California - Desalination Clears Hurdle - NYTimes.com The San Diego County Water Authority announced a tentative agreement Thursday to buy all of the output of what will be the Western Hemisphere's largest seawater desalination plant, clearing a major hurdle for construction. The plant in Carlsbad will produce 50 million gallons a day, enough to supply about 7 percent of the San Diego region in 2020. If the deal is approved by the water authority board, the developer, Poseidon Resources, would sell bonds to finance 82 percent of the project, estimated at $900 million. San Diego would pay $2,042 to $2,290 for an acre-foot of water, more than twice what it pays to buy water from outside the region.