San Diego's water board gave final approval Wednesday for construction of the largest water desalination plant in the Western hemisphere.
The $320 million project proposed by Poseidon Resources could come online by 2012 in Carlsbad and produce 50 million gallons of drinking water a day, or 10 percent of the supply for San Diego County.
The Connecticut-based company secured a key permit from the San Diego Regional Water Quality Control Board.
"It's been six years of permitting, 14 public hearings and over 70 hours of public testimony and debate," company vice president Scott Maloni said.
The pressure to find new sources of clean water has been increasing with drought conditions and as traditional sources across California are becoming more unreliable.
Environmental groups have fought the Poseidon plant, arguing its intake valve would kill marine life.
On Tuesday, however, a judge ruled against a lawsuit by the Surfrider Foundation and Planning and Conservation League aimed at stopping the project.
The groups had sued the California Coastal Commission after it approved construction of the plant.
The groups contended the commission failed to require the developer to reduce damage to marine life, but the judge noted the panel had required Poseidon to restore 55 acres of wetlands.
Surfrider has filed two other lawsuits. One is against the San Diego Regional Water Control Board for approving the plant's permit, and the other targets the State Lands Commission over the plant's lease.
Those cases are scheduled for trial next month.
Surfrider attorney Marco Gonzalez could not be immediately reached for comment Wednesday, but on Tuesday said Poseidon was "anything but in the clear."
"We live in a desert. Why are we watering vast green lawns with expensive desalinated water?" Gonzalez said.
Once built, the plant would suck in 100 million gallons of sea water a day.
The water would then be filtered through reverse-osmosis to remove salt and impurities, with half the water being used by consumers and the rest returned to the ocean.
Other desalination plants are under consideration in California.
Surfrider's other two legal cases are scheduled for trial next month before Judge Hayes.
The plant would produce 50 million gallons of water per day, enough to serve 300,000 residents each year. Poseidon plans to break ground later this year and begin operating the plant in 2012.