Since no govt has ever even considered the idea of constructing city-wide sewer system, complete with treatment plants, then raw sewer and other effluents will continue to pour into the lake, whether the structures mentioned are demolished or not - liquids take the path of least resistenace and the lake being the lowest area will naturally attract the effluent discharge. It's time a proper sewage disposal system was put in place - this is the 21st century, afterall!