The Vermiculite Northwest site (Site) was home to a vermiculite exfoliation plant from 1951 to 1973. The facility was operated by Vermiculite Northwest, Inc. and later by W.R. Grace and Company. Vermiculite ore from Libby, Montana was received at the Site via rail car. The vermiculite product manufactured at the Site was sold under the trade name Zonolite. Both vermiculite ore from Libby and the manufactured product Zonolite are known to contain a significant quantity of amphibole asbestos. Records show that up to 10,317 tons of vermiculite ore were processed at the Site from January 1967 to October 1970.
After 1973, the Site was occupied by the Wilbert Vault Company, which manufactured concrete products, which manufactured concrete products such as septic tanks and burial vaults. Spokane County acquired the Site in January, 2000 and has since used it as an equipment storage and maintenance yard.
In 2000 and 2001, the EPA START contractor conducted two Site visits that included sampling and analysis. The initial visit in 2000 was to determine if asbestos existed in soils or on surfaces at the Site. Eight bulk soil and wipe samples were collected. All samples contained from trace amounts to 2% total asbestos fibers. In 2001 the START contractor was tasked to conduct a removal site evaluation at the facility. The START collected 27 soil samples, which included 14 off-Site samples taken from residential locations. Analytical results showed asbestos levels in 9 samples, and two samples with concentrations of 2% and 3% asbestos. Four of the off-Site samples showed trace levels of asbestos.
In 2002, the EPA Region 10 Office of Environmental Assessment (OEA), conducted a study to determine whether asbestos present in soils at the Site could become airborne when the soil is disturbed, posing a potential exposure risk to people at the Site. The OEA study consisted of three phases: collection and analysis of bulk soil samples; air monitoring in a laboratory enclosure while soils samples from the Site were agitated, and; air monitoring on Site while activities were performed that simulated likely property maintenance or soil excavation activities. That study revealed that asbestos in soil at the Site can become airborne if the soil is disturbed.
In September 2004, Spokane County applied for and was accepted into Washington Department of Ecology’s (Ecology’s) Voluntary Cleanup Program, to conduct remediation activities at the Site. Spokane County had previously, in 2002, demolished, removed and disposed of three buildings at the Site that were formerly used as vermiculite warehouse and processing buildings. In 2005, Spokane County demolished, removed and disposed of an additional building at the Site that contained asbestos. In 2006, Spokane County conducted a study (through a contractor) to identify the vertical extent of asbestos contamination is soils in the former vermiculite processing area (the southwest quadrant of the Site). The study found asbestos present in significant concentrations at depths greater than four feet. As a result of this study, Spokane County and Ecology concluded that encapsulation of asbestos contaminated soils in place, at least in the fairly level southwest quadrant of the Site where asbestos contaminated soils were deep, was a more feasible alternative than removal and disposal. In 2007, Spokane County developed a design and completed work on an asphalt and soil cap and cover over the southwest quadrant of the Site, where the former vermiculite processing and handling buildings were previously located, where the highest concentration of asbestos was found in soils, and where asbestos was found to occur at depth.
In 2009, EPA Region 10 determined that additional information was needed on possible off-site migration of asbestos fibers from the Site, and possible contamination of exposed soils in un-remediated areas of the Site. In June and July, 2009, EPA collected bulk soil samples from nine residential yards and from locations on top of the bluff on the north side of the Site. The bulk soil samples were collected using a multi-increment sampling technique intended to provide representative samples for analysis by PLM using he CARB 435 method. PLM analysis of the bulk samples revealed 0.25% amphibole asbestos (either winchite or richterite) in two samples and trace levels (below a quantifiable detection limit but still observed in the sample) of amphibole asbestos in the remaining samples.
In September, 2009 EPA returned to conduct activity-based sampling at selected locations at and near the Site. The intent of activity-based sampling is to determine if asbestos fibers present in soils at these locations could become airborne at concentrations that pose a risk if the soil is disturbed by normal activity. Activity-based sampling at the Site and two residential locations involved collecting air samples while sample teams agitated the soil by raking. The activity-based sampling locations were chosed based on proximity to, and downwind locations (based on prevailing winds) from, the former vermiculite exfoliation plant, and the presence of asbestos detected during earlier bulk sampling. Activity-based sampling results indicated that there was not a significant release of airborne asbestos within the study locations resulting from the activity.
Concentrations of asbestos in air samples collected during activity based sampling at off-Site locations did not exceed risk-based screening levels that were developed prior to the sampling effort by the EPA Region 10 Toxicologist. As a result, EPA does not anticipate the need for additional sampling at residential off-Site properties.
