Comparing the simulation with B.C. air-quality objectives

Prepared 5 September 2026. Values below come from the province’s 23 December 2025 factsheet, checked against its rendered tables and the official webpage updated 24 February 2026. They are ambient-air benchmarks: a map of the flare’s contribution alone is not a map of total ambient concentration. Objectives are generally non-statutory unless incorporated into a permit or other binding requirement. Official objectives page

Source: B.C. factsheet, Tables 1 and 3, pages 2–3. Gas conversions in Table 1 use 25°C and one atmosphere and are rounded; preserve the original ppb criteria when comparing measurements reported in ppb. For a mass-concentration model, use the published mass values consistently. The CO values are retained from Pollution Control Objectives for reference after the original discharge criteria were rescinded in 2006; do not present them as a new standard.

Canadian standards are a separate selection. The 2025 CAAQS for NO2 are 42 ppb hourly (listed as 79 µg/m³) and 12 ppb annually (23 µg/m³), with the same corresponding statistics above. Current PM2.5 CAAQS remain 27 µg/m³ for 24 hours and 8.8 µg/m³ annually; both use three-year achievement statistics. Future 2030 values are 23 and 8 µg/m³, respectively. Current SO2 CAAQS match the B.C. values above. Do not mix the future PM2.5 values into a “current B.C.” layer. Factsheet, Tables 1–2

What the map may compare

The following are implementation recommendations for this illustrative simulation, not a finding of regulatory compliance:

1. Average first. At every location, integrate the changing concentration over a full 1-, 8-, or 24-hour window, then divide by that duration. An instantaneous snapshot cannot be compared with these values. A partially simulated day cannot be presented as a 24-hour mean.
2. Show the window and the source scope. A rolling event window is useful for exploring a scenario, but differs from calendar-day and annual attainment calculations. If the flare was off before the modelled event, a stated zero flare contribution during that period can be included. Do not silently substitute zero for missing ambient background or the plume’s unmodelled future travel.
3. Use restrained labels. “Scenario mean above the numerical benchmark” or “illustrative benchmark overlap” describes what was calculated. A single event cannot establish a multi-year standard violation, a health-risk probability, or the exposure of everyone in a neighbourhood. A community point represents that point, not every residence.
4. Keep background separate. Measured background can only be added with a defensible choice of location, species and averaging period. An onsite measurement from a different season is not an observed background surface over Squamish.

NO2 needs an additional assumption because the historical source table reports NOx. The province recognizes complete conversion of NOx to NO2 as a conservative chemistry screening method. Confirm that the source mass is expressed as NO2 equivalent before using a one-to-one mass conversion. Label this “NO2 under total-conversion assumption,” rather than measured NO2. This assumption does not make an unvalidated transport model a guaranteed upper bound. More detailed methods use ozone availability and source chemistry. B.C. NO2 modelling guidance, July 2022, section 3.2.1.1, printed page 9

For the historic Woodfibre case, the EA’s indicator definition explicitly expresses NOx as NO2. This supports using the reconstructed 51 g/s NOx rate as NO2-equivalent mass for the labelled total-conversion sensitivity, without an additional molecular-weight multiplier. It does not establish the actual NO2 fraction or present-day source chemistry. January 2015 EA, section 5.2.1.3, page 5.2-5 / PDF page 5

There is no total-VOC ambient objective in the current factsheet. Its formaldehyde criterion is for that specific chemical and cannot stand in for unspecified total VOCs. The same factsheet supplies no CO2 or methane ambient objective. Those layers should show concentration only unless an appropriate separate, clearly described assessment is developed. B.C. factsheet

Full-year Squamish Elementary observations

The acquired 2023–2025 record now supports a separate station comparison. Reported PM₂.₅ annual daily-mean 98th percentiles are 17, 11 and 16 µg/m³; annual means under the explicit provincial quarter-weighted method are 6.0, 4.7 and 5.7 µg/m³. Three-year NO₂ and SO₂ hourly metrics are 20 and 5 ppb respectively. All ordinary completeness checks pass. These historical station comparisons do not attribute a source or determine whole-airshed compliance.

The detailed observation-method note supplies calculation rules beyond the broad table above. In particular, B.C.’s PM₂.₅ implementation guide uses four equally weighted quarterly means; its current webpage is less specific. The 2025 pooled-daily alternative is 5.8 µg/m³, compared with the primary 5.7. Gas annual means use hourly values. Current SO₂ follows CCME 0.1 ppb hourly rounding, while the provincial NO₂ calculation preserves intermediate precision. These distinctions matter when reproducing a value.

Examples using actual onsite measurements

These comparisons align the averaging periods, but do not determine percentile-based attainment or attribute the measurements to flaring. Sources: May 2025 onsite report, Table B.1, PDF page 30 and January 2026 onsite report, Table B.1, PDF page 33. The roughly month-long passive SO2 samples cannot be compared as hourly SO2 results.

An important source correction: some onsite report tables describe the B.C. daily PM2.5 objective using a three-year statistic. The current official factsheet specifies one year for B.C. and three years for the CAAQS. The simulation should use the official distinction. Its colour bands should describe benchmark ratios, with no “safe” boundary, finite pollution travel edge, or operational exposure prediction implied.