Destabilization of sand dunes at the Oceano Dunes State Vehicular Recreation Area is the primary cause of high particulate air pollution on the Nipomo Mesa, according to a scientific study released Monday.
The study by the San Luis Obispo County Air Pollution Control District concluded that break-up by off-highway vehicles of a natural crust that forms on sand dunes and a lack of vegetative cover in areas where OHVs are ridden are the primary causes of dust being blown from the park to populated areas of the Mesa.
All of these act to increase the ability of winds to entrain sand particles from the dunes and carry them to the Mesa, the report concluded.
The study further concluded that exhaust emissions from OHVs and the fact that they can kick sand into the air are only lesser causes of the air pollution.
The study confirms public announcements made recently by Air Pollution Control Officer Larry Allen about the results of the study. OHV activity in the SVRA is a major contributing factor to high PM (particulate matter) concentrations observed on the Mesa, states the studys executive summary.
The report does not contain any recommendation about how the problem can be minimized. The air pollution control district board of directors may begin discussing that when it meets March 24 to be briefed on the study.
In the meantime, a public workshop is scheduled from 6 to 9 p.m., March 3 at the South County Regional Center, 800 W. Branch St., Arroyo Grande. The results of the study will be presented and a panel of experts will be available to answer questions.
The study is based on air monitoring conducted over a year that compared ambient particulate levels to levels of particulates coming off the OHV park. More than two million data points were generated.
The main conclusions are:
· Particulate matter on the Mesa does not originate from an offshore source.
· Neither petroleum coke piles at the ConcoPhillips refinery nor agricultural fields are a significant source of particulates.
· The bulk of the particulate matter is fine sand blown onto the Mesa by strong winds.
· The primary source of these sand particles is the open sand areas of the dunes.
· Open sand dunes where OHVs are ridden emit significantly greater amounts of particulates than the undisturbed sand sheets at the study control sites under the same wind conditions.
· Vegetative areas do not emit wind-blown particles.
The study can be obtained at the air districts Web site: http://www.slocleanair.org