When thinking about asbestos abatement, certain images come to mind: destruction of old buildings, people in white suits, and the knowledge that the asbestos was put there as a fire deterrent or for another specific purpose. At the Calaveras Dam project, however, crews are dealing with a different kind of asbestos—naturally occurring asbestos.
Naturally occurring asbestos comes from a variety of places. At the Calaveras Dam, it primarily comes from the Franciscan group of mineral rock types, specifically the Serpentine group and the Amphibole group. Airborne asbestos fiber can stick to clothing and skin and if inhaled in sufficient amounts can cause lung cancer or mesothelioma, both of which are serious health problems.
Project safety manager Brian Donecker explained that since the asbestos at this project is naturally occurring, the laws the California Division of Occupational Safety and Health have developed to protect people are not always applicable or effective. Brian and Dan Hernandez, certified industrial hygienist, are working with Cal/OSHA to develop new, innovative techniques that are more appropriate for the naturally occurring asbestos on the project.
Asbestos exposure is typically controlled using Tyvek suits and respirators. These suits prevent asbestos from lodging on workers’ clothing, skin and hair. At the end of the day, these suits are rolled down the body to contain asbestos particles. In addition, negative pressure respirators can be used to prevent inhalation.
It is standard practice for crews to use water to suppress dust. As an example, water trucks, water cannons and firefighter nozzles are used to spray a fine mist of water to knock down particulate matter. Sometimes the use of high pressure, high velocity fine-water aerosol systems are used to improve dust controls for specific equipment.
Blueschist, one of the most potent of the naturally occurring asbestos minerals, prompted the safety innovations. Water does not soak the asbestos fiber, making it more difficult to control, requiring a higher level of protection and enhanced decontamination procedures.
Workers are also now using air—instead of water—for decontamination. After following normal decontamination procedures, workers often use an air shower instead of a wet shower as a final cleaning step. Air showers use high-speed air jets to fluff clothing and re-suspend any remaining fibers, then removes them using ultra high-efficiency filtration. This technique is the first of its kind in this field and is similar to what high-tech companies use to prepare people for working in a cleanroom.
Exposure monitoring, extensive training and signage warning people of the presence of asbestos are also required on the project. Nearly 2,000 air samples have been collected for nearly every operation, piece of equipment and workers. Because of this extensive exposure data, Cal/OSHA sometimes calls project personnel for advice on specific operations. These innovative sampling strategies have led to a greater understanding of potential risks to both worker and off-site sensitive receptors. This has enabled Flatiron to provide effective risk reduction procedures to better protect workers and community members at locations outside of the project limits.
All of these new procedures and innovations are contributing to the safety of the crews working at the Calaveras Dam project. In the future they may also be adopted by other entities—and even by Cal/OSHA—as the best practices for dealing with naturally occurring asbestos.