Vermiculite processing facility included an operating furnace

The processing facility was equipped with a vermiculite furnace that expanded vermiculite ore (average density = 55 lbs/ft3), producing a lightweight material (density ~7 lbs/ft3) with a variety of uses. According to a former employee who worked at Vermiculite NW in the 1960s, the process was a dusty one.

The facility received ore from Libby, Montana, in railcars via a railroad spur that ran parallel to the north side of the building. The ore from the railroad cars was unloaded into six storage bins, each with a capacity of 60 tons (~2200 ft3), for a total storage capacity of 360 tons. Ore from the storage bins was transferred into a hopper before being directed to a conveyor belt that fed the furnace at a rate of about one ton per hour.

The vermiculite ore stayed in the furnace for about eight seconds and was subjected to temperatures over 1000E F until it expanded (“popped”). Fans blew the expanded vermiculite through a chute, onto an elevator, and finally onto a vibrating screen that separated the expanded ore from unexpanded ore (commonly referred to as “stoner rock”). Expanded vermiculite was cooled, fed into a hopper, and funneled into open bags.

Workers held the bags at the end of the chute and pulled a tongue in the chute to allow vermiculite to fall into the bag. Once the bag was full, a worker pushed back the tongue, stopping the flow of vermiculite. The bag was then removed and sewn shut. Workers wore broad-brimmed hats to keep dust from falling on their faces. Dust accumulated on the floors, which were swept about every two hours. In general, workers did not wear respiratory protection.

Stoner rock and other by-products were piled on the south side of the facility for disposal at undisclosed locations. A former worker reported that people carted this waste off for use in their yards. One employee transported the waste rock 15 miles north to his home in Chattaroy, Washington, for use as fill in his driveway, yard, and garden.

The facility also had a mixer on site, which combined expanded vermiculite with a variety of other materials, depending on the type of product being made. Other materials included sphagnum, fertilizers, gypsum, bentonite, wood pulp, and asbestos. Chrysotile asbestos was mixed with vermiculite to produce acoustic plaster, further contributing to the amount of asbestos dust associated with the facility.

Courtesy of the Washington Department of Health