Une idée de cons, repeindre le fleuve en vert.
Le billet Wikipédia nous explique que c'est une tradition et que ça ne pollue pas...
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 some 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.