On May 29, 2019 EPA received a call requesting assistance from Colorado Department of Public Health and Environment (CDPHE) regarding a mercury spill at their office in Cherry Creek, Denver, Colorado.  Initial reports indicated a small thermometer had been broken in a storage room in the CDPHE occupied section of the office building. Date of when the spill occurred was unknown but discovered by CDPHE personnel on May 28,2019. The spill occurred in a storage room approximately 25 x 30 feet. Ambient air mercury concentrations in the storage room and hallway area exceeded the recommended levels that are protective of human health for commercial and sensitive populations. CDPHE personnel removed as much mercury as they could and isolated the area but lacked equipment for clearance. CDPHE employees in adjacent cubicles and offices were temporary relocated or offered to work from home during this time.

Upon receiving the CDPHE’s request, EPA deployed an On-Scene Coordinator (OSC) and a Superfund Technical Assessment and Response Team (START) contractor to assess the office. Initial site assessment indicated breathing zone ambient air mercury vapor concentrations greater than 50,000 nanograms per cubic meter (ng/m³)  in the storage room of CDPHE using a Lumex Mercury Vapor Monitor (Lumex). Additional readings of the cubicles, office space and hallway were performed utilizing the Lumex and Jerome 431-X indicated contamination had been spread from the storage room out into the hall way. The highest reading was 140,000 ng/cubic meter of air near a piece of broken glass on the floor of the storage room. 

EPA presented the results of the assessment to CDPHE which asked EPA to support the State in performing a removal action.  EPA called in their Emergency Response and Removal Services (ERRS) contractor to perform the cleanup.  

Access agreement was signed in the morning of May 30, 3019.  

1. Perform an assessment and removal of mercury contamination within the storage room and impacted hallway of CDPHE.

2. Collect clearance data utilizing the Lumex.

On May 30, 2019, EPA’s ERRS contractor was onsite to provide removal of mercury and cleanup of mercury contamination. ERRS removed tile flooring, base layer of tile mastic, decontaminated surfaces, and heated the room with space heaters while maintaining negative air pressure, recycling the air within the storage room. Porous items that were contaminated were disposed of appropriately. CDPHE also surrendered additional mercury thermometers (approximately 14 thermometers) that will taken for proper disposal. START provided air monitoring of the area utilizing the Lumex and Jerome 431-X. The floor was then sealed twice with an epoxy-based sealant. Final ambient air mercury vapor concentrations were below 1,000ng/m³, action level recommended for protection of sensitive populations.

EPA and EPA contractors demobilized personnel and equipment from the site on June 5, 2019.