UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

Office of Air Quality Planning and Standards 

Research Triangle Park, North Carolina 2771 1 

3 0 MAR 1994 

MEMORANDUM 8 

SUBJECT: Nitrogen Oxides (NOx) Questions from the Ohio EPA 

FROM : G.T. Helms, Chief 

Ozone/Carbon (MD-15) 

TO: George Czerniak, Chief 

Regional Air Compliance Branch 

EPA Region V 

This memorandum addresses the NOx reasonably available 

control technology (RACT) issues raised in a November 30, 1993 

memorandum from Richard Schleyer, EPA Region V, to John Silvasi. 

These issues were discussed and resolved by the NOx work group. 

Ouestion 1: Can the NOx RACT rules be made applicable only 

F- during the summer months since ozone is a summer problem? If 

not, why not? 

Answer: The EPAfs RACT guidance for volatile organic 

compounds (VOC) states that seasonal controls are generally not 

allowed (EPA clarification to appendix D of the November 24, 1987 

Federal Reqister, "Issues Relating to VOC Regulations Cutpoints, 

Deficiencies, and DeviationstW revised January 1, 1990). As 

stated in the NOx Supplement to the General Preamble (57 FR 

55625, November 25, 1992), the VOC RACT guidance is generally 

applicable to NOx RACT. Thus, the limitation on seasonal 

controls also applies to NOx RACT. 

The EPAfs definition of RACT is "the lowest emission 

limitation that a particular source is capable of meeting by the 

application of control technology that is reasonably available 

considering technological and economic feasibilitym (44 FR 53762, 

September 17, 1979). Thus, RACT is not generally a function of 

season or other temporal factors. There are limited exceptions, 

however, in the VOC and NOx programs where seasonal controls are 

allowed. For example, EPA has developed RACT guidance for 

seasonal controls concerning cutback asphalt (VOC) and fuel 

switching (NOx) . 

Question 2: Comments have been received that a 30-day - rolling average should be allowed using stack tests. The Ohio 

EPA is not aware of any method other than use of a continuous 
emissions monitor where a 30-day rolling average is possible. Is 

there any other possible method? 

Answer: This issue should be addressed in the context of 

the enhanced compliance monitoring rulemaking, which is in 

process. 

guestion 3: If a source is subject to a bderallyenforceable permit to install, which requires best available 

control technology (BACT), would the facility have to submit a 

RACT study or meet any of the other requirements contained in 

Ohio's NOx RACT rules? 

Answer: RACT requirements can, in some cases, be more 

stringent than the lowest achievable emission rates (LAER) or 

BACT (see February 28, 1990 memorandum from John Calcagni to 

Regional Offices). Therefore, where a source has already 

installed BACT or LAER, the State would still need to complete an 

analysis to show that BACT or LAER is at least as stringent as 

RACT in that cask If RACT is more stringent, then the RACT 

requirements would apply. 

Question 4: Is one-source trading allowed? For example, if 

a source uses selective noncatalytic reduction to control NOx, 

ik could the source simply turn on and turn off this control device, 

as necessary, to comply with NOx RACT? 

Answer: Once a State sets a NOx RACT emission rate limit 

for a source category, individual sources are generally free to 

meet that limit in a variety of ways. For example, where a State 

adopts a NOx RACT emission rate limit with a long averaging time, 

such as 30 days, a source with a continuous emission monitor 

could conceivably turn on and turn off very stringent controls on 

alternate days and still meet the RACT limit. States should, 

however, avoid adopting RACT rules which could result in sources 

maximizing their emissions on high ozone potential days, thus 

jeopardizing attainment. 

Questions 5 & 9: Will partial switching to natural gas (cofiring gas and coal) need a State implementation plan (SIP) 

revision? Are site-specific SIP revisions needed if a source is 

complying with NOx RACT using fuel switching? 

Answer: Individual sources that switch to natural gas do 

not need source-specific SIP revisions as long as the statewide 

NOx RACT rules allow such switching and are consistent with EPA 

guidance (July 30, 1993 memorandum from Michael H. Shapiro to 

Regional Offices on fuel switching to meet the NOx RACT 
requirements). If there is no such statewide rule, then a SIP 

revision would be needed to meet the NOx RACT requirements. 

Question 6: Can major NOx sources that only operate outside 

the ozone season be exempt from NOx RACT? 

Answer: The RACT requirement applies to major stationary 

sources, considering potential annual emission&. However, major 

NOx sources which are prohibited from operating during the ozone 

season might qualify for an exemption from the NOx requirements 

under section 182(f) of the Clean Air Act. The EPA would 

consider a petition requesting such an exemption. 

Question 7: Will compliance schedule changes up to April 1, 

1996 be allowed without a SIP revision? 

Answer: Sources that do not meet milestones contained in 

the State's NOx RACT rule would be subject to enforcement 

actions. 

-. 

Question 8: Is switching from coal to oil, or oil to 

natural gas allowed under the fuel-switching program? If yes, 

what limits would apply in either case? 

n Answer: The EPA's guidance on fuel switching to meet NOx 

RACT (referenced in answer 5) is not limited to coal-to-natural 

gas switches. That guidance would need to be applied in each 

case to determine the applicable emission limits. 

Question 10: Are site-specific SIP revisions needed if a 

source is complying with NOx RACT using an emissions trading 

program? 

Answer: Individual sources that comply with NOx RACT 

through an emissions trading program do not need source-specific 

SIP revisions as long as the statewide NOx RACT rules provide for 

such a trading program and are consistent with EPA guidance 

(reference forthcoming NOx trading guidance memo). If there is 

no such statewide rule, then a SIP revision would be needed to 

meet the NOx RACT requirements. 

cc: Air Branch Chief, Regions I-X 

NOx Work Group