AIR SAMPLING FOR ASBESTOS ON TWO PROJECTS INVOLVING NATURALLY OCCURRING ASBESTOS (NOA)

Air sampling analytical methods and techniques for evaluating asbestos on projects involving NOA have been in the developing stages for the past 10 years, which have resulted in regulations and guidelines by various regulatory agencies in California.

The California Department of Toxic Substances Control (DTSC) has established guidelines for school projects involving NOA. The guidelines include property fence line measurements upwind and downwind of excavation and soil disturbance containing NOA. A Trigger Level of 0.005 asbestos structures per cubic centimeter (s/cc) and an Action Level of 0.01 s/cc have been established to trigger additional engineering controls. In addition, DTSC requires area air samples for total dust air monitoring at upwind and downwind fence lines with 0.05 mg/m³ as a Community Action Level.

This presentation will discuss results of air sampling for asbestos on two large NOA projects in Sacramento County and El Dorado County both located in Northern California.

At Vista Del Lago High School, soil samples collected from the school site were found to contain up to 6% actinolite asbestos by PLM and up to 2% actinolite by TEM. During a 15 month construction project in 2005/2006, Entek collected 639 air samples with analysis by TEM, which included 490 area air samples and 149 personal air samples. The highest area air sample concentration was 0.128 s/cc (upwind), while the highest personal air sample was 0.178 s/cc.

At Oak Ridge High School, soil samples collected by the U.S. EPA identified <0.0001% asbestos up to 8.8% asbestos by weight. The primary asbestiform detected was actinolite; however some soil samples had tremolite, anthophyllite, or chrysotile asbestos detected. During a multi-phase construction project between 2008 and 2009, Entek collected 462 air samples, which included 288 area air samples and 174 personal air samples. The highest area air sample concentration was 0.0092 s/cc, while the highest personal air sample was 0.1972 s/cc.

Actinolite was the primary asbestiform detected on air samples for both studies with analysis by TEM. The Cal/OSHA PEL for asbestos is 0.1 f/cc for fibers greater than 5 microns in length.