IMPLICATIONS OF NATURALLY OCCURRING ASBESTOS DURING CONSTRUCTION

Geomatrix has been retained to conduct environmental and geotechnical investigations associated with the development of a 27 acre property into a research and development facility in South San Francisco, California. As part of these investigations, a large body of serpentinite, which contains naturally occurring asbestos (NOA), was identified and mapped. Bulk samples of the serpentinite typically contain between 0.5 and 2.0 percent NOA as chrysotile, with maximum concentrations of up to 70 percent. Action levels as low as 0.25 percent have been developed to regulate the handling and mitigation of NOA during construction activities (California Air Resources Board Asbestos Air Toxics Control Measure; Title 17, Section 93105).

This talk will focus on the methods used to identify and quantify the presence of NOA throughout the site, along with the mitigation measures employed to limit exposures. Additionally, the extensive efforts employed by the developer, construction team, and health and safety personnel to minimize the costs associated with the handling of suspect material and construction “down time” will be discussed.

These activities are being conducted under a Consent Order with the California Department of Toxic Substances Control (DTSC) and a regulatory-approved site management plan (SMP) that specifies health and safety requirements and outlines mitigation measures for managing material containing NOA.