p.1 

OAR Box 1787 

Prepped by Ollie Stewart 

Document Number: 

7DII-C-29 

Docket Number: 

A-90-37 

Printed 11/4/2008 10:22:19 AM Sheet 71 of 147 
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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

Office of Air Quality Planning and Standards 

Research Triangle Park, North Carolina 27711 

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JUL 28 887 

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HP. Richard E. Grusnldc 

Chief 

Air Division 

Alabama Department of Environmental Management 

1751 Federal Drive 

Montgomery, Alabama 36130 

Dear Mr. Grusnick: 

This is in response to your June 19, 1987, letter concerning best 

available control technology (BACT) determinations. The fssues you raise 

highlight perhaps the most crucial aspects of BACT determinations, and I 

hope that the following responds adequately to them. 

The first issue you raised concerns the role of new source performance 

standards (NSPS) in BACT determinations. The NSPS are established after 

long and careful consideration of a standard that can be reasonably 

achieved by every new source anywhere in the nation. This means that 

even a very recent NSPS does not represent the best technology available; 

it Instead represents the best technology available nationwide, regardless of climate, water availability, and many other highly variable 

case-specific factors. The NSPS 1s the least common denominator and must 

be met; there are no variances. The BACT requirement, on the other hand, 

is the greatest degree of emissions control that can be achieved at a 

specific source and accounts for site-specific variables on a case-by-case 

basis. 

Since an applicable NSPS must always be met, it provides a legal 

"floor" for the BACT, which cannot be less stringent. A BACT determination 

should nearly a7ways be more stringent than the NSPS because the USPS 

establishes what every source can achieve, not the best that a source 

could do. In only a few BACT cases should you encounter the s .me criteria 

that limited the stringency of the NSPS, so BACT should usually be more 

stringent than the NSPS. 

States, as you pointed out, don't always have the technical expertise 

that is available to EPA, For that reason, the BACT determination process 

best for many agencies is that which 1s currently used by many State/local 

permit agencies. This process consists of requiring the source to either 

use the most stringent control technology or to show 1n detail why 1t 

cannot. The BACT/LAER* Clearinghouse is often used-to find the most 

stringent control technology, as are calls to experienced permit review 

* lowest achievable "emission rate 
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engineers in other States, discussions with control equipment manufacturers, 

and reviews of literature such as the Mcllvaine newsletter. This approach 

was alluded to by the EPA Administrator 1n the recent H-Power remand 

(copy enclosed) where it states that "substantial and unique factors must 

be shown to Justify a less efficient control technology.* For additional 

detail on this approach, contact Wayne Blackard, Chief, New Source Section, 

EPA, Region IX, 215 Fremont Street, San Francisco, California 94105, 

(415) 974-8249. 

The second issue involves the relationship between 8ACT and air 

quality Impacts. Tha application of BACT is a specific requirement for a 

prevention of significant deterioration (PSD) permit that stands alone in 

the sense that, as a minimum, a PSD source must Install BACT regardless 

of the air quality impact, Tn other words, BACT 1s BACT, even 1f the 

source would only consume 5 percent of the available Increment. I certainly 

did not mean to imply that EPA "decides" how much increment a source can 

have; EPA does, however, have oversight responsibilities In BACT decisions. 

In your example, EPA would not deny a permit to a source consuming 95 

percent of the increment provided all else was acceptable, including the 

BACT determination. However, modeled violations of a national ambient 

air quality standard or PSD increment may drive a BACT determination to a 

greater level of control. Itfiat we would deny is a permit for a source 

where a BACT determination was "relaxed" (or even no control at all was 

required) simply because the source did not consume all of the increment. 

Other aspects of the environmental impact of the BACT decision occur 

when a control option increases the emissions of one pollutant while 

reducing emissions of another, or a control option may produce an environmentally harmful byproduct. For example, the use of water injection in 

controlling nitrogen oxides from gas turbines will increase carbon monoxide 

emissions. 

In summary, section 169 of the Clean Air Act defines BACT as "based 

on the maximum degree of reduction .. . on a case-by-case basis." Consequently, BACT represents the best level of control the source can provide 

and should not be based on a category-wide minimal standard like an 

applicable NSPS. 

Sincerely, 

CWef 

New Source Review Section 

1 Enclosure 

cc: Bruce Miller 
P.4 

For enclosure to docket item II-C-1, July 28, 1987 letter from Gary McCutchen to Richard 

Grusnick, see docket item indicated. 

II-K-2 Honolulu Resource Recovery Facility PSD Appeal No. 86-8 Remand, June 

22,1987.