Averaging Periods
When reporting measured air quality concentrations, different time averaging periods are used in order to assess concentrations against ambient objectives. In the case of Particulate Matter, there are no 1-hour Alberta Ambient Air Quality Objectives to compare measured PM concentrations to. The 1-hour PM concentrations presented in the graph to the left are displayed to show short term changes in PM, which are typically caused by transient events generating fugitive dust.
The 1-hour averaging periods should be viewed with the understanding that the concentrations can fluctuate significantly from hour to hour due to short-term events. An example of this, in June of 2016, the grass was cut by the Lagoon and this resulted in a large spike in PM for a single hour. The graph also shows hourly wind speeds, which can provide useful information related to TSP concentrations. In the Bow Valley, many of the elevated TSP concentrations are associated with high wind speeds which have the ability to generate fugitive dust. Fugitive dust can come from many places, such as storage piles, roadways, or vehicles.
The 24-hour averaging period (represented as bars) represents the average concentration from midnight to midnight. Both TSP and PM2.5 have 24-hour AAAQOs which are shown on the graph. In the event of an exceedance of a 24-hour objective, Lafarge is required to submit a report to Alberta Environment and Parks.
Alberta Ambient Air Quality Objectives (AAAQO)
AEP have developed, under the Alberta Environment Protection and Enhancement Act (EPEA) a set of ambient air quality objectives to be used to evaluate air quality.
Objectives are used to:
- Determine adequacy of facility design
- Establish required stack heights and other release conditions
- Assess compliance and evaluate facility performance
Lafarge is required to report exceedances of any objectives at the Lagoon location as part of their approval.
More information about the AAAQO can be found on AEP's website.