If you say that a place is a dumping groundfor something, usually something unwanted, you mean that people leave or send large quantities of that thing there.
[disapproval]
...a dumping-ground for radioactive residues. [+ for]
dumping ground in British English
(ˈdʌmpɪŋ ɡraʊnd)
noun
somewhere where people send large quantities of something unwanted
Many states were using it as a dumping ground.
It appalls me how we use the oceans, forests and skies as dumping grounds.