From: "Lindsey W. Kroos" <lkroos@ALL4INC.COM>

To: Ketan Patel/RTP/USEPA/US@EPA

Cc: "Selin Hoboy" <SHoboy@STERICYCLE.com>, "Wigmore, Michael B."

<Michael.Wigmore@bingham.com>, "Kristin Gordon" <kgordon@ALL4INC.COM>,

"William Straub" <wstraub@ALL4INC.COM>

Date: 10/27/2009 09:18 AM

Subject: Question Around Final HMIWI NSPS Emission Limit

Dear Ketan,

As mentioned during our call on October 9, 2009, we have a question around the promulgated

NOx emission limit for the new large HMIWI source category. According to the July 2, 2009

memo entitled “Revised MACT Floors, Data Variability Analysis, and Emission Limits for Existing

and New HMIWI,” there were a few cases where the statistical analysis used to determine

emission limits for the new HMIWI source category resulted in values less stringent (i.e., higher)

than the corresponding emission limits for the existing HMIWI source category. This situation

occurred for CO, CDD/CDF, and NOx for the large HMIWI source category; and HCl and Pb for

the medium HMIWI source category. In these cases, the emission limits for the new HMIWI

source category were set equal to the corresponding emission limits for the existing HMIWI

source category.

For example, the statistical analysis for CO for the new large HMIWI source category resulted in

a 99% UCL value of 11.3, which, when rounded up to two significant figures pursuant to the

standard engineering practices used throughout the rule development, would result in an

emission limit of 12 ppmvd. This emission limit would be less stringent than the 11 ppmvd CO

emission limit for the existing large HMIWI source category. Therefore, according to the

approach described in the memo, the CO emission limit for the new large HMIWI source

category was set equal to the 11 ppmvd emission limit for the existing large HMIWI source

category.

However, it appears that the approach for establishing the NOx emission limit for the new large

HMIWI source category was inconsistent with the approach described in the memo and

highlighted above. The 99% UCL value for NOx for the new large HMIWI source category was

144, which, using the procedure outlined above, would round up to result in an emission limit

of 150 ppmvd. Since this 150 ppmvd emission limit would be less stringent than the 140 ppmvd

NOx emission limit for the existing large HMIWI source category, we anticipated that the NOx

emission limit for the new large HMIWI source category would be set equal to the 140 ppmvd

emission limit for the existing large HMIWI source category. However, the resulting NOx

emission limit for the new large HMIWI source category in the final rule is 130 ppmvd as found

in Table 1B to Subpart Ec of Part 60

– Emission Limits for Small, Medium, and Large HMIWI at

Affected Facilities as Defined in § 60.50c(a)(3) and (4).

For your convenience, the description of the approach used to establish emission limits for the

new HMIWI source category can be found on page 12 of the memo. The resulting NOxemission limit for the new large HMIWI source category can be found in Table 7 entitled

“Summary of MACT Floor Results for Option 1A for New Sources.”

Please don’t hesitate to let us know if you have any questions.

Thank you,

Lindsey

Lindsey W. Kroos

Project Engineer

All4 Inc.

2393 Kimberton Road

— P.O. Box 299

Kimberton, PA 19442

‐ 0299

p: 610.933.5246 x 22

— f: 610.933.5127

lkroos@all4inc.com

www.all4inc.com

Your environmental compliance is clearly our business.