Minn. Stat. § 465.48: POWERS AND DUTIES OF COUNCIL; PENALTIES.

The city council shall have power and it shall be its duty after the construction of such works to maintain the same and to prevent injury or obstruction to the channel or works and contamination of the waters. For such purposes the city council may enact suitable ordinances and prescribe penalties for their violation, not exceeding a fine of $100 for each offense or confinement in the city workhouse not exceeding 90 days. The district court having chambers in the county in which the city is located shall have jurisdiction of the offenses.