On Friday, 2/22/08, Boise Fire Hazmat responded to a reported mercury spill at the St. Joseph's Catholic school in Boise, Idaho. A 6 oz jar that was approximately 3/4 full of mercury had been dropped and broke on the tile floor, spilling the mercury. The children had been evacuated and sent home by the school. Boise Hazmat had the clothing from three children who had reportedly been in the vicinity when the spill occurred bagged and returned to the school. Boise Hazmat isolated the room, had the HVAC system shut down, and cleaned up the visible spilled mercury using a mercury vacuum and mercury amalgam kit. In the evening of 2/22/08, EPA participated in a State Comm bridge call where it was requested that EPA respond with appropriate mercury detection equipment to verify that cleanup achieved safe levels of mercury prior to re-occupancy.
EPA OSC and START contractor responded on morning of 2/23/08 with mercury vapor field analytical equipment. Boise Hazmat responded with EPA and formed Unified Command. Upon entry into the classroom where the spill ocurred, EPA obtained readings of 3,000 nanograms per cubic meter (ng/m3) of mercury in ambient air. Approximately 34,000 ng/m3 mercury was detected in air directly above the spill area. Unified Command determined that additional cleanup was necessary involving the removal of floor tiles in the area of the spill and other hot spots. Additionally, the bags of clothing from the 3 children that were potentially exposed were examined. EPA examined the headspace inside the bags with the mercury vapor analyzer. One child's bag of clothing read approximately 16,000 ng/m3 mercury. The other two bags were well below 1,000 ng/m3. EPA contacted the parents of the child with elevated mercury in her clothing and made arrangements to check the car the child left the school in. Elevated levels of mercury were not detected in the car. The child had removed her clothing prior to entering the house, so it was determined not necessary to check the home.
EPA and Boise Hazmat personnel removed about 60 floor tiles in the classroom, then used a mercury vacuum and mercury amalgam to remove any residual mercury. The room was heated up to approximately 95 degrees F and left overnight. In the morning of 2/24/08, the room was ventilated with a blower and windows open, and examined again with the mercury vapor analyzer. Ambient levels in the room were approximately 300 ng/m3, well below the 1,000 ng/m3 ATSDR established recommended threshold for residential occupancy. Concentrations at ground level above where the spill had occured were 900 ng/m3. EPA set up 3 air samplers in the room to collect an 8 hour air sample for confirmation laboratory analysis. Preliminary lab results were received on 2/25/08 that were non-detect for mercury at a detection limit of 360 ng/m3.
