Application evidence · 5 November 2026
What does the applicant’s modelling predict?
The October 2026 application reports upset-case concentrations below its listed air-quality objectives at the closest Squamish town boundary and Murrin Provincial Park. Across the wider modelling area, it also reports an NO₂ exceedance and, in a separate venting case, sulphur-compound exceedances. Location, operating case and averaging rule matter.
These are the applicant’s model results, transcribed from application 455458. They are separate from our interactive Explorer and have not been independently reproduced. Read the original upset-results table ↗.
Upset flaring: two reported locations
All values below are in µg/m³, including the report’s background and marine-vessel contributions. This case combines HP and LP upset flaring with the furnace and thermal oxidizer at full load, an LNG carrier and assist tugboats. FortisBC sources are not included in this case. Source combinations ↗ · Case description ↗.
| Pollutant | Averaging period | Closest Squamish boundary | Murrin Park | Wider-area maximum | B.C. objective used in report |
|---|---|---|---|---|---|
| NO₂ | 1 hour | 54.9 | 50.7 | 126.5 | 113 |
| SO₂ | 1 hour | 15.2 | 12.5 | 36.3 | 170 |
| PM₂.₅ | 24 hours | 17.9 | 17.8 | 19.2 | 25 |
| CO | 1 hour | 798 | 522 | 1729 | 14300 |
| CO | 8 hours | 523 | 375 | 779 | 5500 |
NO₂/SO₂ use multi-year percentile statistics; PM₂.₅ uses a percentile of daily averages. These are not the highest individual event-hour values. CO uses maximum averages. See the statistical details below.
The wider-area NO₂ result is about 112% of the report’s objective; the closest Squamish boundary value is about 49%. The applicant locates the NO₂ maximum at the northern facility fence. This is not a town-wide concentration. Different pollutants’ maxima need not occur at the same place or time. Location discussion ↗.
How to read the hours, background and locations
NO₂ and SO₂ use multi-year daily-maximum percentile statistics; PM₂.₅ uses an annual percentile of daily means. The table’s “1 hour” heading therefore does not make its NO₂ or SO₂ value the highest individual hour. CO uses maximum one- and eight-hour values. The report’s precise year-selection/post-processing has not been reconstructed here. Statistical rules ↗.
The background inputs are 41.6 for hourly NO₂, 11.1 for hourly SO₂, 17.7 for daily PM₂.₅, and 389.3/338.4 for one-/eight-hour CO, all in µg/m³. They are fixed assessment inputs, not simultaneous observations during a flare event. Background selection ↗.
The report describes Murrin as approximately 2.5 km southeast and the closest town boundary as approximately 7 km northeast. Table 6.7 does not identify their exact receptor IDs/coordinates. It gives no separate Brackendale, Valleycliffe or Garibaldi Highlands result in these columns. A listed sensitive receptor is a point, not coverage of an entire neighbourhood.
The narrative elsewhere gives 56.5 for the Squamish NO₂ result; this transcription retains Table 6.7’s 54.9 and flags the discrepancy rather than resolving it by assumption. All objective values here are those used in the application, not a new compliance determination.
Venting is a different release
The assessment groups diverted acid, flash and condensate-storage gases at the HP flare for the thermal-oxidizer-trip case. The process description distinguishes the physical routing: acid and flash gas go to the flare, while storage vapour leaves a pressure-control vent at the tank top. Its footnote says the storage stream was included at the flare for modelling. Physical routing and modelling footnote ↗. Table 6.9 reports wider-area first-highest hourly values of 278 µg/m³ total reduced sulphur (TRS) and 160 µg/m³ hydrogen sulphide (H₂S), above its comparison values of 7 and 14 µg/m³ respectively. TRS uses a B.C. objective; H₂S uses an Alberta objective. Venting-results table ↗.
These are maxima from a continuous five-year modelling run, not predicted concentrations in Squamish homes. The applicant separately estimates occurrence using 96 venting hours per year and describes the greatest exceedance likelihood near the northern project boundary. Its discussion identifies the H₂S comparator as odour-based. No receptor-specific venting concentrations for the Explorer’s communities were recovered in our targeted review. Venting method ↗ · Applicant’s interpretation ↗.
Why no annual probability is shown here
The application combines a continuously modelled source with an assumed event frequency. Its percentile/rank labels and five-year aggregation need the original electronic results and post-processing to reproduce. We have not converted those assumptions into a probability of exposure or illness for a resident.
What is known about benzene and other VOCs?
The application separately screens individual compounds during normal and stabilizing operations. It reports one-hour benzene maxima of 0.0140 and 0.0407 µg/m³ excluding background, or 2.53 and 2.56 µg/m³ including the older EA background. Its comparison value is an Alberta objective of 30 µg/m³. These are not upset- or venting-case benzene predictions. Screening scope ↗ · Without baseline ↗ · With EA baseline ↗.
Our Explorer’s total VOC layer cannot be read as benzene concentration. The application attributes flare VOC rates to generic EPA emission factors, while its stream-composition table describes gases before combustion. A compound-specific plume requires the corresponding emission calculation. Flare calculation references ↗ · Gas compositions ↗.
Stream-by-stream vent source audit
A new source audit calculates conditional benzene and H₂S mass rates from the published gas compositions and tests the dry/wet flow conventions. It retains the tank vent as a separate physical release and checks water saturation before selecting a mixture model. These are source calculations, not neighbourhood concentrations, and do not change the Explorer’s inputs. Read the source audit and its interpretation limits.
How this relates to the Explorer
The application evaluates terrain, weather, plume rise, chemical conversion and background using its own modelling workflow. Our Explorer lets visitors compare documented emission cases under assumed winds; its current-source calculation does not include buoyant plume rise or vent momentum and reports an air-layer mean. The two sets of numbers should not be divided to estimate how much safer or more dangerous an event is.
The application provides a stronger site-specific assessment basis than the illustrative map, but the summary tables do not answer the question for every community. The next useful step is to recover its hourly concentration files, receptor definitions and emissions worksheets, then reproduce community results under matching assumptions.
Research downloads and next data priorities
- Community results: original CONC.DAT, receptor definitions, source groups and post-processing, including background and statistical rules.
- Chemical releases: species emission worksheets for flaring and venting, with gas-volume conditions, moisture basis and event timelines.
- Site terrain: current engineering grade and the adjusted GEO.dat used by the applicant, with vertical datum.
- Weather performance: hourly source-site observations and wind/temperature profiles for inversion, outflow and inflow episodes.
Review scope: targeted application tables, methods and appendices, with visual checks of the key tables. This is not an exhaustive review of every page or a regulatory determination. Open the full research package.