How does Chicago dye the river green for St. Patrick's Day?

CHICAGO (WLS) -- It has been six years since St. Patrick's Day has fallen on a Saturday, and in that time the dyeing of the Chicago River has been celebrated and improved.

This year's celebration will be bigger than ever as the mighty river attracts visitors by the thousands for a city tradition beloved the world over.

The dyeing is the work of Chicago Plumbers Union Local 130. They use a proprietary dye to turn the Chicago River green.

This year will mark the 55th year the plumbers have taken to the river; this time in three boats, two with the secret sauce and a chaser vessel to mix it up. The river will turn green from Columbus west to State Street, an extension of one block from past years as the city seeks to enhance viewership from the Chicago Riverwalk.

"Four bands coming from Florida, we've got bands coming from Pennsylvania, Ohio, Kansas, Georgia, I mean that speaks volumes itself that these people want to come to Chicago in March," said James Coyne, business manager from Plumbers Union Local 130.

The dye is essentially food coloring concocted by the plumbers years ago to help trace leaks in buildings. Mary Kate Manion, this year's St. Patrick's Day Queen as crowned by the union, said the display is about enhancing traditions.

"It is just about getting all together and having a good time and celebrating what the Irish have done for the city of Chicago," she said.

The mixed water will also be spouting off shoreline tourist boats that will ply the waters as it changes.

"I feel like the Irish have a lot more traditions that stand out in people's eyes, you know, St. Patrick's Day is such a big day and I know for the whole month of march as well people look forward to that day," Manion said.

The dye will stay in the river for 24 to 48 hours. Shoreline tourist boats will start loading for the event at 8 a.m. Saturday. The dyeing begins at 9 a.m.