Why the Sixth Street Viaduct went dark, and why it’s been so hard to protect

By 6:15 pm, the Sixth Street Viaduct was nearly swallowed in darkness.

Downtown’s towers shimmered beyond the river. But the bridge — once celebrated as the “Ribbon of Light” — sat largely in shadow. Headlights briefly washed over the arches before fading. A few cyclists moved by in silhouette. Along the sidewalk leading onto the span, crushed cups and plastic bags gathered against fencing and concrete barriers, while a small encampment dotted the grassy slope nearby.

“I can’t really...