1 day after people, At rail yards, PROCOR
chlorine tanks wait for engines that will never arrive.
50 years after people, The Procor chlorine tanks have deteriorated after 5 decades of corrosion. Their outer steel shell is one-tenth of an inch thick and their plastic insulation is 4 inches. One of the railcar’s undercarriage gives way and the tank spills its chlorine, killing any wild animals nearby. The chlorine cloud advances on a lake and turns it into acid, thus killing everything in it's path (save for bacteria and some lucky invertebrates).