Dust pollution drops dramatically at Oceano Dunes. Are State Parks’ efforts working?
California State Parks has been tasked with finding a way to make a naturally dusty area — Oceano Dunes State Vehicular Recreation Area — less dusty.
Now, recent data collected from last year — when dust mitigation efforts coincided with an unprecedented vehicle closure — show some promising results, in particular a dramatic drop in one measure of airborne particulate pollution.
The preliminary data from the APCD suggest that the mitigation measures might be working — but scientists and officials can’t yet draw solid conclusions as to why that may be.
“Last year was a lot less dusty than previous years,” said Karl Tupper, a senior air quality scientist with the APCD. “And some of that could be just the fact that these foredunes have been growing and other mitigations are here. But some of that could also be because there was no (OHV) riding for seven months due to the COVID(-19) closure.”
The park was closed to off-road riding from March 2020 until Feb. 19 due to coronavirus-related health and safety restrictions.
Reducing dust emission at the Dunes is a monumental task, one that State Parks has long resisted as it has fought closing areas previously open to camping and off-highway vehicles at the popular park along San Luis Obispo County’s southern coast.
Dust from the Oceano Dunes has been a well-known issue for decades, and State Parks was ordered by the San Luis Obispo Air Pollution Control District (APCD) in 2018 to cut the emissions in half by 2023.
On April 15, the California Coastal Commission gave the green light for 93 new acres of dust mitigation area at the Oceano Dunes, bringing the total to 323 acres out of the 3,600-acre park. About 1,500 acres of the park are currently open to OHV use.
By 2023, no OHVs will be allowed at Oceano Dunes State Vehicular Recreation Area following a historic vote by the Coastal Commission on March 18.
Meanwhile, officials and scientists are working to the most efficient and most effective ways at curbing the amount of dust emitted from the Oceano Dunes — from installing sand fencing, planting acres of native vegetation and even growing new dunes.
Why are dust mitigation measures needed at park?
In 2015, an air quality monitor — known as CDF — downwind of the off-road riding area at the Oceano Dunes measured 79 total hours when PM10, or, particulate matter, levels exceeded 300 micrograms per cubic meter.
PM10 are particles such as dust, pollen, smoke and mold with a diameter of 10 micrometers and smaller. These particles can be inhaled and are tiny enough to get into people’s throats and lungs.
The number of hours when PM10 levels exceeded 300 micrograms per cubic meter at the CDF air quality monitor rose to 91 in 2016, then to 100 in 2017, according to the APCD’s data.
PM10 levels in excess of 300 micrograms per cubic meter for that many hours can be catastrophic to the health of those downwind.
Residents of Oceano and Nipomo say the dust pollution coming from the Oceano Dunes has caused health problems such as asthma, cancer and bronchitis.
The dust got so bad that the American Lung Association wrote a letter in January 2018 to San Luis Obispo County officials, urging them to enforce solutions to reduce harmful particle pollution from the Oceano Dunes “as quickly as possible to protect public health.”
In April 2018, State Parks entered into a stipulated order of abatement with the APCD. That court order forced State Parks to draft a plan and implement measures to decrease dust emissions from Oceano Dunes State Vehicular Recreation Area.
Dust mitigation efforts have cost more than $18 million since 2011, according to State Parks, and the agency will spend about $2.8 million in the 2020-21 fiscal year on air quality at the Oceano Dunes.
All of the funds used for dust mitigation are obtained through the OHV trust fund, which collects money from licensing fees paid by owners of off-road vehicles, entrance fees paid at the state’s nine off-highway vehicle recreation areas and a portion of all the gas taxes paid at the pump in California.
Oceano Dunes are unnaturally dusty
Dunes like those at the Oceano Dunes are naturally dusty.
When the wind blows, it picks up finer particles of sand and carries them into the air, creating a dust plume like the one seen throughout southern San Luis Obispo County and northern Santa Barbara County.
Decades of vehicles driving in the Oceano Dunes has made it one of the dustiest areas in the world, according to Ian Walker, a geography professor at UC Santa Barbara. He’s a member of the Scientific Advisory Group formed to assist State Parks and the APCD in creating and implementing successful dust mitigation efforts at the Oceano Dunes.
“This site is one of the most emissive coastal dune sites I’m aware of in the world,” Walker said. “And why is that? There’s this long-standing question: Is it the geology of the site? Or is it vehicle action, or some combination? It’s probably some combination, but we can’t ascribe blame to either of those yet.”
Walker said the sand grains at the Oceano Dunes are a mixture of quartz, feldspar and clay minerals, and that the quartz sand grains have a mineral coating.
Feldspar and the mineral coatings on the quartz grains break down as the wind blows the grains around, causing a cloud of fine dust to blow into the air, Walker said.
“But the other thing we have to talk about is the mechanical action of grains grinding — sand under wheels — exerts forces of different types,” Walker said, specifically torque force. “It’s happening at frequencies and with an amount of force that is much greater than what it would see naturally.
“So the hypothesis here is that in areas where we have more vehicle action, we have more of this grinding and torque force that is wearing those grains down mechanically faster than they would have under natural forces.”
Vehicles could also be mixing the sand unnaturally, bringing finer particles to the top, Walker said.
Those hypotheses are supported by maps included in State Parks’ Draft Particulate Matter Reduction Plan for the Oceano Dunes. The maps show that areas with more vehicle activity emit more dust than other areas at the Oceano Dunes.
So, the Scientific Advisory Group partnered with the Desert Research Institute of Reno, Nevada, to advise State Parks about where the best areas are to implement dust mitigation efforts at Oceano Dunes State Vehicular Recreation Area.
How are California State Parks, scientists reducing dust at Oceano Dunes?
The dust mitigation efforts are spread out around the Oceano Dunes park and consist of different measures to effectively lessen the amount of dust blown into the air.
The first method is sand fencing.
Large fences with orange tarps with holes in them are placed in strategic locations in the park to slow sand transport and blowing dust. The fences are used in about 40 acres of the park, and an additional 33 acres of fencing are being installed in 2021.
Though sand fencing is effective, it’s temporary. The fences become buried over time and require regular maintenance.
State Parks has also fenced off about 186 acres of vegetation islands within the park to allow those areas to continue growing and trapping sand. An additional six acres were fenced off this year adjacent to a vegetated area.
In addition, 137 acres in the park have been vegetated with native dune plants such as lupine and red sand verbena. These help trap blowing sand and aid the creation of natural wind blocks.
OHVs are not allowed in the newly vegetated areas, to allow the plants to grow.
An additional 27 acres will be planted with native seeds in 2021. Some areas that had sand fences are now vegetated.
Scientists grow sand dunes at park
Finally, a 48-acre foredune project was added at the Oceano Dunes in 2019.
In this section of the park, scientists have figured out how to actually grow sand dunes. The Oceano Dunes is the only area in the world where a project of this scale is taking place, Walker said.
By planting native plants and seeds in the sand, researchers can transform a flat area previously used for camping and off-road riding area into a series of small, growing dunes.
These dunes trap sand and then create a wind buffer that decreases the amount of sand blown and carried into the air. And on top of helping to mitigate dust emissions, the dunes will provide habitat for animals, Walker said.
By splitting the 48-acre foredune project into six areas with six different methods of growing foredunes, scientists hope to find the most effective dune-growing method for the Oceano Dunes, Walker said.
“(We’ve) created six egg baskets and put all our eggs in all the baskets,” he explained.
All six areas are “performing well in terms of foredune development,” Walker said, adding that he’s enthusiastic the improvements will become more obvious over the next year.
Are dust mitigation efforts working?
Early data show that the dust mitigation efforts might be working, although it’s hard to tell quite yet.
2020 was a particularly windy year for the Oceano Dunes. The APCD measured more windy days in 2020 than in any of the five years prior, according to Tupper.
But the number of hours where PM10 levels exceeded 300 micrograms per cubic meter significantly decreased, according to the APCD’s data.
In 2020, there were just four hours where PM10 levels exceeded 300 micrograms per cubic meter. That’s compared to 54 hours in 2019, 52 in 2018, and 100 in 2017, according to the APCD.
It’s an incredible improvement, Walker and Tupper said.
Although they said earlier improvements are most likely tied to the dust mitigation efforts, Walker and Tupper couldn’t say whether the huge decrease in dust emitted in 2020 was due solely to those efforts or because the dunes were closed to OHV riding for more than half of the year.
However, preliminary results from ongoing studies showed that the longer vehicles were off the dunes, the less dust that was blown into the air.
“As we got deeper into the closure, emissivity went down,” Tupper said. “This is as you would expect if vehicles were contributing to the dust here.”
That said, dust mitigation efforts banning off-road riding at the Oceano Dunes won’t just “flip a switch” and reduce dust emissions from the dunes overnight, Tupper said. The dunes are a naturally dusty environment, which won’t ever completely change.
The long-term goal is to reduce dust emissions to what they likely were before vehicles were allowed.
“There’s a history of vehicle activity over a century that has made this area a lot dustier than it would otherwise be,” Tupper said. “And so it’s going to take a while, years probably, to revert to that pre-disturbance level of emissions.”
This story was originally published April 28, 2021 at 5:00 AM.
