What Goes Up Must Come Down: Lessons Learned from Emergency Air Monitoring during the Escondido Bomb House Burn

On December 9, 2011, San Diego County authorities intentionally burned a house with the largest stash of homemade explosives and bomb-making material ever discovered in the United States. The cache was discovered when a gardener stepped on an unknown substance in the backyard, touching off an explosion that sent him to the hospital. When county, state, and federal hazardous materials experts surveyed the property they found highly toxic and explosive chemicals along with blasting caps, homemade hand grenades, and improvised explosive devices. Hazmat crews and bomb squads tried repeatedly to enter the home to remove chemicals and explosives. When the situation became too dangerous, the San Diego County Sheriff and Environmental Health Department officials decided the best alternative was to burn the house down.

State-of-the-science plume models were employed to predict the worst-case chemical release. Based on those models, neighbors living close to the home were evacuated and residents, businesses, and schools farther away were provided instructions to "shelter in place" before and during the burn. A multi-agency air monitoring task force consisting of the California Air Resources Board, the San Diego County Air Pollution Control District, and the San Diego County Hazardous Materials Incident Response Team was deployed to monitor and analyze toxics and smoke from community locations immediately adjacent to the “bomb house” and throughout the projected plume path. Some hazardous chemicals, including hydrochloric acid and hydrogen cyanide, were detected in the evacuation zone during the burn but at levels below emergency health action limits. Downwind concentrations of smoke and toxics were not significantly elevated during the height of the burn. However, homes close to the incident did experience smoky conditions overnight as the home was allowed to slowly smolder out. The time and day of the burn were selected to maximize favorable meteorological conditions. This was the key in preventing any reported public exposures. This presentation will detail the interagency monitoring and sampling efforts, a summary of the results of airborne sampling and analysis, and lessons learned from successful efforts to protect public health during such an unprecedented event.