Operations and Maintenance in Vermiculite Exfoliation Plant

Equipment that processed Libby vermiculite until 1986 is installed in an area of a building whose walls and roof deck are corrugated asbestos-cement (Transite). The equipment is currently used to process vermiculite concentrate from South Carolina. Microvac samples (ASTM D5755) were taken from the inside surfaces of the Transite walls and the underside of the roof deck. One sample result was 15,000,000 asbestos str/cm², the highest ever recorded by the laboratory.

Air samples were taken to determine if the vibration from the processing equipment was releasing fibers from the surfaces of the Transite. Analysis by TEM showed an average fiber concentration of 0.0012 f/cc for PCMe fibers (>5µm long) and 0.0017 f/cc for fibers > 0.5 µm long.

The air samples also showed an average concentration of 0.0027 f/cc for Libby amphiboles that originated from residual Libby vermiculite dust remaining in the building. Of the five microvac samples of wall surfaces underneath the accumulated dust, three had one or no Libby amphiboles and the highest was 156,000 Libby amphiboles /cm².

An Operations and Maintenance plan was prepared to manage the Transite roofing and siding, and also the accumulated dust that was protecting the residual Libby amphiboles. The plan prohibits plant personnel from cutting or otherwise disturbing the Transite, and prohibits contact with dust on the walls to preclude disturbing the underlying residual Libby amphiboles. Regular cleaning of plant equipment remains a part of operations. A sign was posted in the supervisor’s office illustrating the Transite and dust and identifying their locations. Awareness training was provided to plant employees to familiarize them with the elements of the O&M program.

(Left) Corrugated Transite roof deck and siding (Right) Dust on walls and beams -- microvac sample location