The opening of the San Diego County facility may herald a new era in water use.

A worker climbs stairs among some of the 2,000 pressure vessels that will be used to convert seawater into fresh water through reverse osmosis in the western hemisphere's largest desalination plant in Carlsbad, California.  (AP Photo/Gregory Bull)

The largest ocean desalination plant in the Western Hemisphere is expected to begin operation within days, heralding what may be a new era in U.S. water use. The Carlsbad, California, plant will serve San Diego County with the capacity to produce 50 million gallons of fresh water daily, about one-tenth of the county's total water use.

Construction of the plant by Poseidon Water of Boston lasted nearly 14 years, and totaled about $1 billion. The project—and the concept of “desal” in general—has received much criticism from the environmental community in particular, who say desalination harms marine ecosystems and costs significantly more than water from sources like conservation, recycling, and stormwater collection.

They’re not wrong: According to the San Diego Union-Tribune, the plant’s desalinated water will clock in at about $2,000 an acre-foot, about twice the cost of water from the region’s largest water wholesaler. Representatives of the Carlsbad facility say there are environmental mitigation measures in place.

Until now, desalination has had a fairly small place in California’s portfolio of water-saving and -generating strategies. But if the plant performs as expected, observers believe it might set a new precedent for the state (which will enter its fifth year of drought in January) and possibly the country. According to the L.A. TImes, about 15 other desalination sites are currently being proposed along the California coast.

The desalination plant borders Interstate 5 on one side and the Pacific Ocean on the other. (AP Photo/Lenny Ignelzi)
Another view of the plant. Large pumps force water through filters in the first stage of desalination. (REUTERS/Earnie Grafton)(REUTERS/Earnie Grafton)
Huge pipes weave through the newly completed facility. (REUTERS/Earnie Grafton)
A large diameter pipe will export fresh water from converted saltwater to the county's water system. (REUTERS/Mike Blake)
Water used to perform a test flows under rows of reverse osmosis tubes. (AP Photo/Gregory Bull)
A worker passes rows of tubes used in the reverse osmosis process. (AP Photo/Gregory Bull)

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