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MWDOC Study Finds Better Options Than Poseidon Desalination Plant

Illustration by Kevin McVeigh

A recently completed study on the cost effectiveness and financial risk of proposals to meet water supply demands through 2050 concludes that the controversial Poseidon desalination project in Huntington Beach would produce more water than the Orange County basin needs and cost ratepayers far more than alternatives such as recycling and capturing rainwater.

Created by the Irvine engineering consultant CDM Smith Inc. for the Municipal Water District of Orange County (MWDOC), the 2018 Reliability Study also concludes that the Doheny Ocean Desalination project in Dana Point is among the best options to meet future South County water demands.

The Doheny plant has the added bonus of being more environmentally friendly than its Poseidon counterpart, which sucks in massive amounts of sea water and whatever is living in it. “Unlike traditional desalination facilities, the Doheny facility would use advanced slant wells that protect marine life by drawing water from beneath the ocean floor,” explains the South Coast Water District. “Environmentalists and state regulators prefer this technology. Built into the system being considered by the district is also an energy recovery process, resulting in 45 to 55 percent less energy usage than systems without that feature.”

The MWDOC reliability evaluation takes into account future droughts, earthquakes and other disasters as it considers various sources for secure water supplies. The aim is to give water agencies the information needed when deciding whether to develop local sources or purchase imported water.


The follow-up to a similar 2016 report, the 2018 model reflects new investments, such as California WaterFix, which was formerly known as the Bay Delta Conservation Plan, as well as the proposed Drought Contingency Plan that would reduce the risk of an official shortage on the Colorado River.

Click here to read the study, which under every scenario concludes Poseidon is the most expensive and most financially risky of the alternative water sources evaluated. [1]

Part of that has to do with the differing demands in North County, where 75 percent of the supply comes from groundwater, and South County, which imports nearly all of its water.

According to the study, which identifies the North County coverage area as the OC Basin, effective groundwater management, capturing and storing rainwater behind Prado Dam and purchasing water from a water recycling project in Carson would be the most cost-effective and financially stable sources for new supplies. Part of the reason Doheny Ocean Desalination makes the most sense for South County is there will be lower operational and maintenance costs compared to Poseidon, the study finds.

Site of the proposed ocean desalination plant in Huntington Beach.

The study concludes with correspondence received during different phases of the roll out from various stakeholders, including the Fountain Valley-based Orange County Water District, whose board has consistently backed the Poseidon project.

Robert Hunter, the MWDOC general manager, authored a point-by-point response to his OCWD counterpart Michael Markus, whose complaints included the MWDOC was telling member agencies which future water supply projects to choose with its rankings.

Hunter denied this, stating that the study simply evaluates each project under different scenarios and that it is up to each individual agency to make its own informed decision on how to proceed.

(Of course, should the OCWD board pursue a project that has already been identified as the worst option for its ratepayers, who is to stop those ratepayers from demanding the heads of OCWD board members?)

Ray Hiemstra of Orange County Coastkeeper (Photo by Nicholas Iverson)

Ray Hiemstra, associate director of Orange County Coastkeeper, a clean-water nonprofit that has been extremely critical of the Poseidon project, takes a decidedly warmer tone in one of his letters to Hunter about the reliability study.

“MWDOC staff have done a great job collecting, consolidating and analyzing the data for this report,” Hiemstra writes. “The background document and presentations produced for the study provide an objective, science-based review of the reliability needs and water-supply options for Orange County.”

He does strongly make one suggestion: “The final document must be designed for use by the general public as well as agency staff and elected officials. … The ratepayers that provide funding for MWDOC and all of the other water suppliers also have a need for and right to objective information on their water supply.”

Hiemstra also defends the final draft including the rankings, which he calls “the most understandable and important part of the report.”

“This much needed simplification of the complicated data in the report clarifies economic, supply and reliability realities and gives important insight into the variety of options for future water supplies. It is not surprising that proponents of some of the projects that did not rank well are calling for the ranking to be eliminated in the final report. MWDOC should not bow to these narrow interests.”