The Chicago River will be dyed green on Saturday ahead of St. Patrick’s Day. The tradition dates back 130 years and is the task of the Chicago Journeymen Plumbers Local 130 plumbers' union. They suggested the idea to begin with. The closely held environmentally friendly dye recipe comes in powder form and it takes two boats - one to spread the powder and one to stir - to make the green magic happen. There will be plenty of online coverage of the river between Saturday and St. Patrick’s Day.