October 1, 1999

Paul Dubenetzky, Chief
Permits Branch
Office of Air Management
Indiana Department of Environmental Management
100 North Senate Avenue
P.O. Box 6015
Indianapolis, Indiana 46206-6015

Dear Mr. Dubenetzky:

This letter will clarify the United States Environmental Protection Agency's (USEPA) positions with regard to emission limits for the AlliedSignal synthetic minor modification in St. Joseph County.  The proposed project includes 21 chemical vapor deposition (CVD) unit flares used to control volatile organic compounds (VOC) from the existing facility which manufactures airline braking systems.  This existing project was constructed without a permit, and is believed to have had VOC emissions in excess of the Prevention of Significant Deterioration (PSD) threshold.

The facility is a major stationary source for VOC’s, and is therefore, subject to the PSD significant emission thresholds of 40 tons per year of nitrogen oxide (NOx) emissions and 100 tons per year for carbon monoxide (CO).

The Indiana Department of Environmental Management (IDEM) has conducted three official stack tests to determine appropriate emission factors for this permit.  The first two tests generated emission factors that calculated CO emissions from the CVD flares to be above the significance threshold.  The third test was conducted above a flare temperature of 1000 degrees Fahrenheit, which calculated emissions to slightly below the CO significance threshold.  AlliedSignal assumed that this single stack test would be representative of the entire process, as long as the flare temperature is consistently held above 1000 degrees Fahrenheit as a federally enforceable condition.  While it is questionable that the source can continuously operate above this temperature level, more official stack testing should be conducted to verify the relationship between flare temperature and emissions of CO and NOx.

The USEPA encourages the use of stack test data for the development of emission factors over the use of AP-42 factors, the unpredictable nature of the CVD process sheds doubt on the accuracy of the third stack test.  USEPA also recalculated the “worst case” Potential to Emit (PTE) emissions for CO and NOx using information provided in the AlliedSignal technical support document.  These calculations indicate that AlliedSignal may exceed the CO PSD modification threshold.  It is at the source’s (and IDEM’s) discretion, however, to use the most accurate emission factor available for the calculation of PTE, as long as the source can show compliance with that limit.

The USEPA is concerned that, due to the highly variable nature of the CVD process, the source may not be capable of complying with their established limits on a continuous basis.  AlliedSignal has suggested an hours of operation and pound per hour (lb/hour) limitation on all their CVD units and flare controls.  Stack tests conducted for purposes of compliance may only show the emissions at a specific moment in time, and not be representative of AlliedSignal’s continuous compliance of the lb/hour limit in this dynamic process.

According to the June 13, 1989 USEPA memorandum, “Guidance on Limiting Potential to Emit in New Source Permitting” from John S. Seitz of the Office of Air Quality Planning and Standards,
USEPA believes, that with the current information available, IDEM should consider the use of a CEM, or, if more official stack testing is conducted to verify the relationship between flare temperature and emissions of CO and NOx, a continuous temperature monitor may be considered for each CVD unit.  These monitors may not only assure that this modification is minor for PSD, but their use will generate additional data for any CVD units permitted in the future.  The USEPA also understands that these CVD units may emit a large amount of hazardous air pollutants (HAPs); such as naphthalene and benzene.  Periodic stack testing


may be needed for HAPs of concern to assure that these units are not subject to section 112(g) of the Clean Air Act.

Finally, IDEM must consider how the November 17, 1998, USEPA memorandum from Eric V. Schaeffer, of the Office of Regulatory Enforcement, titled, “Guidance on the Appropriate Injunctive Relief for Violations of Major New Source Review Requirements”, applies to this source.  This memorandum discusses how PSD requirements may be applied to a source which has constructed without a permit, and had actual emissions at a level above the PSD threshold.

We look forward to working with your office on these permit issues.  If you have any questions, please call Kushal Som, of my staff, at (312) 353-5792.

Sincerely yours,

/s/ (10/01/99)

Pamela Blakley, Acting Chief
Permits & Grants Section (IL/IN/OH)