On September 19, 2008, an antiquated mercury-containing manometer for measuring water level in a water tower ruptured at Seattle City Light’s Bothell Electrical Substation when testing the system for a switch over to city water. The rupture spewed water mixed with mercury into the control room. Water from the main floor of the control room poured into the basement through conduit openings in the floor. EPA was notified of this release on November 4.
Initial cleanup was conducted by substation workers not trained in hazardous material cleanup which resulted in mercury-contaminated water being poured down two different drains and possible cross contamination through poor decontamination. That same day Seattle City Light (SCL) hired NRC Environmental Services, to complete the cleanup.
EPA, Department of Ecology, and START visited the site on November 5th. START screened area of concern with a Lumex mercury vapor analyzer. The drains where water and mercury had been poured were screened and observed to have levels below the commercial re-occupancy level of 3000 micrograms per cubic meter of mercury vapor. The outfall of the drainage system was observed to have readings at the background level of the instrument.
