CHICAGO (CBS) — The Chicago River is a glowing green as the city celebrates St. Patrick’s Day. WBBM’s Mike Krauser spent some time with the crews behind the tradition.

The Shannon Rovers played on the bank of the Chicago River as the Plumbers Union Local 130 carries out a more than 50-year-old tradition of dyeing the river.

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Generations of the Butler and Roan families are behind this tradition. Robert Roan was on the boat spreading the dye that makes the river a luminescent emerald green.

“This is great. You get 30-40,000 people yelling and screaming at you going down the river, it’s great,” said Robert Roan.

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Bill King said this started when the plumbers were checking buildings along the river for illegal sewage dumping. The dye would go through the pipes and where the river turned green, they found the culprits.
He says the dye formula is a closely held secret.

“And there have been over a hundred cities that have contacted the plumbers trying to find out how to do it, but we’re not sharing that,” said King.

When asked why not share it, King responded,” Because it wouldn’t be unique. Everybody knows about Chicago dyeing the river there are thousands of people down here. It is a very unique Chicago thing.”

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For the crews on the dye boats, everything that comes in contact with the dye turns green, eyes, mucus, urine everything.