Ariz. Rev. Stat. § 49-371
A. A county that is required by the clean water act to obtain coverage under a national or state pollutant discharge elimination system stormwater program or a county that is required to obtain coverage under an Arizona pollutant discharge elimination system permit pursuant to article 3.1 of this chapter may do all of the following:
3. Adopt rules, regulations or ordinances regulating the use of lands or rights-of-way owned or leased by the county as may be necessary to implement and enforce its national or state pollutant discharge elimination system stormwater management program. Rules, regulations or ordinances adopted pursuant to this paragraph may include provisions for both of the following:
C. A county that operates a regulated small municipal separate storm sewer system that discharges to a protected surface water shall conduct its pollutant discharge elimination system stormwater management program and shall limit the application of any ordinance, rule or regulation as follows: