Project Number:

1822

Burlington Electric Department

SERVICE:

NO2 Modeling

DESCRIPTION:

Tech provided refined annual and 1-hour NO2 modeling for the McNeil Station for the Burlington Electric Department to assess compliance with the annual ambient air quality standard and 1-hour state guideline. This ISCST3 modeling was performed at the request of the Vermont ANR APCD in support of potential litigation. Despite showing an insignificant annual air quality impact at all modeled receptors, the biomass boiler was modeled with seven interacting sources, as requested by the Vermont Agency of Natural Resources (ANR) Air Pollution Control Division (APCD). The cumulative results were also added to a conservative annual average background concentration for comparison to the annual air quality standard. The modeling followed US EPA and Vermont ANR APCD guidelines. A modeling protocol for this project was approved in advance by the VT ANR APCD.

The modeling demonstrated that the operation of the McNeil boiler results in maximum air quality impacts which are below the significant impact level designed by the US EPA. Maximum predicted total NO2 impacts, including the McNeil boiler, the interacting sources, and a conservative annual average background NO2 concentration, were in compliance with the annual Vermont and National Ambient Air Quality Standards (NAAQS) for NO2. The modeling also indicated that the maximum one-hour NO2 impact from the McNeil Station, when added to a conservative one-hour NO2 background concentration, is less than the value of the Vermont one-hour NO2 standard. Although, there is a federal one-hour NO2 standard today, this Vermont on-hour standard had been proposed in 1989, but was never adopted.

Tech also provided a BACT analysis for biomass boilers for BED as part of this project.

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Key Points

  • The potential impacts of one hour NO2 emissions were estimated and modeled.
  • When added to background, the one hour NO2 impact was determined to be below the threshold of concern.