Friends of Oceano Dunes says the San Luis Obispo County Air Pollution Control District is withholding critical information and misleading the state of California and the general public by hiding data and ignoring potential causes of dust impacting the Nipomo Mesa.
In a March 14 letter to the APCD board, the group claims that the APCD and its lead officer "deliberately made unsupported allegations regarding crystalline silica coming from (Oceano Dunes State Vehicular Recreation Area) when there is no supporting evidence" and that the agency is perpetrating "HUGE falsehoods" as part of a "decade-long political spin."
The letter was circulated as the Air Pollution Control District Hearing Board is scheduled to meet Wednesday to consider an agreement between the APCD and State Parks to close about 100 acres this year to off-road vehicle riding and reduce air pollution emissions from the Oceano Dunes by 5 percent each of the following four years.
Friends of Oceano Dunes is a nonprofit organization representing the interests of users of the Oceano Dunes and local businesses.
"State Parks needs to stop all fencing and planting of vegetation," the group's president, Jim Suty, said in the letter.
APCD Officer Garry Willey denied the allegations and said, "I think this could be construed as a last-minute misdirect."
The letter cites two studies as evidence of a "careless act of misinformation," one that found levels of crystalline silica were not detected on the Oceano Dunes and another that points to offshore phytoplankton blooms and related bacteria as a source of airborne particulate matter.
In a 2017 study, air samplers were worn by a maintenance worker in the OHV riding area for six hours and by a person simulating an OHV rider traversing the dunes for seven hours. Other dust air samplers were placed on a tower for several hours. They found none of the samples obtained exceeded the current occupational health standard for dust, respirable dust or quartz and that crystalline silica results were below the detection limit.
Willey concurred that the amount of crystalline silica "is not violating safety standards," but said that there has not been a formal air quality study on it. He rejected the accusation that he covered up the study, and said, "I have made that statement before in open public comment."
More to the point, he said that the problematic particulate matter in the area is not primarily crystalline silica, but other forms of silica.
"It's still an air quality issue for your health, regardless if it's crystalline silica. It still has health effects. Any small particle gets into your lungs and robs you of your lung function," Willey said.
The second study raised in the letter was performed by the Scripps Institution of Oceanography at UC San Diego and finds that nearby coastal seawater is contributing biological material to PM10 aerosols detected and captured inland at monitoring sites on dunes in the South County, according to a 2018 Scripps report.
Engineering geologist Will Harris with the California Geological Survey sent the report to the director of the Off-Highway Motor Vehicle Division of State Parks, saying that the findings have a bearing on the ongoing efforts to mitigate PM10 detected on the Nipomo Mesa, because all mitigation efforts have been focused on reducing dust from the OHV riding area.
"As demonstrated by the Scripps investigation, the sourcing of airborne PM10 detected in this coastal setting is more complex, a function of several phenomena that occur on land, the ocean, and in the air," Harris says.
When asked about this most recent study, Willey said he had not had time to review the report entirely but that the argument "doesn't make sense to me."
He said if the algae bloom were responsible for the particulate matter pollution, "the bloom would be affecting the entire coast area. We have monitors to the north and south that don't show significant contribution," Will said.
Monitors to the north and to the south of the Oceano Dunes have not measured air pollution that violates state health standards near to the level as those downwind from the Dunes, Willey said.
The APCD asked for a hearing board to order closures at the Oceano Dunes, based in part on the findings of air monitoring studies of unusually high concentrations of particulate pollution on the Nipomo Mesa conducted between 2007 and 2010. Their studies found that the largest fraction of particles were composed of windblown crustal material containing silicon, iron aluminum and calcium and that meteorological data showed high wind events transported crustal particulate from the dune fields at the Oceano Dunes SVRA was the cause.
Phase two of the study explored the role of OHV activity on particulate matter and found that particulate matter concentrations downwind of the riding areas "are significantly higher than those measured downwind of non-riding areas."