Fifteen years ago Thursday, a Dave Matthews Band tour bus infamously dumped 800 pounds of human waste on a hapless river cruise floating at exactly the wrong time under the Kinzie Street Bridge. Boat passengers — including a Chicago Tribune reporter — enjoying an open air architectural river cruise “described a downpour of foul-smelling, brownish-yellow slurry that ruined their clothes and made several of them sick,” on the afternoon of Aug. 8, 2004, the Tribune reported.