Updated flare modelling guidance under the local air quality regulation

The ministry considered the comments related to the proposal received during and after the posting, four comments in total.

The following is an overview of the themes in the comments received during the consultation period and the ministry’s responses:

1. MFR approach is still extremely conservative, so facility still needs to be provided options to develop site-specific alternative approaches.

Response: The Flare Modelling Technical Bulletin is the ministry’s preferred approach to modelling flares. However, the ministry recognizes that facilities may want to use refined alternative approaches to determine the site-specific flare modelling parameters. Accordingly, section 2.4 of the Flare Modelling Technical Bulletin details how facilities that would like to further refine their assessments by incorporating additional site-specific elements (For example, use of hourly variations in flame tilt, use of steam or air assist, consideration of operating conditions in use of stack tip/flame downwash, etc.), can request approval to do so (For example, request a Notice under section 13.1 of O. Reg.419/05).

The ministry has decided not to update the Flare Modelling Technical Bulletin to include a new approach for modelling a phenomenon known as stack tip/flame downwash, which can occur under certain flare operating conditions. This is because as noted above, the new approach, known as the momentum flux ratio approach (MFR), can be considered upon request, on a case-by-case basis.

The ministry is open to continuing to work with facilities to explore opportunities to develop refined alternative approaches. However, all requests must include detailed documentation (For example, rationale/scientific evidence for the approach such as scientific research papers, video evidence, etc., data/assumptions used, sample calculations, etc.) that supports how the alternative approach reasonably captures the flare’s unique behaviour.

2. The requirement for facilities to request ministry approval to use the MFR approach is a regulatory burden that could be reduced.

Response: Under the Local Air Quality regulation (O. Reg. 419/05), facilities are required to obtain approval under section 7(1) to use non-default options, including the MFR approach, when modelling with the ministry’s approved models. This approach is consistent with the U.S. EPA, the developer of the AERMOD model (the ministry’s principle regulatory air dispersion model).

Obtaining approval prior to undertaking any modelling assessment provides certainty to facilities that they have applied the MFR approach reasonably, thus avoiding potential delays and additional costs that could occur if an issue is identified after the modelling assessment has been completed (For example, modelling may need to be re-done).

3. MFR approach will not result in modelled sulphur dioxide (SO₂) concentrations that are reasonably representative of actual conditions given the significant SO₂ levels in the Sarnia area.

Response: The proposed MFR approach, based on the latest peer reviewed science on flare behavior, would allow regulated facilities to better account for the unique properties and behaviour of flares by incorporating additional site-specific elements (see attached Technical Rationale for the Momentum Flux Ratio Approach).

Although the ministry has decided not to update the Flare Modelling Technical Bulletin to include the MFR approach, use of the new, non-default MFR approach can be considered upon request, on a case-by-case basis, provided that there is sufficient technical rationale.

A facility is required to obtain ministry approval before it can use any alternative or non-default approach to modelling, including the MFR approach. All requests must include detailed documentation (For example, rationale/ scientific evidence for the approach such as scientific research papers, video evidence, etc., data/assumptions used, sample calculations, etc.) that supports how the alternative approach reasonably captures the flare’s unique behaviour. Obtaining approval prior to undertaking any modelling assessment ensures that facilities are applying alternate approaches including the MFR approach, appropriately such that the resulting concentrations are reasonably representative.

Additional Comments:

Comments were also received relating to other aspects of the Flare Modelling Technical Bulletin beyond the purpose of the proposal. Consultations were previously conducted for the Air Dispersion Modelling Guideline for Ontario (ADMGO) and the associated Flare Modelling Technical Bulletin through proposal 012-4164 which was posted on the Environmental Registry for 60 days from December 18, 2015 to February 16, 2016.

As such, comments that were not directly relevant to the proposed update to the Flare Modelling Technical Bulletin (i.e., to specifically include the MFR approach) were considered out of scope.