Investigating a lingering smell in company bathroom. Not sewage, but dampness, and almost sewage. Pop this cover off next to the toilet and im standing above some kind of cistern, or something broken.

There is standing water right under the hatch, and its more than 5 feet deep, and goes for about 2 foot in either direction under the hatch. Did not find bottom after extending entire broom handle down there.

Question, WTF is this? It CANT be by design, or maybe it can, I know next to nothing about plumbing except how to put in some copper lines and sinks and stuff

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