Leading Orange County’s PFAS Response
When per- and polyfluoroalkyl substances (PFAS) were detected in very tiny concentrations , measured in parts per trillion, in portions of the Orange County Groundwater Basin, the Orange County Water District (OCWD) moved decisively to implement treatment, expand monitoring and protect water quality for the communities it serves. The basin, managed by OCWD, provides about 85% of the drinking water supply for 2.5 million people in north and central Orange County, so our commitment was clear: move early, build on sound science and give our local water agencies a clear path forward to continue delivering safe, reliable groundwater to their communities.
OCWD manages one of the most monitored groundwater basins in the state, supported by more than 200 production wells that our 19 cities and retail water districts pump water from. Following evolving state and federal regulatory standards, more than 100 of those wells were forced to be taken offline. This scale illustrates both the breadth of the challenge and the need for a comprehensive, regional solution. Despite playing no role in the release of PFAS into the environment, OCWD acted quickly to develop a robust PFAS policy based on an “all for one, one for all” framework, ensuring consistent support, resources, shared costs and access to treatment solutions across all member agencies.
In December 2019, OCWD launched the nation’s largest pilot program to evaluate treatment technologies for PFAS removal from groundwater. By the time the U.S. Environmental Protection Agency finalized its first national PFAS drinking water regulation in April 2024, OCWD had already established a strong technical foundation through extensive research and testing. The District’s laboratory, recognized as the first public agency lab in California certified to analyze PFAS in drinking water, enabled rapid, reliable testing to support both regulatory compliance and infrastructure planning.
The pilot program tested 14 different treatment media and the results helped confirm ion exchange and granular activated carbon as the most effective treatment methods for our needs and for full-scale implementation. That work continues today through additional pilot testing at the Yorba Linda Water District (YLWD) PFAS Treatment Plant, where OCWD is evaluating proven treatment media alongside emerging materials to help identify high-performing, cost-effective options for water agencies who are just beginning their PFAS response.
At OCWD, the next step was turning pilot results into a regional construction program. Under the District’s PFAS treatment policy, OCWD funds 100% of design and construction costs for impacted local water suppliers, while operations and maintenance costs are shared 50/50. This approach has helped our partner cities and retail water districts move more quickly from planning to delivery and has safely brought 53 of more than 100 impacted wells back online, with additional systems in design and construction. This is a significant step toward protecting public health and ensuring the long-term reliability of local groundwater supplies.
A prominent example of this infrastructure at scale is the YLWD PFAS Treatment Plant, the largest ion exchange treatment facility of its kind. Designed to treat up to 25 million gallons per day, the facility includes 22 ion exchange vessels, six pre-filters, a booster pump station and backup power systems. The plant enabled the restoration of all ten impacted wells within the district, allowing for increased use of local groundwater resources and reinforcing system resiliency.
The financial commitment associated with this effort is substantial. OCWD’s PFAS program is estimated at approximately $1.8 billion over 30 years, including roughly $620 million in capital investment for treatment infrastructure. These investments support the design and construction of advanced treatment facilities, system integration and long-term operational reliability. For a region that depends heavily on groundwater, restoring impacted wells is critical to maintaining a cost-effective water supply. To further protect our ratepayers, the District continues to pursue state and federal funding and advocate for policies that hold chemical manufacturers accountable, with the goal of reducing the financial burden on local agencies and ratepayers.
OCWD’s response to PFAS reflects a comprehensive, infrastructure-driven strategy that integrates scientific research, regional coordination and large-scale capital investment. By advancing treatment solutions and restoring groundwater production capacity, the District is strengthening the reliability of Orange County’s water supply system and establishing a model for utilities facing similar challenges nationwide.
By Chris Olsen, P.E. He is the Executive Director of Engineering and Water Resources at Orange County Water District. He can be reached at colsen@ocwd.com
This story is featured in our May/June issue of American Infrastructure, read the print version here.
