Postal workers returned last month to a mail processing facility in northeast Washington, D.C., that was the site of the largest anthrax remediation project in the U.S.
The 17.5 million cubic ft. building had been closed since Oct. 21, 2001, following the discovery of two anthrax-laced letters addressed to Capitol Hill recipients. Only a few days earlier, traces of anthrax had been found in mail delivered to the 100,000 sf. Hart Senate Office Building. It was then closed until January, 2002 for inspection and remediation.
More than 2,000 air and surface samples were taken prior to the fumigation of the postal building with chlorine dioxide gas, which was essentially distributed through the building's HVAC system. The fumigation took two days, as the gas was slowly built up until it reached its required level of concentration. It was then left in place for the 12 hours that are required for it to be effective.
Additional samples were taken after the fumigation was completed to verify the effectiveness of the chlorine dioxide, increasing the number of samples to about 5,000. No anthrax spores were found.
The chlorine dioxide left a powderlike residue which causes chemical changes in materials and surface corrosion on unfinished surfaces. It was removed by wiping.
The remediation process delayed the start of a planned renovation of the postal facility, which was constructed in the mid-1980s. Crews from Clark Construction Group were unable to enter the building until May 2003 (beginning in March of last year, crews were allowed to work inside the building without protective suits or precautionary antibiotics).
Performed under a separate contract, this work included renovation of more than 30 toilet rooms, replacement of acoustical ceilings, and installation of a new structured wiring system for voice, security and data. Lockwood Greene was architect for the renovation.
Before the fumigation operation began, plastic was taped over windows and the building's more than 200 small skylights to prevent the chlorine dioxide from escaping.
The U.S. Environmental Protection Agency's mobile air laboratory, which has an atmospheric gas analyzer that can record chemical concentrations of as little as parts per trillion, monitored for possible leakage.
The cost of the fumigation and renovation was about $130 million, according to Thomas Day, the Postal Service's vice president for engineering.
Marco Aquino, the project's on-site EPA coordinator, says one possible way of averting future acts of biological terrorism might be the incorporation of detection equipment that would prompt early shutdowns of elevators and the HVAC system to reduce the spread of a contaminant.