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OAR Box 1787 

Prepped by Ollie Stewart 

Document Number: 

49) ll-C-7 

Docket Number: 

A-90-37 

Printed 11/4/2008 10:22:19 AM Sheet 49 of 147 
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MAR ciT 1294. 

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

REGION 5 

AIR AND RADIATION DIVISION 

77 WEST JACKSON BOULEVARD 

CHICAGO, IL 60604-3590 

APR OS 1993 

REPLY TO THE ATTENTION OF: 

(AT-18J) 

jib 

Dennis Drake, Acting Chief 

Air Quality Division 

Michigan Department of Natural Resources 

P.O. Box 30028 

Lansing, Michigan 48909 

Dear Mr. Drake: 

This letter concerns a proposal by General Motors (GM) to burn 

natural gas in existing industrial boilers at an estimated 16 sites 

in the State of Michigan, and 12 other sites in Region 5. The units 

at issue currently burn coal or fuel oil. During a February 23, 

1993, telephone conference between GM, the United States 

Environmental Protection Agency (USEPA), and the Michigan Depa:rtment 

of Nattiral Resources to discuss these alternate fuel projects, GM was 

asked to provide a demonstration that a change in fuels would not 

affect future auto production rates at these facilities. 

The data provided by GM in a March 9, 1993, letter indicate that the 

utilization rate of the boilers would not be influenced by a switch 

to this more economical fuel because (1) the total steam cost at a 

given plant is insignificant when compared to the total operating 

cost at that plant, and (2) the steam production is primarily 

determined by climate conditions, not auto production rates. 

The New Source Review (NSR) regulatory provisions require that a 

proposed pnysical change result in an increase in actual emissions in 

order for the change to be considered a modification and therefore 

subject to NSR. See, e.g., 40 Code of Federal Regulations 

52.21(2)(i). In this case, the proposed switch to natural gas at 

various GM facilities will result in substantial reductions in the 

emissions factors of particulate matter, sulfur dioxide, and, in most 

cases, oxides of nitrogen, as well as air toxics. The use of natural 

gas will also result in a substantial cost savings for the source. 

In general, where a source makes a change that reduces the costs of 

production, such changes usually affect the utilization of the 

facility. In this case, GM has clearly demonstrated that the 

utilization rate of the boilers will not be affected by the proposed 

fuel switch to natural gas. Consequently since the emissions factors 

for all relevant pollutants will decrease and neither the rate of 

production nor hours of operations of the facilities will increase as 

a result of the change, USEPA has determined that the proposed 
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projects will not result in an increase in emissions. Therefore, 

based on the specific circumstances and data presented, it is USEPA's 

view that GM's proposed natural gas conversion projects should not be 

considered a major modification under the Federal New Source Review 

regulations. 

If you have any questions with regard to this letter, please contact 

me. 

Sincerely yours, 

— y 

David Kee, Director 

Air and Radiation Division 
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standard bcc's: official file copy w/attachment(s) 

originator's file copy w/attachment(s) 

originating organization reading file w/attachment(s) 

other bcc's: D. Kee, ARD 

K. Berry, OAQPS 

B. Tyndall, OGC 

:D. Crumpler, OAQPS 

S. Rothblatt, RDB 

G. Gulezian, ATRB 

G. Czerniak, AEB 

R. Van Mersbergen, RDB 

ARD:ATRB:GMPES:CAMPBELL:cc:4/1/93 

DISKETTE/FILE:F:\USER\CCAMPBEL\MDNR.GM 

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