Ms. Lynorae Benjamin 

Georgia Environmental Protection Division 

Air Protection Branch 

4244 International Parkway • Suite 120 • Atlanta • Georgia 30354 

404/363-7000 • Fax: 404/363-7100 

Judson H. Turner, Director 

APR 0 7 2015 

Chief, Air Regulatory Management Section 

U.S. EPA, Region 4 

61 Forsyth Street, S.W. 

Atlanta, Georgia 30303-3104 

RE: Correction to the School Bus Replacement Program Emissions Pertaining to the 

December 23, 2014 SIP Submittal: Revisions to Georgia Rule (mmm), NOx 

Emissions from Stationary Gas Turbines and Stationary Engines, Removal of 

Georgia Rule (aaa), Consumer and Commercial Products, Removal of Georgia 

Rule (bbb), Gasoline Marketing Rule 

Dear Ms. Benjamin: 

With this letter the Georgia Environmental Protection Division (EPD) is submitting additional 

information to the U.S. Environmental Protection Agency (U.S. EPA) pertaining to the 

calculation of school bus replacement program NOx emissions that were used as offset 

emissions in EPD's December 23, 2014 110(1) SIP submittal for the removal of Georgia Rule 

391-3-1-.02(bbb). 

The NOx emission reductions from the school bus replacement program that were presented in 

the SIP were calculated using the Diesel Emission Quantifier (DEQ). EPA has notified Georgia 

EPD that while the DEQ is an acceptable approach for emission calculations for grant 

applications, it is not acceptable for SIP submittals or offset calculations. As such, Georgia EPD 

has recalculated the NOx emissions benefits from the school bus replacements using EPA 

certification data and school bus route mileage as requested by U.S. EPA. A summary of the 

changes is shown below: 

NOx Emission Offset Calculation Method NOx Reductions from the School Bus 

Replacement Program 

Submittal dated 12/23/2015 5.08 tons per year 

Corrected in this submittal as per EPA's 6.42 tons per year 

requested dated 3/26/2015 

As a result of this correction, the emission offsets in the 11 0(1) submittal dated December 23, 

2015, continue to be sufficient to offset the potential emission increases that may result from the 

removal of Georgia Rule 391-3-1-.02(bbb) from our SIP. Appendix A contains the approach 

used to calculate the NOx emissions reductions and how the emission reductions fit into the 

offset calculations. Appendix B contains the EPA certification data for model years (MY) 1996, 

1998, 2001-2003, and 2015; and Appendix C contains detailed calculations for the NOx 

emission reductions. 
Ms. Lenorae Benjamin 

Page 2 

Thank you in advance for your prompt review of our request. Should you or your staff have any 

questions, please feel free to contact me at (404) 363-7131. 

Sincerely, 

(.J.<s,o.t.._'f... rvjv-sy 

Elisabeth Munsey 

Manager, Planning & Regulatory Development Unit 

EM:EM 

c: Richard Wong, EPA Region 4 

Keith Bentley, Branch Chief, EPD Air Protection Branch 

Karen Hays, EPD Air Protection Branch 

James Boylan, EPD Air Protection Branch 
Ms. Lenorae Benjamin 

Page3 

Appendix A 

The NOx emission reductions for the early school bus replacements occurring in 2015 were 

calculated using EPA certification data (see Appendix B) and school bus route mileage data. 

See Appendix B for the EPA certification data and conversion factor information. 

The following assumptions were made: 

• All school buses are equipped with engines classified for on-highway application and that all 

buses are diesel powered. (i.e., no gasoline, natural gas or propane powered engines). 

• The EPA certification data for model year 1996 was used instead of 1994 or 1995 data 

because there is no readily available EPA certification data for model year 1994 and model 

year 1995. This is not expected to increase the calculated NOx emission reductions since 

newer engines have better emission controls. 

• The daily emissions from the old and new buses are based on daily miles traveled for 

corresponding bus routes reported to EPD by the respective school systems. There is 180 

days in a typical school year that buses would operate, which is used to determine the 

annual emissions. More detailed calculations can be found in Appendix C. 

• The model year of the engine and the model year of the school bus are assumed to be the 

same. 

For each corresponding model year, the EPA certification data was sorted and the average NOx 

emissions were calculated (units: g/bhp-hr). 

EPA document (EPA420-R-02-005) which can be found in Appendix B contains information to 

convert brake horse power hours (bhp-hr) to miles traveled by a school bus. The certification 

data was converted accordingly, and the average NOx emission value for each respective 

model year was used to provide the most realistic emission reduction scenario. 

Table 1. Emissions Decrease Due to School Bus Replacements 

Corrected for SIP: NOx Data For School Buses 

Tons/yr 

School Numbers Nox 

System Grant fund of Buses Reduced 

DeKalb CMAQ 09-11 leftover 10 1.37 

Fayette CMAQ13 44 4.26 

Henry GP Donaldson Recall 3 0.38 

Madison GP Donaldson Recall 1 0.15 

Madison 2012-13 DERA 2 0.26 

6.42 
Ms. Lenorae Benjamin 

Page4 

In Georgia's December 23, 2014, SIP submittal, EPD stated that its school bus early 

replacement program had resulted in NOx emissions reductions of 5.08 tons per year in the 45-

county area covered by Georgia Rule (bbb). The calculations of NOx emissions were used for 

emissions offsets for the 11 0(1) demonstration. 

Using the corrected method of calculating NOx emissions reductions, Georgia EPD continues to 

have offsets in excess of the increase in emissions due to the removal of Georgia Rules (aaa) 

and (bbb). Table 2 shows in detail the difference between the new and previous calculations 

and the offsets available from the school bus replacements. 

Table 2. Emissions Decrease Due to All Retrofits/Replacements 

...,.. ~ · .. . 

Source of Offset Locomotive Retrofits· ·• School Bus Total Decrease .... ·. Replacements 

NOx Emissions 

Decrease 199.20 5.08 204.28 

(tons/year) 

Original SIP 

Submittal Dated 

12/23/2014 

NOx Emissions 

Decrease 

(tons/year) 199.20 6.42 205.62 

Based on EPA 

Certification Data 

and Mileage 

The offsets available, from both school bus replacements and rail locomotive diesel retrofits, are 

a total of 205.62 tons per year of NOx. 

As shown in Table 3, the annual NOx decrease from the school bus replacements and 

locomotive retrofits are more than adequate to offset the maximum NOx and VOC increase 

expected from the repeal of rules 391-3-1-.02(2)(aaa) and (bbb). The increase in emissions 

from removal of these rules is at a maximum immediately following their repeal and gradually 

decreases over time. 
Ms. Lenorae Benjamin 

PageS 

Table 3. Emissions Increases Compared to Available Emissions Offsets