,089 20%

By comparing the 2007 and 2008 inventories, we see that total direct PM2.5 emissions 

were reduced by 300 tons per year, and that NOx emissions decreased by 2,580 tons per year. 

These reductions were primarily from on-road and non-road mobile sources. 

4.3 Enforceable and Permanent PM2.5, NOx and SO2 Measures that Contributed to 

Improved Air Quality between 2007 and 2008

4.3.1 Delaware-specific Control Measures

 7 DE Admin. Code 1144, Control of Stationary Generator Emissions, SO2, PM, VOC and 

NOX emission control, State-wide, Effective January 2006; EPA SIP approval date 

08/11/2010 (75 FR 48566).

 7 DE Admin. Code 1148, Control of Stationary Combustion Turbine Electric Generating 

Unit Emissions, NOX emission control, State-wide, Effective July, 2007. This regulation 

was approved into the Delaware SIP by EPA on 08/11/2010. (75 FR 48566).

 7 DE Admin. Code 1142, Section 1, Control of NOX Emissions from Industrial Boilers, 

NOX emission control, Effective December 2001. This regulation was approved into the 

Delaware SIP by EPA on 11/22/01 (67 FR 70315) Section 2, Control of NOX Emissions 

from Industrial Boilers and Process Heaters at Petroleum Refineries, NOX emission 

control, New Castle County, Effective July 2007. This regulation was revised and 

approved into the Delaware SIP by EPA on 5/15/12 (77 FR 28489).

 7 DE Admin. Code 1131- Low Enhanced Inspection and Maintenance. Delaware’s 

enhanced I/M program was approved into the Delaware SIP by EPA on September 30, 

1999 (64 FR 52657). Revisions to the enhanced I/M program were approved by EPA on 

11/26/2003 (68 FR 228). 
Delaware Redesignation Request and Maintenance Plan– 2006 Daily PM2.5 NAAQS

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4.3.2 Federal Control Measures

Area Sources

EPA’s New Source Performance Standards for Woodstoves (NSPS). These standards are 

codified at 40 CFR Part 60, subpart AAA. The final standards were promulgated in 1988 (53 FR 

5860). The rule requires manufacturers of new residential wood heaters (e.g., wood stoves) to 

design heaters to meet particulate emission (PM) limits, have representative model lines tested 

by EPA-accredited labs, and attach EPA labels and hangtags after EPA approval. 

Control Programs Included in the NMIM/NONROAD Model

Under 40 CFR Part 89, EPA adopted standards for emissions of NOX, hydrocarbons

(HC), and carbon monoxide (CO) from several groups of nonroad engines, including industrial 

spark-ignition engines and recreational nonroad vehicles. Industrial spark-ignition engines 

power commercial and industrial applications and include forklifts, electric generators, airport 

baggage transport vehicles, and a variety of farm and construction applications. Nonroad 

recreational vehicles include snowmobiles, off-highway motorcycles, and all-terrain vehicles. 

These rules were initially effective in 2004 and will be fully phased in by 2012.

Control of Air Pollution; Determination of Significance for Nonroad Sources and 

Emission Standards for New Nonroad Compression Ignition Engines at or Above 37 Kilowatts 

59 FR 31036, June 17, 1994. This rule establishes Tier 1 exhaust emission standards for HC, 

NOx, CO, and PM for nonroad compression-ignition (CI) engines ≥37kW (≥50hp). Marine 

engines are not included in this rule. The start dates and pollutants affected vary by hp category 

as follows: 

 50-100 hp: Tier 1,1998; NOx only

 100-175 hp: Tier 1, 1997; NOx only

 175-750 hp: Tier 1, 1996; HC, CO, NOx, PM

 >750 hp: Tier 1, 2000; HC, CO, NOx, PM

Emissions for New Non-road Spark-Ignition Engines At or Below 19 Kilowatts; Final 

Rule 60 FR 34581. July 3, 1995. This rule establishes Phase 1 exhaust emission standards for 

HC, NOx, and CO for nonroad spark-ignition engines ≤19kW (≤25hp). This rule includes both 

handheld (HH) and non-handheld (NHH) engines. The Phase 1 standards became effective in 

1997 for: 

 Class I NHH engines (<225cc), 

 Class II NHH engines (≥225cc), 

 Class III HH engines (<20cc), and 

 Class IV HH engines (≥20cc and <50cc). 

The Phase 1 standards become effective in 1998 for: Class V HH engines (≥50cc). 
Delaware Redesignation Request and Maintenance Plan– 2006 Daily PM2.5 NAAQS

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Final Rule for New Gasoline Spark-Ignition Marine Engines; Exemptions for New 

Nonroad Compression-Ignition Engines at or Above 37 Kilowatts and New Nonroad SparkIgnition Engines at or Below 19 Kilowatts 61 FR 52088. October 4, 1996. This rule establishes

exhaust emission standards for HC+NOx for personal watercraft and outboard (PWC/OB) 

marine spark-ignited (SI) engines. The standards are phased in from 1998-2006.

Control of Emissions of Air Pollution from Nonroad Diesel Engines 63 FR 56967 

October 23, 1998. This final rule sets Tier 1 standards for engines under 50 hp, phasing in from 

1999 to 2000. The rule also phases in more stringent Tier 2 standards for all engine sizes from 

2001 to 2006, and yet more stringent Tier 3 standards for engines rated over 50 hp from 2006 to 

2008. The Tier 2 and Tier 3 standards apply to NMHC+NOx, CO, and PM. The start dates by 

hp category and tier are as follows: 

 hp: < 8kW and 8-19kW: Tier 1, 2000; Tier 2, 2005; no Tier 3

 19-37kW: Tier 1, 1999; Tier 2, 2004; no Tier 3

 37-75kW: Tier 2, 2004; Tier 3, 2008

 75-130kW: Tier 2, 2003; Tier 3, 2007

 130-225kW: Tier 2, 2003; Tier 3, 2006

 225-450kW: Tier 2, 2001, Tier 3, 2006

 450-560kW: Tier 2, 2002; Tier 3, 2006

 >560kW: Tier 2, 2006, no Tier 3

This rule does not apply to marine diesel engines above 50 hp.

Phase 2: Emission Standards for New Nonroad Non-handheld Spark Ignition Engines At 

or Below 19 Kilowatts 64 FR 15207. March 30, 1999. This rule establishes Phase 2 exhaust 

emission standards for HC+NOx for nonroad non-handheld (NHH) spark-ignition engines 

≤19kW (≤25hp). The Phase 2 standards for Class I NHH engines (<225cc) become effective on 

August 1, 2007 (or August 1, 2003 for any engine initially produced on or after that date). The 

Phase 2 standards for Class II NHH engines (≥225cc) were phased in from 2001-2005.

Phase 2: Emission Standards for New Nonroad Spark-Ignition Handheld Engines At or 

Below 19 Kilowatts and Minor Amendments to Emission Requirements Applicable to Small 

Spark-Ignition Engines and Marine Spark-Ignition Engines; Final Rule 65 FR 24268 April 25, 

2000. This rule establishes Phase 2 exhaust emission standards for HC+NOx for nonroad

handheld (HH) spark-ignition engines ≤19kW (≤25hp). The Phase 2 standards were phased in 

from 2002-2005 for Class III and Class IV engines and were phased in from 2004-2007 for Class 

V engines.
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Control of Emissions From Nonroad Large Spark-Ignition Engines and Recreational 

Engines (Marine and Land-Based); Final Rule 67 FR 68241. November 8, 2002. This rule 

establishes exhaust and evaporative standards for several nonroad categories: 

1) Two tiers of emission standards are established for large spark-ignition engines over 19 

kW. Tier 1 includes exhaust standards for HC+NOx and CO and was phased in from 

2004-2006. Tier 2 became effective in 2007 and includes exhaust standards for HC+NOx 

and CO as well as evaporative controls affecting fuel line permeation, diurnal emissions 

and running loss emissions.

2) Exhaust and evaporative emission standards are established for recreational vehicles, 

which include snowmobiles, off-highway motorcycles, and all-terrain vehicles (ATVs). 

For snowmobiles, HC and CO exhaust standards are phased-in from 2006-2012. For offhighway motorcycles, HC+NOx and CO exhaust emission standards are phased in from 

2006-2007. For ATVs, HC+NOx and CO exhaust emission standards are phased in from 

2006-2007. Evaporative emission standards for fuel tank and hose permeation apply to 

all recreational vehicles beginning in 2008.

3) Exhaust emission standards for HC+NOx, CO, and PM for recreational marine diesel 

engines over 50 hp begin in 2006-2009, depending on the engine displacement. These 

are “Tier 2” equivalent standards.

Control of Emissions of Air Pollution from Nonroad Diesel Engines and Fuel; Final Rule 

(Clean Air Nonroad Diesel Rule – Tier 4)69 FR 38958, June 29, 2004. This final rule sets Tier 4 

exhaust standards for CI engines covering all hp categories (except marine and locomotives), and 

also regulates nonroad diesel fuel sulfur content.

 1) The Tier 4 start dates and pollutants affected vary by hp and tier as follows:

Rated Power First Year that

Standards Apply

PM

(g/hp-hr)

NOx

(g/hp-hr)

hp < 25 2008 0.30 -

25 ≤ hp < 75 2013 0.02 3.5*

75 ≤ hp < 175 2012-2013 0.01 0.30

175 ≤ hp < 750 2011-2013 0.01 0.30

hp ≥ 750 2011-2014

2015

0.075

 0.02/0.03**

2.6/0.50†

0.50††

* The 3.5 g/hp-hr standard includes both NOx and nonmethane hydrocarbons. 

† The 0.50 g/hp-hr standard applies to gensets over 1200 hp. 
Delaware Redesignation Request and Maintenance Plan– 2006 Daily PM2.5 NAAQS

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** The 0.02 g/hp-hr standard applies to gensets; the 0.03 g/hp-hr standard applies 

to other engines.

†† Applies to all gensets only.

2) This rule will reduce nonroad diesel fuel sulfur levels in two steps. First, starting in 2007, 

fuel sulfur levels in nonroad diesel fuel will be limited to a maximum of 500 ppm, the 

same as for current highway diesel fuel. Second, starting in 2010, fuel sulfur levels in 

most nonroad diesel fuel will be reduced to 15 ppm.

Control of Emissions from Nonroad Spark-Ignition Engines and Equipment; Final Rule 

(Bond Rule), 73 FR 59034 October 8, 2008. This rule establishes exhaust and evaporative 

standards for small SI engines and marine SI engines:

1) Phase 3 HC+NOx exhaust emission standards are established for Class I NHH engines 

starting in 2012 and for Class II NHH engines starting in 2011. There are no new exhaust 

emission standards for handheld engines. New evaporative standards are adopted for 

both handheld and non-handheld equipment. The new evaporative standards control fuel 

tank permeation, fuel hose permeation, and diffusion losses. The evaporative standards 

begin in 2012 for Class I NHH engines and 2011 for Class II NHH engines. For 

handheld engines, the evaporative standards are phased-in from 2012-2016.

2) More stringent HC+NOx and CO standards are established for marine SI PWC/OB 

engines beginning in 2010. In addition, new exhaust HC+NOx and CO standards are 

established for stern-drive and inboard (SD/I) marine SI engines also beginning in 2010. 

High performance SD/I engines are subject to separate HC+NOx and CO exhaust 

standards that are phased-in from 2010-2011. 

On-Road Emissions Programs

In the 2007 heavy-duty highway rule, which is codified in 40 CFR Part 86, Subpart P, 

EPA set a PM emission standard for new heavy-duty engines of 0.01 grams per brake 

horsepower-hour (g/bhp-hr). This standard took full effect for diesel engines in the 2007 model 

year. This rule included standards for NOX and non-methane hydrocarbons (NMHC) of 0.20 

g/bhp-hr and 0.14 g/bhp-hr, respectively. These diesel engine NOX and NMHC standards were 

successfully phased in together between 2007 and 2010. The rule also required that sulfur in 

diesel fuel be reduced to facilitate the use of modern pollution control technology on these trucks 

and buses. EPA required a 97% reduction in the sulfur content of highway diesel fuel -- from 

levels of 500 parts per million (ppm) for low sulfur diesel to 15 ppm for ultra-low sulfur diesel.

The reductions in sulfur content engendered similar reductions in SO2 emissions. These 

requirements were successfully implemented on the timeline in the regulation.

Federal Tier 1 New Vehicle Emission and New Federal Evaporative Emission Standards:

Under CAA Section 202, EPA established federal motor vehicle emission standards (Tier I 

standards), which were phased in beginning with model year 1994. The benefits of this program 

are reflected in the 2007 base year inventory and the 2008 attainment year inventory. This 

federally implemented program affects light duty vehicles and light duty trucks. The regulations 
Delaware Redesignation Request and Maintenance Plan– 2006 Daily PM2.5 NAAQS

33

require more stringent exhaust emission standards as well as a uniform level of evaporative 

emission controls.

The Tier 2 vehicle and gasoline sulfur program, as codified in Subpart H of 40 CFR Part 

80, 40 CFR Part 85, and 40 CFR Part 86, became effective in the 2005 model year. This 

program for fleet averaging of on-road vehicles is modeled after the California LEV II 

standards. The Tier 2 program allows manufacturers to produce vehicles with emissions ranging 

from relatively dirty to very clean, but the mix of vehicles a manufacturer sells each year must 

have average NOX emissions below a specified value. Mobile emissions continue to benefit 

from this program as motorists replace older, more polluting vehicles, with cleaner vehicles. 

Delaware participated in the Ozone Transport Commission (OTC) National Low 

Emission Vehicle Program: Under the OTC National Low Emission Vehicle (NLEV) program, 

automobile manufacturers agreed to comply with tailpipe standards that were more stringent than 

EPA could mandate prior to model year 2004. For the OTC states, starting with the model year 

1999 all new vehicles sold in the region must comply with the more stringent LEV standards. 

Once manufacturers committed to the program, the standards became enforceable in the same 

manner in which other federal motor vehicle emission control requirements were enforceable.

The program was in place nationwide for model year 2001, and the benefits of this program are 

reflected in the 2007 base year inventory and the 2008 attainment year inventory.

In addition to the federal Tier 1 and 2 programs, NLEV, and the federal 2007 heavy duty 

highway rule, Delaware has instituted enhanced vehicle emissions inspection and maintenance 

(DE Admin Code 1131-Low Enhanced Inspection and Maintenance) requirements in New Castle 

County and Kent County. The requirements involve mandating regional vehicle emission I/M 

programs that are stricter than basic programs, as required under Section182 and 202 of the 

CAA. Before 1994, basic automobile emissions testing checked only tailpipe emissions while 

idling and sometimes at 2,500 rpm. For Delaware, the Low Enhanced I/M procedures include the 

use of On Board Diagnostic (OBD) system evaluations, fuel system pressure test and a gas cap 

test. The procedures also include anti-tampering inspections of the catalytic converter, gas cap 

and fuel inlet restrictor. The OBD evaluations provide a more complete inspection, checking for 

excess evaporative emissions and other issues that might affect emissions from the vehicle. 

5 SIP Completeness - Fully Approved SIP, Section 110 and Part D Requirements 

5.1 EPA Requirements

States must provide assurances that the applicable implementation plan has been fully 

approved by EPA under Section 110(k) and must satisfy all requirements that apply to the area. 

An area cannot be redesignated if a required element of its plan is the subject of disapproval; a 

finding of failure to submit or to implement the SIP; or partial, conditional, or limited approval.

For purposes of redesignation, states must also meet all requirements of Section 110 and 

Part D of the CAA that were applicable prior to submittal of the complete redesignation request. 

The general elements required in a SIP are listed in Section 110(a). These elements include 

procedures for air quality monitoring and modeling; criteria for establishing stationary source 
Delaware Redesignation Request and Maintenance Plan– 2006 Daily PM2.5 NAAQS

34

controls, monitoring and reporting; implementation of permitting programs under Part C 

(Prevention of Significant Deterioration or PSD) and Part D (New Source Review or NSR); and 

provisions for public involvement. Subpart 1 of Part D consists of general requirements 

applicable to all areas which are designated nonattainment based on a violation of the NAAQS. 

Subpart 4 of Part D consists of more specific requirements applicable to particulate matter 

(specifically to address PM10). 

5.2 Delaware Approach

Section 110(a) of the CAA contains the general requirements for a SIP. Delaware 

concludes that, as EPA has stated in previous rulemaking,11 only the section 110 and part D 

requirements that are linked with a particular area’s designation are the relevant measures which 

DAQ may consider in evaluating a redesignation request. Further, DAQ believes that the other

section 110 elements that are not connected with nonattainment plan submissions and not linked 

with an area’s attainment status are also not applicable requirements for purposes of 

redesignation. DAQ understands that a state remains subject to these requirements after an area 

is redesignated to attainment.

The requirements of section 110(a)(2) are statewide requirements that are not linked to 

the PM2.5 nonattainment status of the Philadelphia NAA. Therefore, DAQ believes that these 

SIP elements are not applicable requirements for purposes of review of the state’s PM2.5

redesignation request. 

5.3 Part D Plan Requirements for Nonattainment Areas

Nonattainment Areas in General 

CAA Section 172(c) – In accordance with EPA’s applicable PM2.5 implementation rule,

EPA’s planned Rulemaking by December, 2012 on Philadelphia’s Clean Data Determination

will suspend the attainment demonstration, reasonably available control measures/reasonably 

available control technology (RACM/RACT), reasonable further progress (RFP), and 

contingency measure requirements under 172(c) related to attainment of the 2006 daily PM2.5

NAAQS, for so long as the area continues to attain the 2006 daily PM2.5 NAAQS. Therefore, 

EPA will not consider those SIP requirements for the purposes of redesignation. However, the 

base year inventory requirement under 172(c)(3) is not suspended. Delaware will meet this 

requirement when EPA fully approves the 2007 base year inventory submitted with this daily 

PM2.5 NAAQS redesignation and maintenance SIP.[

12]

 

11 See EPA’s proposed approval of Ohio’s redesignation request for the Ohio portion of the Huntington-Ashland 

nonattainment area for the 1997 PM2.5 NAAQS, (76 FR 79593).

[

12 The inventory required under CAA Section 172(c)(3) must be a comprehensive, accurate, and current 

inventory. EPA stated in their October 22, 2012 comments on this Plan that Delaware has the “option” of 

submitting its 2008 or 2007 inventory to meet the requirements of sections 172(c)(3). In order to maintain 

consistency in this Plan (i.e. “base year” = 2007) and to avoid possible confusion, Delaware has elected to use 

the 2007 inventory to meet CAA Section 172(c)(3).] 
Delaware Redesignation Request and Maintenance Plan– 2006 Daily PM2.5 NAAQS

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CAA Section 176(c) was established under the CAA to address conformity. Conformity 

plays an important role in helping states and tribal regions improve air quality in those areas that 

do not meet the NAAQS. Under the separate general and transportation conformity rules, federal 

agencies must work with state, tribal, and local governments in nonattainment and maintenance 

areas to ensure that federal actions, including highway and transit projects, conform to the 

initiatives established in the applicable state or tribal implementation plan.

General Conformity

On November 30, 1993, EPA promulgated a set of regulations, known as the General 

Conformity Regulations, which apply to non-transportation projects (i.e., projects not adding or 

expanding highways and transit). These regulations ensured that these types of federal actions 

also conformed to the SIPs (58 FR 63214). The purpose of the General Conformity Rule is to:

 Ensure that federal activities do not interfere with the budgets in the state implementation 

plans (SIPs); 

 Ensure the attainment and maintenance of the national ambient air quality standards 

(NAAQS); and 

 Ensure that actions do not cause or contribute to new violations of a NAAQS.

General conformity must be met for any federal action, defined as an activity engaged in 

by a department or agency of the federal government, or supported in any way by the federal 

government (including via financial assistance, licenses, permits, or approvals). The Federal 

Agency must make a determination that the activity conforms to the applicable State 

Implementation Plan before commencing the activity. 

A conformity analysis must be conducted by the lead Federal Agency if a federal action 

would result in the generation of air emissions that would exceed conformity threshold levels of 

pollutants for which an air basin that is designated as a nonattainment or maintenance area under 

the NAAQS, or if emissions from the action are deemed regionally significant. A conformity 

analysis must demonstrate that the project emissions would conform, and thus would not degrade 

air quality in the impacted air basin. Conformity can be demonstrated via emission offsets, SIP 

provisions, or air quality modeling. The EPA is responsible for reviewing and approving SIPs, 

which are prepared and submitted to EPA by state environmental agencies.

Transportation Conformity

Transportation conformity is a provision in the CAA, which requires that a conformity 

demonstration be performed by either Federal Highway Administration (FHWA) or Federal 

Transit Administration (FTA) demonstrating that transportation-related highway construction 

will not interfere with achieving NAAQS. The concept of transportation conformity was 

introduced in the Clean Air Act of 1977, but the requirements became substantially more 

rigorous in the Amendments of 1990. The CAA and the Safe, Accountable, Flexible, Efficient 

Transportation Equity Act – A Legacy for Users (SAFETEA-LU) define the framework for 

effective integration of transportation and air quality planning. 
Delaware Redesignation Request and Maintenance Plan– 2006 Daily PM2.5 NAAQS

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Transportation conformity is a process by which it is determined that on-road mobile 

(highway) source emissions evaluated from the Transportation Improvement Program (TIP) 

and/or Long Range Transportation Plan (LRTP) will not adversely impact air quality in a 

determined area of nonattainment. Federal funding and approval are given to transportation 

activities that are consistent with air quality goals. 

As discussed in more detail in Section 8 of this plan, Delaware revised its 2008 Annual 

PM2.5 Attainment Demonstration SIP in 2012, to address the emission factor changes in the new 

EPA MOVES model, and to establish new budgets for the purposes of addressing transportation 

conformity. Development of the 2008 Annual PM2.5 SIP involved the interagency consultative 

process between EPA, DNREC, Delaware Department of Transportation and local transportation 

agencies such as the Wilmington Area Planning Council (WILMAPCO). WILMAPCO is the 

metropolitan planning organization for New Castle County, Delaware and Cecil County, 

Maryland, and also facilitates the public participation process for stakeholders and citizens in the 

State of Delaware. The 2012 SIP revision to the April 2008 PM2.5 Attainment Demonstration 

SIP was a change to Delaware’s motor vehicle emissions budgets under the PM2.5 annual 

NAAQS, and was submitted to EPA on May 3, 2012.

13

 However, EPA has not completed 

rulemaking on the 2008 SIP and the May 3, 2012 Revision.

Delaware’s SIP contains provisions that are consistent with the Section176(c) conformity 

requirements. In Delaware’s SIP, general conformity requirements are contained in 7 DE 

Admin. Code 1135, Conformity of General Federal Actions to the State Implementation Plans 

(Regulation for General Conformity) which was approved into the Delaware SIP by EPA on 

08/11/2010 (75 FR 48566). Transportation conformity requirements are contained in 7 DE 

Admin. Code 1132, Transportation Conformity which was approved into the Delaware SIP by 

EPA on 08/11/2010, (75 FR 48566).

6 Maintenance Plan

6.1 EPA Requirements

Section 107(d)(3)(E) of the CAA requires a maintenance plan to meet the requirements of 

Section 175(A). The maintenance plan constitutes a SIP revision and must provide for 

maintenance of the relevant NAAQS in the area for at least 10 years after redesignation, 

including contingency measures to ensure prompt correction of any violation of the NAAQS. 

Section 175(A) further states that the plan shall contain such additional measures, if any, as may 

be necessary to ensure such maintenance. Mobile vehicle emission budgets for transportation 

conformity purposes are also established within the maintenance plans. States must submit a SIP 

revision eight years after the original redesignation request is approved to provide for 

maintenance of the NAAQS for an additional 10 years following the first 10-year period.

 

13 This daily maintenance plan SIP revision will establish motor vehicle emission budgets for NOx and primary 

PM2.5 for the interim year 2017, and the final year of the maintenance plan, which is 2025. These budgets are 

adopted from the 2008 PM2.5 SIP revision, submitted to EPA in May, 2012. 
Delaware Redesignation Request and Maintenance Plan– 2006 Daily PM2.5 NAAQS

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EPA provided guidance dated September 4, 1992 on the redesignation request and 

maintenance plan process in the memorandum from John Calcagni, Director, Air Quality 

Management Division to Regional Air Directions entitled Procedures for Processing Requests to 

Redesignate Areas to Attainment (redesignation and maintenance plan guidance). Other 

requirements are provided in 40 CFR 51 Subpart Z, entitled Provisions for Implementation of 

PM2.5 National Ambient Air Quality Standards (PM2.5 implementation rule). Additional 

guidance was received from EPA regional staff in the development of this maintenance plan 

through participation in the Mid-Atlantic Regional Air Management Association (MARAMA) 

PM2.5 workgroup, emails and conference calls, as well as reviewing and providing comments on 

several technical support documents developed through the regional modeling efforts.

EPA requires the following provisions to ensure maintenance of the NAAQS:

 The state must develop an attainment emissions inventory to identify the level of 

emissions in the area which is sufficient to attain the NAAQS.

 A state may generally demonstrate maintenance by showing that future emissions of a 

pollutant or its precursors will not exceed the level of the attainment inventory over the 

10-year period following redesignation.

 Once an area has been redesignated, the state must continue to operate an appropriate air 

quality monitoring network in order to verify the area's attainment status.

 The state must ensure that it has the legal authority to implement and enforce all 

measures necessary to attain and maintain the NAAQS. Continued attainment must be 

verified by the state by indicating how maintenance plan progress will be tracked.

 Contingency measures must be available to promptly correct any NAAQS violation. At a 

minimum, the contingency measures must include a requirement that the state will 

implement all measures contained in the nonattainment SIP prior to redesignation. 

6.2 Delaware Approach

The State of Delaware has developed this maintenance plan which meets all of EPA

requirements and demonstrates that because of permanent and enforceable measures, emissions 

will remain below the 2008 attainment year levels over the 10 years following redesignation 

approval will while allowing for growth in population and vehicle miles traveled. The period 

covered by this maintenance plan is 2008 through 2025, with an interim year of 2017.

Delaware has developed an emissions inventory in accordance with EPA guidance that 

identifies the level of emissions sufficient to achieve the 2006 PM2.5 NAAQS. This attainment 

inventory consists of the actual 2008 emissions (i.e., a year during the three-year period 

associated with the 2008-2010 monitoring data showing attainment of the 2006 PM2.5 NAAQS). 

The plan includes a demonstration that emissions will remain beneath the 2008 levels for a 10-

year period following redesignation, by keeping in place all elements of the current federal and 

state regulatory programs and putting in place additional controls. 
Delaware Redesignation Request and Maintenance Plan– 2006 Daily PM2.5 NAAQS

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As discussed in Section 3.5.1, the State of Delaware will continue to operate and 

maintain its air quality monitoring network. Delaware has the legal authority to implement and 

enforce specified measures necessary to attain and maintain the NAAQS.

In addition to maintaining key elements of its regulatory program, the State of Delaware 

will acquire air quality monitoring and source emissions data to track attainment and 

maintenance. The maintenance plan includes contingency measures, as necessary, to promptly 

correct any NAAQS violation that occurs after redesignation of the area. 

The following sections provide detail on each of the above requirements, and the State of 

Delaware approach to meeting each requirement.

7 Attainment Inventory

7.1 EPA Requirements

The State of Delaware must develop an attainment year emissions inventory to identify the 

level of emissions sufficient to achieve the NAAQS. This inventory should be consistent with 

EPA's most recent guidance on emission inventories for nonattainment areas available at the 

time, and should include emissions during the time period associated with the monitoring data 

showing attainment of the 2006 PM2.5 NAAQS. Where a state has made an adequate 

demonstration that air quality has improved as a result of their State Implementation Plan (SIP), 

the attainment inventory will generally be the actual inventory during the time period the area 

attained the standard. The inventory should be based on emissions of SO2, NOX, and primary 

PM2.5 in units of tons per year (tpy) during the attainment year.

In March, 2012 EPA released guidance addressing Implementation of the 2006 24-hr 

PM2.5 NAAQS.14 The guidance states: 

“Statewide annual emission inventories are required under 40 CFR Part 51, Subpart A. 

[EPA] expect that for many nonattainment areas, these annual inventories will serve as an 

appropriate starting point for the emissions inventories used for SIP development. In 

contrast with the 1997 annual PM2.5 NAAQS, where states rely only on annual inventories 

in the implementation process, the 2006 24-hour PM2.5 NAAQS is designed to protect 

against peak exposures. Thus, for the 2006 24-hour PM2.5 NAAQS, there are some 

circumstances in which the EPA believes that seasonal inventories may be useful for SIP 

planning purposes. For example, we have observed that in some nonattainment areas, all 

of the highest fine particle concentrations over the course of a year occur in one season. If 

exceedances occur during only one season for each of the years on which the 

nonattainment designation is based, and this is the case for all subsequent years, [EPA] 

recommends that states develop a seasonal inventory and that they use this inventory for 

SIP planning purposes.... [EPA] also observed that some areas in the northern states 

 

14 Memorandum from Stephen Page, OAQPS to Regional Air Directors entitled, Implementation Guidance for the 

2006 24-Hour Fine Particulate National Ambient Air Quality Standard (NAAQS).
Delaware Redesignation Request and Maintenance Plan– 2006 Daily PM2.5 NAAQS

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have elevated ammonium nitrate levels in the winter, as nitrate remains in particle form 

and does not volatilize at lower temperatures. 

7.2 Delaware Approach

Seasonal Versus Annual Inventories

The State of Delaware developed an attainment year emissions inventory that identifies the 

level of emissions sufficient to achieve the 2006 daily PM2.5 NAAQS. The attainment inventory 

consists of actual emissions for a year during the three-year period associated with the 

monitoring data showing attainment of the PM2.5 standard, that is, 2008 for the daily NAAQS 

maintenance plan. The 2008 inventory is appropriate to use because it represents the typical 

inventory for the first three-year period demonstrating attainment of the standard (2008-2010). 

The 2008 inventory is consistent with EPA inventory guidance; is based on annual emissions of 

SO2, NOX, and primary PM2.5 during 2008; and contains a list of sources and emissions in tpy. 

The following analysis describes Delaware’s rationale for using annual emissions instead of 

daily emissions.

Analysis of Top 10 Days per Year - Seasonal Percentages 

States and the City of Philadelphia in the Philadelphia NAA were asked by the 

MARAMA PM2.5 redesignations workgroup to provide the top 10 percent of values for each 

monitor. Specifically, the following monitor attributes were requested of each State/City (via 

spreadsheet template): Year, Season, Month, Date, Rank and Sample Value. 

Data Completeness & Consistency

For the Gibbstown, NJ monitor, 2006 data was not included in the analysis since only 

January through March readings were recorded for that year. The Camden, NJ monitor for 2008 

has no readings after 9/19/2008. In reviewing the data from the other monitors in the NAA area 

for the time period in 2008 that Camden had no readings, there is only one reading (24.4 μg/m3

at Bristol, PA) that makes the top 10. Based on data from the other monitors, we did not see a 

loss of data that would affect the seasonality analysis, so we included Camden’s 2008 data. The 

Camden monitor did not operate in 2009 or 2010, so data from Camden biases the earlier 

evaluation years. 

The City of Philadelphia has several monitors that did not operate throughout the 2006-

2010 timeframe. Elmwood Avenue (ELM-FD) did not operate in 2008, 2009 and 2010. FAB-F 

did not operate during 2006 and 2007. Normalizing the dataset due to lack of data for those 

years was not taken into account for this analysis due to time constraints. Furthermore, for 

purposes of this assessment on whether to use summer or winter, or neither; it was decided that 

because fourteen of the seventeen monitors operated continuously, their large dataset provides 

enough information to make a good decision. 

Regional Consistency 
Delaware Redesignation Request and Maintenance Plan– 2006 Daily PM2.5 NAAQS

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Table 7-1 shows the total number of exceedances between 2006 and 2010, and the 

number of times four or more monitors in the Philadelphia NAA exceeded the standard on the 

same day (if we looked at two or more monitors, the percent of dates would rise to 82%). There 

is good consistency between monitors, including across states, for many of the high reading 

episodes, in the summer and the other seasons because in 73% of the exceedances, four or more 

monitors exceeded the same day. 

Table 7-1 Summer vs. Winter – Regional Consistency

Date # of Monitors Exceeding NAAQS

8/7/2007 14

7/29/2008 11

6/19/2006 10

12/30/2010 9

11/28/2006 8

8/3/2006 8

1/19/2009 8

6/7/2008 7

1/29/2008 6

3/15/2009 6

7/12/2006 5

6/26/2007 5

8/8/2007 5

7/18/2008 5

7/11/2006 4

8/6/2007 4

11/9/2009 4

7/10/2007 4

7/9/2007 4

Sum 127

Total Exceed 173

% of dates more than 4 monitors 

exceeded NAAQS 73%

The next step was to tabulate a summary table of all monitors in the NAA for a given 

time period (ex. 2006-2010), and average the percentage per season of the top 10 values. Table 
Delaware Redesignation Request and Maintenance Plan– 2006 Daily PM2.5 NAAQS

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7-2 provides percentages by season. It is evident from looking at Table 7-2 both summer and 

winter are dominant seasons for PM2.5. 

Table 7-2 2006-2010 Seasonal PM2.5 Average Percentages

Season Philadelphia NAA Average

2006-2010

Summer 43%

Fall 9%

Winter 38%

Spring 10%

Analysis of Top 10 Days per Year – Number of Exceedances

As the previous section showed, the top 10 monitored values were dominant during 

summer and winter, based on percentages. However, the percentages included many values 

below the standard. With this in mind, AQM analyzed the data based on the number of 

exceedance readings to see if the summer vs. winter relationships would change. DAQ assessed

rolling three-year exceedances for 2006-2008, 2007-2009, 2008-2010 and finally all years (2006-

2010). 

When looking at the winter to summer relationships over the course of the years 2006 to 

2008, summer exceedances dominate (79% summer: 11% winter), but becomes more in line with 

winter when looking at 2008-2010 data (42% summer: 41% winter). Figure 7-1 illustrates the 

winter vs. summer relationship over time (fall and spring are relatively insignificant and removed 

for contrast purposes). 

Figure 7-1 Number of Winter vs. Summer Exceedances
Delaware Redesignation Request and Maintenance Plan– 2006 Daily PM2.5 NAAQS

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In summary, exceedances of the daily PM2.5 standard can and do occur in all four seasons 

of the year, with the summer and winter seasons dominating. Therefore, Delaware believes an 

annual inventory of emissions for the 2008 attainment year and future years adequately addresses

emissions of PM2.5 and its precursors for purposes of maintaining the daily PM2.5 NAAQS. In 

support of this determination, PM control measures implemented by Delaware are effective 

throughout the calendar year. 

7.3 2008 Attainment Year Inventory

The Delaware DAQ prepared a comprehensive emissions inventory for New Castle 

County (which represents Delaware’s portion of the Philadelphia NAA), including point, area, 

and on-road and off-road mobile sources for primary PM2.5 as well as precursors of PM2.5 (NOx

and SO2) for the year 2008. EPA guidance requires the “attainment year” fall within the 3-year

period (2008-2010) which demonstrates monitored attainment. 

This inventory is based on actual activity levels and was developed in-house by the 

Delaware DAQ Inventory Group. Point source information was collected from Delaware 

industrial, commercial and institutional sources. Non-point (area) source emissions were

calculated using the most recently available methodologies and emissions factors from EPA

along with activity data (typically population, employment, fuel use, etc.) specific to 2008. Onroad mobile source emissions were calculated using EPA’s Motor Vehicle Emission Simulator

(MOVES) model with 2008 vehicle miles traveled (VMT) data provided by the Delaware 

Department of Transportation (DelDOT). Off-road mobile source exhaust emissions, such as

those from lawn and garden equipment, agricultural equipment, and construction equipment were 

calculated for 2008 using the EPA’s NONROAD emissions model. Emissions sources such as 

commercial marine vessels, aircraft and locomotives (MAR) are not modeled by NONROAD

and thus were calculated separately. 

2006-2008 2007-2009 2008-2010 2006-2010

Summer 106 67 33 110

Winter 15 22 32 36

0

20

40

60

80

100

120

Exceedances

Summer vs. Winter
Delaware Redesignation Request and Maintenance Plan– 2006 Daily PM2.5 NAAQS

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The details of the 2008 emissions inventory are presented in “2008 Attainment Year State 

Implementation Plan Emissions Inventory for PM2.5, SO2, and NOx” provided in the supporting 

documentation. Table 7-3 summarizes the 2008 emissions estimates for New Castle County.

Table 7-3 2008 New Castle County Emissions (tpy)

2008

Sector NOx PM2.5 SO2

Point 5,589 1,109 10,576

Non-point 1,287 1,191 402

On-road 9,311 282 94

Non-road 4,317 312 1,067

All Sectors 20,504 2,894 12,139

Note: sum of emissions may not match the total due to independent rounding.

8 Maintenance Demonstration

8.1 EPA Requirements 

The 1992 EPA Calcagni Memo15, entitled Procedures for Processing Requests to 

Redesignate Areas to Attainment, discusses how states may demonstrate maintenance of the 

NAAQS by showing that future emissions of a pollutant or its precursors will not exceed the 

level of the attainment inventory. The demonstration should be for a period of 10 years 

following the redesignation. The projected inventory should consider future growth, including 

population and industry. It should also be consistent with the attainment inventory, and it should 

document data inputs and assumptions. All elements of the demonstration should be consistent 

with current EPA guidance. Enforceability through regulations must also be demonstrated.

The Calcagni Memo goes on to say that any assumptions concerning emission rates must 

reflect permanent, enforceable measures. States generally cannot take credit for reductions 

unless there are regulations in place requiring those reductions or the reductions are otherwise 

shown to be permanent. Therefore, states are expected to maintain the implemented control 

strategy despite redesignation to attainment, unless such measures are shown to be unnecessary 

for maintenance or are replaced with measures that achieve equivalent reductions. Emission 

reductions from source shutdowns can be considered permanent and enforceable to the extent 

that those shutdowns have been reflected in the SIP and all applicable permits have been 

modified accordingly.

8.2 Delaware Approach

 

15 http://www.epa.gov/ttn/oarpg/t5/memoranda/redesignmem090492.pdf
Delaware Redesignation Request and Maintenance Plan– 2006 Daily PM2.5 NAAQS

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A Maintenance Plan must contain a demonstration that the level of emissions projected 

for the ten-year period following redesignation is sufficient to maintain the NAAQS. Because 

Delaware is submitting this Plan in 2012, and EPA has a maximum of 18 months to approve it, 

the EPA approval date for redesignation is expected to be before 2015, and ten (10) years after 

that is 2025. Accordingly, the State of Delaware projected 2008 PM2.5, NOx, and SO2

emissions for the Delaware portion of the Philadelphia NAA for 2025 to represent the end year 

of the maintenance plan. Delaware also projected emissions to 2017 to represent an interim 

year during the maintenance period. Emissions for the 2017 and 2025 projection years are 

compared to emissions levels in 2008 to determine if emissions are sufficient to maintain the

NAAQS during this period (i.e. they must be lower than 2008).

8.2.1 2017 and 2025 Projection Inventories

New Castle County point and area source emissions for 2017 and 2025 were estimated 

using the 2008 attainment inventory and growth/control factors appropriate for each source 

category. DAQ adjusted the 2007 future year growth factors to a 2008 base year by using the 

same methodologies as those found in the Technical Support Document for the Development of 

the 2025 Emission Inventory for PM2.5 Nonattainment Counties in the MANE-VU Region, 

January 2012 (MARAMA 2025 TSD). For 2017 emission projections, the emission 

methodologies and growth factors can be found in the Technical Support Document for the 

Development of the 2013/2017/2020 Emission Inventories for Regional Air Quality Modeling 

in the Northeast/Mid-Atlantic Region (MARAMA 2017 TSD). The following Delawareadjusted growth factor methods were applied per sector.

Commercial Marine, Aircraft and Railroad Projections

 Aircraft

o Per MARAMA 2025 TSD, airport/airplane growth factors are based upon 

2009 FAA Terminal Area Forecast (TAF) data. 

o The 2009 FAA TAF data is sorted for New Castle County data, using the 

same criteria as used by MARAMA.

o Growth factors for 2017 and 2025 were calculated by dividing the projection 

year flight data by 2008 base year data.

 Rail & Commercial Marine

o Per MARAMA TSD, rail and marine growth factors are based upon Table 7 

“Transportation Sector Key Indicators and Delivered Energy Consumption” of 

the AEO 2010 data for energy consumption.

o Growth factors for 2017 and 2025 were calculated by dividing the projection 

year energy use data by 2008 base year data.

 EGU Projections
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o Per MARAMA TSD, EGU growth factors are based upon 2011 AEO 

electricity generation data, by various regions.

o For Delaware, it was determined that the best data to use was from the 

Reliability First Corporation / East (RFCE) region.

o Growth factors for 2017 and 2025 were calculated by dividing the amount of 

electricity generated in the projection years by 2008 base year data.

Non-EGU Projections

o Non-EGU growth factors are based solely on Delaware employment data.

o The Delaware Department of Labor provided employment data, by NAICS 

from 2007 through 2018.

o Following guidance by the MARAMA TSD, Delaware employment data was 

calculated for 2019 through 2025.

o Growth factors for 2017 and 2025 were calculated by dividing the number of 

employees, by NAICS, in the projection years by 2008 base year data.

Area Projections

 If original growth factors for projecting 2007 emissions to 2017 and 2025 are 1.0, the 

growth factors for projecting 2008 emissions are kept as 1.0.

o Fuel Combustion

 Per MARAMA TSD, growth factors for area source fuel combustion 

categories are based upon 2010 AEO energy consumption data, by 

various regions.

 For Delaware it was determined that the best data to use was for the 

South Atlantic Region.

 Growth factors for 2017 and 2025 were calculated by dividing the 

energy consumption in the projection years by the 2008 base year data.

 Industrial Fuel Combustion – Natural Gas

 Per MARAMA TSD, one exemption to using 2010 AEO 

energy consumption data was when there was a difference of 

greater than 1% between the energy consumption data of 2010 

and 2011.

 Since there was such a difference in the natural gas 

consumption data for natural gas in 2011, the 2011 AEO data 

was determined to be the best data for Delaware for Industrial 

Fuel Combustion of natural gas.

 Growth factors for 2017 and 2025 were calculated by dividing 

the energy consumption in the projection years by the 2008 

base year data.

 Residential Wood Combustion
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o Per MARAMA TSD, residential wood combustion growth factors are based 

upon EPA emission projection parameters.

o Growth factors for 2017 and 2025 were calculated by inserting the appropriate 

base year (BYR) and future (i.e., projection) year (FYR) into the EPA

developed equations of (Formula=1 + 0.01*( FYR - BYR )), (Formula=1 -

0.02*( FYR - BYR )), or (Formula=1 + 0.02*( FYR - BYR )), depending on 

the equipment type.

 Residential Fuel Combustion – Kerosene

o Per MARAMA TSD, growth factors for residential fuel combustion 

equipment using kerosene are based upon 2010 AEO energy consumption 

data, by various regions.

o For Delaware it was determined that the best data to use was for the South 

Atlantic Region.

o Growth factors for 2017 and 2025 were calculated by dividing the energy 

consumption in the projection years by the 2008 base year data.

 Paved Roads

o Per MARAMA 2025 TSD, growth factors for paved roads are based upon 

county specific VMT used in MOVES.

o Growth factors for 2017 and 2025 were calculated by dividing the VMT of the 

projection years by the VMT of the 2008 base year.

 Commercial Cooking

o The Delaware Department of Labor provided employment data, by NAICS 

from 2007 through 2018.

o Following guidance by the MARAMA 2025 TSD, Delaware employment data 

was calculated for 2019 through 2025.

o Growth factors for 2017 and 2025 were calculated by dividing the number of 

employees, by NAICS, in the projection years by 2008 base year data.

 Construction

o The Delaware Department of Labor provided employment data, by NAICS 

from 2007 through 2018.

o Following guidance by the MARAMA TSD, Delaware employment data was 

calculated for 2019 through 2025.

o Growth factors for 2017 and 2025 were calculated by dividing the number of 

employees, by NAICS, in the projection years by 2008 base year data.

NMIM/NONROAD Growth and Control Information
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In estimating future year emissions, the EPA NMIM/NONROAD model includes growth 

and scrappage rates for equipment in addition to a variety of control programs. It is not possible 

to separate out the future year emissions due to “growth only” or “control only” in a single run. 

That is, the model run provides a single future year estimate that is a “growth and control” 

scenario.

The growth data used in the NMIM/NONROAD model is documented in an EPA

report.

16 The GROWTH packet of the NONROAD model cross-references each SCC to a 

growth indicator code. The indicator is an arbitrary code that identifies an actual predicted value 

such as human population or employment that is used to estimate the future year equipment 

population. The GROWTH packet also defines the scrappage curves used to estimate the future 

year model year distribution.

The NMIM/NONROAD model also accounts for all EPA emission standards for nonroad 

equipment. There are multiple standards that vary by equipment type, rated power, model year, 

and pollutant. A summary of the nonroad equipment emission standards can be found in Section 

4.3.2, Control Programs Included in the NMIM/NONROAD Model.

ONROAD 

For mobile projections and mobile budget purposes, Delaware is using the 2012 mobile 

emissions from its PM2.5 Attainment Demonstration Revision, submitted to EPA on May 3, 

2012. Delaware used 2012 mobile emissions in lieu of projected mobile emissions because:

1) They are based on the most up-to-date mobile source assumptions available. 

2) 2012 emission budgets are 33% and 35% less than the onroad NOx and PM2.5, 

respectively, found in the 2008 attainment year. (see table 8-2 and 8-3)

3) Additional reductions are not necessary in the context of this maintenance plan.

The 2012 emission inventory modeling of the on-road mobile source sector was 

performed by WRA Associates LLP, Wilmington, Delaware, under contract to DelDOT with 

technical support from the Division of Air Quality (DAQ) staff. The on-road mobile sources 

cover all highway vehicles including passenger cars, light-duty trucks, sport utility vehicles, 

heavy-duty trucks, buses, and motorcycles, which travel on Delaware’s roadways in 2012. 

Delaware Department of Transportation (DelDOT) staff provided the vehicle miles traveled 

(VMT) on Delaware’s roadways. DAQ staff also evaluated all information concerning control 

measures that would be effective in 2012. With the vehicle mix data and control information, 

the EPA’s MOVES model was used to generate monthly emissions for PM2.5, NOx and SO2. 

After QC/QA reviews and revision by DAQ staff the emission data were finalized, and 

included in the final inventory. The on-road mobile source controls for New Castle County in 

the input files for the 2012 MOVES model runs include the following: 

 

16 U.S. Environmental Protection Agency. Nonroad Engine Growth Estimates, EPA-420/P-04-08, April 2004. 

Also available at: http://www.epa.gov/otaq/models/nonrdmdl/nonrdmdl2004/420p04008.pdf
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1) Low enhanced I/M program of model years 1968 through 1995,

2) On-Board Diagnostic checks of model years 1996 and newer,

3) National Low Emission Vehicle program,

4) Tier 2 emission standards/low sulfur rule, and

5) Heavy Duty Diesel Rule/low sulfur rule.

Table 8-1 provides a comparison of emissions for the years 2008, 2017 and 2025. The

table demonstrates that the level of emissions projected through the maintenance period are

less than emissions estimated for the attainment year and are, therefore, sufficient to maintain 

the PM2.5 NAAQS. Tables 8-2 through 8-4 show NOx, PM2.5 and SO2 reductions (tpy) 

between 2008 and 2017 and 2025. The tables also provide the percent reduction of NOx, 

PM2.5 and SO2 by sector for those same years. It is readily apparent from these tables that SO2

and NOx emissions are expected to decrease significantly between 2008 and 2025 (i.e., 38% 

and 61% for NOx and SO2, respectively). PM2.5 decreases less significantly (14%), primarily 

due to increased road dust from increased VMT. Projected emissions of those pollutants for the

mid-point year of 2017 are also significantly less than their respective emissions levels in 

2008. Based on these emissions trends it is expected that air quality will continue to meet the

PM2.5 NAAQS throughout the maintenance period.

Table 8-1 Comparison of emissions for the years 2008, 2017 and 2025

Sector

NOx PM25 SO2

2008 2017 2025 2008 2017 2025 2008 2017 2025

Area 1,287 1,299 1,297 1,191 1,247 1,327 402 336 286

Nonroad MAR 2,641 1,760 1,247 164 59 42 1,039 120 39

Nonroad-NMIM 1,676 997 837 148 106 103 28 2 3

Onroad MOVES 9,311 6,273 6,273 282 199 199 94 98 98

Point – EGU 2,185 1,629 1,707 396 410 427 7,122 2,017 2,161

Point - nonEGU 3,404 1,724 1,421 713 504 398 3,454 2,559 2,096

All Sectors 20,504 13,682 12,782 2,894 2,524 2,497 12,139 5,132 4,683
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Table 8-2 Reductions and % Change of NOx emissions for the years 2008, 2017 and 2025

NOx Reduction 

(tpy)

Change 

(%)

Reduction 

(tpy)

Change 

(%)

Sector 2008 2017 2025 2008-2017 2008 to 

2017 2008 to 2025 2008 to 2025

Area 1,287 1,299 1,297 -12 0.9% -10 0.8%

Nonroad MAR 2,641 1,760 1,247 881 -33.3% 1,394 -52.8%

Nonroad-NMIM 1,676 997 837 679 -40.5% 840 -50.1%

Onroad MOVES 9,311 6,273 6,273 3,038 -32.6% 3,038 -32.6%

Point - EGU 2,185 1,629 1,707 556 -25.4% 478 -21.9%

Point - nonEGU 3,404 1,724 1,421 1,680 -49.4% 1,983 -58.3%

Total tpy 20,504 13,682 12,782 6,822 -33% 7,722 -38%

Table 8-3 Reductions and % Change of PM2.5 emissions for the years 2008, 2017 and 2025

PM25 Reduction 

(tpy)

Change 

(%)

Reduction 

(tpy)

Change 

(%)

Sector 2008 2017 2025 2008-2017 2008 to 

2017 2008 to 2025 2008 to 2025

Area 1,191 1,247 1,327 -56 4.7% -136 11.4%

Nonroad MAR 164 59 42 106 -64.3% 122 -74.3%

Nonroad-NMIM 148 106 103 42 -28.6% 45 -30.2%

Onroad MOVES 282 199 199 83 -29.4% 83 -29.4%

Point - EGU 396 410 427 -14 3.5% -32 8.0%

Point - nonEGU 713 504 398 209 -29.3% 315 -44.1%

Total tpy 2,894 2,524 2,497 370 -13% 396 -14%
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Table 8-4 Reductions and % Change of SO2 emissions for the years 2008, 2017 and 2025

SO2 Reduction 

(tpy)

Change 

(%)

Reduction 

(tpy)

Change 

(%)

Sector 2008 2017 2025 2008-2017 2008 to 

2017 2008 to 2025 2008 to 2025

Area 402 336 286 66 -16.5% 116 -28.8%

Nonroad MAR 1,039 120 39 919 -88.4% 1,000 -96.2%

Nonroad-NMIM 28 2 3 25 -91.0% 25 -88.4%

Onroad MOVES 94 98 98 -3 3.4% -3 3.4%

Point - EGU 7,122 2,017 2,161 5,104 -71.7% 4,960 -69.7%

Point - nonEGU 3,454 2,559 2,096 895 -25.9% 1,358 -39.3%

Total tpy 12,139 5,132 4,683 7,007 -58% 7,456 -61%

8.2.2 2017 and 2025 Mobile Source Emissions Budgets

Transportation conformity is a way to ensure that federal funding and approval are given 

to those transportation activities that are consistent with air quality goals. Transportation 

activities should not worsen air quality or interfere with an area’s continued compliance in 

regards to the 2006 PM2.5 NAAQS. The federal transportation conformity rule is codified in 40 

CFR Part 93, Subpart A, titled Determining Conformity of Federal Actions to State or Federal 

Implementation Plans (transportation conformity rule). This rule applies to areas designated as 

nonattainment for one or more NAAQS or that have been redesignated to attainment with 

federally approved air quality maintenance plans. The responsible transportation planning 

entities for the New Castle County, Delaware portion of the Philadelphia 2006 PM2.5 NAA is the 

Delaware Department of Transportation (DelDOT) and the Wilmington Area Planning Council 

(WILMAPCO). In the transportation conformity process, overall emissions estimates by 

analysis year that take into account future traffic activity and projects expected to be completed 

are compared to a base year, a no build scenario, or emission budgets. Emission budgets are 

used in this maintenance plan only if EPA has approved or found adequate emissions budgets 

that have been submitted as a SIP revision. 

The purpose of this section is to describe and establish the New Castle County motor

vehicle emissions budgets associated with the PM2.5 Maintenance Plan SIP. Annual motor

vehicle emissions budgets are being proposed for the final year of the Maintenance Plan, which 

is 2025. The Maintenance Plan also includes motor vehicle emissions budgets for the interim

year 2017.
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Delaware is proposing to establish mobile budgets for PM2.5 and NOx.17 Ammonia and 

volatile organic compounds (VOC) are precursors; however, they are not considered significant 

overall contributors to PM2.5 air quality issues, as noted in the PM2.5 implementation rule at 40 

CFR 51.1002(c)(3). For other pollutants such as SO2, the highway contribution to those 

emissions may be insignificant. In that case, the transportation conformity rule allows such 

pollutants and precursors to be exempt from conformity analysis under certain circumstances:

40 CFR 93.109 (k), Areas with insignificant motor vehicle emissions

Notwithstanding the other paragraphs in this section, an area is not required to satisfy 

regional emissions analysis for §93.118 and/or §93.119 for a given pollutant/precursor 

and NAAQS, if EPA finds through the adequacy or approval process that a SIP 

demonstrates that regional motor vehicle emissions are an insignificant contributor to 

the air quality problem for that pollutant/precursor and NAAQS. The SIP would have to 

demonstrate that it would be unreasonable to expect that such an area would experience 

enough motor vehicle emissions growth in that pollutant/precursor for a NAAQS 

violation to occur. Such 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. 

Delaware is herein making a finding that highway emissions of SO2 are insignificant 

contributors to the PM2.5 air quality of the New Castle County portion of the Philadelphia NAA. 

This finding is due to the fact that the SO2 emissions inventory constitutes a very small fraction 

(less than 1.5 percent) of the overall SO2 in the 2008, 2017 and 2025 emissions inventories. The 

finding will become final if EPA concurs and approves this maintenance plan. 

A motor vehicle emissions budget is that portion of the total allowable emissions 

allocated to highway and transit vehicle use that are defined in the SIP for a certain year. The

rules governing transportation conformity require certain transportation activities to be consistent 

with motor vehicle emissions budgets contained in control strategy implementation plans (40 

CFR § 93.118). Section 93.101 of the rule defines a “control strategy [State] implementation 

plan revision” as a “plan which contains specific strategies for controlling the emissions and 

reducing ambient levels of pollutants in order to satisfy CAA requirements of reasonable further

progress and attainment.” In order to demonstrate conformity to the motor vehicle emissions 

budget, emissions from the implementation of a transportation plan or a transportation 

improvement program (TIP) must be less than or equal to the budget level (40 CFR § 93.118(a)).

Delaware’s proposed 2012 NOx and PM2.5 budgets in its Proposed Revision to 

Delaware’s 2008 State Implementation Plan for Attainment of the PM2.5 Annual National 

 

17 As discussed in Delaware’s 2008 Annual PM2.5 Attainment Demonstration, and revised in Delaware’s Proposed 

Revision to Delaware’s 2008 State Implementation Plan For Attainment of the PM2.5 Annual National Ambient Air 

Quality Standard - Attainment Demonstration, submitted to EPA May 3, 2012.
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Ambient Air Quality Standard - Attainment Demonstration (submitted to EPA on May 3, 2012).

These budgets represent a level of mobile emissions lower than what existed during the years 

attainment was reached (i.e., 2008-2010 and 2009-2011). Furthermore, because of significant 

reductions in other source categories, mobile reductions are not necessary to demonstrate 

maintenance (i.e., the 2025 NOx PM2.5 and SO2 emissions are well below 2008 levels), there is 

no need to develop new mobile budgets as this time.18 Therefore, Delaware proposes to use 

existing 2012 budgets for the 2017 interim year, as well as the end year, 2025.

19

Table 8-6 summarizes the budgets for each relevant year.

Table 8-5 New Castle County Mobile Source Emissions Budgets

Year NOX On-Road

Emissions (tpy)

PM2.5 On-Road 

Emissions (tpy)

2012 Attainment SIP 

Revision – Mobile Budgets 6,273 199

2017 Interim Budget 6,273 199

2025 Final Budget 6,273 199

8.2.3 Control Measures for Maintenance of Good Air Quality

Point, area, non-road and on-road emission projections for 2017 and 2025 include a 

variety of control strategies that will reduce emissions of PM2.5, NOX, and SO2 in the future 

years. The sections below describe the major control programs in each category. Many of these 

programs are federal programs that are enforced on a regional or national level. In cases where 

the programs are delegated programs or state programs, EPA has approved these programs into 

the Delaware SIP. The State of Delaware commits to the continuation of these programs, to 

include compliance and enforcement mechanisms as appropriate to ensure that reductions 

assumed in 2017 and 2025 will be achieved. 

Tables 8-2 through 8-4 show that that projected 2008 to 2025 reductions are 7,722 tpy for 

NOx, 396 tpy for PM2.5 and 7,456 tpy for SO2. In terms of percent reductions, this equates to 

38%, 14% and 61% reductions of NOx, PM2.5 and SO2, respectively. The same tables show 

projections from 2008 to the 2017 interim year. 2008-2017 reductions are 6,822 tpy for NOx, 

370 tpy for PM2.5 and 7,007 tpy for SO2. In terms of percent reductions, this equates to 33%, 

13% and 58% reductions of NOx, PM2.5 and SO2, respectively. 

However, not all of these reductions are due to control measures. Projected emissions 

can be higher or lower due to growth factors alone, or in combination with controls (assuming 

 

18 DAQ may require new budgets should the Philadelphia maintenance area lapse into nonattainment, 

(see Section 10).

19 New Castle County has been designated as nonattainment under the new ozone NAAQS. Therefore, new and 

stricter budgets for NOx will be included in the ozone attainment demonstration and/or reasonable progress SIP(s).

The stricter budgets will require mobile control measures and reduced VMT. Consequently, there will be a 

collateral benefit in the form of PM2.5 reductions. 
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controls exist for a certain source category). DAQ calculated reductions that will occur after 

2008 due only to control measures, (no growth), for EGUs, non-EGU point sources, area and 

“marine, aircraft and locomotive” (MAR) sources. Because onroad and non-MAR off-road 

sources are estimated using EPA models (MOVES and NMIM), and inherently include growth in 

the form of fleet turnover, equipment turnover, ex. lawnmowers, etc., it is not feasible to break 

out onroad and non-MAR off-road reductions due exclusively to controls. 

Looking at Table 8-6, it is evident that all but the area source sectors had significant 

decreases for NOx (particularly onroad), SO2 and/or PM2.5 due to control measures. 
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Table 8-6 [Post-]2008 [to 2025] Emission Reductions due to Control Measures

2008-2025 Reductions due to controls only (no growth)

NOx PM2.5 SO2

EGUs

DE Admin Code 1146 (Multi-Pollutant 

Regulation) 953.4 3.5 5,171.1

nonEGU

Delaware City Refinery NOx CAP 

(1650 tpy) post-2015 874.7 0.0 0.0

Reciprocating Internal Combustion 

Engines -

0.0 0.1 0.0

Maximum Achievable Control 

Technology

(RICE MACT) (76 FR 12863)

Chrysler Plant Shutdown 8.4 0.7 6.0

AREA

2010 RICE MACT 42.5 0.3 0.3

EPA New Source Performance 

Standards for Woodstoves (NSPS).

These standards are codified at 40 CFR 

part 60, subpart AAA. The final 

standards were promulgated in 1988 

(53 FR 5860).

4.9 74.1 0.8

NMIN 840 45 25

ONROAD 3,038 83 -3

Marine Vessels, Aircraft and 

Locomotives (MAR)

Control of Emissions of Air Pollution 

From Locomotive Engines and Marine 

Compression-Ignition Engines Less 

Than 30 Liters per Cylinder; 

Republication; Final Rule. (73 FR 

37096)

862.3 32.9 150.1

Control of Emissions From New 

Marine Compression-Ignition Engines 

at or Above 30 Liters per Cylinder(75 

FR 22895)

597.3 90.7 850.7

TOTALS 7,221 330 6,200
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8.2.4 Delaware-specific NOx, PM2.5 or SO2 Control Measures (Effective Post 2008)

 7 DE Admin. Code 1146, EGUs, Electric Generating Unit (EGU) Multi-Pollutant 

Regulation, SO2 and NOX emission control, State-wide, Effective December 200620, 

approved into Delaware’s SIP August 28, 2008 (73 FR 50723), March 16, 2010 (75 FR 

12449), and August 11, 2010 (75 FR 48566).

 7 DE Admin. Code 1142, Section 2, Control of NOX Emissions from Industrial Boilers 

and Process Heaters at Petroleum Refineries, NOX emission control, New Castle County, 

Effective July 2007; approved into Delaware’s SIP June 4, 2010 (75 FR 31711) and 

August 11, 2010 (75 FR 48566); revisions approved May 15, 2012 (77 FR 28489).

 7 DE Admin. Code 1148, Control of Stationary Combustion Turbine Electric Generating 

Unit Emissions, approved into Delaware’s SIP on November 10, 2008 (73 FR 66554) and 

August 11, 2010 (75 FR 48566).

EGU reductions

EGUs are a subset of point source emissions and include the following New Castle 

County facilities: 

 Conectiv Delmarva Generation-Del City

 Conectiv Delmarva Generation-West Substation

 Conectiv Delmarva Generation-Edge Moor

 Conectiv Delmarva Generation-Christiana

 Conectiv Delmarva Generation-Hay Road

Edge Moor is the only New Castle EGU which burned coal and residual oil in 2008. The 

rest fired natural gas or distillate oil, and thus had insignificant PM2.5 and SO2 emissions in 2008

and are projected to have insignificant emissions in PM2.5 and SO2 emissions in 2025. In 2008, 

total EGU emissions of NOx, PM2.5 and SO2 were 2,185 tpy, 396 tpy and 7122 tpy, respectively. 

Of this amount, Edge Moor’s NOx, PM2.5 and SO2 emissions were 1,980 tpy, 360 tpy and 7,110

tpy, respectively. Consequently, Edge Moor was the largest EGU emitter, e.g. its 2008

emissions represented 99% of NOx, PM2.5 and SO2, respectively for all New Castle County 

EGUs. Because Units 3 and 4 were coal-fired in 2008, and Unit 5 operates primarily on residual 

oil, it is subject to 7 DE Admin Code 1146, which is Delaware’s EGU Multi-pollutant 

Regulation. 7 DE Admin Code 1146 is a non-trading program/regulation that was established 

primarily as a measure to aid in the attainment of the ozone and fine particulate matter ambient 

air quality standards. As Tables 8-2 through 8-4 show, 7 DE Admin Code 1146 will reduce 

EGU emissions in 2025 by 22% for NOx, and 70% for SO2. PM2.5 emission controls are not part 

 

20 Although effective in 2006, NOx controls were not required until January 1, 2009 and SO2 controls were not 

required until January 1, 2012. 
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of Regulation 1146, but there were some co-benefits by requiring 0.5% by weight low-sulfur 

residual oil on Unit 5, which will yield 8% reductions. 

Non-EGU reductions

Delaware Source Shutdowns (post-2008)

The Chrysler automotive plant ceased commercial operation in January, 2009. However, 

only a 25% reduction was applied, since Chrysler maintains 50% of the emission credits and 

Delaware Economic Development Office retains the remaining 25%. Reductions are shown in 

Table 8-[6][7].

Delaware On-road 

In additional to the federal Tier 1 and 2 program, NLEV, and the federal 2007 heavy duty 

highway rule, Delaware has instituted Enhanced Vehicle Emissions Inspection And Maintenance

(enhanced I/M) requirements in New Castle County. The requirements involve mandating

regional vehicle emission I/M programs that are stricter than basic programs, as required under 

§§182 and 202 of the CAA. Before 1994, basic automobile emissions testing checked only 

tailpipe emissions while idling and sometimes at 2,500 rpm. Enhanced I/M procedures include 

the use of On Board Diagnostic (OBD) system evaluations, a wider range of vehicles tested, and 

may include a dynamometer (treadmill) test that checks the car’s emissions under driving 

conditions. The OBD evaluations provide a more complete inspection, checking for excess 

evaporative emissions and other issues that might affect emissions from the vehicle. Delaware’s 

enhanced I/M program was approved into the Delaware SIP by EPA on September 30, 1999 (64 

FR 52657). Revisions to the enhanced I/M program were approved by EPA on 11/26/2003 (68 

FR 228). 

8.2.5 Federal Control Measures (Effective or Phased-in Post 2008)

Because federal control measures that are either effective or phased in after 2008 are the 

same as those discussed in Section 4.3.2, please refer to that Section. Note that the Woodstove 

NSPS and many of the non-road and on-road federal control measures have effective dates prior 

to, during, or after 2008. However, other than fuel standards; all of the measures are phased in 

over many years through fleet or equipment “turnover.” For example, in the case of non-road 

sources, fleet turnover includes sales of new engines replacing older ones over the years. 

Therefore, it is expected that reductions will continue well past the 2008 attainment year.

8.2.6 Future Point Source Emissions Reductions Programs 

Delaware 

New Delaware regulations and federally enforceable permit changes will reduce 

emissions of NOx, PM2.5 and SO2 even further, although these rules are not yet finalized and 

therefore were not considered in the 2017 and 2025 estimates included in this document. Under 

development are:
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 Low-sulfur distillate and residual fuel regulation

 Calpine - Edge Moor Power Plant (fuel switch from coal to natural gas)

Federal

Three new federal regulations will reduce emissions of SO2 even further, although these 

rules are not yet finalized and therefore were not considered in the 2017 and 2025 estimates 

included in this document. If these regulations are finalized, each should instigate significant 

further reductions, both within and outside the Philadelphia NAA.

 Mercury and Air Toxics Rule: On March 16, 2011, EPA proposed the Mercury and Air 

Toxics Rule to reduce emissions of toxic air pollutants from new and existing coal and 

oil-fired EGUs. The proposed rule would establish numerical emission limits for 

hydrogen chloride (HCl) as a surrogate for toxic acid gases, or alternative standards for 

SO2. EPA estimates that this rule would affect approximately 1,200 coal-fired units 

nationwide and would reduce SO2 emissions from power plants by 55%. The final rule is 

expected to be published in 2012 so that existing sources may be required to demonstrate 

compliance with applicable standards by 2015. National Emission Standards for 

Hazardous Air Pollutants From Coal and Oil-Fired Electric Utility Steam Generating 

Units and Standards of Performance for Fossil-Fuel-Fired Electric Utility, IndustrialCommercial-Institutional, and Small Industrial-Commercial-Institutional Steam 

Generating Units, Final Rule published February 16, 2012 (77 FR 9304); Correction 

published April 19, 2012 (77 FR 23399).

21

 2010 SO2 NAAQS: On June 2, 2010, EPA strengthened the primary NAAQS for SO2 by 

revising the primary SO2 standard to 75 ppb averaged over one hour. This short term 

standard is significantly more stringent than the revoked standards of 140 ppb averaged 

over 24 hours and 30 ppb averaged over a year. Under the new standard’s proposed 

guidance, facilities emitting more than 100 tpy of SO2, many of which are EGUs, will be 

required to demonstrate compliance with the standard no later than 2017. 

 Industrial/Commercial/Institutional (ICI) Boiler Maximum Achievable Control 

Technology (MACT) Standard: EPA finalized the revised ICI Boiler MACT on February 

21, 2011, although portions of the rule are under reconsideration. EPA estimates that 

implementation of the revised rulemaking will reduce emissions nationwide from major 

source boilers and process heaters by 47,000 tpy of PM, 440,000 tpy of SO2, and 7,000 

tpy of VOCs. 

 Tier 4 Standards: On May 11, 2004, the EPA signed the final rule introducing Tier 4 

emission standards, which are to be phased-in over the period of 2008-2015 [69 FR 

38957-39273, 29 Jun 2004]. The Tier 4 standards require that emissions of PM and NOx 

be further reduced by about 90%. Such emission reductions will be achieved through the 

 

21 This rule is under reconsideration. EPA expects to complete ruling-making in March, 2013 (July 20, 2012 letter

from Gina Mcarthy, EPA Administrator, to Patricia T. Barmeyer).
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use of control technologies—including advanced exhaust gas after-treatment. 

8.2.7 Controls to Remain in Effect

Delaware will maintain all of the control measures listed in this Section to ensure 

maintenance of the daily PM2.5 NAAQS. Any revisions to the control measures included as part 

of the Maintenance Plan will be submitted as a SIP revision to EPA for approval, and will be

accompanied by a showing that such changes will not interfere with maintenance of the NAAQS. 

The Delaware DAQ has the necessary resources to enforce any violations of its rules or permit 

provisions. After redesignation, it intends to continue enforcing all rules that relate to the

emissions of primary PM2.5 and precursors to secondary PM2.5 which may impact New Castle 

County ambient PM2.5 concentrations.

Although Delaware believes that control of organic compounds and ammonia may help 

improve PM air quality, we have not relied on the control of organics or ammonia, consistent 

with the PM2.5 Implementation Rule.

9 Verify Continued Attainment

9.1 EPA Requirements

States must ensure that they have the legal authority to implement and enforce all 

measures necessary to attain and maintain the NAAQS. Sections 110(a)(2)(B) and (F) of the 

CAA suggest that one such measure is the acquisition of air quality and source emission data to 

demonstrate attainment and maintenance. 

9.2 Delaware Approach

The State of Delaware has the legal authority to implement and enforce specified 

measures necessary to attain and maintain the 2006 daily PM2.5 NAAQS. Delaware concludes 

that, as EPA has stated in previous rulemaking,22 only the Section 110 and Part D requirements 

that are linked with a particular area’s designation are the relevant measures which Delaware 

must consider in evaluating a redesignation request. Further, DAQ believes that the other 

Section 110 elements that are not connected with nonattainment plan submissions and not linked 

with an area’s attainment status are also not applicable requirements for purposes of 

redesignation. A state remains subject to these requirements after an area is redesignated to 

attainment.

The requirements of Section 110(a)(2) are statewide requirements that are not linked to 

the PM2.5 nonattainment status of the Philadelphia NAA. Therefore, Delaware believes that 

these SIP elements are not applicable requirements for purposes of review of the state’s PM2.5

redesignation request. 

 

22 See EPA’s proposed approval of Ohio’s redesignation request for the Ohio portion of the Huntington-Ashland 

nonattainment area for the 1997 PM2.5 NAAQS. (76 FR 79593)
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In addition to maintaining key elements of its regulatory program in place in Delaware’s 

SIP, Delaware will acquire ambient monitoring and source emission data to track attainment and 

maintenance as described in Sections 3 and 7. Delaware will also track the progress of the 

maintenance demonstration by periodically updating the emissions inventory as required by the 

Air Emissions Reporting Requirements Rule, or as required by federal regulation during the 

maintenance plan period. This includes developing annual inventories for major point sources 

and a comprehensive periodic inventory covering all source categories every three years. 

Tracking will include the evaluation of annual and periodic evaluations for any significant 

emission increases above the 2008 attainment year levels. 

10 Contingency Measures 

10.1 EPA Requirements 

Section 175(A) of the CAA specifies the requirements for Maintenance Plans, including 

provisions for contingency measures

23 that will be implemented if violations of the 2006 daily 

PM2.5 NAAQS are measured after redesignation to attainment. A list of potential contingency

measures that would be implemented in such an event should also be included in the

Maintenance Plan. Finally, the plan should provide a commitment to submit a revised 

Maintenance Plan eight years after redesignation to ensure continued maintenance for the next 

ten-year maintenance period.

Contingency measures are intended to provide further emissions reductions in the event 

that violations of the 2006 daily PM2.5 NAAQS occur after redesignation to attainment. While

these measures do not need to be fully adopted by the State of Delaware prior to the occurrence

of NAAQS violations, the contingency plan should ensure that the contingency measures are

adopted expeditiously once they are triggered. The Maintenance Plan must identify the triggers 

that determine when contingency measures will be adopted, and the measures that the state will 

consider. It should also include a schedule and procedures for adoption and implementation, and 

a specific time limit for action. Specific triggers that would put the plan into motion must be 

identified. This plan is considered to be an enforceable part of the SIP and should ensure that the 

contingency measures are adopted explicitly once they are triggered.

10.2 Delaware Approach

Consistent with this plan, Delaware agrees to adopt and implement the necessary

corrective actions in the event that violations of the 2006 daily PM2.5 NAAQS occur within the 

Philadelphia maintenance area after its redesignation to attainment.

24 As described in Section 5 

 

23 CAA Section 107(d)(3)(E)(v).

24 NJ, DE and PA are each submitting their own redesignation requests and maintenance plans. After each State’s 

Plans are approved by EPA, the Philadelphia NAA will be re-defined as the Philadelphia Maintenance Area, It is 

also possible that a portion of the area may be redesignated to attainment (i.e., a maintenance area) and a portion 

may still be nonattainment. Therefore, for the purposes of this maintenance plan, the “Philadelphia Maintenance 

Area” also includes any areas of the Philadelphia NAA that have not been redesignated to attainment. 
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of this report, EPA and Delaware have adopted and are continuing to implement a range of

control measures that will greatly reduce precursor emissions - locally, statewide and nationwide. 

Delaware commits to continue to implement the identified statewide and local control measures. 

The Delaware DAQ anticipates that post-2008 emissions reductions will be sufficient to mitigate

exceedances or violations of the daily PM2.5 NAAQS that may occur in the coming years without 

further regulatory action. However, in the event of a future violation or exceedance of the daily 

PM2.5 NAAQS, the Delaware DAQ will use the following triggers (determination of when to 

start an action) and perform the following actions in accordance with the described schedule, 

as its contingency plan:

1. Warning Level Response (one or both of the following events occur)

a. A warning level response shall be prompted whenever the 98th percentile 24-hour 

PM2.5 concentration of 35.5 μg/m3or greater occurs [at any monitoring] site in a 

single calendar year within the Philadelphia maintenance area.

b. The New Castle County, Delaware maintenance area total PM2.5, NOx and SO2

emissions increase more than 10% above the levels in the 2008 attainment year 

emissions inventory. 

2. Action Level Response

An action level response shall be prompted whenever a two-year average of the 98th 

percentile 24-hour PM2.5 concentration of 35.5 μg/m3or greater occurs [at any monitoring]

within the Philadelphia maintenance area. A violation of the standard (three-year average of 

the 98th percentile of 35.5 μg/m3 or greater), shall also prompt an action level response. 

3. Study and data analysis 

In order to select appropriate corrective measures for warning or action level triggers, the 

Delaware DAQ will work independently, or in conjunction with the States of Pennsylvania and 

New Jersey, and the City of Philadelphia to conduct a comprehensive study to determine the 

causes of the violation and the control measures necessary to mitigate the problem. This analysis 

may include all or some of the following factors as necessary, to determine the cause of the 

exceedance, emissions increase or violation:

• The location and severity of the ambient PM2.5 exceedances;

• The weather patterns contributing to the elevated PM2.5 levels;

• Potential contributing emissions sources;

• The geographic applicability of possible contingency measures;

• Emissions trends, including timeliness of implementation of scheduled control 

measures;

• Current and recently identified control technologies; 

• Air quality contributions from outside the maintenance area;
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• Activity data for relevant sources;

• Information on any unusual events (e.g. forest fires, natural disasters), transport from out 

of state sources;

• Violation of an existing rule or permit, and;

• Any other related data to try to determine the cause of the violation. 

The study will evaluate whether the trend, if any, is likely to continue and if so, the 

control measures necessary to reverse the trend taking into consideration ease and timing for 

implementation as well as economic and social considerations. In the event that the trigger is not 

found to be due to an exceptional event, malfunction, or noncompliance with a permit condition 

or rule requirement, Delaware DAQ will work with the States of Pennsylvania and New Jersey, 

and the City of Philadelphia as necessary, to determine additional control measures needed to 

assure future attainment of the 2006 daily, PM2.5 NAAQS.

Based on the results of the analysis, contingency measures will be selected from those 

listed below, or from any other measure deemed appropriate and effective at the time the 

selection is made. However, if a new measure or control is already promulgated and scheduled 

to be implemented at the federal or state level at such time after the exceedance, and that 

measure or control is determined to be sufficient to address the upward trend in air quality, 

additional local measures may be unnecessary. It is expected that implementation of only a few 

of these measures would be necessary. The selection between measures will be based upon costeffectiveness, emissions reduction potential, ease and timing of implementation, and other 

appropriate factors. [Delaware will submit to EPA an analysis to demonstrate the proposed 

measures are adequate to return the area to attainment.]

Adoption of additional control measures is subject to necessary administrative and legal 

processes. The Delaware DAQ will solicit input from all interested and affected persons in the 

area prior to selecting appropriate control measures. No contingency measure shall be 

implemented without providing the opportunity for full public participation during which the 

relative costs and benefits of individual measures, at the time they are under consideration, can 

be fully evaluated. This process will include publication of notices, an opportunity for public 

hearing, and other measures required by Delaware law. 

4. Timing of contingency measure implementation

A timeline for the development of NOX, PM2.5 and/or SO2 regulations or permit 

conditions follows. This schedule initiates with certification of ambient air quality monitoring 

data indicating a violation of the daily PM2.5 NAAQS:

a. Warning Level Response

Should a warning level response be triggered, measures that can be implemented in a 

short time will be selected in order to be in place within 18 months from the close of 

the calendar year that prompted the warning level.

b. Action Level Response 
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Should an action level response be triggered, implementation of necessary control 

measures will take place as expeditiously as possible, but in no event later than 18 

months after the Delaware DAQ makes a determination, based on quality-assured 

ambient data, that a violation of the NAAQS has occurred.

Table 10-1 Schedule for Permit Revisions or Rule Revisions for Contingency Measures25

Identify and quantify the emissions reductions expected to result in the future 

from existing and future state and federal regulatory programs. 3 months

Use the best available air quality modeling to evaluate the air quality 

improvement expected to result in the Philadelphia MA from the programs and 

emissions reductions identified in step 5 below.

6 months

Draft any needed permit conditions or SIP regulations. 3 months

Complete rulemaking or permit revision process and submit to EPA. 6 months

Completion no later than 18 months

5. List of Potential Contingency Measures

 Lower particulate limits for No. 6 fuel oil-fired boilers.

 Working with the local metropolitan planning agencies to implement transportation 

control measures such as: traffic flow improvements, transit improvements, trip 

reduction programs, arterial and signal improvement projects, bicycle projects, or other 

new transportation measures.

 Low-sulfur distillate and residual fuels.

 Additional PM2.5 controls for EGUs and large industrial boilers burning fuels other than 

distillate fuel or natural gas. 

 Calpine Edge Moor power plant – Units 3 and 4 fuel switch from coal to natural gas.

 Vehicle inspection and maintenance program enhancements (increase weight limit, 

addition of diesel vehicles, etc.).

 Alternative fuel and additional diesel retrofit programs for fleet vehicle operations.

 Require NOx or SO2 emission offsets for new and modified major sources.

 Increase the ratio of emission offsets required for new sources.

 

25 This schedule initiates with certification of ambient air quality monitoring data indicating a violation of the 2006 

24-hour PM2.5 NAAQS. [An action level response is triggered by a violation as well as when a two-year 

average of the annual PM2.5 concentration is 15.1 μg/m3or greater.] 
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 Require NOx or SO2 controls on new minor sources (less than 100 tons).

 Require increased recovery efficiency at sulfur recovery plants.

 Broader geographic applicability of existing measures.

11 Other Delaware Commitments 

11.1 Commitment to Revise Plan

Delaware DAQ commits to submit a second 10-year Maintenance Plan eight years after

redesignation, as required by Section 175(A)(b) of the CAA. The Maintenance Plan revision is 

intended to ensure continued attainment of the 2006 daily PM2.5 NAAQS for an additional tenyear period.

11.2 Public Participation

In accordance with Section 110(a)(2) of the CAA, Delaware is required to have a public 

comment period and provide the opportunity for a public hearing on the Maintenance Plan prior

to adoption. Public participation in the Delaware SIP process is required by Delaware law26 as 

follows: 

 Notice of availability of the SIP document and the time and date of the public hearing are 

published as a Legal Notice in the News Journal and Delaware State News, 30 days prior 

to the hearing, and is submitted along with this redesignation request and maintenance 

plan 

 A public hearing is required for all Delaware State Implementation Plans and Regulations, 

and was held on October 23, 2012. 

 A 30-day public comment period is open before the public hearing to receive comments 

on the Maintenance Plan. A summary of any comments received and Delaware DAQ’s 

responses is included with this SIP submittal to the EPA.

 The Legal Notices, Comments and other documentation as required by EPA and 

Delaware Law and DNREC policies will also be submitted to the EPA.

 

26 TITLE 29, General Regulations for State Agencies, Chapter 101, Administrative Procedures Subchapter II,

Agency Regulations.
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12 CONCLUSIONS

The Philadelphia nonattainment area has attained the 2006 daily PM2.5 NAAQS and has 

complied with the applicable provisions of the CAA required of the PM2.5 NAAQS. Delaware 

demonstrated that the Philadelphia NAA has attained the 2006 daily PM2.5 NAAQS and that the

air quality improvements are due to permanent and enforceable control measures. 

The Delaware DAQ has prepared a Maintenance Plan that meets the requirement of

175A of the Clean Air Act. This Maintenance Plan provides for the continued attainment of the

2006 daily PM2.5 NAAQS for a period of at least ten years after EPA has formally redesignated 

the area to attainment. This Maintenance Plan provides adequate contingency measures for

potential, additional emissions reductions in the event that future violations of the 2006 daily 

PM2.5 NAAQS are observed in the area. 

Delaware has performed an analysis that shows the air quality improvements are due to 

permanent and enforceable measures and that additional significant regional NOx and SO2

reductions following implementation of federal and state measures will ensure continued 

compliance (maintenance) with the standard. Furthermore, emission projections in the 

Maintenance Plan indicate that NOx, PM2.5 and SO2 emissions will continue to decline, ensuring 

that the area continues to maintain compliance with the standard and provide for an increased 

margin of safety.

The Delaware DAQ has prepared a comprehensive emissions inventory of PM2.5 and its 

precursors for the “attainment” year, (2008), and has prepared projections of the emissions 

inventory to 2017 and 2025. These emissions projections indicate that emissions levels in the

New Castle portion of the Philadelphia NAA will continue to remain much lower than emissions 

from the attainment year 2008 levels, thereby maintaining the PM2.5 NAAQS in future years.27 

The Delaware DAQ commits to continue to operate an appropriate air quality monitoring

network to verify the maintenance of the attainment status once the area has been redesignated. 

The Delaware DAQ has the legal authority to implement and enforce all control measures.

The Delaware DAQ has prepared a comprehensive emissions inventory of PM2.5 and its 

precursors for the “base year” year, 2007 to meet CAA 172(c)(3) requirements.

Finally, the Delaware PM2.5 Maintenance Plan includes year 2017 and 2025 on-road 

motor vehicle emissions budgets for PM2.5 and NOx for use in transportation conformity 

determinations to assure that any increases in emissions from this sector do not jeopardize

continued attainment of the 2006 daily PM2.5 NAAQS standard during the ten-year maintenance

period. Delaware’s Maintenance Plan has been prepared in accordance with the requirements 

specified in EPA’s guidance document, and additional guidance received from EPA staff.

Based on this presentation, New Castle County, Delaware meets the requirements for 

redesignation under the CAA (Section 107(d)(3)) and EPA guidance for fine particles. 

 

27 Based on MARAMA work, and consultation with PA and NJ, emissions for all of the Philadelphia NAA will 

decrease significantly by 2017 and 2025.
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Consistent with the authority granted to EPA, the State of Delaware requests that New Castle 

County, Delaware be redesignated to attainment for the 2006 daily fine particles standard 

simultaneously with EPA approval of this Delaware State redesignation request and daily PM2.5

Maintenance Plan for the New Castle County portion of the Philadelphia NAA.