South Orange Coastal
Ocean Desalination Project

Project Purpose

South Coast Water District has been working with the Municipal Water District of Orange County and South Orange County cities and water agencies to demonstrate the feasibility of using environmentally-friendly "slant" intake wells below Doheny State Beach and the ocean floor to supply water to a reverse osmosis desalination plant. Click here for most recent project newsletter. (PDF; 1.2MB)

Project Participants

The Project Participants in Phase 3 Extended Pumping and Pilot Plant Testing are: South Coast Water District; Laguna Beach County Water District; Moulton Niguel Water District; City of San Clemente; and City of San Juan Capistrano. Project Supporters include the Municipal Water District of Orange County (project initiator and facilitator) and the Metropolitan Water District of Southern California (future operating subsidies).

Project Participant Meetings

The next Project Participant meeting is July 14, 2010, 2:30 PM at
Dana Hills Tennis Center. Click here for agenda for July 14, 2010 meeting.
Note: Project Participants have decided that their meetings involve a matter of public interest and shall be open to the public. While the group is not subject to the Brown Act, participants will voluntarily follow Brown Act procedures as a courtesy and a convenience for the public and for members.

Project Benefits: New Local Source Water

The project provides key benefits:

  • It creates a new local source of water for South Orange County which continues to face reductions in its imported water supplies. A 2007 project feasibility study indicated that it would be possible to construct a 15 million gallon a day ocean desalination plant using nine ocean intake “slant” wells. The plant could begin operating as early as 2015 and could supply about 25% of the potable water needed in the coastal areas between Laguna Beach and San Clemente. For South Coast Water District this could mean a new local source for about 30% of the water needed in our service area. Click here for slides on need to diversify supply. (PDF 133kb)
  • It improves the ability of the local area to maintain water service during earthquakes or other events that can disrupt the imported water system into South Orange County (similar to a storage reservoir).

Project Approach: Environmentally-Friendly Intake & Cost Effective Pre-Treatment

This project is also one of the most watched ocean water desalination projects in California because it proposes an environmentally-friendly and cost-effective "slant" well intake system. The main benefit of this type of system is:

  • It does not harm marine organisms either through entrapment or entrainment; as a result, the project’s Phase 3 Feasibility Test Phase is supported by the environmental community.
  • The quality of water is very good due to 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 source does not require any pre-treatment before undergoing the reverse osmosis membrane desalination process.

Project Timeframe/Cost

The plant could begin operating as early as 2015. From now until then, some of the key activities would include completion of feasibility testing, securing necessary permits for construction in the coastal zone, design of the intake well system and reverse osmosis process, construction of the well system, and construction of the treatment facility. The location of the proposed treatment facility is on District property next to San Juan Creek in Capistrano Beach.

The estimated cost for the design and construction of the intake well system and reverse osmosis plant is $136 million; the water produced is estimated to cost about $1300 per acre-foot, which is about double the current cost of water imported into the region. The Metropolitan Water District of Southern California will provide a subsidy of $250 per acre-foot of potable water produced and this would bring the estimated cost of water to $1,050 per acre foot.

The cost per acre-foot of imported water is expected to rise over the next 20 years, while the cost of desalinated ocean water is expected to decline.

Final Phase 3 Feasibility Testing

Phase 3 is the final phase of feasibility testing for the project and is projected to last for approximately three years and is underway. Key activities include:

  • Pumping the slant well installed in 2006 for about a year to assess water quality.
  • Assessing the efficiency of the slant well intake system.
  • Gathering data on the groundwater basin beneath the ocean.
  • Determining the best membrane process(es) to remove the salt from the water.

The cost of Phase 3 Feasibility Testing is estimated at about $5 million. The State Department of Water Resources has contributed $1.5 million toward it, and other grants are being sought as well. The local Project Participants are contributing the balance of funding to this phase of work.