Maricopa County (Unincorporated County)
Maricopa County is located in central Arizona in the Sonoran Desert, which is characterized by long, hot summers and short, mild winters. Precipitation in the County averages approx. 7 inches per year (based on 50 years of rainfall data), and falls primarily during the summer monsoon season and during winter storms. With approximately 3.2 million residents, it is the most populous county in the state and the fourth most populous county in the United States, according to the 2000 U.S. census. The County’s area is 9,226 square miles, of which 1,441 are incorporated and 7,785 are unincorporated. Approximately 96 square miles are within the urbanized area of the unincorporated County. The confluence of the Salt and Gila rivers, which drain most of eastern Arizona, is located in western Maricopa County. The Verde River, which drains much of north-central Arizona, joins the Salt River just east of the Phoenix metropolitan area. The Salt and Gila rivers are effluent-dominated streams west of Phoenix and are generally dry in the Phoenix metropolitan area due to the presence of upstream impoundments.
In December 1999, the federal stormwater program promulgated by the United States Environmental Protection Agency identified Maricopa County as a Phase II municipality requiring permit coverage under the Phase II stormwater program. This program requires municipalities to develop a stormwater program to meet six minimum control measures including:
- Public Education and Outreach
- Public Involvement/Participation
- Illicit Discharge Detection and Elimination
- Construction Site Runoff Control
- Post-Construction Stormwater Management
- Pollution Prevention/Good Housekeeping
In Arizona, the program is administered by the Arizona Department of Environmental Quality (ADEQ) and the program is called the Arizona Pollutant Discharge Elimination System (AZPDES) Program. The County’s municipal separate storm sewer system (MS4) is comprised mainly of County owned streets and flood control conveyance systems. On March 10, 2003 Maricopa County filed for an individual Phase II stormwater permit. This permit application includes Best Management Practices (BMPs) to address the 6 Minimum Control Measures (MCMs) outlined in the federal rule.
For further information on Maricopa County’s Stormwater Quality Program, please click here. To talk to Maricopa County’s stormwater program coordinator, please call 602-506-6666.