Subsurface water intakes feasible for desalination plant, study finds
A study regarding a controversial proposed desalination plant in Huntington Beach determined that subsurface intakes are technically feasible for the project.
A panel of experts selected by the California Coastal Commission and plant builder Poseidon Water concluded that two types of systems — seabed and beach intakes — are possible to build at the proposed site, according to a draft report published Sept. 22. The desalination facility would be built at the AES natural gas-powered electricity plant off Pacific Coast Highway at Newland Street.
The Orange County Water District — which covers Costa Mesa, Newport Beach, Huntington Beach and Fountain Valley — decided in June to pay a consultant to study the cost of buying water from the Poseidon plant.
There has been talk of the desalination plant using pipes under Costa Mesa to distribute water to water districts. However, Poseidon would need proof of interest from Costa Mesa, Huntington Beach and AES for that to happen.
The intake study, organized by Concur Inc., a Berkeley firm that specializes in complex environmental issues, analyzed nine subsurface methods over several months this summer.
Because the report is a draft, changes could still be made, said Concur principal Scott McCreary, who oversaw the study. The final draft is expected to be completed this week, he said.
The report will complete one of two stages of the analysis of subsurface intakes. The second part will look into economic feasibility and environmental effects, McCreary said.
Once all aspects of the study are finalized, it will be brought before the Coastal Commission when Poseidon resubmits its application to build the plant.
Seabed infiltration galleries — a method in which intake pipes to collect seawater are placed under the ocean floor — can withstand natural events such as earthquakes and can be built off Huntington’s shore, according to the report.
Beach galleries are similar but are constructed closer to shore.
Because subsurface intake pipes are under the surf zone, the breaking waves and sand would act as a self-cleaning filter for the plant, according to the report.
However, the panel said both types of subsurface intakes would involve complex engineering and could have a negative impact on the beach during construction.
“We’re very encouraged by the conclusions, findings and recommendations, and we’ll see what happens when the panel finalizes,” said Scott Maloni, vice president of Poseidon.
Though his company has been pushing for open-water intakes, in which pipes are placed in the water above the sea floor, Maloni said subsurface intakes would be considered if they were found technically and economically feasible. Open-water intakes would use the cooling pipes from the AES power plant.
Joe Geever, a consultant for the Surfrider Foundation, said he and other desalination proponents are glad that a report on subsurface intakes has been done.
“We’ve been requesting this for over 10 years,” he said. “We finally got a report that indicates that subsurface intakes are technically feasible, which is what we suspected all along.”
Other methods studied included vertical wells, which take in water directly underneath the well station. That method was found to be infeasible because it could draw water from the Orange County groundwater basin, according to the report. Additionally, it was estimated that more than 200 wells would be needed to draw about 127 million gallons of seawater a day.
Slant wells were deemed infeasible because they too could draw large amounts of water from the groundwater basin and it is unknown how reliable they are in the long run, panelists concluded.
Radial collectors, which consist of a vertical, water-tight chamber with horizontal intakes protruding from it, were found infeasible because there are limits on how long the intakes can be, and the terrain is inappropriate for the system, according to the report.
The study was conducted as a result of a Coastal Commission meeting in November, when Poseidon’s conditional use permit for the project was under review.
After an hours-long public hearing, Poseidon decided to withdraw its application, and commissioners asked the company to conduct additional research on the project, including subsurface intakes.
Though Geever was pleased with the draft report, he said he realizes that more research and analysis needs to be done.
“But we think the panel is on the right road,” he said.
The proposed desalination facility would provide water districts with 50 million gallons of water a day, according to Poseidon, which hopes to have the plant operating by 2018.
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