Rubbish left on common property

We have a recurring problem of residents in our building leaving rubbish on the street verge and on the common property rather than putting it in the bin. It usually happens when people are moving in or out but there have been instances where people have just been too lazy to put their rubbish in the bin.

We’ve written letters to all residents reminding them of the bylaws on rubbish and put notices up in the notice board asking people to do the right thing but this doesn’t work. We really can’t issue notices to comply because we don’t have any evidence of who dumped what, unless we employ a policeman or install a security camera to guard around the clock.

I am looking for practical solutions to this problem. Any thoughts would be appreciated.