Eleven members of the California Coastal Commission voted against the facility, which water treatment developer Poseidon Water has been trying to build for decades.
Poseidon said the plant would be capable of producing up to 50 million gallons of drinking water a day, helping to make the region more drought resilient.
The commission, which is charged with "protecting and enhancing" the state's extensive coastline, heard public comments on the project throughout the day Thursday, with a majority of speakers opposing it. Others who expressed concern about a lack of water resources in the future argued that, whenever possible, additional water resources should be developed.
Poseidon released a statement following the vote thanking Gov. Gavin Newsom for his support and reiterating its belief that the plant would be an important tool in maintaining the state's water supply.
"This was not the decision we were hoping for today," said Poseidon Director of Communications Jessica Jones. "California continues to face a punishing drought, with no end in sight. ... Every day, we see new calls for conservation as reservoir levels drop to dangerous lows. We firmly believe that this desalination project would have created a sustainable, drought-tolerant source of water for Orange County, just as it has for San Diego County."
But desalination opponents argue less expensive and less harmful conservation tactics should be the first resort.
The commission is appointed or chosen by state lawmakers and the governor. Ahead of the vote, its staff recommended against the facility, pointing in part to desalination's incredible energy consumption, its impacts on marine life, projected sea-level rise and the cost of the resulting water itself -- with that cost being passed on to customers.
Commission staff did acknowledge in the report that its findings do not mean that the project is "unapprovable," nor that it is completely against desalination, writing: "Staff acknowledge the need to develop new, reliable sources of water in southern California, and believe that well-planned and sited desalination facilities will likely play a role in providing these supplies."
Desalination works by separating water molecules from salty seawater through reverse osmosis. The leftover high-salinity brine is sent back to the ocean.
One plant of this scale -- the Claude "Bud" Lewis Carlsbad Desalination Plant in San Diego County -- is already in service. Poseidon began operating that facility in late 2015, selling its entire output to the San Diego County Water Authority in a 30-year contract.
Scientists reported earlier this year that the West's current megadrought
is the worst in at least 1,200 years. Southern Californians
are already seeing unprecedented water restrictions ahead of the summer.
Newsom has voiced support for building the plant, noting California's extended droughts and challenged water supply. He recently told the Bay Area News Group editorial board, "What more evidence do you need that you need to have more tools in the tool kit than what we've experienced? Seven out of the last 10 years have been severe drought."
But those against the desalination plant argue there are other ways to battle the drought.
On its website dedicated to fighting the Huntington Beach plant, the non-profit Surfrider Foundation indicates the water the project would provide is not needed, calling the potential plant "a waste of money."
In fact, research by the Pacific Institute, a water-focused think tank, found California could substantially reduce its urban water use by 30 to 48% with existing and cutting-edge technologies. In its recent report, the institute argued that "water efficiency opportunities can be found across the state but are highest in the South Coast hydrologic region." It pointed to solutions that cost very little compared to desalination, including increased wastewater recycling and stormwater capture -- with about two-thirds of the region's potential water savings coming from the residential sector.
"Seawater desalination is among the most expensive water supply options," Heather Cooley, Pacific Institute's director of research, told CNN. "From a cost perspective, from an environmental one, from an energy perspective, doing these other alternatives first makes the most sense for California."