Largest Seawater Desalination Plant to Open Next Year

The San Diego area will soon be the home of the largest seawater desalination plant in the Western Hemisphere. But with a steep $1 billion price tag, the question is whether the Carlsbad Desalination Project will be worth it from a financial and environmental perspective.

Drought-plagued farmers probably think so, because after three years of drought they can’t irrigate: California’s reservoirs are filled with more mud than water. When operational in 2016, the plant will provide up to 50 million gallons of water daily to San Diego county’s 3 million residents. Still, that’s only 7 percent of the region’s water needs.

But a recent article in Fortune notes that desalination is “far more expensive than damming rivers and pumping ground water. Furthermore, critics worry about the environmental consequences and argue that water conservation is a much cheaper option.”

Water conservation is a good option, assuming that there is water available to conserve.

Regarding desalination, “We end up spending a lot of money and getting very little water,” says Conner Everts, executive director of the Southern California Watershed Alliance, who was quoted in the Fortune article. He opposes desalination plants because of their cost and their potential impact on the environment. “Don’t think of the ocean as an endless reservoir, but a fragile ecosystem,” he continued. Everts says the briny waste that goes back into the ocean could kill marine life.

It has taken 12 years of planning, including more than six years in the state’s permitting process, to get the final approvals from state regulatory agencies. Construction was also delayed by more than a dozen lawsuits that raised environmental concerns.

A 30-year Water Purchase Agreement is in place between the San Diego County Water Authority (SDCWA) and Poseidon Water for the entire output of the plant. Poseidon specializes in developing and financing water infrastructure projects, primarily seawater desalination and water treatment plants.

The desalination plant site is a 6-acre parcel in an area that leaves the majority of the Encina Power Station (EPS) property open for potential recreational or redevelopment activity at some future date.

The desalination facility is connected to the discharge channel of the EPS at two locations. The intake pump station is connected to the upstream portion of the discharge channel and delivers 100 million gallons per day of seawater to the desalination facility. Half the seawater processed by the desalination facility will be converted to high-quality drinking water. This water is delivered to Carlsbad and the surrounding communities.

The remaining water, 50 million gallons per day of seawater with an elevated salt content, is returned to the discharge channel where it is diluted with additional seawater prior to being discharged to the ocean. “This ensures that the increased salinity will not impact the marine organisms in the vicinity of the discharge channel,” according to the plant’s project overview.

To desalinate or not to desalinate? This is another of those “it’s complicated” climate change infrastructure issues that will become even more so as water battles come to the fore in areas where there is too little of it -- and other areas where rising sea levels will provide too much of it.

Image credit: Arial view of the desalination site from the Carlsberg Desalination Project website