Is that right? I’ve never heard of it before but a single-point failure of a regulator like that could possibly put high pressure onto the low pressure distribution lines. What an awful piece of engineering if so! Seems pretty clear that high pressure gas is involved here.
That’s just how it was done with some old systems, there’d have to be a couple failures but it can be possible to overpressure downstream. Depending on the utility, usually those systems are checked often so that never happens.
Don’t know what went on here..