Just 1. The feet of the towers are simply accessible, so there's nothing stopping people from even just using a metal file. It wouldn't be safe, but you'd get

Just 1. The feet of the towers are simply accessible, so there's nothing stopping people from even just using a metal file. It wouldn't be safe, but you'd get the job done. Or just plow a truck into their feet. You only really need to bend one of the feet and the wind will do the rest.