Minor spoilers - at the end...
... in that, what, automatic swing-related what mining field, how come not a single person was around to witness Caine's Carter and that dude fighting? Thanks.
shareSlag!
No not you. Waste coal, well not coal but the slag that is left over from getting the coal out of the ground, from nearby mines was being dumped just off-shore. Or it could have been waste coke (slag) from nearby steelworks etc. Slag is basically waste material of any type. Its why its used as an insult.
No one was around because, as can clearly be seen, its not a very nice place to be. Its not a lovely bracing coastal walk or recreation area, its a bit of industrial wasteland.
Much nicer now of course, though it remains stubbornly in the North-East.