I was part of a volunteer work crew planting beavertail cacti all over the slopes along the sides of a newly constructed road to allow the highway going past the Hoover dam to now bypass it instead of having to go over it. We also planted a species of barrel cacti, but the beavertail spines- tiny little hairs- were so much worse. They got onto your skin and clothing if you shook the plant a tiny bit, and you felt these tiny prickly things all over you from then on. It was an interesting job.. but it's definitely cool to know I helped plant those cacti that will hopefully be growing there for a long time to come.
Like I said, steep hills reconstructed alongside new paved roads. This was planted as part of a restoration project.