Teague said he’s especially concerned about the concentration of mercury in the wastewater from the SpaceX water deluge system. The levels disclosed in the document represent “very large exceedances of the mercury water quality criteria,” Teague said.

I’m confused as to how the mercury got in the water in the first place. Is it leeching out of the storage tanks, or was it already present in the water prior to its delivery to SpaceX?

As far as I am aware, no part of the launch system relies on mercury as a major (or even minor) component. Where is the mercury coming from?