South County Looks to Diversify Water Portfolio with Desalination, Direct Potable Reuse

South Orange County is heavily reliant on imported water, with the price of that water continuing to rise. 

Without readily available water to help the area through emergency situations, water districts serving South Orange County residents such as South Coast Water District and Moulton Niguel Water District are looking to diversify their water supplies with ocean water desalination and direct potable reuse. 

Ocean desalination’s growing role in Southern California’s water supply is “a positive move towards overall regional reliability by having a new local source of supply in an area that currently is limited on water resources," South Coast Water District Assistant General Manager Marc Serna said. 

“We're very dependent on imported water supply, and we have a very limited groundwater basin,” Serna continued. “So, we have less opportunities than maybe some of our Northern Orange County areas where they have more groundwater storage readily available to them, to help them get through emergency situations and long-term outages or long-term drought situations.”

Serna explained that bringing in seawater desalination to the area not only supports the water needs of the district, but “it also frees up water for other areas and makes it available during difficult conditions like emergency situations or drought.”

South Coast Water District is continuing to make progress toward constructing a seawater desalination plant at Doheny State Beach, completing geotechnical testing and monitoring at the project site in February, Serna said.

Exploratory boring and monitoring wells sought to determine the best location for the plant’s slant wells that will draw in water from beneath the ocean floor, by evaluating the subsurface conditions and “confirm some of the conditions that we expect to see out there from a geologic standpoint for our slant wells,” Serna said. 

Having completed geotechnical testing and monitoring, the water district has now put out a request for proposals (RFP) for the design, build and operation of the plant. 

“We hope to award that in May this year, which will then initiate essentially the first step towards that ultimate construction and operation of the plant, which we currently have on schedule for producing water in 2028,” Serna said. 

The next major milestone for the project would be completing the design build process, Serna explained, which would help the water district define the cost of water for itself and its project partners. South Coast Water District anticipates having the guaranteed max price for the project, which would set the cost for desalinated water, by the end of 2024, Serna said. 

Since the Doheny Desalination Plant is anticipated to produce up to five million gallons of water per day (MGD) once in operation, South Coast Water District is looking to bring in project participants to share in the desalinated water. 

“Right now, we have an agreement with Eastern Municipal Water District; they approved moving forward with signing an agreement for a share of the capacity,” Serna said. “We are currently still working with three other agencies, two local and one in the Inland Empire for finalizing that cost share agreement for the first phase of the design, which would get us to the (guaranteed max price).”

Serna explained that once the guaranteed max price is set, the water district will move forward with “finalizing amended contracts with those agencies to hopefully move forward with the full five MGD and all the participants,” Serna said. 

The local partnering agencies would be able to share in the potable water generated at the plant, whereas partnering agencies that are farther away would participate in a water exchange agreement. 

With a water exchange agreement, desalinated water would not be transported to far away agencies. Instead, supplemented by desalinated water, South Coast Water District would use a smaller portion of imported water, freeing up some of the water supply for other districts. 

Moulton Niguel Water District is currently evaluating the feasibility of entering a similar water exchange agreement with San Diego County Water Authority, as its desalination plant in Carlsbad produces nearly 50 million gallons of water per day. 

During a special meeting on Feb. 29, Moulton Niguel Water District signed an agreement with San Diego County Water Authority to begin exploring the feasibility of partnering with the water authority for a water transfer. 

A water transfer would not entail transporting potable drinking water, but instead would mean Moulton Niguel Water District would take a portion of the water supply that San Diego Water Authority imports from Metropolitan Water District, while the San Diego Water Authority would use more of its own desalinated water supply.

“For Moulton Niguel, the things that we’re looking for is when we need water, we want that emergency water available, because we know that the cycles of the climate are getting more extreme and more frequent,” Moulton Niguel Water District General Manager Joone Kim-Lopez said. 

“We’re seeing more severe droughts, more frequent and when that happens, particularly in South Orange County, we don’t have a groundwater basin like the northern part of the county,” Kim-Lopez continued.

Dana Point relies on imported water from the Metropolitan Water District for the majority of its water supply. However, as water from Metropolitan becomes less available, allocation goes into effect, Kim-Lopez explained. 

“If Metropolitan goes into allocation, it’s not a rationing. It’s not that you only get this water and that’s it,” Kim-Lopez said.

“What Metropolitan does ‘is say you get this much water, which is less than what you typically get, and if you use above that, it goes into higher penalty up to $8,000 an acre foot,’” Kim-Lopez continued. “So, it’s substantially higher than what we normally get the water for.”

Moulton Niguel Water District is looking to increase reliability of the water supply with the potential partnership with the San Diego County Water Authority so that there are other available sources of water if imported water goes into allocation. 

“We also know that Metropolitan water rates are increasing much more than what was projected,” Kim-Lopez said. “So, from all these standpoints, I’m looking at supplies that can give me water when I need it in a way that’s reasonable for our ratepayers investment and also have as low risk as possible.”

Kim-Lopez clarified that by signing the Memorandum of Understanding with San Diego County Water Authority in late February, the water district is not committed to anything. 

“We’re just committing to a process to look at if there are opportunities that can be beneficial to both parties,” Kim-Lopez said.  

Since the Moulton Niguel Water District Board of Directors voted to give staff up to three years to explore a potential water transfer agreement with San Diego County Water Authority, Kim-Lopez explained that staff will begin to develop terms and negotiate a potential agreement that would be amenable for the two water districts. 

Moulton Niguel Water District would also need to work with the Municipal Water District of Orange County and Metropolitan Water District to work out a water transfer agreement, Kim-Lopez said.

“It’s going to take several steps; that’s why we have the timeline that we have. That doesn’t mean that it will take all three years,” Kim-Lopez said. “But the immediate next step is to sit down with those parties and make sure that we’re all looking at all the terms and trying to develop something that works for both sides.” 

Kim-Lopez added that this will be an incremental process as potential agreements will return to the Board of Directors along the way. 

Entering into an agreement with San Diego County Water Authority for a water transfer would “ensure greater reliability, because we have a source that’s available in times of need,” Kim-Lopez said.

“It will certainly help the economy, because a lot of times, when you don’t have water, the economy suffers,” Kim-Lopez said. “So, all in all, it’s a very positive thing for our communities. As far as what it will do to rates, we don’t know that yet.”

“We do know based upon what we’ve heard from Metropolitan Water District, which provides water to all of Southern California … they’re projecting rate increases far beyond what they had told us even a couple of years ago, and that always impacts our rates at the ground level,” Kim-Lopez continued. 

Kim-Lopez added that “time is of the essence” in the case of finding additional, reliable water sources. 

While the Doheny Desalination plant is still a few years off from producing water, Kim-Lopez explained that Poseidon’s desalination plant in Carlsbad is already online. 

“You hear about a lot of projects up and down the state that have not come to fruition yet, and while they sound great, there's a certain amount of risk associated because the cost of those projects can go up because of inflation, supply chain,” Kim-Lopez said. 

“The chances of those projects actually coming online relies on CEQA, environmental impact report, a lot of other hurdles that projects have to overcome,” Kim-Lopez continued. “The thing that's interesting about Carlsbad is it's already producing water. I don't have to worry if the project will come online or not. I know there's water there.”

Kim-Lopez added that Moulton Niguel Water District is looking for a way to get an emergency supply of water only when it's needed.

“A lot of other projects that are being contemplated, I would call base-loaded, meaning whether I need the water or not, I have to take that water, because when you have a facility that’s running, they have to run at a certain level,” Kim-Lopez said.

However, once the Doheny Desalination plant is running and producing water, Kim-Lopez said Moulton Niguel Water District would look into the project.

In addition to ocean desalination, Moulton Niguel is also working on a direct potable reuse project called OASIS or Optimized Adaptive Sustainable Integrated Supply. 

“It will be the first direct potable reuse pilot program in California, and we’re looking to develop that project,” Kim-Lopez said. “So we’re not just looking at other projects; we’re also developing our own projects to enhance local supply reliability, something that can help regional reliability as well, beyond our service area.”

In December, 2023, the California Water Control Board approved regulations for direct potable reuse, opening the door for agencies to “convert wastewater into high-quality drinking water,” according to a media release from the state board. 

Kim-Lopez explained that while the regulations are restrictive, Moulton Niguel’s OASIS project meets them. 

“For example, there are only 25 individuals in the States of California and Nevada combined that have the certification to run a direct potable reuse facility, and we have one of them,” Kim-Lopez said. “So, we are very well-prepared and positioned to take on this project.”

“What we’re doing for OASIS, envisioning this as a pilot, so that before we start putting the water into the potable system, that we show the public the safety and the quality of this water, because direct potable reuse is being done in other parts of the country and the world, but we want to demonstrate that,” Kim-Lopez continued. 

Moulton Niguel Water District envisions that the project will be online within four to five years, Kim-Lopez said. 

“It's a project that everybody really loves, because it reduces ocean discharge, which we know is incredibly important for South Orange County, the coastal cities,” Kim-Lopez said. “It has urban runoff reduction, sort of our version of stormwater capture and also increases reliability for drinking water, and just the environmental and all around benefit of this project is really exciting.”

South Coast Water District is also evaluating the feasibility of including direct potable reuse in its water supply, though in the early stages of exploration, Serna said. Serna noted that direct potable reuse could potentially augment the Doheny Desalination Project in the future.  

Kim-Lopez emphasized the need for water districts to diversify their water portfolios, adding that “in these uncertain times, it's really important that we look at all the possibilities and make the evaluation based upon the needs and preferences of the communities that we serve.”