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OAR Box 1778 

Prepped by Ollie Stewart 

Document Number: 

93) ll-C-35 

Docket Number: 

A-90-06 

Printed 10/28/2008 9:50:55 AM Sheet 93 of 276 
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£%"\ UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

-• ^&7 S Office of Air Quality Planning and Standards 

i^lhfr'/ Research Triangle Park, North Carolina 27711 

JAN 1 8 1990 

Mr. Morton Sterling, Director 

Environmental Protection 

Detroit Edison Company \X<y ,-,• n 

200 Second Avenue, 482 WCB \xi'\\ m \ ? ^ ' \ 

Detroit, Michigan 48226 fe.; J .;. 

Dear Mr. Sterling: 

This is a followup to the October 19, 1989 meeting during which Detroit 

Edison further discussed its position that the addition of natural gas firing 

capacity to the Greenwood Unit I Power Plant should not be subject to a 

prevention of significant deterioration (PSD) review. At the meeting, you 

requested that Environmental Protection Agency (EPA) Headquarters review 

Region V s previous determination that the proposed fuel conversion was a 

"major modification" for PSD purposes. 

As you are aware, in a letter dated December 20, 1988, EPA Region V 

concluded that the proposed conversion of the oil-fired Greenwood Unit to dual 

capacity for oil and gas firing would subject the plant to a PSD review for 

nitrogen oxides (NOx). The Region's conclusion was based on a determination 

that 1) the source was not capable of firing natural gas prior to January 6, 

1975 (and therefore was not covered by the PSD exemption for modifications 

under 40 CFR 52.21(b)(2)(iii)(e)(l)); and 2) there would be a significant net 

increase of N0X resulting from the change. As you have requested, we have 

reevaluated this finding in light of the additional information submitted by 

Detroit Edison during the October 19 meeting. 

The information presented by Detroit Edison indicates that the emissions 

unit at the source was initially designed and permitted to fire both oil and 

gas. However, there is no evidence to demonstrate that the source as a whole 

had, or at any time initiated construction on, the equipment necessary to 

deliver natural gas to the combustion unit. Without such equipment, it would 

not be possible for the source to utilize natural gas as an alternate fuel. 

Consequently, it is our view that the source was not capable of accommodating 

natural gas prior to January 6, 1975. Therefore, the changes necessary to 

accommodate the firing of natural gas at the Greenwood Plant would, for PSD 

purposes, be considered a "physical change" to the source. 

As requested, we have also evaluated the net emissions change at the 

source that would result from the modification. It is Detroit Edison's 

position that the large decreases in "allowable" emissions of sulfur dioxide, 

particulate matter, and NOx when burning natural gas rather than oil as a 

result of the modification, warrants special consideration. Specifically, 

Detroit Edison feels that the use of a cleaner fuel at the Greenwood Plant 

warrants a finding that there is no increase in actual emissions and 

accordingly no "major modification." 
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Under the PSD regulation, a "major modification" occurs when the 

physical or operational change at the source (in this case the installation of 

natural gas handling facilities and the firing of natural gas) would result in 

a significant net emissions increase for any regulated pollutant at the 

source. Whether the proposed use of natural gas at the Greenwood Plant would 

result in a "significant net emissions increase" depends on a comparison 

between the "actual emissions" before and after the physical or operational 

change. Where, as here, the source has not yet begun operations firing 

natural gas, "actual emissions" after the change to natural gas firing are 

deemed to be the source's "potential to emit" for that fuel [see 40 CFR 

52.21(b)(21)(iv)]. Potential annual N0X emissions when firing natural gas at 

the Greenwood Plant greatly exceed its current actual emissions. Therefore, 

as a result of the ability to fire natural gas after the change, the emissions 

of N0X at the source would experience a "significant net emissions increase," 

within the meaning of the PSD regulations. The fact that current annual 

"allowable emissions" for the Greenwood Plant when firing oil may greatly 

exceed future allowable (or potential) emissions when firing natural gas is 

not relevant for PSD applicability purposes. See Puerto Rican Cement Co.. 

Inc. v. EPA No.89-1070 (First Circuit) (slip op. October 31,. 1989). 

In summary, our review indicates that Region V correctly applied the PSD 

applicability criteria. 

The PSD requirements include an air quality and additional impact 

analysis and the application of best available control technology (BACT). The 

BACT requirement applies to "each proposed emissions unit at which a net 

emissions increase would occur as a result of a physical change or change in 

the method of operation in the unit" [see 52.21(j)(3)]. Consequently, 

although the addition of gas firing would subject the source as a whole to a 

PSD review, the requirement to apply BACT is applicable only to those 

emissions units at the source which undergo both a physical or operational 

change and a significant net emissions increase. It appears that the only 

emissions unit at the Greenwood Plant affected by the proposal to fire gas 

would be the existing boiler. Historically, it has been EPA's policy that 

where the individual boiler being converted is capable of accommodating the 

alternate fuel, BACT would not apply. 

In this case, in addition to the physical changes at the source 

necessary to deliver natural gas to the existing boiler, a number of canes 

capable of burning natural gas would be installed in the existing burner 

assemblies. Modifications to the unit's overfired air duct are also planned. 

We also understand that there will be no changes in the present oil burning 

system, which will be retained. 

Our review indicates that, bv itself, the addition of gas canes to the 

burners is not a physical change or change in the method of operation in the 

unit and, consequently, would not subject the boiler to a BACT review. 

Therefore, if the sole change to the boiler is the addition of the canes, 

then, in this case, the only requirements necessary for a PSD permit are an 

air quality analysis, additional impacts analyses, and (if applicable) a 

Class I impact analysis--the application of BACT is not required. However, 

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the information submitted by Detroit Edison indicates that changes to the 

boiler's overfired air duct are also planned. At this time, without 

additional information on the nature and scope of the work to be done on the 

overfired air duct, we cannot determine whether these are physical or 

operational changes to the boiler that are necessary to make the boiler 

capable of accommodating natural gas. If the ducting work is necessary for 

this purpose, then a BACT analysis would likely be required. 

In addition, it is unclear from the information submitted whether 

Detroit Edison plans to undertake further modifications to the boiler which 

would allow 100 percent load when firing natural gas. Currently, the unit as 

presently configured has the potential of'achieving only 75 percent load when 

firing natural gas. To achieve a higher load, substantial modifications to 

the unit apparently would be required. These types of physical changes to the 

boiler likely would require a full PSD review, including a BACT analysis for 

the boiler. The BACT analysis would require that the source evaluate the use 

of all available additional air pollution controls for reducing N0X emissions. 

The analysis would consider retrofit costs for add-on controls and the fact 

that gas is a relatively clean-burning fuel. Consequently, in this case, it 

is possible that the currently planned use of a low-N0x burner design may be 

BACT for gas firing. However, such a conclusion would have to be demonstrated 

through the requisite BACT analysis. I have asked Region V to work with you 

should you need assistance in preparing the analysis. 

Gerald A. Emison 

Director 

Office of Air Quality Planning 

and Standards 

cc: J. Calcagni, EPA/AQMD 

D. Kee, EPA/Region V 

G. Foote, EPA/OGC