It is unlawful for any person to willfully or carelessly break, injure, mar, deface, disturb, or in any way interfere with any building, attachment, machinery, apparatus, fixture, or appurtenance of any municipal utility system or with any part or portion of the same, or without permission, commit any act tending to obstruct or impair the use of any municipal utility.
('69 Code, § 3.06, Subd. 2) Penalty, see § 10.99