Attachment to:

Technical Support Document For the Modeling and Weight of Evidence (WOE) Portions of the 

Document Entitled “Cecil County, Maryland 8-Hour Ozone State Implementation Plan and Base 

Year Inventory SIP Revision: 07-05, June 15, 2007

Technical Support Document for the Modeling and Weight of Evidence (WOE) Portions of the 

State of Delaware’s Ozone State Implementation Plan (SIP) Entitled “Delaware State 

Implementation Plan for Attainment of the 8-Hour Ozone National Ambient Air Quality

Standard Reasonable Further Progress and Attainment Demonstration, June 2007”

Technical Support Document for the Modeling and Weight of Evidence (WOE) Portions of the 

Commonwealth of Pennsylvania’s Ozone State Implementation Plan (SIP) Entitled 

“Commonwealth of Pennsylvania Department of Environmental Protection State Implementation 

Plan Revision: Attainment Plan and Base Year Inventory Bucks, Chester, Delaware, 

Montgomery and Philadelphia Counties located in the Philadelphia-Wilmington-Atlantic City, 

PA-NJ-DE Eight-Hour Ozone Nonattainment Area July 2007”

SCOPE:

This attachment supplies some estimates of additional reductions anticipated to occur between 

2007 and 2009 and between 2008 and 2009.

I. Estimation of emission reductions from fleet turnover between 2007 and 2009.

A. Background:

A typical State SIP submittal includes the 2002 base year emissions, 2008 projected controlled 

emissions in the RFP plan and 2009 projected controlled emissions in the attainment 

demonstration. The expected decrease or reduction in emissions between 2008 and 2009 can be 

determined directly. One way to estimate the emissions reductions for 2007 to 2009 would be to 

double the reduction from 2008 to 2009. This method assumes the change in emissions is linear 

over time. 

Mobile Source Estimation Methodologies:

Mobile source emissions are estimated for future years using the MOBILE6.2 emission factor 

models for on-road (or highway) sources and the NONROAD model for off-road or nonroad 

sources. On-road mobile source emissions are typically developed using the MOBILE6.2 model 

to generate the emission factors and a travel demand model (TDM) is used to generate the 

vehicle miles travelled (VMT) which is the activity level. Conceptually, the on-road mobile 

source emissions are determined by multiplying the VMT in miles by the emission factor (EF) in 

grams per mile:

Emissions = EF ∙ VMT.
2

Because the EF generated by MOBILE6.2 is a function of speed, vehicle type, vehicle age and 

other factors, the overall emissions are a summation of many VMT values representing each link 

or roadway class multiplied by many emission factors corresponding to the vehicle mix and 

speed on that roadway class. 

Emissions = ∑ (EF ∙ VMT )

B. On-Road Mobile Source Emissions Changes Over Time:

In future years the on-road mobile source emissions are affected by changes in VMT and 

changes in emission factors. The TDM projections tend predict VMT will increase over time 

while speeds may or may not change generally decreasing (due to congestion). The VMT/speed 

changes will cause future year projection VMT to be higher resulting in higher emissions than if 

VMT remained constant. The EF values decrease dramatically because the future year fleet is 

predicted to be made up of a higher percentage of newer vehicles then the 2002 fleet (motor 

vehicles must be replaced over time as they wear out, corrode, are involved in collisions, etc.). 

These newer vehicles meet the more stringent standards such as the Tier 2 standards which 

started only in model year 2004 and the heavy-duty standards which took effect with the model 

year 2002 standards with more stringent standards applying to model year 2007 and newer 

vehicle. The effect of the decreasing EFs is a net overall decrease in projected on-road vehicle 

emissions in future years (as evinced by the much lower 2009 emission estimates). 

Due to the competing effects of VMT (tending to increase future year emissions) and of the EF 

value declines (tending to decrease future year emissions) one should not expect the change over 

time to be linear between 2002 and 2009.

Simple examination of plotting the emissions provided in the plan will show that the emissions 

change over time is non-linear.

Consider for example the on-road NOx emissions for the Pennsylvania portion of the 

Philadelphia area. 

On-road NOx emissions for the Pennsylvania (in tons per day (TPD))

Year 2002 2008 2009

Emissions of Nox 

(TPD)

184.66 108.78 101.6

Plotted graphically one sees this is the case:
3

If one linearly interpolates a 2008 value between 2002 and 2009 one gets:

113.457 = 184.66 – [(101.60 – 184.66)/7 ∙ 5], which is more than the value in the SIP.

This suggests that linear interpolation between 2002 and 2009 will over estimate 2007 emissions 

levels.

C. Nonroad Mobile Source Emissions Changes Over Time:

The nonroad mobile source emissions are determined conceptually in the same manner – EFS are 

multiplied by an activity levels and these products for all over all nonroad engine types are 

summed. The NONROAD model packages this process within one model. 

The NONROAD model will predict higher activity levels for future years but lower EF values as 

the nonroad fleet turns over. Generally, the net effect is an overall decrease in nonroad mobile 

sources after the 2002 base year. 

Due to the competing effects of increased projected activity levels (tending to increase future 

year emissions) and of the EF value declines (tending to decrease future year emissions) one 

should not expect the change over time to be linear between 2002 and 2009.

Simple examination of plotting the emissions provided in the plan will show that the emissions 

change over time is non-linear.

Consider for example the non-road NOx emissions for the Pennsylvania portion of the 

Philadelphia area. 

Non-road NOx emissions (in TPD)

Year 2002 2008 2009

Emissions of Nox 70.95 62.67 61.13

PA Portion of Philadelphia Area On-Road NOx

0

50

100

150

200

2000 2002 2004 2006 2008 2010

Year

NOx (TPD)
4

If one linearly interpolates a 2008 value between 2002 and 2009 one gets:

62.53 = 70.95 – [(61.13 – 70.95)/7 ∙ 5], which is less than the value in the SIP.

(The non-linearity is not as pronounced graphically for the nonroad case as for the on-road case.)

D. Conclusion:

Linear Interpolation between 2002 and 2009 may not be the best method to estimate 2007 mobile 

source emissions.

E. Non-Linear Interpolation:

Because there are three data points (except in the case for Delaware)1one can fit a quadratic 

equation of the form AY2 + By + C = Eyyyy where:

A, B and C are constants, 

Y is the number of years after 2002 (hence Y = 0 for 2002, 5 for 2007, 6 for 2008 and 7 

for 2009) and 

Eyyyy is the year of emissions (yyyy = 2002, 2007, etc.).

Because Y = 0 for 2002, C = E2002 the base year level.

The formulae used to calculate A and B from E2002, the base year emissions, E2008,the 2008 

projected emissions and E2009, the 2009 projected emissions are derived in Section IV below.

Using the coefficients derived for each State and source sector, a quadratic equation was used to 

estimate the 2007 on-road mobile source and 2007 nonroad mobile source NOx emissions for 

each state (with the exception of Delaware’s 2007 nonroad NOx emissions which were a linear 

interpolation between 2002 and 2009).

F. Summary of Interpolation Results:

Summary of Estimated 2007 to 2009 Nonroad Mobile Source NOx Reductions

DE MD NJ PA Total

A * -0.00619 0.0023809 -0.022857

1 Delaware’s RFP plan relied upon a demonstration that sufficient VOC reductions would be achieved by 2008 to 

meet the 15% RFP requirement. Therefore, Delaware’s RFP plan did not need to (nor did it) include 2008 

projections of NOx emissions for the source sectors of point, area and nonroad mobile sources. Delaware’s RFP 

plan did include 2008 projections of VOC emissions for all source sectors. Delaware did include 2008 NOx 

emissions projections for on-road sources to set NOx motor vehicle emissions budgets (MVEBs) for 2008 in 

addition to 2008 VOC MVEBs. For this analysis, a linear interpolation was used to estimate nonroad mobile source 

NOx emissions in Delaware for 2007.
5

B * 0.020476 -1.230952 -1.242857

C * 2.97 70.6 70.95

Estimated 2007 Nonroad NOx = 25 ∙ A 

+ 5 ∙ B + C

50.5* 2.92 64.5 64.16

Projected 2009 On-Road NOx from the 

SIP Submittal

49.59 2.81 62.1 61.13

Reductions 2007 to 2009 0.91 0.11 2.40 3.03 6.46

Note: * Linear Interpolation used: E2007 = E2002 - (E2009 - E2002)/7 * 5

Summary of Estimated 2007 to 2009 On-Road Mobile Source NOx Reductions

DE MD NJ PA Total

A 0.07142857 0.10326190 0.859523 0.780952

B -4.6185714 -1.6640476 -16.5738 -17.3323

C 69.03 14.22 179.8 184.66

Estimated 2007 Nonroad NOx = 25 

∙ A + 5 ∙ B + C

47.72 8.47 118.42 117.52

Projected 2009 On-Road NOx 

from the SIP Submittal

40.2 7.60 105.9 101.60

Reductions 2007 to 2009 7.52 0.87 12.52 15.92 36.83

Summary of Estimated 2007 to 2009 Nonroad Mobile Source VOC Reductions

DE MD NJ PA Total

A -0.0021429 0.0271428 -0.107142 -0.003809

B -0.8121429 -0.352857 -2.507142 -2.680476

C 26.77 8.37 99.00 79.06

Estimated 2007 Nonroad NOx = 

25 ∙ A + 5 ∙ B + C

22.66 7.28 83.78 65.56

Projected 2009 On-Road NOx 

from the SIP Submittal

20.98 7.23 76.2 60.11

Reductions 2007 to 2009 1.68 0.05 7.59 5.45 14.77

Summary of Estimated 2007 to 2009 On-Road Mobile Source VOC Reductions

DE MD NJ PA Total

A 0.1152381 0.0278571 0.538095 0.556904

B -2.448095 -0.452142 -10.3952 -9.61976

C 32.38 4.00 91.8 98.76

Estimated 2007 Nonroad NOx = 25 ∙ 

A + 5 ∙ B + C

23.02 2.44 53.28 64.58

Projected 2009 On-Road NOx from 

the SIP Submittal

20.89 2.29 45.4 58.71

Reductions 2007 to 2009 2.13 0.24 7.88 5.87 16.11
6

The expected magnitude of reductions remaining is simply the difference between the 2007 

estimates and the 2009 projections provided in the State submittals.

G. Data and computations:

The emissions estimates and computations are in the attached printouts of the worksheet titled 

“Mobile Emissions Estimates” in a Microsoft® Excel 2003 spreadsheet, a copy of which is 

included in the docket for this action. 

H. Sources of Data for the Shreadsheets:

Tables 3-3, 3-4, Section 5.5, Tables 6-4, 6-10 and 6-11 from “Final Submittal, Delaware State 

Implementation Plan For Attainment Of The 8-Hour Ozone National Ambient Air Quality

Standard, Reasonable Further Progress and Attainment Demonstration, Submitted To U.S. 

Environmental Protection Agency, By Delaware Department of Natural Resources and 

Environmental Control,” June 2007.

Tables 3-1, 4-3 and 4-4 to “Cecil County, Maryland 8-Hour Ozone State Implementation Plan 

and Base Year Inventory,” SIP Revision: 07-05, June 15, 2007.

Tables 4-1, 4-2, 4-7 to “Commonwealth of Pennsylvania, Department of Environmental 

Protection, State Implementation Plan Revision: Attainment Demonstration and Base Year 

Inventory, Bucks, Chester, Delaware, Montgomery and Philadelphia Counties located in the 

Philadelphia-Wilmington-Atlantic City, PA-NJ-DE Eight-Hour Ozone Nonattainment Area,”

August 2007.

Table 6.3: Projected Emissions and Control Measure Benefits New Jersey Portion of Southern 

New Jersey/Philadelphia Nonattainment Area in Chapter 6.0 “Reasonable Further Progress 

(RFP)” of “State Implementation Plan (SIP) Revision for the Attainment and Maintenance of the 

Ozone National Ambient Air Quality Standard 8-Hour Ozone Attainment Demonstration, Final,” 

dated October 29, 2007. Available at http://www.nj.gov/dep/baqp/8hrsip/8hrsip.html#final (last 

checked Thursday, December 11, 2008) and at http://www.regulations.gov, docket EPA-R02-

OAR-2008-0497. 

II. Remaining Reductions from Delaware’s Multi Pollutant Regulation:

A. The Multi Pollutant Regulation and Requirements 

The implementing regulations for Delaware’s Multi Pollutant Regulation are found in Regulation 

No. 1146, “Electric Generating Unit (EGU) Multi-Pollutant Regulation” which was approved 

into the Maryland SIP on August 28, 2008 (73 FR 50723).2

2 A copy of Regulation No. 1146: Electric Generating Unit (EGU) Multi-Pollutant Regulation

is attached. The Delaware SIP can be viewed on line at http://yosemite.epa.gov/r3/r3sips.nsf/SIPIndex!OpenForm

(last accessed December 12, 2008). 
7

The relevant provisions of Regulation No. 1146 are as follows:

Regulation .01 (COMAR 26.11.27.01) provides the following pertinent definitions in sections A 

and B as follows: 

Section 2.0 “Applicability” States:

This regulation applies to coal-fired and residual oil-fired electric generating units 

located in Delaware with a nameplate capacity rating of 25 MW or greater that 

commenced operation on or before the effective date of this regulation.

Section 3.0 “Definitions” conatins the following definitions:

“Unit” means, for the purposes of this regulation, a stationary, fossil-fuel-fired

boiler supplying all or part of its output to an electric generating device.

Section 4.0 “NOx Emissions Limitations” sets the following requirments for affected units:

4.1 From May 1, 2009 through December 31, 2011, no unit subject to this

regulation shall emit NOx at a rate exceeding 0.15 lb/MMBTU.

4.1.1 Compliance with the requirements of paragraph 4.1 of this section shall be 

demonstrated on a rolling 24-hour average basis.

In Table 6-1 “Delaware 2009 VOC and NOx Emission Projections (TPD) for Electric Generating 

Units (EGUs)” Delaware identified eight units affected by regulation 1146. These are 

Facility Name Unit Description

City Of Dover - McKee Run Generating Sta Boiler #3 

Conectiv Delmarva Generation-Edge Moor Boiler #3

Conectiv Delmarva Generation-Edge Moor Boiler # 4

Conectiv Delmarva Generation-Edge Moor Boiler # 5

Indian River Generating Station Boiler #1

Indian River Generating Station Boiler # 2 

Indian River Generating Station Boiler # 3

Indian River Generating Station Boiler # 4

B. Actual 2007 Emissions and Preliminary 2008 Emissions Data

For EPA’s review, the 2007 actual emissions levels at the affected units are known. This data is 

available at the EPA’s “Clean Air Markets - Data and Maps” web portal 

(http://camddataandmaps.epa.gov/gdm/index.cfm) maintained by EPA’s Clean Air Markets 

Division (CAMD). Data for the eight affected units was downloaded on December 12, 2009. 

The data downloaded included information identifying the facility and units, NOx mass 

emissions (in tons) for each season, and the heat input for the unit (in mmBTU) for each season. 
8

EPA obtained the data for two seasons: the regulatory ozone season (May 1

st through September 

30th)and the peak ozone season (June 1st through August 31st). For the full ozone season, the 

sum of the actual emissions for the regulatory ozone season was divided by 153 days in the 

period to obtain an average daily actual emissions amount for the 2007 regulatory ozone season. 

For the peak ozone season the average daily emissions was divided by 92 days in the period to 

obtain an average daily actual emissions amount for the 2007 peak ozone season.

To estimate the effect of regulation 1146, the heat input for each season was multiplied by 0.15 

pounds NOx/mmBTU to estimate the levels of NOx emissions in tons for each season that would 

have been allowed if Regulation 1148 had been in effect. 

The estimated allowable emissions for each unit were subtracted from the actual emissions for 

each season to obtain the estimated reductions over the period. The estimated reduction each 

season was divided by the number of days in each season (153 for the regulatory ozone season 

and 92 for the peak ozone season) to obtain an average reduction in tons per day for that season.

C. Summary of results 2007 to 2009:

Regulation No. 1146, “Electric Generating Unit (EGU) Multi-Pollutant Regulation” 2007-2009

Full Regulatory Ozone Season Peak ozone Season

Seasonal 2007 NOx 

Emissions

3994.985 3491.336

Seasonal 2007 NOx 

Emissions at 0.15 lbs 

NOx/mmBTU Heat Input

1995.103 1742.436

Estimated seasonal reductions 

available

1999.882 1748.900

Estimated daily Reductions 

Between 2007 and 2009

13.071 19.010

D. Summary of results 2008 to 2009:

A similar process to that described in section II. C above was applied to the preliminary 2008 

emissions date available at the “Clean Air Markets - Data and Maps” web portal which was 

downloaded December 12, 2008. The results are:

Regulation No. 1146, “Electric Generating Unit (EGU) Multi-Pollutant Regulation” 2008-2009

Full Regulatory Ozone Season Peak ozone Season

Seasonal 2007 NOx 

Emissions

3008.733 2075.988

Seasonal 2007 NOx 

Emissions at 0.15 lbs 

NOx/mmBTU Heat Input

1519.851 1042.854

Estimated seasonal reductions 

available

1437.282 1033.134
9

Estimated daily Reductions 

Between 2007 and 2009

9.394 11.230

E. Data and computations:

The CAMD data and computations are in the attached printouts of the worksheets titled “2008 

Full Ozone Season,” “2008 Peak Ozone Season,” “2007 Ozone Full Season,” and “2007 Peak 

Ozone Season” in a Microsoft® Excel 2003 spreadsheet, a copy of which is included in the 

docket for this action. 

III. Other Regulations taking Effect after January 1, 2007.

A. NOx Measures:

New Jersey identified several additional measures scheduled to take effect after January 1, 2007.

These include the Refinery Enforcement Initiative, and Certain Categories of ICI Boilers for 

which New Jersey projected 0.3 tpd and 2.0 tpd in NOx emissions reductions, respectively, 

commencing in 2009. See Table 6.3 “Projected Emissions and Control Measure Benefits New 

Jersey Portion of Southern New Jersey/Philadelphia Nonattainment Area” in Chapter 6.0 

“Reasonable Further Progress (RFP)” of “State Implementation Plan (SIP) Revision for the 

Attainment and Maintenance of the Ozone National Ambient Air Quality Standard 8-Hour 

Ozone Attainment Demonstration, Final,” dated October 29, 2007, of New Jersey’s SIP 

submittal. Additionally, New Jersey’s NOx RACT Rule 2006 (which includes distributed 

generation) is discussed in section 4.3.1.4.3 in Chapter 4.0 Control Measures of the New Jersey

SIP submittal. This rule has a number of compliance dates in 2007. See 72 FR 11812, March 

14, 2007 and 72 FR 41626, July 31, 2007. New Jersey estimated reductions in NOx emissions of 

2.1 TPD. See Table 6.3 “Projected Emissions and Control Measure Benefits New Jersey

Portion of Southern New Jersey/Philadelphia Nonattainment Area” of New Jersey’s SIP 

submittal.

B. VOC Measures:

The plans for the Philadelphia area identified VOC control regulations for which the plan 

projected no reductions in 2008 but did project reductions for 2009. These three regulations are 

summarized in the table below:

Estimate of VOPC Reductions From Stationary Sources 2007-2009

State Measure Reductions Source

MD OTC - Consumer Products 

Phase 2

0.02 Table 6.1: Control Measures Summary3

MD OTC - PFC Phase 1 0.06 Ditto

3

From “Cecil County, Maryland 8-Hour Ozone State Implementation Plan and Base Year Inventory,” SIP Revision: 

07-05, June 15, 2007.
10

MD OTC - PFC Phase 2 0.03 Ditto

MD OTC – Industrial 

Adhesives

0.10 Ditto

NJ EPA MACT Standards 1.1 Table 6.3: Projected Emissions and 

Control Measure Benefits New Jersey

Portion of Southern New 

Jersey/Philadelphia Nonattainment 

Area4

NJ Refinery Enforcement 

Initiative

0.9 Ditto

NJ Consumer Products 2009 

Amendments

0.4 Ditto

NJ Adhesives and Sealants 2.2 Ditto

NJ Asphalt Paving (Cutback 

and Emulsified Asphalt)

1.5 Ditto

NJ Portable Fuel Containers 

(2005 + 2009)

0.8 Ditto

DE Regulation 1124 Section 

46, Crude Oil Lightering 

Operations

2.58 Section 5.1.1 A. Crude Oil Lightering 

Operations5

Totals ................ 9.69

The portable fuel containers (PFC) rules are projected to achieve vastly (in a relative sense) more 

reductions in 2009 than in 2008. Some of these reductions will only offset growth in activity

levels, but for this analysis EPA will assume all reductions from 2008 to 2009 are net of growth 

as the amounts are small in relation to the reductions from 2002 through 2009. The PFC rules 

achieve additional reductions after the implementation date as new containers meeting the PFC 

rule replace older ones. The differences that could be readily discerned from the plans are: 

Cecil County Maryland: For the Phase I PFC rule, the State projected 0.26 tons per day 

reduction in 2008 and 0.32 for 2009 for difference of 0.06. The M<Maryland Phase 2 PFC rule 

is an additional rule.

New Jersey Portion of Southern New Jersey/Philadelphia Nonattainment Area: The State 

projected 1.3 tons per day reduction in 2008 and 2.1 for 2009 for difference of 0.8 tons per day.

IV. Derivation of A, B and C:

4

From Chapter 6.0 “Reasonable Further Progress (RFP)” of “State Implementation Plan (SIP) Revision for the 

Attainment and Maintenance of the Ozone National Ambient Air Quality Standard 8-Hour Ozone Attainment 

Demonstration, Final,” dated October 29, 2007. 

5

“Final Submittal, Delaware State Implementation Plan For Attainment Of The 8-Hour Ozone National Ambient 

Air Quality Standard, Reasonable Further Progress and Attainment Demonstration, Submitted To U.S. 

Environmental Protection Agency, By Delaware Department of Natural Resources and Environmental Control,” 

June 2007.
11

Given A ∙Y2 + B ∙Y + C = Eyyyy where:

A, B and C are constants, 

Y is the number of years after 2002 (hence Y = 0 for 2002, 5 for 2007, 6 for 2008 and 7 

for 2009) and 

Eyyyy is the year of emissions (yyyy = 2002, 2007, etc.). 

Now, E2, E8 and E9 are known.

For the 2002 year, E2, Y is zero by definition.

Thus, C = E2002 because A ∙ 02 + B ∙ 0 + C = E2002.

For 2008, Y = 6 and 

A ∙62 + B ∙6 + C = E2008. [Eqn 1]

For 2009 Y = 7, and , 

A ∙72 + B ∙7 + C = E2009. [Eqn 2] 

Multiply Eqn 1 by 7 and Eqn 2 by 6 to get:

7 ∙ A ∙62 + B ∙ 42 + 7 ∙ C = 7 ∙ E2008. [Eqn 1A]

6 ∙ A ∙72 + B ∙ 42 + 6 ∙ C = 6 ∙ E2009. [Eqn 2A]

Subtract Eqn 1B from Eqn 1A to get:

7 ∙ A ∙62 - 6 ∙ A ∙72 + + 7 ∙ C - 6 ∙ C = 7 ∙ E2008 - 6 ∙ E2009 [Eqn 3]

A ∙ (7 ∙ 62 - 6 A ∙72 ) + C = 7 ∙ E2008 - 6 ∙ E2009

Solving for A:

A = (7 ∙ E2008 - 6 ∙ E2009 – C)

(7 ∙ 62 - 6 A ∙72 )

Now, C = E2002 yielding:

A = (7 ∙ E2008 - 6 ∙ E2009 – E2002) [Eqn 4]

(7 ∙ 62 - 6 A ∙72 )

Taking equation Eqn 2A, A ∙62 + B ∙ 6 + C = E2008, knowing C = E2002 and solving for B yields:
12

B ∙ 6 = E2008 - A ∙62 - E2002

B= (E2008 - A ∙62 - E2002) where Eqn 4 is used to calculate A. [Eqn 5]

6
13

PRINOUT OF WORKSHEETS (18 Pages):

“Mobile Emissions Estimates,” “2008 Full Ozone Season,” “2008 Peak Ozone Season,” “2007 

Ozone Full Season,” and “2007 Peak Ozone Season” in a Microsoft® Excel 2003 spreadsheet, a 

copy of which is included in the docket for this action.