Proposed Revision to 

Delaware’s 2008 State Implementation Plan

For Attainment of the PM2.5 Annual

National Ambient Air Quality Standard - Attainment 

Demonstration

October 2011
Section 1. Introduction

In April, 2008 Delaware submitted to the EPA its “State Implementation Plan for Attainment of 

the PM2.5 Annual National Ambient Air Quality Standard - Attainment Demonstration” (the 

“2008 PM2.5 SIP”). 1 The 2008 PM2.5 SIP set out to accomplish four primary goals:

 Demonstrate that with all existing and proposed controls, all of Delaware’s PM2.5

monitors will show attainment in 2009.

 Demonstrate that the entire Philadelphia-Wilmington, PA-NJ-DE non-attainment area 

will attain the annual PM2.5 NAAQS in 2009.

 Establish Delaware’s 2009 mobile source budgets for transportation conformity 

determinations under Regulation No. 1132, Transportation Conformity.

 Treat emission reduction credits (ERCs) banked under 7 DE Admin. Code 1134, 

Emissions Banking and Trading Program, as “emitted.” As such, the future use of 

these credits is consistent with, and will not interfere with any calculation or 

provision of this SIP.

This SIP revision is related to the PM2.5 and NOx on-road mobile source budgets that were 

established in the 2008 PM2.5 SIP. Those SIP budgets were established using EPA’s 

MOBILE6.2 model.2 However, effective March 2012 3a new on-road mobile emissions model –

Motor Vehicle Emissions Simulator (MOVES) – is required to be used in all planning and 

transportation conformity determinations. 

The purpose of this SIP revision is to 1) replace the on-road mobile emissions budget in the 2008 

PM2.5 SIP with a budget that is based on the MOVES model, 2) demonstrate that the MOVES 

based mobile source budget is consistent with attainment of the PM2.5 NAAQS by 2010, and 3) 

demonstrate that the contingency requirements of the Clean Air Act (CAA) are met. No other 

changes or revisions to the 2008 PM2.5 SIP are proposed.

Note that this SIP revision impacts only PM2.5 and NOx emissions and calculations. While 

sulfur dioxide (SO2) is a pollutant of concern relative to PM2.5 it is not a pollutant of concern for 

mobile budgets, and therefore no SO2 changes are proposed as part of this SIP revision. The 

treatment of SO2 emissions in the 2008 PM2.5 SIP is unchanged.

Questions or comments regarding this SIP revision should be addressed to Phil Wheeler, M.S. 

Project Leader for Transportation Conformity, Planning Branch, Division of Air Quality, 

Delaware Department of Natural Resources and Environmental Control, at 

philip.wheeler@state.de.us. 

 

1

http://www.awm.delaware.gov/Info/Regs/Documents/DE_PM25_SIP_AD_fnl.pdf

2 Details of the MOBILE6 budget calculations are included in Section 8.2 of the 2008 PM2.5 SIP.

3

 EPA has proposed to extend this date by one year; to March 2013.
Section 2. Revised On-Road Mobile Source Budgets

This SIP revision establishes on-road mobile emissions budget for New Castle County for PM2.5

and NOx. When approved by the EPA, all subsequent PM2.5 conformity analyses will test future 

on-road mobile emissions calculated for transportation plans in New Castle County with this new 

budget.

2.1 EPA’s MOVES model was used to quantify PM2.5 and NOx emission from on-road 

mobile sources. These emissions are shown in Table 2-1 below. The associated 2012 

MOVES input and output files are included in Appendix A of this SIP revision. 

Table 2-1 On-Road Mobile Emission Budget (Tons per Year (tpy))

County Emissions Budget

New Castle

NOx PM2.5

6,273 199

2.2 This SIP revision establishes the emission levels identified in Table 2-1 as the on-road 

mobile emissions budget for New Castle County for PM2.5 and NOx. 

Section 3. Demonstration that 2009 MOVES based On-Road Mobile Source Emissions

are Consistent with Attainment of the PM2.5 NAAQS by 2010 

Delaware demonstrated attainment of the annual PM2.5 NAAQS in its 2008 PM2.5 SIP by 

showing that Projected 2009 Emissions (i.e., the 2009 emission levels after the implementation 

of all state and federal control requirements) were less than the Attainment Targets (i.e., the 

emission levels needed for attainment based on modeling). This same methodology is used 

below to demonstrate that the MOVES based mobile budgets presented in Section 2 above are 

consistent with attainment of the PM2.5 NAAQS.

3.1 Community Multi-scale Air Quality Model (CMAQ) modeling was conducted in the 

2008 PM2.5 SIP to demonstrate that Delaware and the entire Philadelphia based nonattainment area would attain the PM2.5 NAAQS in 2010 4

. CMAQ modeling 

demonstrated that the Delaware emission levels shown in Table 3-1 are the levels that are 

necessary for, and consistent with attainment of the annual PM2.5 NAAQS. These 

emission levels reflect the level of emissions needed for attainment, and are therefore 

referred to as the “2009 Attainment Target.” 5, 6

 

4 A detailed discussion of the CMAQ modeling and modeling results can be found in Section 6 of the 2008 PM2.5 

SIP. 

5 Although New Castle County is the only nonattainment county, emission levels of all three counties are used in the 

attainment demonstration. This is discussed in Sections 3 and 4 of this SIP revision. 

6 A detailed discussion of the emission inventories associated with the Attainment Target can be found in Section 5

of the 2008 PM2.5 SIP.
Table 3-1 2009 Attainment Target (tpy)

County NOx PM2.5

Kent 8,554 1,185

New Castle 23,048 3,249

Sussex 18,001 3,581

Statewide Total 49,603 8,015

3.2 Attainment year (i.e., 2009) emission levels were projected in the 2008 PM2.5 SIP based 

on final and enforceable State and Federal emission control requirements.7 These 

projected 2009 emission levels, which are referred to as the “Delaware Projected 2009 

Emissions,” are shown in Table 3-2. 

Table 3-2 Delaware Projected 2009 Emissions (tpy)

County NOx PM2.5

Kent 7,799 989

New Castle 21,807 3,015

Sussex 11,591 2,571

Statewide Total 41,197 6,575

3.4 Table 3-3 compares the 2009 mobile emissions calculated using MOBILE6 and MOVES. 

The associated 2009 MOBILE6 and MOVES input and output files are included in 

Appendix B of this SIP revision.

Table 3-3 2009 MOBILE6, MOVES and Increase due to MOVES (tpy)

2009 Mobile6 2009 MOVES MOVES Increase

County NOx PM2.5 NOx PM2.5 NOx PM2.5

Kent 1,922 32 3,488 109 1,566 77

New Castle 4,904 87 8,448 257 3,544 170

Sussex 2,707 41 4,764 147 2,057 106

Totals 9,533 160 16,700 513 7,167 353

3.5 Adding the “MOVES Increase” emissions from Table 3-3 to the “Delaware Projected 

2009 Emissions” from Table 3-2 yields a projected Delaware 2009 Emission level that 

reflects the use of the MOVES model instead of the MOBILE6 model. This revised 

emissions projection is shown in Table 3-4, and is referred to as the “Revised Delaware 

Projected 2009 Emissions.”

 

7 A detailed discussion of Delaware’s projected 2009 emission levels can be found in Section 4 of the 2008 PM2.5

SIP. 
Table 3-4 Revised Delaware Projected 2009 Emissions (tpy)

County NOx PM2.5

Kent 9,365 1,066

New Castle 25,351 3,185

Sussex 13,648 2,677

Statewide Total 48,364 6,928

3.5 The “Revised Delaware Projected 2009 Emissions” (i.e., Table 3-4) are demonstrated to 

be consistent with attainment if they are equal to or lower than the “2009 Attainment 

Target” (i.e., Table 3-1). The “Revised Delaware Projected 2009 emissions” are 

compared to the “Attainment Target” in Table 3-5 below. 

Table 3-5 Shortfall and Surplus by County and Statewide (tpy)

County

Attainment Target Revised Delaware Projected 

2009 Emissions 

Surplus/Shortfall

NOx PM2.5 NOx PM2.5 NOx PM2.5

Kent 8,554 1,185 9,365 1,066 -811 119

New Castle 23,048 3,249 25,351 3,185 -2,303 64

Sussex 18,001 3,581 13,648 2,677 4,353 904

Statewide 49,603 8,015 48,364 6,928 1,239 1,087

This comparison shows that there is a 64 tpy PM2.5 surplus in New Castle County, and a 

2,303 tpy NOx shortfall for New Castle County. This demonstrates that, relative to direct 

PM2.5, the MOVES based mobile budgets are consistent with attainment. These results 

also indicate that NOx requires further analysis. 

3.6 Because of the regional nature of secondarily-formed sulfate and nitrate, and the broad 

modeling domain of the CMAQ modeling, which included all of Delaware, emission 

reductions from Kent and Sussex counties will contribute to attainment within New 

Castle County and the Philadelphia based non-attainment area. Kent and Sussex counties 

are within the State of Delaware, contiguous to New Castle County, and are less than 200 

kilometers away. EPA’s PM2.5 Implementation Rule specifically provides for the 

consideration of in-state NOX and SO2 reductions in their SIPs from sources up to 200 

kilometers away from the non-attainment area boundaries.

8

Consistent with this EPA rule, emissions from Kent and Sussex Counties were analyzed. 

Using the same methodology as above, statewide emissions are calculated and presented 

in Table 3-5. These results indicate that while there is a 2009 NOx shortfall of 2,303 tpy

in New Castle County, there is a statewide NOx surplus of 1,239 tpy. The analysis 

 

8

PM2.5 Implementation Rule, April 25, 2007 (72 FR 20586 at 20636)
demonstrates that the 2009 MOVES based emission shown in Table 3-3 do not impair 

Delaware’s ability to meet its SIP emissions targets or meeting EPA’s National Ambient 

Air Quality Standards for particulate matter. 9

Section 4. Demonstration that the Contingency Measure Requirements of the CAA are 

Met

Contingency measures are additional control measures to be implemented in the event that an 

area fails to either meet “reasonable further progress” or attain the standards by its attainment 

date. The quantity of emission reductions needed to satisfy contingency requirements is an 

amount equal to one year’s worth of required reductions. 

Delaware demonstrated that the contingency requirements of the CAA were met in Section 9 of 

its 2008 PM2.5 SIP by showing that the Delaware control measures have reduced NOx and 

primary PM2.5 by more than is necessary to attain compliance with the PM2.5 NAAQS. This 

same methodology is used below to demonstrate that the “Revised Delaware Projected 2009 

Emissions” in Table 3-4 are low enough to satisfy contingency requirements. 

4.1 Quantification of the contingency requirement is discussed in detail in Section 9.1 of the 

2008 PM2.5 SIP. The contingency requirement for NOx and PM2.5 is presented in Table 

9-3 of the 2008 PM2.5 SIP, and shown below in Table 4-1.

Table 4-1 Contingency Requirement (tpy)

County NOX PM2.5

New Castle 1,100 26

4.2 Demonstration that contingency requirement is met is shown if the “Revised Delaware 

Projected 2009 Emissions” shown in Table 3-4 are lower than the “Attainment Target” 

shown in Table 3-1 by at least the amount of the amount of the contingency requirement 

shown in Table 4-1. Table 3-5 shows this calculation.

Table 3-5 shows that a 64 tpy reduction of PM2.5 emissions are above and beyond that 

necessary for attainment. Since 64 tpy is greater than the contingency requirement of 26 

tpy PM2.5, the contingency requirement is demonstrated relative to the pollutant primary 

PM2.5. Table 3-5 also indicates that NOx requires further analysis.

4.3 Because of the regional nature of secondarily-formed sulfate and nitrate, and the broad 

modeling domain of the CMAQ modeling, which included all of Delaware, emission 

reductions from Kent and Sussex counties will contribute to attainment within New 

Castle County and the Philadelphia based non-attainment area. Kent and Sussex counties 

are within the State of Delaware, contiguous to New Castle County, and are less than 200 

kilometers away. EPA’s PM2.5 Implementation Rule specifically provides for the 

 

9 Note that this is similar to the approach used in the 2008 PM2.5 SIP to address SO2 emissions. See Section 5 (page 

65) of the 2008 PM2.5 SIP.
consideration of in-state NOX and SO2 reductions in their SIPs from sources up to 200 

kilometers away from the non-attainment area boundaries.

Consistent with this EPA rule, emissions from Kent and Sussex Counties were analyzed. 

Using the same methodology as above, statewide emissions are calculated and presented 

in Table 3-5. This indicates that while there is a 2009 NOx shortfall of 2,303 tpy in New 

Castle County, there is a statewide NOx surplus of 1,239 tpy. Since 1,239 tpy is greater 

than the contingency requirement of 1,100 tpy NOx, the contingency requirement is 

demonstrated as met relative to the pollutant NOx.

Section 5. Summary

The analysis in Section 3 and Section 4 above demonstrates that 2009 MOVES based emission 

levels in table 3-3 are consistent with attainment and the contingency requirements of the CAA. 

This SIP revision is anticipated to be approved by the EPA in 2012. Because the 2012 based 

mobile budgets established in Section 2 of this SIP revision are less than the 2009 MOVES based 

emission levels shown in Table 3-3, Section 3 and Section 4 above also demonstrate that mobile 

budgets established in Section 2 are consistent with attainment and contingency requirements of 

the CAA. 

Appendix A. 2012 MOVES input and output files

Appendix B. 2009 MOVES and 2009 MOBILE6 Input and Output Files