Chicago River

As part of a more than fifty-year-old Chicago tradition, the Chicago River is dyed green in observance of St. Patrick's Day. The actual event does not necessarily occur on St. Patrick's Day and is scheduled for the Saturday of the closest weekend. The dye takes days to dissipate. The tradition of dyeing the river green arose by accident when plumbers used fluorescein dye to trace sources of illegal pollution discharges. The dyeing of the river is still sponsored by the local plumbers union. The United States Environmental Protection Agency (EPA) outlawed the use of fluorescein for this purpose, since it was shown to be harmful to the river. The parade committee has since switched to a mix involving forty pounds of powdered vegetable dye. Though the committee closely guards the exact formula, they insist that it has been tested and verified safe for the environment. Furthermore, since the environmental organization Friends of the Chicago River believes the dye is probably not harmful, they do not oppose the practice. In 2009 First Lady Michelle Obama, a Chicago native, requested that the White House fountains be dyed green to celebrate St. Patrick's Day. The Chicago River is a system of rivers and canals with a combined length of 156 miles (251 km) that runs through the city of Chicago, including its center (the Chicago Loop). Though not especially long, the river is notable for being a reason why Chicago became an important location, with the related Chicago Portage being a link between the Great Lakes and the Mississippi Valleywaterways and eventually the Gulf of Mexico. The River is also noteworthy for its natural and man-made history. In 1887, the Illinois General Assembly, partly in response to concerns arising out of an extreme weather event in 1885 that threatened the city's water supply, decided to reverse the flow of the Chicago River through civil engineering by taking water from Lake Michigan and discharging it into the Mississippi River watershed. In 1889, the Illinois General Assembly created the Chicago Sanitary District (now The Metropolitan Water Reclamation District) to replace the Illinois-Michigan Canal, which had become inadequate to carry the city's increasing sewage and commercial navigation needs, with the Chicago Sanitary and Ship Canal, a much larger waterway. The District completed this man-made hydrologic connection between the Great Lakes and Mississippi watershed in 1900 by reversing the flow of the Main Stem and South Branch of the river using a series of canal locks, and increasing the river's flow from Lake Michigan, causing it to empty into the new Canal. In 1999, this system was named a 'Civil Engineering Monument of the Millennium' by the American Society of Civil Engineers(ASCE).