SLO County air pollution agency to discuss dust abatement

June 17, 2022

By KAREN VELIE

The San Luis Obispo County Air Pollution Control District (APCD) is scheduled to discuss changes to its controversial agreement with State Parks on Friday, even though the APCD has not yet done a proportional analysis to determine how much of the particulate matter 10 microns or less in diameter blowing on the Nipomo Mesa is mineral dust from the Oceano Dunes.

State Parks entered into a stipulated order of abatement with the APCD in 2018 based on a disputed assertion the dust on the mesa is primarily mineral dust. The order requires the state to reduce wind-blown dust, specifically dust particles that are 10 microns or less in diameter, on the Nipomo Mesa by 50%. The APCD plans to discuss changing that parameter during Friday’s meeting.

In Dec. 2021, State Parks Off-Highway motor Vehicle Recreation Commission board members chastised APCD staff for their alleged false claims regarding the origin and content of particulate pollution detected on the mesa. A scientist with the prestigious Scripps Institution of Oceanography had analyzed the particulate and determined only 14% of the particles blowing on the mesa consist of mineral dust.

Footage from a Dec. 2021 California Off-Highway Motor Vehicle Recreation Commission meeting where attendees refute the APCD’s findings.

In May, the state commissioners accused APCD staff of failing to follow the basic standard of practice for computer modeling in determining the origin of dust blowing on the Nipomo Mesa, according to a May 13 letter from the State Parks Off-Highway motor Vehicle Recreation Commission to the APCD.

Jack Gillies, one of the scientists who created the computer model for the APCD, argues that even though their model does not distinguish what each particle is, “there are essentially no other sources that would be making any significant contribution to the PM10.”

Critics of the APCD argue that the agency’s failure to determine how much dust is coming from agricultural fields, from roads, from other dunes outside the state parks diminishes their findings.

At a cost of $22 million, the state has installed more than 230 acres of dust mitigation measures within the 1,000-acre off-highway vehicle riding area at the Oceano Dunes. Even so, the number of violations for exceeding the state’s pollution standard on the Nipomo Mesa in May 2022 was the highest in eight years, which further refutes the argument that vehicles on the dunes are the cause of pollution on the mesa.