As dirt bikes and dune buggies buzzed in the background, parts of Oceano Dunes State Vehicular Recreation Area this week were transformed into a field laboratory for the study of wind-blown dust and ways to minimize it.
In a curious mix of high- and low-tech, a team of about 20 environmental scientists, engineers and workers deployed numerous sand-movement sensors, collected data with portable wind tunnels and set out more than an acre of hay bales.
It’s all part of a three-week pilot program testing ways to reduce sand blowing off the park. A scientific study has determined that dust from Oceano Dunes frequently creates unhealthy air quality downwind on the Nipomo Mesa.
“It’s quite the undertaking,” said Stephanie Little, an environmental scientist at Oceano Dunes, as California Conservation Corps members unloaded hundreds of hay bales and placed them in a grid pattern covering nearly an acre and a quarter.
They were in a hurry to get the pilot program set up because the research must take place in the spring, the windiest period on the Dunes and the time when air quality on the Mesa is most likely to exceed state health standards.
The Dunes are a dynamic place in the springtime, Little explained. Visit a spot one day and come back several days later and the wind will have completely reshaped the dunes. By the time the three-week pilot project is over, some of the hay bales will be buried by sand and others will have large hummocks on their downwind side.
After the hay bales were in place, teams of technicians placed three types of devices that monitor sand movement downwind of the bales. These devices were also deployed in vegetated areas of the park as well as in areas of open sand.
Dust pollution experts with the Desert Research Institute of Nevada have determined that hay bales and vegetation are likely to be the most effective ways of reducing fugitive dust. The sand-movement sensors will help determine which method works best.
Dave Whitney, an engineer with the county Air Pollution Control District, explained how the devices work. Two are simple static collection devices.
Receptacles at the bottom of the devices collect the sand that blows through an opening of a specific size. Technicians can estimate levels of sand movement in a given area by measuring the amount of sand the device collects in a day. The third instrument is a wand with a metal band that electronically records when a sand particle strikes it.
If hay bales prove to be an effective dust-control method, does this mean that the riding area at Oceano Dunes could someday be covered with hay bales? No, said Ronnie Glick, senior environmental scientist at the park.
“They could be a good solution for hotspots, though,” he said.
Only about 5 percent of the sand found in the park is in the form of particles small enough to become windborne and blow onto the Nipomo Mesa, Glick explained. And they tend to be concentrated in hotspots.
Finding those hotspots could be a challenge. Other devices at work on the dunes this week could help overcome that challenge.
Technicians with the Desert Research Institute pushed specially converted baby strollers across the dunes and unloaded two curious-looking mobile wind tunnels in an area of undisturbed, open sand. The devices, called Pi-Swerls, look like aluminum cooking pots with electrical motors and other gear attached to the bottom and foam rubber lining the rim.
The technicians place the pots, open side down, onto the sand sheet. A few computer keystrokes later, fan blades within the pots begin turning. A laser beam inside the pots records how much wind it takes to get the sand on the surface of the dunes airborne.
“It’s actually an elegant little device, assuming it works as advertised,” Glick said.
One of the key findings of the dunes particulate study was that undisturbed dunes form a crust that inhibits sand from becoming airborne. Vehicle riding on the dunes breaks down that crust and exacerbates air pollution problems on the Nipomo Mesa, the study found.
The Pi-Swerls will give scientists more detailed information about the surface composition of the dunes inside and outside the riding areas and could be used to find dust hotspots. The devices have been used to successfully gather data in other dusty locations, including Owens Valley in eastern California.
“The physics are the same,” said Vic Etyemezian, a research professor the Desert Research Institute. “The data doesn’t care if it’s a coastal dune or dry lake bed.”
Once the three-week pilot project is complete, the institute will analyze all the data collected and recommend to county air officials a course of action for reducing fugitive dust from the park.
“The real challenge is going to be finding measures that can be done on a large scale, but that’s not going to stop us from trying,” Glick said.
Although the State Parks Department disagrees with parts of the dunes particulate study, the agency agreed to carry out the pilot program in cooperation with county administrators and the Air Pollution Control District.
Reach David Sneed at 781-7930.