Air quality near Oceano Dunes is still violating state standards despite closure. Here’s why.
The air quality near the Nipomo Mesa has continued to violate state standards even though the Oceano Dunes State Vehicular Recreation Area has been closed to vehicles since mid-March due to COVID-19.
However, the severity of those violations — 30 recorded as of June 28 in 2020 — are dramatically less than previous years, according to a Tribune analysis of the data.
Although some wonder if the violations prove the poor air quality isn’t a result of off-road riding at the Oceano Dunes, scientists with the Scientific Advisory Group say it would require years of closure and re-vegetation to see notable improvements in air quality in the area — not just a few months.
“Neither the district nor the Scientific Advisory Group expect the temporary cessation of (off-roading vehicle) activity to have any immediate or significant impact on dust levels downwind of the ODSVRA,” according to a frequently asked questions document by the San Luis Obispo County Air Pollution Control District.
Even though the dunes will be closed to vehicles until at least Oct. 1 due to nesting of endangered snowy plovers, it will take years of ceased activity to see notable change.
Air quality monitors on the Mesa have frequently registered levels of particulate matter called PM 10 and PM 2.5 air pollution that the World Health Organization deems unsafe. Particulate matter is small enough to travel through the respiratory system into the lungs and bloodstream.
In January 2020, California State Parks banned camping and vehicles from a section of the park to comply with orders to reduce air pollution after years of failing to comply with clean air regulations.
It was the first step in a stipulated abatement order to reduce dust emissions from the park by 50% by 2023.
Air quality on the Nipomo Mesa
The Tribune pulled data collected by the California Air Resources Board from an air quality monitor on Willow Road in Nipomo from the past six years from June 1 to June 28.
After analyzing the hourly data and averaging the 24 hourly data points for each day where more than 50 micrograms per cubic meter was recorded at least once, The Tribune requested information from the APCD. Its data confirmed The Tribune’s findings.
From Jan. 1 to June 28, there were 30 violations of California’s air quality levels at the Nipomo Mesa CDF (county fire department) monitor. According to state standards, PM 10 particulate matter should not exceed an average of 50 micrograms per cubic meter per 24-hour period.
In that same time frame, there have been 55 high-wind event days in that time frame. High wind event days are defined as 24-hour periods when the winds are strong enough that the state standard is likely to be exceeded 0.8 micrograms per cubic meter.
In 2019, there were only 30 high-wind event days and 16 air quality violations between Jan. 1 and June 28 at the CDF monitor.
In the last five years, in both 2017 and 2016, there were 44 state PM10 violations by June 28. While the data analyzed only shows half of the year, 2017 had the highest number of air quality violations at 97, according to past reports.
How wind affects Oceano Dunes dust levels
Gary Willey, director of the San Luis Obispo County Air Pollution Control District, said 2020’s violations have a lot to do with the wind.
“2020 is by far the windiest of the last six years, while 2019 was the least windy,” Willey said.
That being said, the wind is not the only factor in high PM10 levels, even now, according to Willey.
The Scientific Advisory Group told The Tribune in October 2019 that based on measurements of emission strength, “areas where it is most likely OHV activity is higher, the emissivity of those areas is relatively higher than low-use or non-riding areas.
That means that there is more dust in the air when it’s windy because of vehicle activity that has destroyed the foredunes over many years.
According to the APCD FAQ, so-called “rooster tails” from vehicles — which occur when sand is kicked up into the air from vehicles — are not the issue, nor are tailpipe emissions.
The degradation of foredunes and vegetation is what leads to more wind erosion and therefore more dust emissions, according to the APCD.
“It’s not when they’re on the sand running the vehicles, it’s what’s been done to the sand,” Willey said. “And it will take decades to restore itself if you don’t help it along, and it will never restore itself if you keep riding on it.”
Violations continue, but the peaks are lower
While the number of 2020 air quality violations is significant, that metric doesn’t show the full scale of poor air quality because the state standard is only measured by 24-hour averages.
On some days, air quality in the Nipomo Mesa area has doubled or even tripled the state standard for short periods of time throughout the day, but has not counted as a violation because at other times in the day, the PM 10 levels are low so the average does not exceed 50 micrograms per cubic meter.
The health effects of short-term spikes hasn’t been the focus of air quality research.
There have been no days this year where the daily average PM 10 levels reached 100 micrograms per cubic meter, which is twice the state health standard.
As of June 28, there had only been three hours recorded where PM10 levels reached above 300 micrograms per cubic meter, and no hours had exceeded 400 micrograms per cubic meter or higher.
By the same time of year in 2019, there were two days that had averages doubling the state standard, 22 hours of PM 10 levels exceeding 300 micrograms per cubic meter and five hours of levels exceeding 400 micrograms per cubic meter.
Even after accounting for changing winds, dust emission levels have been 33% lower this year during high wind times.
According to Willey and the APCD, the lower peaks this year are a result of the mitigation efforts, not the park closure.
“We have seen real, significant improvements in air quality, especially at CDF, and especially after taking meteorology (wind) into account,” the ACPD FAQ reads.
Willey said it is far too soon to see any effects from the off-highway vehicle park closure, and a Scientific Advisory Group letter written in April backs up his claim.
“The SAG does not expect a few weeks or months of temporary OHV restrictions to substantially alter the balance of human versus natural contributions to PM emissions at ODSVRA,” the scientific advisory wrote in April.
A California Coastal Commission meeting was held Thursday to provide an update about State Parks’ public works plan.
This story was originally published July 9, 2020 at 11:38 AM.
