Frequently Asked Questions


What are the primary contaminants?
PCBs, dioxin/furans, TPH (petroleum hydrocarbons, like heavy oils and diesel) and heavy metals such as arsenic, silver, lead, zinc and copper.
Is there enough data to understand the source of dioxins in the neighborhood?
Extensive technical information to definitively state that historical activities at T-117 are the major source of dioxins/furans in yards and adjacent streets is not available, but it is likely a source, especially as tracked by trucks in the area. Aerial deposition is another potential source of dioxins/furans contamination in nearby streets and yards; however, at this time it has not been determined how much of this potential contamination is from T-117 versus other sources in the Lower Duwamish area.
What has the City of Seattle done to address the communities’ concerns about dioxins? Is the City planning any additional studies or investigations for dioxins?
To best understand and move forward on this issue, we need to understand what is contaminated due to historical industrial activities at the T-117 site, (which we are firmly committed to remediate), and what is contaminated due to regional sources. The City, Ecology and EPA have invested significant resources in sampling dedicated to understanding the science and sources of dioxins related to the T-117 site. In addition, the City assisted Ecology in its recent regional study of dioxins in soil in the Seattle area.
We’ve heard a lot about mercury being emitted from the cement plants and other sources around the Duwamish. Are you looking for mercury as part of your study?
Yes, soil samples were tested for mercury at and around T-117 and in the river. It was found that mercury was not elevated above the level of concern. Although mercury is a risk driver for the larger Lower Duwamish Waterway cleanup project, it is not a contaminant of concern at T-117.