OAR Box 1830 

Prepped by Ollie Stewart 

Document Number: 

35) IV-C-1 

Docket Number: 

A-87-11 

Printed 11/13/2008 7:20:52 AM Sheet 35 of 232 

p.1 
P.2 

^ # %

 Ti UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

ft - 8 7 - iJHT - d -D/ 

J 

MS*' 

ANN ARBOR. MICHIGAN 48105 

MJ6 2T1987 

OFFICE OF 

AIR AND RADIATION 

Mr. William F. Marshall 

Manager - Fuels/Engines Research 

National institute for Petroleum and Energy Research 

P.O. Box 2128 

Bartlesville, OK 74005 

Dear Mr. Marshall: 

Thanks very much for providing us a copy of your proposal 

to the Citizens for Improved Air Quality for quantification of 

emptying losses. We appreciate the opportunity to provide 

these comments and suggestions on your test plan. The thoughts 

here focus primarily on your actual approach to measuring 

underground tank emissions (Task 2). To assist you in 

responding to Task 1, you should have already received a copy 

of the 1962 county of Los Angeles APCD report which serves as 

the basis for the current uncontrolled emission factor, please 

note that this factor actually represents the sum of both 

breathing and emptying losses from the underground tank. No 

attempt was made to discriminate between the two types of 

emissions. However, the assertion is that Stage II would 

reduce only emptying losses. 

Turning now to Task 2, we have a few specific comments on 

your test plan and a few general thoughts. First, if possible, 

the approach used should allow for differentiation between 

breathing and emptying losses. This may be difficult for 

several reasons. Both types of emissions emanate from the vent 

tube, and there is probably no easy way to physically or 

chemically discriminate between them. Also, the timing of the 

emissions is somewhat unpredictable. Determination of emptying 

losses may require an approach in which combined breathing and 

emptying losses are measured in one program and breathing 

losses alone (no refuelings) are measured in a second program 

and the two values subtracted. Of course, designing an 

approach such as this would require extreme care to be sure 

that conditions and variables in the two programs are 

essentially identical. 
P.3 

-2-

Second, in terms of the underground storage tank itself, 

your underground storage tank volume is at the low end of the 

present range, of in-use tanks and thus could affect the 

representativeness of the emission results. In the field, 

current underground tanks range in volume from 4,000-6,000 

gallons for older stations to 8,000-12,000 gallons for newer 

stations. This is important because the emissions could be 

affected by the tank., dimensions (which affect the shape, 

volume, and liquid surface area), the number, length and 

diameter of the vent tubes, and the points at which the vent 

tube(s) and Stage II returned vapors enter the tank. Most 

tanks are cylindrical in shape with a length greater than their 

diameter and lie on their side thus creating a large liquid 

surface area and a short distance between the liquid level and 

the vent tube outlet from the tank. 

Third, the underground tank fuel level, and RVP as well as 

the fuel and vapor temperature would affect emissions. Your 

test plan should specifically include provisions for monitoring 

the RVP of the fuel in the underground tank. Monitoring at the 

beginning of each day of testing would be advisable. Of 

course, an initial fuel/vapor equilibrium must exist in the 

underground tank before beginning any measurements. 

Fourth, your test plan should specifically address 

dispensing rates, the frequency of refueling events, and the 

amount of fuel to be dispensed during each refueling event 

since these factors are likely to affect emissions. High and 

low bound values may be a useful approach. Also, since 

emissions could occur even when the pumps are closed, emission 

measurements should be taken continuously (24 hours a day) over 

a number of days for each condition. Testing over a number of 

days would also account for any meteorological effects (temp, 

pressure, relative humidity) on emissions. 

Fifth, when evaluating the effect of Stage II controls on 

emission rates your test plan should ensure that the fuel/vapor 

in the experimental fuel tank is typical of that which would be 

expected for those ambient conditions. Fuel in the 

experimental tank should be 5 to 10 °F warmer than ambient 

temperature and weathered approximately 0.5 - 1.0 psi as 

compared to the fuel being dispensed. Also, the test approach 

used should ensure that the vapor space in the experimental 

tank is saturated before fuel is dispensed. This will ensure 

that the vapors returned to the underground tank are typical of 

that expected in the field, and will allow the emission effects 

of vapor cooling and liquid/vapor equilibrium for all the 

species to occur. As part of any experiment it would be 

important to have an idea of the efficiency of the Stage II 

system being used. 
• - * - -3-

Fmally, a few other thoughts. First, your 

instrumentation approach looks good; it should allow continuous 

monitoring of the vent outlet. Second,, it might be worthwhile 

to speciate the liquid fuel and samples of the underground tank 

vapor, breathing/emptying losses, and the vapor returned to the 

underground? tank from the experimental tank during the Stage II 

portion of the program. This information could prove useful in 

any later analyses. Also, since the instrumentation and other 

apparatus are already set up, it would definitely be worthwhile 

to measure breathing loss emissions alone (no refueling events) 

and breathing/emptying loss emissions with a pressure/vacuum 

valve or limiting orifice within the vent tube to control 

emissions. This could prove to be a very inexpensive control 

technique. 

I hope these ideas are useful. if we can provide any 

further ideas or information please contact Glenn Passavant of 

my staff at 374-8408 (FTS). 

Sincerely yours, 

ORIGINAL SIGNED BY 

CHARLES L GRAY, JR. 

Charles L. Gray, Jr. 

Director 

Emission Control Technology Division 

cc: Teri Richman, Citizens for Improved Air Quality 

Docket A-87-11