Guzziwest Inspection And Consulting

Naturally Occurring Asbestos


Asbestos is a group of silicate minerals that occur as asbestiform fibers having high tensile strength, flexibility, heat and chemical resistance.  

Naturally occurring asbestos (NOA) is the term applied to the natural geologic occurrence of various types of asbestos. NOA is present in the majority of counties in California. It is commonly found in ultramafic rock formations, including serpentine, and in soils where these rock types are located. You can download a state-wide map of asbestos locations produced by the California Geological Survey (CGS) under our helpful links!

Serpentine, the California State Rock, contains asbestos. It is found throughout the State. It’s typically grayish-green to bluish-black in color and its surface often has a shiny or wax-like appearance and has a slightly soapy feel. 


In California, regulations have been implemented to protect the public from exposure to NOA. The most common type of NOA asbestos is chrysotile, other types such as tremolite and actinolite are also found in California. The California Air Resources Board (CARB) identified all asbestos fibers, irrespective of length, with an aspect ratio greater than or equal to 3, equally hazardous to public health.  

In 1990, the CARB adopted an asbestos Airborne Toxic Control Measure (ATCM) that restricted the use of serpentine rock aggregate for surfacing applications. The Surfacing ATCM sought to reduce asbestos emissions from unpaved roads and other applications by limiting the sale and use of asbestos-containing serpentine rock for surfacing applications. In July 2000, the CARB adopted amendments that added ultramafic rock ( and lowered the threshold asbestos content to less than 0.25% as determined by CARB Method 435 (  

In July 2001, the CARB adopted additional asbestos amendments for construction, grading, quarrying, and surface mining operations ( The Construction ATCM was adopted to reduce asbestos exposure associated with dust emissions from construction, grading, quarrying and surface mining activities in areas where NOA is known or likely to be present. This statewide regulation is applicable to grading or any other projects disturbing soil in areas of California where asbestos may exist, as determined by the California Geological Survey (CGS). 

Determination for the applicability of a project falling into an area containing NOA and having to comply with these regulations is often made during the environmental review process (CEQA/NEPA) and/or environmental planning process.  For instance, Federal and State Agencies such as Caltrans, as well as local municipalities will review if a given project falls into an area expected to contain NOA early in their planning processes and then require further studies to definitively identify NOA as present or absent. Once the determination of the presence of NOA is made, contract bid documents will require compliance plans during the implementation of the project. A general exemption from the Construction ATCM may be sought and granted if a registered geologist conducts a geologic evaluation that determines that no asbestos or ultramafic rock is present in the area to be disturbed.

Naturally Occurring Asbestos Testing in Redding, California!

Guzi-West has geologists on staff with years of experience evaluating sites for the presence of Naturally Occurring Asbestos; preparing site specific work plans, dust mitigation plans and site health and safety plans; overseeing and monitoring the implementation of projects occurring with NOA; as well as determining if a project qualifies for the general exemption.  Please contact our office for assistance addressing NOA and your projects.

We Handle Inspection/Testing for Asbestos, Lead-Based Paint, Mold, Methamphetamine, PCBs, Silica, Smoke Damage, Sewage/Bacteria, Waste Characterization and More in Your Area

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