Asbestos Abatement >> How To Choose An Asbestos Removal

Vermiculite is a nonfibrous silicate mineral with many commercial and consumer applications. Its usefulness comes from its ability at high temperatures to expand (i.e., exfoliate) up to 20 times its original size (EPA 1991). Additionally, vermiculite has a high-ion exchange capacity, making it useful for absorbing liquids or How To Choose An Asbestos Removal chemicals. 

The density of raw vermiculite ore is approximately 55 pounds per cubic foot, How To Choose An Asbestos Removal while the density of finished vermiculite is in the range of 6 to 8 pounds per cubic foot. The raw vermiculite ore mined in Libby, Montana, is estimated to have contained up to approximately 21–26% fibrous amphibole asbestos of the tremolite series (MRI 1982). 

Mining companies extracted the raw ore by open-pit mining methods and How To Choose An Asbestos Removal transferred it to a milling operation to remove waste rock. Mining facilities in Libby then screened the concentrate into several size ranges (from #0, coarse, to #5, fine) for processing into finished vermiculite for shipment, usually by rail, to a number of exfoliation (expansion) plants across the United States and Canada. 

Some studies suggest that the different ore grades may have had varying asbestos contents, How To Choose An Asbestos Removal with finer grades being the more contaminated (EPA 1991). Other data suggest that in the various grades of ore the tremolite content was typically 0.3%–7% (MRI 1982). 

A 1977 internal W.R. Grace memorandum estimates that 28% of all workers with over 10 years’ service and who had been exposed to ore concentrate from Libby, Montana, How To Choose An Asbestos Removal had contracted asbestosis (MDH 2000). Former workers at other sites using the ore from the Libby mine have reported cases of asbestos-related disease to the media. 

The W.R Grace facility in Phoenix received by rail vermiculite concentrate from the mining operation in Libby, Montana, How To Choose An Asbestos Removal from 1964 to 1992 (EPA 2001). The facility stopped processing vermiculite from the Libby mine in 1992. The facility currently processes vermiculite from a mine in South Carolina. 

When amphibole asbestos has been detected in vermiculite from mines other than Libby, the reported amounts have been much lower than those in Libby vermiculite (ATSDR 2001). South African expanded and How To Choose An Asbestos Removal unexpanded samples showed 0.4% and 0.0% amphibole content, respectively (Moatamed et al. 1986). 

In another investigation, total asbestiform fibers (i.e., classified as tremolite-actinolite) represented less than 1% of the weight of samples of raw ore and vermiculite concentrate from Enoree and How To Choose An Asbestos Removal Patterson, South Carolina. This is compared with ~21% to 26% and 0.3% to 7% of the weight of raw ore and vermiculite concentrate samples from Libby, Montana (Atkinson et al. 1982). 

Expanded and unexpanded percentages of the Virginia ore were 1.3% amphibole by weight; Moatamed (1986) notes, however, How To Choose An Asbestos Removal that the Virginia and South African amphiboles were predominantly nonasbestiform, while the Montana (Libby) amphibole was predominantly asbestiform. 

Mining companies shipped the concentrate in railroad cars with an approximate capacity of 45– 50 tons per car. Ore was stored in bins outside the facility prior to being fed into an exfoliation furnace. Prior to 1977, How To Choose An Asbestos Removal vermiculite ore was unloaded using an open conveyor to an enclosed elevator (Grace 1977a). 

A front end loader took the vermiculite concentrate from the bin to the expanding furnace loading hopper (Grace 1977a). In 1977, new material handling equipment, consisting of a railroad hopper car unloading pit, enclosed conveyors, and How To Choose An Asbestos Removal feed elevator were installed. 

The new system consisted of a belly dump sump, into which the raw ore was gravity fed from the ore car, after which it was transported to a holding bin. From the holding bin, How To Choose An Asbestos Removal the ore traveled to the furnace on a conveyor type system. 

The facility used a furnace, designated as a Model A type, specifically designed to expand the vermiculite concentrate and to facilitate packaging of the finished product. W.R. Grace installed this furnace in 1964 and How To Choose An Asbestos Removal added another Model D-18 exfoliation furnace during the 1970s. 

Waste rock is currently separated from the finished product and How To Choose An Asbestos Removal placed in 52-cubic foot bags. In the past the bags containing waste rock were stored on site in a holding container until removed for disposal at a local landfill. Employees may have taken home some of the waste rock (EPA 2001). 

From 1964 to 1992, the W.R. Grace Phoenix facility used Vermiculite ore from the Libby, Montana, How To Choose An Asbestos Removal mine to make commercial products. From 1971 to 1992, W.R. Grace processed approximately 204,000 tons of Libby ore at the site (EPA 2001). 

Vermiculite is generally used for insulation, as a lightweight aggregate in construction materials, and as a soil additive for gardening. Vermiculite also has many other industrial uses, How To Choose An Asbestos Removal including as a fireproofing material, as an absorbent, and as a filter medium (Vermiculite Association 2000). 

Dust inside the facility became a significant problem in 1971 when a concrete aggregate bulk system was installed. The system consisted of an overhead conveyor, How To Choose An Asbestos Removal which allowed dust to fall over the warehouse. A further change to "Number 4 Concrete” created additional dust problems. 

Because of the increased dust levels, How To Choose An Asbestos Removal W.R. Grace enclosed the conveyor system, and in 1976 installed a wet dust collector system. These changes resulted in a 99% reduction in dust levels (Grace 1977b). 

In addition, in 1975 and 1976 dust collection baghouses were installed on the furnaces. Removal Action Pursuant to an Administrative Order on Consent (AOC) (EPA 2002d), W.R. Grace as the site owner and How To Choose An Asbestos Removal operator performed all removal work. EPA provided oversight of the removal action. 

In the railroad loading area, soil containing asbestos concentrations greater than 1% was removed to a depth of 1 foot below the surface, the excavation was backfilled with clean soil, and How To Choose An Asbestos Removal was capped with concrete or asphalt (EPA 2002d). 

Upward-facing horizontal surfaces where microvacuum samples showed greater than 10,000 TA asbestos structures/cm2 (Silo Area and How To Choose An Asbestos Removal Maintenance Building) were microvacuumed (using HEPA filter vacuum) and wet wiped to remove any asbestos-containing dust (EPA 2002d). All asbestos was transported offsite to an approved disposal facility (EPA 2002d). All work was completed by December 2001.

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