CHICAGO (CBS) — Thousands of people lined the banks of the Chicago River Saturday morning for the annual tradition of dyeing the river green.

WBBM’s Mike Krauser reports.

Crowds erupted in cheers as the Plumbers Union Local 130 sprayed dye from nozzles on the back of a large boat that spun in circles. Two smaller boats followed as the larger one churned the water and spread the dye. The powder colorant is orange when it goes into the water and then becomes a luminescent green.

The Union planned the dyeing and parade this year. Pat Fitzgerald with the parade committee said the tradition dates back to 1962. He also said his organization will never give up the dye’s secret formula.

“We would probably give out social security numbers before we gave out that formula, we will not give that up,” he said.

Fitzgerald claimed people call year round from all over the world for the environmentally safe dye’s formula. He said the dye is used by plumbers for leak detection.

The dyeing of the Chicago River kicked off festivities on Saturday such as the noon St. Patrick’s Day Parade downtown. Thousands of people are also expected to attend the South Side Irish Parade on Sunday on South Western Avenue. The event features marching bands and Irish dancers.

The city’s Office of Emergency Management and Communications said parking restrictions and road closures will be in place. Officials also encouraged people to celebrate responsibly.

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