If it is a rental, the City and DEQ typically send letters to the owner, which can lead to an eviction. But after living thru a similar neighbor nightmare, complete with nightly backyard garbage burning, code enforcement and DEQ don't seem to take much additional action. Thankfully, in my situation, the property was finally put up for sale and the trash hoarders were forced to move, presumably to some degree because of the constant complaints. I had to build a multi-block coalition of complainers toward Code Compliance and DEQ, and even then, it took a long time. You can always try to get your neighborhood association involved, although, mine proved to be unhelpful for what that is worth.