Pinal County, Arizona: drinking water report. Pinal County between Phoenix and Tucson has about 450,000 residents in one of the fastest-growing corridors
Pinal County between Phoenix and Tucson has about 450,000 residents in one of the fastest-growing corridors in the country. Communities like Casa Grande, Maricopa, and Apache Junction draw from a mix of Central Arizona Project canal water, local groundwater, and reclaimed water. The desert climate and historic mining activity create a water quality environment dominated by naturally occurring contaminants and legacy mine contamination.
Arsenic in groundwater is widespread in Pinal County. According to ADEQ's 2024 drinking water compliance data, nine public water systems in the county have reported arsenic levels between 8-15 ppb, with several exceeding the MCL of 10 ppb. The arsenic is naturally occurring, dissolved from volcanic rock formations in the basin fill aquifer. Systems must either treat the water or blend it with lower-arsenic sources.
The ASARCO smelter complex in the northern part of the county operated for nearly a century, leaving heavy metal contamination in soil and groundwater across a wide area. A 2024 EPA assessment documented elevated lead and arsenic in residential soils near the former facility. PFAS from military operations at the Florence Military Reservation has been detected at 11 ppt in monitoring wells.
Pinal County's rapid growth means new homes are being built over aquifer zones with documented arsenic. If you are in a new development served by a small water system, verify that arsenic treatment is in place – not all systems have installed it yet.
Check your water for data at your address. For arsenic, reverse osmosis is the most effective household option. Our water filter guide identifies systems certified for arsenic removal. Pull your detailed report for local levels, and visit our Arizona page for statewide context.