Orange County, California: drinking water report. Orange County serves about 3.2 million residents through a network of 27 retail water agencies and the…
Orange County serves about 3.2 million residents through a network of 27 retail water agencies and the Orange County Water District (OCWD), which manages the massive groundwater basin beneath the northern half of the county. OCWD operates the Groundwater Replenishment System – the largest water purification facility of its kind in the world – which takes treated wastewater, purifies it through microfiltration, reverse osmosis, and UV treatment, then injects it into the groundwater basin. Southern Orange County relies more on imported water from Metropolitan Water District.
Orange County has one of the most well-documented PFAS contamination histories in California. Two former military installations – the former Marine Corps Air Station El Toro and the former Marine Corps Air Station Tustin – are confirmed sources of PFAS groundwater contamination. The Orange County Water District detected PFAS in monitoring wells as early as 2016 and has invested over $50 million in treatment infrastructure to address the contamination.
The OCWD's advanced purification process at the Groundwater Replenishment System effectively removes PFAS, but not all wells feeding the basin go through this treatment. According to state monitoring data, 19 public water systems in Orange County reported PFAS detections during UCMR5 sampling.
Your exposure depends on whether your water agency draws from the OCWD groundwater basin, imported water, or a blend. North county communities are more likely to be served by groundwater that may carry PFAS from the El Toro and Tustin plumes.
Check your water to see what monitoring data exists for your ZIP code. If PFAS is present, a reverse osmosis filter provides the most thorough removal. Our water filter guide compares systems by independent test results. For trend data and historical readings, pull your detailed report. Visit our California page for the statewide picture.
Drinking water is one exposure route. These federal datasets also cover Orange County, CA.
The EPA places Orange County, CA in Zone 3 - the EPA's lowest-risk category, with a predicted average indoor radon level below 2 pCi/L. Zone maps predict an area's radon potential from geology and existing indoor readings; they say nothing about a specific house. Testing is the only way to know your own level.
58% of homes in Orange County, CA were built before 1980, and 4% before 1950. Residential lead paint was banned in 1978, so housing age is the strongest available proxy for lead-paint exposure. This describes the county's housing stock, not any one home.
Modelled annual fine-particle pollution (PM2.5) in Orange County, CA averages 10.1 µg/m³, above the EPA's annual standard of 9 µg/m³. These are CDC modelled county estimates rather than readings from a specific monitor.
How radon zones work · Air quality by county · Lead exposure guide