FWIW I do freshwater fish surveys and just happened to be in Gippsland somewhere near Warragul late last year.

We'd come across a couple of the original underground Esso BHP dual pipeline creek crossings complete with signage. One pipe is oil from memory and the other is definitely LPG. Goes from somewhere near Longford to Melb and is connected to Coode Is., Mobil in Altona and Shell in Geelong, etc.

Coincidentally met a bloke staying at the same motel who works for Esso and is in charge of organising the replacement of both pipes, they're past use by date. They are 180km long.

Expect another 40 years boys.

cheers, DL