Water Chamber Inside Neighbour Wall

My neighbor has built his boundry wall and inside that wall they have made underground water chamber for bathroom drain. All this water rinsing through underground wall (dunga). We have raised this issue so many time and asked them to do the proper arrangement for there bathroom drain but nothing has happend. Also complaint file in revenue department they came and nothing has happened. My main concern as follows; 1. Isn't this wrong to through directly or indirectly bathroom drain in others land. 2. Can i contact state pollution control department for not arranging the bathroom drain/tank properly and drain water going in others land. 3. He have build the water chamber/tank inside there boundry and water rinsing from there. Can i built a RCC dunga/wall by touching his wall and not keeping any space between both walls. By law is this ok to do. Please awaiting your kind advice.