I live in an older neighborhood. My house always had real AC but all around me everyone had swamp coolers. Every year a few more people would move up to AC and the first time the temp went over 110 the nearest pole transformer would blow up because the AC takes so much more power, then the whole block would be without electricity. Scared me the first couple of times I heard it, like a big skyrocket only down close. Eventually all the old transformers were replaced and it doesn't happen so often anymore. A hospital near me, also built in the 50s, had all their transformers in a little building to the side of the main hospital. One summer a transformer blew up and started a fire which cause all the other transformers to blow up, it was a real disaster but fortunately no one was hurt. However, the hospital had to be evacuated, about 200 patients, no elevators, ICU on the top floor so the patients with machine support had to be carried down steps and manually ventilated, or whatever. A real miracle everyone got out without incident.

Those Depression era projects are well engineered and constructed. I haven't been on it since the new road was opened. The dam was a major bottleneck in getting to Las Vegas, the worst part of US 60, which was one of the most dangerous roads in AZ. There have always been many, many eyes on everything around there. There are sniper positions, I think. And off the road for miles around, the land is extremely rock and hostile, not exactly a place where you could get away with much.

Those transformers are very large, oil filled transformers. So when one overheats and explodes, it would create lots of black smoke.