For more than forty years, Chicago has kept its tradition of dyeing its river green for St. Patrick's Day. Contrary to popular belief, although the city promotes the event, it does not pay for it. It's sponsored by the local plumbers' union and started when that group used fluorescein dye to trace illegal substances that were polluting the river more than 40 years ago. The EPA has since banned the use of fluorescein for this purpose and today more than 40 gallons pounds of vegetable dye are used to turn the river green.
Although the dying of the river is to celebrate St. Patrick's Day, the event itself takes place on the closest Saturday to St. Patrick's Day. This year, it fell on Saturday, March 10, just prior to the official start of AIChE Spring 2011. But several staff members were there and captured some photos from this year's "greening of the river." I like to think of it as "ChEnected Green," or at least pretty close!
Gallery of Chicago Green:
Time Lapse Video of the Dyeing of the Chicago River in 2008
Interested in learning more? Check out the official website, GreenChicagoRiver.com