Dispersion Modelling Reviews

Metro Vancouver staff include qualified professionals who conduct dispersion model reviews to ensure consistency between projects and maintain a level playing field.  Metro Vancouver also requests that other agencies provide comment on dispersion model results in specific areas such as human health.

Internal Dispersion Modelling Review Process

Metro Vancouver has a rigorous, two-stage internal review process of the dispersion modelling methodology and results.

Stage 1

Review and approve a detailed dispersion modelling plan of the proposed methodology and inputs using the template available on this page. This stage typically involves several iterations of Metro Vancouver staff providing comments on a draft plan and the applicant’s consultant responding.  The methodology is expected to be mostly consistent with the BC Air Quality Dispersion Modelling Guideline.

Stage 2

Review the dispersion modelling report. Metro Vancouver:

  • checks to ensure that the dispersion modelling was conducted in accordance with the approved plan;
  • carefully reviews the meteorology that was used to drive the dispersion model;
  • analyzes tables and figures of the model results, looking for potential issues with the meteorology or inconsistencies between the model inputs and expected results; and
  • compares the results to Metro Vancouver ambient air quality objectives or criteria from other jurisdictions if Metro Vancouver does not have objectives for a given air contaminant.

This stage also typically involves several iterations of Metro Vancouver asking questions and the consultant responding. It is not uncommon for Metro Vancouver to uncover an issue that requires the consultant to remodel.

External Review

Once Metro Vancouver is satisfied that the dispersion modelling methodology and model results are reasonable, staff form conclusions on the potential effects on ambient air quality and then forward the report to the relevant health authority – Fraser Health or Vancouver Coastal Health – for their interpretation of the model results in terms of human health impacts, as Metro Vancouver is not an expert in that field. Metro Vancouver may also forward the report to other agencies for their comments on potential effects to other environmental aspects, such as soil or water, if Metro Vancouver has received comments from concerned persons regarding those areas.

All comments received from other agencies are provided to the District Director for consideration when reviewing staff’s recommendation on a permit application.