illegal construction over rain water drainage

Hi, Actually one person has illegally occupied the rain water drainage by putting granite slabs on it. I was fighting with the local municipal from past 6 month and later the officials came and remove the illegal construction and cleared it. But now again the person wants yo put the granite slabs on it and he is trying to influence the officials in the municipal office. So its becoming a big head ache as our sanitary pipes and bath room pipes are connected to the drainage and it will get jam again if that guy put them. When we ask him he is not listening and he want to put the slabs again. Please let me know how can I fight this in the court please. Nandish