Officials this week unveiled the latest step in a multi-organization effort to tap into the “world’s largest reservoir,” the Pacific Ocean, for drinking water that would serve residents in San Clemente, Dana Point, San Juan Capistrano, Laguna Beach and Laguna Niguel.

The newest phase of the $150-million project is in a trailer at Doheny State Beach, but the simple structure hides a complex set of equipment that will suck water from beneath the sea floor, pump it through membranes and filters and make it ready for consumers to drink.

Water officials are launching an 18-month test phase that is critical to the future of the project.

“This phase gives us the information to design the plant correctly,” said Dick Dietmier, the director of South Coast Water District. “That’s the critical part of building the desal plant, to get the design right the first time.”

Ultimately, the system could supply up to 25 percent of San Clemente’s water needs. The city uses 10.5 million gallons of water a day. The vast majority of San Clemente’s water—85 to 90 percent—is imported from elsewhere, although the city does get about 7 percent of its supply from two local wells, and another 8 percent by recycling water.

But the amount of money the city is charged to bring in outside water has steadily climbed over the years, and the politics of water statewide has seen reductions in the amount available.

“It would be nice to have an additional local supply and become less reliant on imported water, especially with some of the challenges in the water supply in Northern California,” City Assistant Engineer David Rebensdorf said.

Like an octopus’ tentacles, the South Orange Coastal Ocean Desalination Project will ultimately rely on nine wells drilled at a slant beneath the ocean floor. The water will be sucked through the ocean floor.

Officials say the design makes it one of the most watched ocean water desalination projects in the state, largely because the slant wells are touted as environmentally friendly. The main benefit of this type of system is:

• It does not harm marine organisms either through entrapment or entrainment; so the project’s new test phase is supported by the environmental community.

• The quality of water is very good because of the natural filtration that occurs as the water is drawn through the sand and gravel under the beach and below the ocean floor.

• The slant-well intake system saves money because the high quality water does not require pre-treatment before undergoing the reverse-osmosis membrane desalination process.

A private firm is building a desalination plant in Carlsbad, but that project does not use slant wells. Surfrider appealed the permits for that project, but the move was denied. Officials there say that project will produce 50 million gallons of water a day for 300,000 residents in several North San Diego County cities. That plant is scheduled to be operational in 2012.

Locally, a 2007 project-feasibility study indicated that it would be possible to construct a 15-million-gallon-a-day ocean desalination plant at Doheny Beach. The plant could begin operating in 2015, officials said.

But the project is expensive to build and operate. While the agencies involved—South Coast Water District, which serves Dana Point is the lead agency and the Municipal Water District of Orange County is playing a large support role—have obtained a $1.5 million grant, more state and federal money is being sought.

Each agency involved so far has chipped in $250,000 through fiscal year 2010, with an estimated total of $660,000 needed from each. The contract, however, gives each agency mileposts at which they can opt out of the project, and even sell their shares to another agency.

Project supporters say while the initial costs of producing the desalinated water are high, the plant will allow local officials to control the cost and supply.

Once the entire facility is up and running, the agencies will pay an estimated $1,300 to produce an acre-foot of water, compared to buying imported water, now sold at $700 an acre foot. Generally, an average suburban family uses about an acre foot of water a year, although conservation efforts can reduce that by 75 percent.

The pilot project unveiled Wednesday will allow engineers to get a better idea of the actual water quality, and what level of treatment will be necessary to make the water drinkable, Rebensdorf said.

It will also help engineers determine how removing water from the Pacific will affect an underground basin that runs roughly along San Juan Creek. The city of San Juan Capistrano has a $35-million groundwater plant that can produce up to half of that city’s drinking water needs. While Capistrano is a partner in the desal plant, officials there have raised concerns that pulling the water from the Pacific will reduce the effectiveness of a water barrier that keeps the ocean salt water from mixing with the underground basin.

Capistrano officials are concerned any change in that natural barrier could cause the water level in the San Juan Basin to drop and decrease the effectiveness of the Capistrano’s groundwater plant.

“There’s a question of whether this is this going to cause an overdraft on the San Juan Basin, which would be a concern to us,” San Juan Capistrano Councilman Tom Hribar, who represents his city on the desalination project committee. “But this is a very sophisticated program with lots of testing and lots of evaluation.”

Another issue that the new testing will help explore: The impact of MtBE pools throughout the area on the water quality. The spills are near the Union station on Del Obispo, the Arco station and the former gas station—now a truck and equipment rental—on Doheny Park Road.

Dietmier said water officials will solve any issue that comes up. They have to.

“If it doesn’t work the first time, we will find another way,” he said. “Ninety-seven percent of all of the available water in the world is in the ocean.”