Vermiculite expansion process yielded amphibole asbestos waste product

The Site in Hamilton Township, New Jersey, received Libby ore by rail in nominal 100-ton capacity hopper rail cars. W.R. Grace operated three vermiculite expanding furnaces and one product mixer for the manufacture of vermiculite-based products, including structural fireproofing, thermal insulation for masonry, lightweight concrete aggregates, and horticultural vermiculite.

The vermiculite concentrate, or raw ore, was stored in a series of wooden bins inside the building during the approximate time period of 1951 - 1973. Then, in 1973, six - 200 ton capacity steel upright silos were erected on the outside of the northeastern corner of the building. The vermiculite concentrates were unloaded from the bottom of the hopper cars into an under track screw conveyor which moved the concentrate to a bucket elevator. The bucket elevator lifted the concentrates and discharged them through a distributor to the silos. The silos were dismantled and removed upon closure of the facility in 1994.

Expansion of the raw ore occurred inside the building at 35 Industrial Drive. Expansion was accomplished by heating the ore, usually in a dry kiln, to approximately 2000 F, which boiled the water trapped in the crystalline matrix of the vermiculite, thus expanding the material by a factor of 10 to 15 fold.

The waste product from the expansion process contained high concentrations of amphibole asbestos. Two primary types of waste products were generated; they were known as "Stoner Rock" and baghouse fines. The stoner rock was produced as a result of the raw vermiculite ores which did not expand or exfoliate. The baghouse fines were collected as a dust particle in the furnace vent system. Based upon historical aerial photography from the time period 1961 - 1970 and current sampling data, some of these waste materials appeared to be disposed of outside the building.

A structural fireproofing (Monokote®) was also produced using a dry mixture of exfoliated vermiculite, gypsum, cellulose, glass fibers and a powdered surfactant. Prior to 1973, the fire protection product formulation contained chrysotile asbestos. Baghouse fines from this mixing operation were also collected as wastes.