is this an outsource contract?
If no, then raise exposure within the LA bureaucracy. Go right to the top (CEO) enlisting local councilor and MP. From a sufficient height the jobsworths will melt away
If yes, then raise issue with the waste department. Identify whether this behaviour is outside the terms of the SLA. Almost certainly it is and they will agree to remind the site people of this.
Either way, test for greenie-wankers and make sure that you are not dealing with anyone on a mission. Keep in mind that these are failed conservation officers. Unless your address is the Royal Crescent in Bath there is probably no reason for their existence.