The green you see is not pollution. But it can help identify pollution sources.
When our Water Quality & Industrial Surveillance team is called in to find the source of a hazardous spill or an illegal discharge—like this one in Rocky River last year—the crew conducts dye testing like this. Investigators release an environmentally safe dye into the collection system, most commonly storm sewers in the area, to confirm the flow's source, route, and ultimate destination.
If you ever see a suspicious discharge in a Northeast Ohio waterway, you can contact our Environmental & Maintenance Services Center at (216) 641-6000 or tweet @neorsd.