UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

NATIONAL VEHICLE AND FUEL EMISSIONS LABORATORY

2565 PLYMOUTH ROAD

ANN ARBOR, MICHIGAN 48105-2498

MEMORANDUM September24, 2012

OFFICE 

OF

AIR AND 

RADIATION

SUBJECT: Calculation of Emissions from GDFs

FROM: Glenn W. Passavant, Office of Transportation and AirQuality

TO: Public Docket EPA-HQ-OAR-2011-0151

A. Introduction:

This memo addresses technical and emission aspects of how the emission and 

throughput values in Table 3 of the proposed rule (General Permits and Permits 

by Rule for the Tribal Minor New Source Review Program) were calculated. The

table is copied below for ease of reference:

Table 3 .Emissions from Gasoline Dispensing Facilities with ORVR Consideration

NSR 

CATEGORY

End of 

Calendar 

Year

% 

ORVR

Disp. 

lb/1000 

gal

Breathing

Losses 

lb/1000 

gal

Stage I

lb/1000

. gal

Total 

lb/1000 

gal

Gallons per 

year (gpy) 

Equivalent

Gallons

per month 

(gpm) 

Equivalent

1a 2

tpy

Ozone

NA 2011 72% 2.1 0.25 0.3 2.65 1,509,434 125,786

1b 2

tpy

Ozone

NA 2014 82% 1.35 0.25 0.3 1.9 2,105,263 175,439

1c 2

tpy

Ozone

NA 2020 92% 0.60 0.25 0.3 1.15 3,478,261 289,855

1d 2

tpy

Ozone

NA

2025 96% 0.3 0.25 0.3 0.85 4,705,882 392,157

2a 5

tpy

Ozone

attain 2011 72% 3.02 0.25 0.3 3.57 2,801,112 233,427

2b 5

tpy

Ozone

attain 2014 82% 1.94 0.25 0.3 2.49 4.016,064 334,673

2c 5

tpy

Ozone

attain 2020 92% 0.86 0.25 0.3 1.41 7,142,857 595,238

2d 5

tpy

Ozone

attain 2025 96% 0.43 0.25 0.3 0.98 10,204,082 850,340
Gasoline vapor emissions from operations at GDFs arise from four major categories normally 

identified as occurring either in Stage I or Stage II operations at the GDF. Stage I involves

transfer of gasoline from the tanker truck to the storage tank while Stage II involves transfer

of gasoline from the storage tank to the vehicle/equipment. EPA's emission factors document

AP-42 contains background information on these sources and some information on

emission rates.

1

B. Discussion

Stage I GDF emissions are those vented from the storage tank when gasoline is off-loaded 

from the tanker truck. As indicated in AP-42, if uncontrolled these emissions can be quite 

large (11.5 lb/1000 gal). However, vapor balance submerged filling technology reduces these 

emissions by over 95 percent and this control technology is commonly required. The 0.3 

lb/1000 gal emission rate listed above includes implementation of vapor balance submerged 

filling technology.

Stage II refueling emissions from GDFs are comprised of three different segments including 

vapor displacement from the vehicle gasoline tank, gasoline spillage during refueling related to 

system design and by the person handling the nozzle, and breathing losses related to the

storage tank drawing in fresh air after refueling events and as a result of diurnal changes in

atmospheric pressure and temperature. Most breathing loss emissions occur during extended 

periods of very low or no dispenser activity such as in the late evening and overnight hours.

Displacement emissions are a function of the gasoline Reid vapor pressure (RVP), the 

temperature of the dispensed gasoline, and the temperature of the fuel in the vehicle's gasoline 

tank. AP-42 estimates a national average annual value of about 11 lbs VOC/ per 1000 gallons

of gasoline dispensed, but this value is substantially lower in states with vapor pressure control. 

In this analysis, displacement losses are being modeled using 7 RVP for ozone non- attainment

areas with dispensed and tank fuel temperatures representative of the summer time western US

and 10 RVP gasoline for ozone attainment areas with dispensed and tank fuel

temperatures representative of the summertime US national average.

3 The emission rate was then reduced

by applying the onboard refueling vapor recovery (ORVR) control technology required by section

202(a)(6) of the Clean Air Act. Other analyses conducted by EPA show that ORVR is 98 percent

efficient and that the percentage of gasoline dispensed to ORVR equipped vehicles will increase over time

as ORVR-equipped vehicles replace those without ORVR. 4'

5

AP-42 estimates breathing losses to average about 1 lb VOC /1000 gallons of fuel dispensed. 

Under the requirements of 40CFR63 CCCCCC, most GDFs have installed pressure/vacuum 

valves on storage tank vent pipes which suppress air inflow and vapor outflow. Test data 

available to EPA indicates that these p/v valves are at 50-75 percent efficient. The 

uncontrolled emission rate measured in the referenced study was less than ten percent of the 

value cited in AP-42, so the higher end of the efficiency range was used here, yielding an

emission rate of about 0.25 lb VOC /1000 gallon dispensed.

6

1 US EPA, AP-42,Compilation of Air Pollutant Emission Factors, Volume I, Fifth Edition, Chapter S. 2 The equation for calculating the emission rate was taken from the 1988 CRC report prepared by ATL entitled,A Study of Uncontrolled

Automotive Refueling Emissions. This report is availablee in public docket A-87-11. The emission rate in g/gal = exp[-1.2798-

.0049(L'-T)+.0203(Td)+0.1315(RVP)]. 3 See EPA report, Refueling Emissionsfrom Uncontrolled Vehicles, EPA-AA-SDSB-85-6, 1985. This report is available in public docket A-87-11.

4

See EPA Memorandum, Updated ORVR In-Use Efficiency, Glenn W. Passavant, EPA Office of Transportation and Air Quality, February 7, 2012. 

This is available at EPA public docket EPA-HQ-OAR-2010-1076. 5 See EPA Memorandum, Updated ORVR Widespread Use Assessment, Glenn W.Passavant, EPA Office of Transportation and Air Quality, February

29, 2012. This is available at EPA public docket EPA-HQ-OAR-2010-1076. 6 Underground Storage Tank Vent Line Emissionsfrom Retail Gasoline Outlets, Western States Petroleum Association, project FR-92-01-204R2, May,

I 994. This is available at EPA public docket EPA-HQ-OAR-2010-1076. 2
The three emission rates in lb VOC/1000 gallons dispensed are then sum med to get a total

rate for the GDF. These were then converted to tons VOC/1000 gal and divided into the 2 ton/ 

year and 5 ton/year threshold values to get the annual value or further divided by 12 to get the 

monthly values as shown above

Gasoline spillage is a source of emissions in the refueling event, but could be considered a 

fugitive emission for NSR purposes under current EPA regulations and thus would not be part of

the overall inventory calculation. Early studies of gasoline spillage during refueling indicated

that spillage was about 0.7lb VOC/1000 gallons of fuel dispensed. Of this amount, about onehalf was related to either incompatibility between the vehicle fill pipe design and the dispensing

rate and the other half was related to the design of the nozzle and the effects of handling of the

nozzle as it was removed from and replaced in the dispenser.

7 EPA regulatory actions in the

1990's reduced spillage in-use through emission standards and test procedures which encouraged

compatibility between fill pipe designs, nozzle geometries, and dispensing rates and EPA also

limited dispensing rates in-use.

8 EPA estimates that these actions have reduced spillage

emission rates by about 50 percent relative to the values in AP-42 or about 0.35 lb/1000 gal. 9 If

spillage was included, the gpy and gpm values would be proportionally lower. For example, in

2014 the ozone nonattainment values would be calculated by dividing the 2 tons/yr (4000 lb/yr)

value by 2.25 lb/1000 gal instead of the value shown in Table 5, column 9 (1.9 lb/1000gal).

7 Investigation of Passenger Car Refueling Losses: Malcolmm Smith, Scott Research Laboratories, Society of Automotive Engineers, Paper

720931 . This is available at EPA public docket EPA-HQ-OAR-2010-1076. 8 See EPA regulatory requirementsfor in-use dispensing rate limits (61 FR 33034, June 26, 1996) and the fuel dispensing spit back standard (58 FR

16021, March 24, 1993) and ORVR test procedures which require that any fuel spilled in the SHED be counted in the 0.20 g/gal amount allowed for by 

the emission standard under 40 CFR 86 Subpart B. 9 US EPA report: Development of Evaporative EmissionsCalculations for the Motor Vehicle Emissions Simulator MOVES 20I0, EPA-420-R-12-027,

September 2012. 3