Re:Pioneering study finds more than 200,000 rats in Barcelon...
by toast0 on Tuesday September 25, 2018 @11:26AM
(#18067125)
Barcelona has very old sewers, which means there are many places for rats to gain entrance to the sewers, as well as places to live and hide. It's not a battle that's easily won.
Modern sewer systems separate storm runoff from sanitary sewers, and try to keep the sanitary sewers sealed off from animals. It's hard to change the infrastructure under a bustling city though, so most major cities tend to have the sewers they were built with, or whatever was retrofitted when it became apparent that sewage in the streets was worse than the expense of building a sewer system. However, rats are clever and do occasionally find their way in and around modern sewers as well.
Modern sewer systems separate storm runoff from sanitary sewers, and try to keep the sanitary sewers sealed off from animals. It's hard to change the infrastructure under a bustling city though, so most major cities tend to have the sewers they were built with, or whatever was retrofitted when it became apparent that sewage in the streets was worse than the expense of building a sewer system. However, rats are clever and do occasionally find their way in and around modern sewers as well.