Making the case for desalination
San Diego Union Tribune – Michael Burge, staff writer
SAN DIEGO – After a year of pleading its cause through letters and stacks of documents, a private company will get a shot Thursday at persuading the state Coastal Commission to let it build the Western Hemisphere’s largest desalination plant on the Carlsbad coast.
To approve the project, the 12-member commission will have to override its own staff, which recommends against allowing the plant. The commission’s staff says the plant would degrade water quality and harm marine life in Agua Hedionda Lagoon, the source of the ocean water that would be desalinated.
The developer, Poseidon Resources, argues that if it can build the plant, it will care for the lagoon and assure its future health.
Company officials also say the desalination process it proposes is more environmentally friendly than any alternative.
From the outset – even before Poseidon submitted an application to build its plant last year – commission staff members have differed on the best way to turn ocean water into drinking water.
<strong>Water source debated</strong>
Poseidon Resources proposes tapping into the ocean-water stream that NRG Energy uses to cool its steam-driven turbines at the Encina Power Station on the south shore of Agua Hedionda Lagoon.
This method takes advantage of existing water intake and outfall pipes, which Poseidon says would cost $150 million to build, and makes it easier to treat the seawater because the power plant has warmed it up.
The Coastal Commission staff has long objected to this method because thousands of fish, larvae and other marine organisms are killed as water is drawn into and circulates through the power plant.
Commission analysts prefer a more benign technology of drawing water from beneath the ocean floor, either through wells or “galleries” of buried pipe.
The idea involves sinking a pipe in the sea bed, akin to a fresh-water well, or excavating a wide area of ocean floor, lining it with pipes and covering it with sand. The pipes would be connected to the onshore desalination plant.
The sand blanket would act as a natural filter for the ocean water, commission staff argues.
Commission analysts acknowledge that building such intakes is costly, but say the natural pre-filtering reduces operating costs.
Poseidon estimates such an ocean-floor system would more than double the construction cost, to $650 million from $300 million, and could destroy 150 acres of seafloor.
Although this technology has never been used on the scale envisioned for Carlsbad, the Coastal Commission staff points out it has been used on small-scale projects in the state.
<strong>Intake systems varied</strong>
Poseidon plans to draw 100 million gallons of seawater a day as it leaves the Encina Power Station, filter it and force it through reverse-osmosis membranes to produce 50 million gallons of drinking water. The other 50 million gallons would be returned to the cooling stream and on to the ocean twice as salty as when it came in.
While Poseidon rejects the commission staff’s idea, two Southern California water agencies are investigating wells or buried pipes as intake systems for desalination.
The Municipal Water District of Orange County drilled a test well earlier this year at Dana Point that it regards as promising, and Long Beach is exploring a buried chamber.
The San Diego County Water Authority also is studying the feasibility of a desalination plant at Camp Pendleton.
“As part of that, we’re looking at the possibility of both a subsurface intake and an open-ocean intake,” which would draw directly from open water, said Bob Yamada, the county water authority’s water resources manager.
He said the authority also will study a combined seawater/groundwater desalination plant in South Bay.
The Long Beach Water Department recently won Coastal Commission approval to dig an undersea intake system as a test this winter.
Department spokesman Ryan Alsop said officials there were discussing their offshore geology when they learned that Fukuoka, Japan, a city of 1.4 million, installed a sub-ocean-floor intake in 2005.
Fukuoka desalinates 13 million gallons of ocean water a day.
Alsop described Long Beach’s test chamber as a sandbox lined with pipes and covered with sand.
“The advantages are, we think, a reduction in pre-treatment costs,” Alsop said.
Karl Seckel, assistant manager and engineer for the Municipal Water District of Orange County, said his agency began exploring a buried intake on the advice of Coastal Commission staff. The water district is considering building a desalination plant at Doheny State Beach in Dana Point.
“They said if you can look at any other ways of bringing the water in you should do that,” he said.
In April the district drilled a test well – a perforated pipe – at an angle into the ocean bed. Seckel said the test was a success, and had the benefit of not affecting the ocean environment.
Poseidon is not sold on subsurface intakes, claiming they are more environmentally harmful than its proposal.
“If you look at everything that the Coastal Act serves to protect, had we proposed any one of those systems we would have been laughed out of the room,” Peter MacLaggan, Poseidon’s senior vice president, said.
He said an ocean-floor chamber “would be a three-intake system, each a mile long, 400 feet wide and 15 feet deep,” through kelp beds. It would need 76 pipes from the beach to the ocean, with pump houses for each pipe.
He said Poseidon’s proposal would kill 2 pounds of fish a day and destroy about 12 percent of the fish larvae in the lagoon, which he considers minor, given the plenitude of the species involved.
The company is proposing to restore 37 acres of habitat in compensation.
The commission staff disputes the idea that fish kills would be minor.
Significant numbers of sensitive and sport fish larvae, including California halibut, northern anchovy and Garibaldi would be killed by the plant, a staff report states. Six percent of the killed larvae would be Garibaldi, and there is a state ban on killing the species for recreational or commercial purposes.
MacLaggan said Garibaldi are more common at Agua Hedionda Lagoon than elsewhere, so the impact would not be significant.
The Coastal Commission’s desalination expert, Tom Luster, said he doubts Poseidon’s facts and figures particularly about the size of alternate intakes.
“They describe large concrete bulkheads up and down the beach,” Luster said. “That’s not really needed.”