What is this strange thing in the sewer?

Me and my friend Felix were gallivanting in an empty lot. We walked on the side of the creek, and there were houses on either side of us. We found an ending, where we were in somebody's front yard. We came across a sewer and and it had this wire with a handle hanging out of a whole in the sewer. We pulled on it, and the rubber handle came off. We pulled on just the wire itself, and whenever we pull we heard something like a pound. We pulled and pulled, until the wire got disconnected. What is this?