When I was younger, around St. Patrick's day, I remember the news story's  about Chicago turning the river green before the big parade. I always wondered, how they did it, what kind of dye they used and how much it took to dye the water. According to the Chicago Tribune, usually they start dyeing it the Saturday before St. Patrick's Day unless the holiday falls on a Saturday.

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They start the dyeing process on Michigan Avenue, right on the river. First, the crew arrives early in the morning at the boat slip at the north side of the river and they all wear clothes that they're not afraid of getting dirty. The crew gets onto 2 small boats. At 9am, the larger boat of the two starts dyeing the river right when it's under the Michigan avenue bridge. But how do they do it you say? They actually use large flour sifters. It only takes about 3 men to do the job. They use about 40 pounds of an orange environmentally friendly powder. The formula for the powder is a big secret so no one's telling.

Finally the smaller boat, chases the bigger one to stir up the water and powder. They usually stop around Columbus drive. The city of Chicago definitely has it down to a science. If you remember, Savannah Georgia tried to do the same thing but failed miserably.