Ariz. Rev. Stat. § 12-552
B. Notwithstanding any other statute, a municipality or a county may not institute or maintain an action or arbitration against a person who develops or develops and sells real property or performs or furnishes the design, specifications, surveying, planning, supervision, testing, construction or observation of construction of an improvement to real property that is dedicated to the municipality or county more than eight years after the improvement to real property has been accepted by the municipality or county for ownership, operation and maintenance if the action or arbitration is based on either:
H. For the purposes of subsections A, E and F of this section, an improvement to real property is considered substantially complete when any of the following first occurs: