Safety Reg or are we just beaten with the stick, until we take the carrot.....One never knows how their culture will change. On the East Coast, home heating oil USTs became a nightmare: A National Nightmare in the 90's. Though in the 40's to 50's this was what everyone did. They dug a hole, but in a tank, and ran an oil furnace. Then, oil got expensive, and people switched over to Natural Gas - the new clean energy. And all those old tanks had to be decommissioned. Which was also expensive. So after that conversion, we now have a new conversion and natural gas is now the evil heating source, rather expensive, and we should all switch to electric. There is a pattern here.
While I've never been a fan of underground steel tanks like that (they leak, relatively quickly), we went through the same cycle. Even older houses here mostly had oil tanks in the basement. Esp. with a concrete floor, you'd have to be a specific type of fool to not notice that tank leaking..... but no matter, they all had to come out too. Most people here went to natgas, or maybe propane in rural areas.
IMO, where that "Safety" reg was deficient was in decommissioning. Until most of the market was off heating oil, every once in a while you'd read about a delivery screw-up. Fuel truck rolls up to a city address, driver misreads # and goes to the house next door and proceeds to fill a good part of their basement with fuel-oil. Code should have been that the fill-pipe had to be removed when the oil tank was pulled, or at the very least welded shut and tagged-out.
Rgds, D.