Every year, the Chicago River is dyed green for the St. Patricks Day parade. This time-lapse video taken yesterday may seem like it’s in black-and-white at first, but that’s just the colors of the city. It’s a slight shock when the green starts! The dumping was done by members of the Chicago Journeymen Plumbers Union Local 130. Here’s a view from a little closer to the action.
The area of the greening was restricted somewhat by construction further up the river. The green only lasted for the day, but brightened things up for the parade.
50 years ago, plumbers used fluorescein dye to trace sources of illegal pollution discharges and they discovered that the river could show the green dye.
When the EPA decided fluorescein could not be used because it was potentially harmful, the Plumbers Union who dyes the river, switched to a mixture made of powdered vegetable dyes.