It shall be unlawful for any person or firm to engage in the business or occupation of pruning, treating, or removing street or park trees within the city without certification from the International Society of Arboriculture. Such certification is not required for any public service company or city employee doing such work in the pursuit of their official responsibilities. Additionally each operator or firm shall possess liability insurance in the minimum amounts of one million dollars per person, two million dollars per occurrence, and shall name the city as an additional insured. (Ord. 690 (part), 2011)