GUIDELINES FOR GEOLOGIC INVESTIGATIONS OF NATURALLY OCCURRING ASBESTOS IN CALIFORNIA

California has experienced a rising concern over potential public exposure to naturally occurring asbestos (NOA) in recent years. Consequently, geologists in California are increasingly called upon to evaluate the NOA potential of property prior to land-use decisions, land acquisition, or property development. However, many geologists currently have limited knowledge of the geology/mineralogy of asbestos or of some of the methods that can be used to study NOA. In response to this situation, the California Geological Survey (CGS) has developed a NOA guidelines document. This document contains basic information on NOA mineralogy, geologic occurrence, sampling and analytical methods, regulations, and provides general guidance for conducting geologic investigations of NOA in California.

The CGS developed these guidelines with the assistance of a committee of volunteers with expertise in the various fields related to the geologic investigation of NOA. The committee included geologists/mineralogists with in-depth knowledge of California geology, the mineralogy and petrology of serpentinites and ultramafic rocks, asbestos mineralogy, and the occurrence of asbestos. The committee also included a geostatistician, a soil scientist, an environmental scientist, an environmental engineer, and an industrial hygienist. Numerous geologists and other scientists in consulting, industry and regulatory agencies reviewed a draft of the guidelines.

Geologists may be called upon to assess the potential for NOA at sites having widely varying degrees of development, disturbance, and prior geologic observation. Also, the purpose, scope, and methods of a NOA investigation will vary depending on site-specific conditions and the nature of the proposed development or project. For these reasons the guidelines are general, rather than prescriptive, in their recommendations for approaching NOA investigations. In addition to scope of work and report format recommendations, the guidelines discuss various topics of importance for NOA investigations, such as sampling and analytical methods. Current California regulations related to NOA are also summarized.