The readings for the offsite community air monitoring show higher dust or particulate levels. What does this mean?

Ascon is not the source of the higher dust levels. The offsite air monitoring readings can have higher dust levels because they are impacted directly by activities in the neighborhoods. These higher readings have occurred on holidays and weekend days when there is no personnel or activity at the Ascon site.

The terms dust and particulate matter (PM) have the same meaning and are used interchangeably in Ascon and South Coast Air Quality Management District (SCAQMD) publications.

  • On the Ascon property: There are active mitigation measures to control dust and odor on an ongoing basis, including during work suspension. The air data results for onsite air monitoring collected by the downwind perimeter stations confirm these actions successfully control particulates or dust.
  • In the neighborhood: There are no mitigation measures conducted by the Ascon project for impacts unrelated to the landfill cleanup. Offsite air monitoring equipment is impacted by nearby construction or industrial facilities, landscaping activities, leaf blowers, renovation projects, painting, parking lot or road resurfacing, roof tar, fireplace smoke, and vehicle emissions. Air quality technicians note these activities as part of their reporting.

What else can affect air monitoring data?

  • Marine layer: Along the coast, the marine layer (fog) can cause increased particulate or dust readings recorded by monitoring equipment. The combination of this weather—low wind speed and wet air—affects the air monitoring equipment mechanism and impacts the readings. SCAQMD acknowledged this as a known issue at a recent City meeting and it also has been discussed with the California Department of Toxic Substances Control (DTSC).
  • Wind: On windy days, beach sand may be detected by monitoring equipment.
  • Residential fireplace smoke – Local residents are using their fireplaces now that the weather is cooler.
  • Wild fires – There were major wild fires in late October and November that may be the cause of some of the higher readings.
  • AES commissioning activity – As the power facility progresses through the commissioning process, they are testing equipment and visibly venting. This potentially may generate impacts to air monitoring equipment.

Should I be concerned about dust readings over 50 µg/m3?

The 50 µg/m3 (micrograms, or one-millionth of a gram, per cubic meter air) California Ambient Air Quality Standard is a 24-hour average. SCAQMD evaluates data based a 24-hour average concentration for comparison to the ambient air quality standards. It is important to know if the reading is sustained over a 24-hour period.

An isolated or short-term average of data—for example a one or two-hour average reading out of many during a 24-hour period—is not used to evaluate air quality. The average of total readings over a 24-hour period are compared with the regulatory standard (California Ambient Air Quality Standard) to evaluate air quality.

Who establishes the particulate or PM levels?

The State of California and the U.S. Environmental Protection Agency (USEPA) established the dust or particulate standards for PM10 for 24-hour exposure of 50 ug/m3 and 150 ug/m3 (micrograms, or one-millionth of a gram, per cubic meter air), respectively. These values are used with the 24-hour concentration average to calculate an Air Quality Index (AQI), which is a measure of air quality.

The AQI was developed by the USEPA to help communities assess the health of their air. The AQI information for the Huntington Beach area can be found at the following website under North Coastal Orange County subregion:

SCAQMD approved a Rule 1466 particulate or dust limit of 50 ug/m3 (micrograms, or one-millionth of a gram, per cubic meter air) for the Ascon site when active work is being conducted. This limit was confirmed to be health protective for the site by the SCAQMD.

See anything that may affect monitoring?

The community can help by calling the project hotline to report activities observed near offsite air quality monitoring stations that may affect air monitoring, 714-388-1825.

Call 911 if you see tampering: The community air quality stations are installed to provide additional assurance for residents with additional air quality data. The community is asked to call 911 to report tampering or vandalism of the air quality monitoring trailers, which impacts data collection.

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