FROM: David Randall, RTI International 

TO: Brenda Shine, EPA/OAQPS/SPPD 

FOR: Docket ID No. EPA-HQ-OAR-2010-0682 

DATE: April 26, 2012 

SUBJECT: Evaluation of the Stringency of Potential Standards for Gasoline Loading Racks 

at Petroleum Refineries 

1. Purpose 

The purpose of this memorandum is to assess the relative stringency of two potential standards 

for gasoline loading racks at refineries: 1) the current requirements as specified in 40 CFR part 

63, subpart CC and 2) a requirement to use submerged loading and reduce transfer operations 

emissions by at least 95 percent. 

2. Background 

Section 112(f) of the Clean Air Act Amendments (CAA) directs the U.S. Environmental 

Protection Agency (EPA) to assess source categories regulated under section 112(d) of the CAA 

and determine whether any human health or environmental risks remain from the continued 

emissions of hazardous air pollutants (HAP) following implementation of maximum achievable 

control technology (MACT) standards. The CAA further states that if the MACT standards do 

not reduce lifetime excess cancer risk to the most exposed individual to less than one in one 

million, the EPA must set additional standards to protect human health and the environment. 

Additionally, the EPA is required to review these technology-based standards and to revise them 

“as necessary (taking into account developments in practices, processes and control 

technologies)” no less frequently than every 8 years, under CAA section 112(d)(6). The Refinery 

MACT 1 (40 CFR part 63, subpart CC) was promulgated over 8 years ago and is now being 

reviewed. 

One aspect of the technology review involves evaluation of control practices and technologies 

for gasoline loading racks. Refinery MACT 1 currently requires Group 1 gasoline loading racks 

to meet the requirements in the National Emission Standards for Gasoline Distribution Facilities 

(Bulk Gasoline Terminals and Pipeline Breakout Stations) in 40 CFR part 63, subpart R. Group 1 

gasoline loading racks are loading racks that have a maximum calculated design throughput 

greater than about 20,000 gallons per day (gal/d) of gasoline; and gasoline is defined as any 

petroleum distillate having a Reid vapor pressure (RVP) greater than 4 pounds per square inch 

absolute (psia) that is used as a fuel for internal combustion engines. The standard specified in 

40 CFR part 63, subpart R is an emission limit of 10 milligrams of total organic compounds per 

liter of gasoline loaded (mg/liter). All tank trucks and railcars that are loaded with gasoline must 
Technical Memorandum – Evaluation of the Stringency of Potential Standards for Gasoline Loading 

Racks at Petroleum Refineries 

April 26, 2012 

2 

undergo annual vapor tightness testing in accordance with Method 27 of 40 CFR part 60, 

appendix A-8. The maximum allowable pressure change is 25 millimeters of water in 5 minutes 

for tank trucks and railcars larger than 2,500 gallons (greater pressure changes are allowed for 

smaller tank trucks and railcars). 

The EPA recently conducted a survey of control technologies for transfer operations (Randall, et 

al., 2012). One of the more cost-effective control options identified by this analysis would 

require, a facility that transfers more than 35 million gallons per year (gal/yr) (equal to about 

100,000 gal/d) of liquids with a weighted average maximum true vapor pressure (MTVP) equal 

to or greater than 4 psia use submerged loading and to vent displaced emissions from the 

transport vehicles through a closed vent system to an air pollution control device (APCD) that 

reduces organic regulated material emissions by at least 95 percent. Other techniques that 

achieve equivalent or better control would also be allowed as an alternative to the 95 percent 

reduction option. These alternatives include vapor balancing to the storage vessel that is 

supplying the transferred liquid or routing displaced emissions to a fuel gas system. 

3. Analysis of Transfer Operations Standards 

This analysis compares the control efficiency required under the current Refinery MACT 1 

requirements to the 95 percent emission reduction option for transfers of several grades of 

gasoline at a model transfer rack. 

Model characteristics. The model transfer rack has one loading arm and transfers 10 million 

gal/yr of gasoline. The temperature of the gasoline was assumed to be 65 degrees Fahrenheit 

(°F), which is a rough approximation of the average annual temperature across the southern half 

of the United States. Seven grades of gasoline were evaluated. The RVP, true vapor pressure at 

65 °F, and vapor molecular weight for each grade of gasoline from section 7 of the AP-42 are 

presented in Table 1 (EPA, 1995). 

Table 1. Characteristics of Different Grades of Gasoline 

Parameters Characteristics for different grades of gasolinea

RVP, psia 4 7 7.8 8.3 10 11.5 13.5 

True vapor pressure at 65 °F 2.1 3.5 3.963 4.2188 5.2 6.069 7.2573 

Vapor molecular weight, lb/lb-molb 68 68 68 68 66 65 62 

a

 The true vapor pressure and vapor molecular weight for gasoline with RVP between 7 psia and 13.5 psia were 

taken from Table 7.1-2 in AP-42. For gasoline with a RVP of 4 psia, the true vapor pressure was calculated 

using Equation 7.1-14b in AP-42, and the vapor molecular weight was assumed to be the same as for gasoline 

with a RVP of 7 psia. b

 lb/lb-mol = pounds per pound-mole. 
Technical Memorandum – Evaluation of the Stringency of Potential Standards for Gasoline Loading 

Racks at Petroleum Refineries 

April 26, 2012 

3 

Uncontrolled emissions. Uncontrolled emissions from transfers to tank trucks and railcars were 

estimated using the following equation from AP-42 section 5.2.2.1.1 with the saturation factor 

for splash loading (EPA, 1995): 

      

  10.73 ft psia / lb - mol R ( R)

psia lb/lb - mol gal 35.3145 ft / 264.17 gal ton/2,000 lb

3

3

     T

S P M Q E

where: 

 E = Volatile organic compound (VOC) emissions, pounds per year (lb/yr). 

 S = Saturation factor (1.45 for splash loading; 0.6 for submerged loading). 

 P = True vapor pressure of transferred liquid, psia. 

 M = Molecular weight of vapors, lb/lb-mol. 

 Q = Quantity of liquid transferred, gal/yr. 

 T = Temperature of transferred liquid, degrees Rankine (°R). 

Controlled emissions under current Refinery MACT 1 requirements. Regardless of the grade of 

gasoline or the type of control implemented, the controlled emissions must be no more than 

10 mg/liter. 

Controlled emissions under 95 percent emission reduction option. Displaced emissions from tank 

trucks and railcars loaded by submerged loading were estimated using the same equation 

presented above, with the saturation factor for submerged loading. Final emissions out of the 

control device were assumed to be equal to 5 percent of the inlet emissions. 

Results. Table 2 presents the uncontrolled emissions, controlled emissions (both total tons per 

year and mg/liter of gasoline transferred), and the percent reduction for the model transfer racks 

under both standards. The analysis shows that the 10 mg/liter standard in Refinery MACT 1 is 

more stringent than the alternative to require submerged loading and a 95 percent reduction of 

emissions for all grades of gasoline. The outlet emissions range from 12 to 42 mg/liter under the 

alternative control option rather than 10 mg/liter as required in Refinery MACT 1. In addition, 

the overall control efficiency is always 97.9 percent under the alternative control option, whereas 

the control efficiency ranges from 98.3 percent to 99.5 percent under the current Refinery 

MACT 1 requirements. The current requirements in Refinery MACT 1 also are the MACT floor 

for petroleum refineries. Therefore, Refinery MACT 1 cannot be revised to be use the alternative 

control option of submerged fill and 95 percent control because the alternative control option is 

less stringent than the existing MACT floor control requirement. 
Technical Memorandum – Evaluation of the Stringency of Potential Standards for Gasoline Loading 

Racks at Petroleum Refineries 

April 26, 2012 

4 

Table 2. Emissions and Control Efficiency to Meet Gasoline Loading Standards in 

Refinery MACT 1 and the 95 Percent Reduction Option 

Parameter 

Emissions and control efficiencies for model transfer 

racks 

RVP, psia 4 7 7.8 8.3 10 11.5 13.5 

Uncontrolled emissions, tons per year (tpy) 24.3 45.6 51.1 54.7 64.7 74.8 85.2 

Control option 1: Submerged loading and venting to APCD as required in Uniform Standards 

Vented emissions from submerged loading, 

tpy 10.1 18.9 21.1 22.6 26.8 31 35.2 

Controlled emissions out of APCD, tpy 0.504 0.944 1.06 1.13 1.34 1.55 1.76 

Controlled emissions out of APCD, mg/liter 12.1 22.6 25.3 27.1 32.1 37.1 42.2 

Overall control efficiency, percent 97.9 97.9 97.9 97.9 97.9 97.9 97.9 

Control Option 2: Outlet emissions level as specified in Refinery MACT 1 

Overall control efficiency, percent 98.3 99.1 99.2 99.2 99.4 99.4 99.5 

4. References 

EPA (U.S. Environmental Protection Agency). 1995. Compilation of Air Pollutant Emission 

Factors, Volume 1: Stationary Point and Area Sources, AP-42, Fifth Edition, U.S. 

Environmental Protection Agency, Office of Air Quality Planning and Standards. January 

1995. 

Randall, D., C. Richardson Fry, and K. Schaffner. 2012. Memorandum from David Randall, 

Carrie Richardson Fry, and Karen Schaffner, RTI International, to Nick Parsons, 

EPA/OAQPS, for Project Docket File (EPA Docket No. EPA-HQ-OAR-2010-0871). Survey 

of Control Technology for Transfer Operation and Analysis of Impacts for Transfer 

Operation Control Options. January 20, 2012. Docket Item No. EPA-HQ-OAR-2010-0871-

0021.