Desalination Plant To Begin Construction This Month
You may recognize the spot: it’s visible from Interstate 5, just north of the distinctive tower of the Encina power plant in Carlsbad. There are many reasons a private company, Poseidon Resources, chose this site for a huge desalination plant.
Poseidon’s Peter Maclaggan said one is that San Diego badly needs an independent source of water in case it gets cut off.
“We get almost 90 percent of our water from somewhere outside San Diego County, “ he said as the Coaster train rolled past the lagoon behind him. “That water from somewhere else is the subject of intense competition, so we’re looking to the Pacific Ocean for a partial solution to San Diego’s supplies. It’s at least one source that’s under local control, drought proof and not dependent on snow pack or rainfall.”
Another reason this is a good site is because Poseidon will be able to use the ocean intake and outfall channels built by the Encina power plant for its cooling system. MacLaggan said the desalination plant will use 300 million gallons of ocean water a day. Of that, 100 million will go through a reverse osmosis system.
“You introduce the seawater though these little holes under high pressure,” MacLaggan said, demonstrating a cut-away of one of the filters that will be used at the plant. “As you introduce the water, some of it is going to pass across the membrane and become fresh water and enter this center collection tube. The fresh water comes out the middle and the remaining salts and seawater will flow straight through out the back.”
Water goes through these filters eight times before it’s drinkable. MacLaggan said the membranes inside are enough to stretch all the way from San Diego to Sacramento. The extra salty seawater goes back to the ocean. This is where the other 200 million gallons of water pulled in the intake pipe is used.
“For every gallon of water that’s returned here,” MacLaggan said, “we bring in two gallons of sea water to mix with it, before the combined flow goes out to the ocean.”
Critics of the plant say the company will not be able to dilute the salty water enough to avoid harming marine life. They accuse the project of making money for investors at the expense of ratepayers.
They also argue recycling existing water supplies water to drinkable standards would be cheaper. The unfortunate phrase “toilet to tap” has made recycling more difficult for the public to swallow. Orange County already has a big water recycling or IPR (Independent Potable Reuse) plant that generates drinking water for the community north of San Diego. But Orange County was able to obtain permits for its IPR plant because it feeds water from the plant into a huge natural ground water basin before treating it again and reintroducing it into the water supply. San Diego does not have a natural underground holding tank, and getting state permits will be more difficult.
Sandra Kerl, deputy general manager of the San Diego’s Water Authority, said the county could not afford to pass up this shovel-ready desalination project.
“I believe we need both IPR and desal,” she said, “It’s part of a full diversification of a portfolio of regional supply. This project is ready to go at this point, and I think when IPR is ready, there will be a need for that too.”
Ratepayers will see the benefit of building the desalination plant now, because interest rates are really low and borrowing money for the project is cheap.
“It’s a very good time to be hitting the bond market. “ Kerl said. In December, bonds to finance the project sold at 4.78 percent. The cost of borrowing to build the $900 million plant is important because ratepayers will pay back the investors as they purchase the water.
Twenty-four different water districts are represented on the San Diego County Water Authority. Gary Arant is general manager of the Valley Center Water District. He supported the decision to enter a contract to buy 50 million gallons a day of desalinated drinking water once the project is up and running.
“The reality is that the cheap water supplies, the state water project, the Colorado River...that’s over,” Arant said. “The next increment of supply is going to be much more expensive.”
But like several other water districts, Arant is worried that some districts might end up bearing the brunt of the higher cost of the desalinated water. He has concerns about how the extra costs will be shared across the region.
“There’s no certainly as to how it’s going to turn out,” he said.
The County Water Authority will begin a process this year to determine how to charge individual districts for water from the desalination plant. The costs could add several dollars a month to the average water bill.
But, Arant said, one thing is certain.
“Make a copy of your water bill and stick it in a drawer and pull it out in 10 years. It’ll look very cheap.“
Sandra Kerl said a lot of people are watching how this project goes.
“There’s 12 desal projects in various stages of consideration in the state of California,” she said. “Depending on how this project goes will, I’m sure, impact whether or not those projects move forward. California, that is very challenged by water sources, it could provide an opening to the state that hasn’t been there before to a much more dependable source of supply.“
The ocean could be supplementing San Diego’s drinking water by 2016. But it will be many more years before it becomes cost competitive with other sources of water and we find out if the investment really pays off.