Risk Management Review/Ambient Air Quality Analysis Process

During the course of the project evaluation process, the District must perform an analysis to evaluate the potential impact of the proposed project on the health of the surrounding public. The District does not issue permits for projects that will create a significant health risk.

This analysis evaluates three areas of exposure:

The cancer risk, defined as the long term exposure to the emissions from a project over a lifetime (70 years),
The Acute Hazard Index, defined as the short term exposure to the maximum 1 hour emissions from a project, and
The Chronic Hazard Index which is the long term non-cancer exposure, greater than 1 hour and less than or equal to 1 year, to the emissions from a project.

To perform a Risk Management Analysis, a complex computer modeling program is used to determine the concentration of the identified pollutant(s) at the location of the nearest resident(s) or worksite(s). The projected concentration of each pollutant is then compared to National and State standards, and is analyzed for the potential to create a health risk.

Projects or permit units with a cancer risk equal to or exceeding 1 in one million are required to satisfy Toxic Best Available Control Technology (T-BACT) requirements, by installing the best technology to control those emissions. Projects or total facilities with cancer risk equal to or exceeding 20 in one million are not approvable. Projects or total facilities with acute or chronic hazard index equal to or exceeding 1 are not approvable.

In addition, per District Rule 2201, an Ambient Air Quality Analysis (AAQA) is required to be performed for all New Source Review (NSR) projects subject to public notice. The purpose of the AAQA analysis is to determine whether a new or modified Stationary Source will cause or make worse a violation of a State or National ambient Air Quality Standard (AAQS).