Ontario proposes changes to air dispersal models for regulatory compliance

By Dr. Franco Di-Giovanni, AirZOne Inc.

The Ontario Ministry of Environment proposed replacing the Regulation 346 dispersal model with models from the US Environmental Protection Agency on March 20, 2001. The MOE plans a revised modelling guide describing a tiered approach for Certificate of Approval (CoA) applications. The screening-level SCREEN3 model will be used for the first tier as an interim until a screening version of AERMOD is produced. If necessary, more sophisticated second tier models will be used, AERMOD and ISC-PRIME (in case of appreciable pollutant downwash, until AERMOD is modified with the PRIME code as proposed).

The new guide will be finalized in 2002 with a 3-5 year phase-in period. In the interim, CoAs can use the old model. If, under certain conditions, the old and new models differ, possibly affecting facilities' regulatory status, it is the responsibility of the facility to apply the new models and ensure regulatory compliance.

Comprehensive Certificates of Approval (Air)

To streamline management of CoAs and MOE's approval process, Comprehensive CoAs are now acceptable. Unlike standard, source-specific CoAs, Comprehensive CoAs itemize all sources of a facility's air emission on one Certificate, to enhance operational flexibility, since amendments are no longer needed when circumstances change as long as compliance is demonstrated. It requires, as a prerequisite, maintenance of an emission inventory database and participation in the Ministry's Air Standard-setting process. This permitting alternative is a valuable tool for larger facilities, or those where plant modifications are frequent.

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