The South Coast Air Quality Management District (South Coast AQMD) operated a Beta Attenuation Monitor (BAM) to measure particulate matter with a diameter of 10 µm or less (PM10) in the City of Duarte from October 2013 to September 2020. The purpose of this monitoring was to address public concerns of possible fugitive dust emissions from the Vulcan Materials Azusa Rock Quarry.
An analysis of the data from this monitor showed very little impact on air quality from the Vulcan Materials facility at this location. The highest levels of PM10 measured at the monitoring site typically occurred in the middle of the day and when the winds were blowing from the South. As shown in Figure 3, the Vulcan Materials Azusa Rock Quarry is located to the North of the monitoring site.
During the seven-year monitoring period, the daily average PM10 levels measured at this site exceeded the Federal 24-hour PM10 standard of 150 µg/m³ only once on December 2, 2016. Consequently, the BAM was removed on September 2, 2020. A summary of the collected data follows.
PM10 levels measured at the Duarte BAM showed similar year to year variation with slight annual average reduction in 2019, the last full year of monitoring.
The figure below shows that the highest levels of PM10 were measured in the middle of the day and when the winds were blowing from the south.
