Keith R. Solar is an attorney. He lives in Point Loma.
California’s acceptance of desalination has ebbed and flowed over the years as the state grapples with shoring up water security in the face of constant drought conditions. Recent discussions over “water swaps” have generated excitement over the possibilities.
While regional water-sharing arrangements between neighboring states and California could result in new desalination facilities, the process of converting seawater into drinking water comes with a host of regulatory hurdles that make planning, permitting and operating reverse osmosis plants extremely challenging in California.
The idea of using California’s relatively low-cost Colorado River water as a tradeable asset while out-of-state partners help finance new or expanded desalination facilities along the California coast could be beneficial to all stakeholders. In particular, the San Diego County Water Authority is considering selling part of its Colorado River allotment to other Western states while relying on the Carlsbad seawater desalination plant to backfill its own supply, effectively turning desal capacity into financial- and water-security levers.
However, the new possibility for desalinated and surface water swaps must be tempered with the reality that California has one of the most complex regulatory environments for drinking-water treatment and coastal infrastructure anywhere in the country.
For public water systems using membranes, California’s primary regulator is the State Water Resources Control Board’s Division of Drinking Water (DDW), which enforces the California Code of Regulations together with the system-specific domestic water supply permit. Any new California filtration or disinfection facility—or any modification that changes capacity or a major process—triggers a formal engineering report and permit amendment spelling out how the plant will meet stringent performance, reliability, and monitoring requirements.
Also, coastal desalination projects must pass a separate and demanding layer of environmental review under the California Environmental Quality Act (CEQA), along with permits from local municipalities, regional water boards, the Coastal Commission, and sometimes federal agencies, particularly around intake and brine discharge impacts on marine ecosystems. This means that the legal “permission” to operate a membrane facility is not a single approval; it is the cumulative result of CEQA certification, intake and outfall approvals, waste-discharge requirements, and a highly specific DDW permit that defines the allowable operating envelope of the desalination facility.
A useful way to see how demanding California can be is to contrast it with a typical brackish reverse osmosis (RO) plant in Florida. Florida’s Department of Environmental Protection regulates public water systems through a state code which sets design and construction standards for public water systems and incorporates federal regulations.
Florida’s framework does not embed the same level of process-specific, continuous integrity verification in rule language that California applies to membrane systems used as alternative filtration processes. Rather, the technical start-up sequence—flushing preservatives at low pressure, gradually ramping pressure and flow, stabilizing flux and recovery, confirming pretreatment and permeate quality—is driven mainly by engineering practice, manufacturer guidelines, warranty requirements, and the plant’s operations and maintenance manual rather than detailed, technology-specific state rules.
In contrast, California’s approach folds engineering practice into the regulatory fabric. Gradual ramp-up, filter-to-waste, integrity testing, and performance confirmation are not just operational, engineering details, they are explicitly tied to permit conditions. Developers accustomed to more flexible frameworks may be surprised that California expects a documented, auditable sequence every time a train is brought into or out of service.
The current wave of interest in California desalination and water swaps can mask how hard-won each increment of capacity is under this regulatory regime. While recent initiatives show that regulators and policymakers now see desalination as part of California’s climate-resilient supply mix, they have not relaxed expectations on environmental protection, treatment reliability, or operational oversight.
This means project sponsors must have a realistic appreciation of California’s permitting timeline, the need for robust pilot work and technology validation, and the operational culture shift required to run membrane systems as regulated public-health barriers rather than purely mechanical assets. Developers entering the California market with a Florida mindset are likely to encounter delays, redesigns, and unexpected compliance obligations.
The opportunity is clear: if California can successfully integrate desalination into regional water-swap agreements and broader supply strategies, it can unlock both local resilience and interstate collaboration on the Colorado River.
But the challenge is just as clear: every new California membrane plant must thread the needle of stringent environmental review, detailed operating conditions, and a regulatory culture that treats start-up, shutdown, and integrity testing as core compliance events, not just operational details.