The bit where the London rubbish barges go to tip their stuff is called... (appropriately) ... Mucking! Apparently it's full or very nearly full so another hole will have to be found. Downstream from here there are huge areas at the side of the Thames, eg. opposite Erith, where at first there appear to be green rolling hills which look a bit odd in an otherwise flat tidal estuary, then you see lots of little vents all over them and realise that they are grassed-over enormous mounds of rubbish.
...it's the same for the home-ground of my team - Reading FC...the Madejski Stadium is built on landfill, so there are lots of unusual looking funnels poking up out of the ground all around the stadium. The area constantly smells of burning potatoes, which is the methane etc. escaping.