To add to this question, are these kinds of sites found often by archeologists? Are there any popular landfills of note from any century discovered?
A lot of everyday waste was thrown in the outhouse. My friend is an antique bottle hunter so he digs up latrines from the 1850's all the time. Inside those old latrines, you can find bottles, cans, and all other manner of things. My friend has found pistols and old wooden douches. When the latrine started to fill up too much, they would throw large stones in to pack it all down again.
How does he find the latrine? He looks at old maps of the city where he does his hunting. Maps which show the property lines. Based on his past experience, he usually can deduce where the latrine would be. He does some probing around the property and then begins his dig.
source: fieldwork with my buddy.
not an answer, but just FYI, the term for this is a midden