136.4. The Community may require a person who discharges waste water or other substances into a purification works or watercourse in contravention of a by-law passed under section 136.1 to carry out, at his own expense, the work required to clean or repair, as the case may be, the purification works or to eliminate the harmful or hazardous substances he has unlawfully discharged into the watercourse, or to reimburse the Community for the costs incurred by it for such work.