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 072015 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 letterthe Georgia Environmental Protection Division (EPD) is submitting additional information tothe U.S. Environmental Protection Agency (U.S. EPA) pertaining to the calculation ofschool bus replacement program NOx emissions that were used as offset emissions in EPD's December23, 2014 110(1) SIP submittal forthe removal ofGeorgia Rule 391-3-1-.02(bbb). The NOx emission reductions from the school bus replacement program thatwere 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 acceptablefor SIP submittals oroffset 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 ofthe changes is shown below: NOx Emission Offset Calculation Method NOx Reductions from the School Bus Replacement Program Submittal dated 12/23/2015 5.08tons peryear Corrected in this submittal as per EPA's 6.42 tons peryear requested dated 3/26/2015
As a result ofthis correction, the emission offsets in the 110(1) submittal dated December23, 2015, continue to be sufficient to offsetthe potential emission increasesthat may resultfrom the removal ofGeorgia Rule 391-3-1-.02(bbb) from our SIP. AppendixA contains the approach used to calculate the NOx emissions reductions and howthe emission reductions fit intothe offset calculations. Appendix B contains the EPAcertification datafor model years (MY) 1996, 1998, 2001-2003, and 2015; andAppendix C contains detailed calculations forthe NOx emission reductions.Ms. Lenorae Benjamin Page 2

Thank you in advanceforyour prompt review ofour request. Should you oryourstaffhave 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 BranchMs. Lenorae Benjamin Page3 AppendixA The NOxemission reductions forthe early school bus replacements occurring in 2015were calculated using EPA certification data (seeAppendix B) and school bus route mileage data. SeeAppendix Bfor the EPA certification data and conversion factor information. Thefollowing assumptionswere made:
• All school buses are equipped with engines classified foron-highway application and that all buses are diesel powered. (i.e., no gasoline, natural gas or propane powered engines).
• The EPA certification datafor model year 1996was 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 newerengines 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 atypical school yearthat buseswould operate, which is used to determine the annual emissions. More detailed calculations can be found in Appendix C.
• The model year ofthe engine and the model year ofthe school bus are assumed to be the same.
For each corresponding model year, the EPA certification data was sorted and the average NOx emissionswere 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 foreach respective model yearwas used to provide the most realistic emission reduction scenario.
Table 1. Emissions Decrease Dueto School Bus Replacements

Corrected for SIP: NOx Data For School Buses Tons/yr School Numbers Nox System Grantfund 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 6.42Ms. Lenorae Benjamin Page4

In Georgia's December23, 2014, SIP submittal, EPD statedthat its school bus early replacement program had resulted in NOxemissions reductions of 5.08tons peryear in the 45- county area covered by Georgia Rule (bbb). The calculations of NOx emissionswere used for emissions offsets forthe 110(1) demonstration. Using the corrected method ofcalculating NOxemissions reductions, Georgia EPD continues to have offsets in excess ofthe increase in emissions dueto the removal ofGeorgia 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 Dueto All Retrofits/Replacements



### ...,..**~** ·.. . Source

### ofOffset Locomotive Retrofits··• SchoolBus 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 atotal of205.62 tons peryear of NOx. As shown in Table 3, the annual NOx decreasefrom the school bus replacements and locomotive retrofits are morethan adequate to offsetthe 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 ofthese rules is at a maximum immediatelyfollowing their repeal and gradually decreases overtime.

### Ms. Lenorae Benjamin PageS

Table 3. Emissions Increases ComparedtoAvailable EmissionsOffsets