Sunday, September 12, 2010

Michigan General Permit for Diesel Generators Suspended

The Michigan Department of Natural Resources and Environment (MDNRE) General Permit to Install for Diesel Fuel-Fired Engine Generators has been suspended from use due to the new federal National Ambient Air Quality Standard (NAAQS) for nitrogen dioxide (NO2). Any general permits previously issued for diesel-fired generators will remain in effect.

On January 22, 2010, the US EPA promulgated a final rule containing a new NAAQS for NO2 based on a 1-hour averaging time. On April 12, 2010, 188 µg/m3 became effective as the 1-hour NAAQS for NO2 . The applicability criteria and special conditions in the general permit for generators have been reevaluated by MDNRE to determine the impact of this new standard. Dispersion modeling was done for a hypothetical generator to determine the maximum ambient 1-hour N02 concentration. A representative building and various stack parameters were used and the modeling assumed the generator stack to be an isolated facility with no other sources considered in the analysis. All alternative stacks showed a total impact to be above the 1-hour NO2 NAAQS.

Because the current general permit for diesel generators does not limit NO2 emissions to adequately ensure compliance with the new 1-hour NO2 limit the permit is being suspended from use at this time. Until the general permit for diesel-fired generators is revised, a case-by-case permit to install pursuant to Rule 201 is being used for diesel-fired generators.

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