SLO approves bike recreation in asbestos-rich soil



img3818The San Luis Obispo City Council on Aug. 17 approved a donor agreement with a mountain biking group to develop a recreation facility in a city-owned area with a soil type rich with asbestos.

The group, Central Coast Concerned Mountain Bikers, hopes to build a bicycle skills course in the Stenner Springs Natural Reserve, a 363-acre area four miles north of SLO. Much of the landscape of Stenner Springs is made up of serpentine soil, according to staff reports. That’s a type of material that the state and the federal governments have
designated as a source of naturally occurring asbestos. Asbestos is known to cause lung cancer and mesothelioma, a cancer of the lining of lung tissue that’s nearly always fatal.

Though serpentine soil is relatively common in California, scientists and government regulators have recently stepped up efforts to study the effects of naturally occurring asbestos in dust and warn people of the danger.

In a study released in 2009 by the University of California Department of Agriculture and Natural Resources, dust from serpentine soil is cited as a potential cause of cancer. The study says, “People may inhale or swallow dust containing asbestos fibers. These fibers can cause cancer and other diseases by remaining in the lungs or traveling to the lining of the lungs or the abdominal cavity.”

The California Air Resources Board identified asbestos as a toxic air contaminant with no safe threshold level in 1986.

“In general, people are not aware of the dangers of serpentine soil,” said Toby O’Geen, a soil scientist at the University of California, Davis. “I wouldn’t make a trail over it unless they import trail material. If they are laying down bicycle trails over crushed rock and soil and don’t put down a layer of topsoil, the risk may be much higher.”

He added: “There’s no way to know how much of a problem you have unless you take samples.”

According to Neil Havlik, natural resources manager for the city, the city hasn’t tested for asbestos at the site. Havlik said the state air resources board only requires asbestos testing when a grading project is larger than an acre.

“My guess is there is asbestos there, but it’s far below the threshold,” Havlik said, adding that the construction of the bicycle skills park won’t require much below-ground work.

“Asbestos is a concern in certain circumstances,” he explained. “Our expectation in this particular project is that the ground disturbance is very minor.”

According to the environmental impact study that’s part of the project report, one of the few potentially significant environmental impacts of the project is “substantial soil erosion or the loss of topsoil.” Due to a fire in the area in 1994, the mineral soil under the future location of the bicycle skills area has been exposed, Havlik said during the council meeting.

According to the 2009 asbestos study: “No one knows how many fibers are needed to cause lung cancer or other diseases. Heavy and frequent occupational exposures are more likely to cause the disease than are nonoccupational exposures; however, a lifetime of exposure to low levels is also recognized as a potential hazard.

“Environmental health scientists have suggested that children have a higher risk of exposure than adults in the same environment due to their faster breathing rates, time spent outdoors, and greater time for disease to develop.”

The 84-page report detailing the city’s plans for the Stenner Springs area mentions asbestos only twice: “Serpentine carries the risk of asbestos. Be sure to patrol erosion areas, as these areas are subject to asbestos.”

Both the study and the federal government’s Agency for Toxic Substances and Disease Registry advise people living or working near naturally occurring asbestos to “walk, run, hike, and bike only on paved trails and pave over unpaved walkways, driveways, or roadways that may have asbestos-containing rock or soil.” They also advise that recreational activity in serpentine soil in outdoor areas be restricted to “outdoor areas with a ground covering such as wood chips, mulch, sand, pea gravel, grass, asphalt, shredded rubber, or rubber mats.”


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