Capped off by the "Grand Recycle" event, which is part 2 for with progress comes with dumping out the trash. The city itself cycles the machinery used, broken, or beyond repair. The first year of the grand excavation, the forefathers were scared witless when much of the plates separated and a massive furnace came to light. They initially thought it was simply a superweapon of hellfirey proportions but no, much of the cityscapers - people who love to delve into the ancient mechanical parts of this grand city - have discovered that the city itself mines out parts of The Great Chasm for metals and ores to create new Centibeetles and other mechanisms. For some of the mechanisms that have been repaired too many times or fallen into disrepair are stored away for this day when the city itself burns & resmelts much of the materia for reuse next year. This has taken on both a scientific and religious manifestation in the city for people to dump out mostly metallic trash or projects or stuff that have not worked but materials can be reused. It is what caps off this grand occasion by having all of the old things that have outlived their usefulness or served well be brought to a final resting place for use in the city's continued growth.
Things are slithered down to dusts or slag the city uses. The conglomerates put in rules not to throw in volatile or dormant magics or phrax, lest there be a plague of living spells.