Oxnard is the largest city in Ventura County, sitting on a flat coastal plain where intensive agriculture meets Southern California suburbia. The city grows more strawberries than just about anywhere in the world, processes more lemons than any US city, and sits directly over a groundwater basin being squeezed from both sides — saltwater pushing in from the Pacific and agricultural chemicals percolating down from above.
The Oxnard Plain Aquifer: Under Siege
The Oxnard Plain Groundwater Basin is the primary water source for the region, but it faces an existential threat: seawater intrusion. As overdrafting — pumping more water than naturally recharges — draws the water table down, the natural pressure barrier that keeps ocean saltwater out weakens. Saltwater migrates inland through the aquifer, rendering wells unusable and irreversibly altering water chemistry.
Seawater intrusion has been documented across the coastal edge of the Oxnard Plain for decades. The United Water Conservation District, which manages the basin, has implemented a hydraulic barrier — a series of injection wells that maintain water pressure along the coast to slow or stop saltwater advance. This barrier requires continuous operation and millions of gallons of injection water, much of it recycled wastewater or imported State Water Project supplies.
The Fox Canyon Groundwater Management Agency, created under California’s Sustainable Groundwater Management Act, is now tasked with developing a Groundwater Sustainability Plan for the Oxnard Plain. Achieving sustainability will require reducing agricultural and urban pumping — a politically and economically difficult task in a county where agriculture generates over $2 billion in annual revenue.
Point Mugu: PFAS from the Navy
Naval Base Ventura County (NBVC) Point Mugu sits on the southern edge of Oxnard, where the Navy has operated aircraft testing, weapons systems development, and airfield operations since World War II. Decades of AFFF firefighting foam use at the airfield has resulted in PFAS contamination in groundwater on and around the base.
The Navy has confirmed PFAS in monitoring wells at Point Mugu at concentrations well above EPA health advisory levels. The contamination plume extends beyond the base perimeter, and some residential areas on Oxnard’s southern edge are in the investigation zone.
The Oxnard Water Division samples its supply for PFAS. Oxnard’s water system draws from both the local groundwater basin and imported Metropolitan Water District supplies, and PFAS levels in treated water have been a focus of testing. Some wells have required treatment or monitoring adjustments as PFAS standards tighten under the EPA’s 2024 MCLs.
Agricultural Nitrate and Pesticides
The Oxnard Plain is one of the most intensively farmed coastal areas in California. Strawberries, celery, lemons, cabbage, and other crops are grown year-round under plastic mulch with intensive fertilizer applications. The sandy soils that make this area so productive for agriculture also allow rapid percolation of agricultural chemicals into the shallow aquifer.
Nitrate from fertilizer applications has been detected in monitoring wells across the Oxnard Plain at levels that require management. The California Regional Water Quality Control Board’s Irrigated Lands Regulatory Program requires growers in the basin to monitor for nitrate and develop management plans, but compliance is uneven and nitrate levels in some areas exceed the drinking water MCL.
1,3-Dichloropropene (Telone) — a widely used soil fumigant for nematode control in strawberry production — has been detected in air around Oxnard at levels that concern environmental health advocates. Its groundwater behavior is less documented than DBCP or TCP, but soil fumigant applications in an area of shallow, permeable aquifer always warrant attention.
Water Reliability: The Imported Supply Question
Oxnard’s water reliability depends heavily on imported Metropolitan Water District water delivered via the State Water Project and Colorado River Aqueduct. During California droughts, those imported supplies are curtailed, forcing greater reliance on local groundwater — which accelerates overdrafting and worsens seawater intrusion.
The city has been investing in water recycling to reduce both imported water dependence and groundwater demand. Recycled water for agricultural irrigation can significantly reduce potable groundwater use for farming, but the transition requires investment and buy-in from growers.
What Oxnard Residents Can Do
Oxnard’s municipal water meets federal standards, but the PFAS situation at Point Mugu and the groundwater quality dynamics warrant awareness:
- Review the annual CCR — Oxnard Water Division publishes detailed water quality reports including PFAS testing results.
- Monitor PFAS developments — as NBVC Point Mugu’s remedial investigation advances, watch for updated plume data and well sampling results.
- Private well users near the base or in agricultural areas should test for PFAS, nitrate, and soil fumigant residues.
- Consider a point-of-use filter — reverse osmosis removes PFAS, nitrate, and most agricultural contaminants.
If you’re concerned about your water quality, a certified water treatment professional can help you test your water and recommend the right solution for your home.