As Dave Randolph approaches the pedestrian suspension bridge from Canada Island, it’s unmistakable: bright, freshly painted graffiti covering a retaining wall just above the river. He has just started his daily vandalism check of Riverfront Park, a walk that begins at 4:30 a.m. or earlier with a goal that’s sometimes hard to achieve: remove graffiti before it’s noticed. This find, along the steep riverbank, will make that goal nearly impossible to reach today. He or one of his employees must strap up in a harness to cover it safely – as was done a couple weeks ago when the wall was hit last.