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"A diverse portfolio of water supply sources is needed throughout Southern California"

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The Doheny Ocean Desalination Project was the first desalination plant approved by the California Coastal Commission since more strict regulations were adopted in 2019. It will provide a reliable, local and drought-proof source of drinking water for the South Coast Water District and its customers.

As California continues to endure drought conditions, communities are looking into water supply options that are resilient to climate change and reduce their reliance on imported water. The South Coast Water District (SCWD) provides water and wastewater services to about 35,000 residents and 2 million visitors per year in South Orange Country, California. It will be home to the first desalination facility in the state to be compliant with the California Ocean Plan. SWM had the chance to interview Rick Shintaku, General Manager at SCWD, about the proposed project and what it entails for the region.

Can you tell us briefly about your career path and your current role at South Coast Water District (SCWD)?

I am the General Manager of the South Coast Water District (SCWD or District). SCWD serves approximately 35,000 residents and 2 million visitors a year in Dana Point, South Laguna Beach, and portions of San Juan Capistrano and San Clemente. Under my leadership, SCWD has developed and led the planning and implementation of capital improvement, water resources, and water development programmes and projects, including the $100 million Tunnel Stabilization Revitalization Project (a 5-year project with an estimated completion date of June 2023) and the Doheny Ocean Desalination Project (Project), which will provide a new, reliable, drought-proof, high-quality drinking water and locally controlled emergency water supply for the community, and potentially the region.

The feasibility of the Doheny Project has been studied since the early 2000s, and SCWD is fortunate to have an optimal location for it

I am a registered Civil Engineer in California with over 30 years of experience in water/wastewater systems and environmental engineering. Before becoming General Manager at SCWD, I was the Assistant General Manager and Chief Engineer, having joined the District in 2015. Prior to joining SCWD, I served as an Engineering Manager for the City of Anaheim Water Division, as an engineer at the State Water Resources Control Board and spent my early career in the private sector working in the environmental engineering field.

I received my Bachelor of Science degree in Civil Engineering from Cal Poly Pomona and earned a Master of Science degree in Civil Engineering (Water Resources) from the University of California, Irvine. 

  • The project will also include significant photovoltaic solar panels onsite and potential offsite renewable energy options

California regulators recently approved the Doheny Ocean Desalination Project, the first desalination that the Coastal Commission has approved since more strict regulations were adopted under the Ocean Plan. What are the keys to this successful approval?

First and foremost, planning and preparation. The feasibility of the Doheny Project has been studied, researched, and tested since the early 2000s. Everything from the long-term effects of our brine discharge on marine organisms to the slant well technology and everything in between. In addition to the research, SCWD is fortunate to have an optimal location for desalination. The District already owns the property where the facility will be built (which happens to be adjacent to a wastewater treatment plant and a two-mile outfall). Furthermore, the regional water transmission pipelines that serve imported water from the Irvine area to the northern section of San Diego County are located adjacent to the Project property as well, which lends itself to a regional solution to water supply shortages. In addition, the treatment plant property is about 300 m from Doheny State Beach which contains the perfect geology for slant wells. The above benefits also contribute to the cost-effectiveness of the product water. 

Can you tell us about the technology that will be used at the Doheny Ocean Desalination Project?

Subsurface slant wells will be used to intake ocean water, which eliminates the environmental impacts of open ocean intakes

Key technological components of the Doheny Ocean Desalination Project include a subsurface slant well intake system, a seawater desalination plant, and brine disposal through an existing wastewater ocean outfall. Other components of the project include raw ocean water conveyance to the desalination plant site, solids handling facilities, and potable water storage and conveyance to adjacent distribution infrastructure. The project will also include significant photovoltaic solar panels onsite and potential offsite renewable energy options.

The project will use subsurface slant wells to intake ocean water which eliminates adverse environmental impacts typically associated with open ocean water intakes and serves as a seawater intrusion barrier to protect the basin's groundwater quality. The slant wells will be fully buried in well vaults at Doheny State Beach and will not breach the surface of the ocean floor.

Reverse osmosis membrane filtration will be used to desalinate ocean water for potable use. Reverse osmosis, also referred to as RO, is a process where salts are removed by pushing water under pressure through a semi-permeable RO membrane.  This process can recover approximately 50% of highly brackish seawater as fresh potable water. The RO process is so effective at removing salts that some remineralization is necessary before it can be distributed as drinking water.  The most energy-intensive aspect of a desalination facility is the high-pressure RO pump system. The Doheny Desalination Plant will employ an energy recovery system significantly reducing the overall system energy demand. 

The Doheny Desalination Plant will employ an energy recovery system significantly reducing the overall system energy demand

The brine leaving the plant is essentially twice-concentrated ocean water. The brine will be blended with existing treated wastewater and discharged to the ocean using an existing wastewater ocean outfall that employs diffusers to minimize the shear effects of the discharge plume on ocean life and improve the mixing of the discharge with the surrounding ocean water. The benefits of this approach include avoiding the need for offshore construction of new discharge facilities and blending of the brine and wastewater bringing the salt concentration of the discharge water closer in-line with the ambient ocean water salinity, further improving mixing and minimizing impacts.

New ideas are emerging to mitigate brine disposal that would take advantage of the extraction of minerals for commercial use. Do you foresee exploring those options in the future?

The current plant design and layout include over 10,000 square feet dedicated to a research and development (R&D) pad and alternative energy pad, where innovative technologies can be tested on actual samples of water entering and exiting the plant (along with the demonstration of alternative energy technologies). I agree that it is prudent to explore technologies for extracting minerals from desalination brine that may be commercially viable, so our design leaves room for future exploration.

How does the Doheny Ocean Desalination Project compare with other water sources or measures to augment the water supply in terms of costs and reliability?

SCWD believes that a diverse portfolio of water supply sources and enhanced water conservation is needed throughout our region to remedy the droughts and emergency supply needs during water system interruptions. The portfolio planned for the South Orange County region includes brackish groundwater desalination, indirect potable reuse, direct potable reuse, ocean water desalination, and storm flow capture. The region continues to be aggressive in overall water use efficiency (with significant permanent reductions over the past several drought periods) and continues to be a leader in water system loss control as well. 

The brine will be blended with existing treated wastewater and discharged to the ocean using an existing wastewater ocean outfall

The Doheny Ocean Desalination Project would provide a new, local, drought-proof supply of drinking water to the region. We completed a comprehensive water supply reliability study in December 2017, building from prior regional water supply reliability studies conducted by SCWD and the Municipal Water District of Orange County (MWDOC) – a local wholesale water provider and resource planning agency. The report indicated that the Doheny Project ranks well above all other available water supply options for SCWD and is a recommended core strategy for South Orange County (along with IPR and DPR) to meet the water supply and system reliability gaps.

Per the report, the Doheny Ocean Desalination Project also has the following benefits:

  1. High system and supply reliability benefits due to hydrologic cycle independence and climate change resilience;
  2. High resiliency to unknowns (climate change; reductions in imported water supply; increased regulations or reduced access to imported water supplies);
  3. High level of local control over operations and cost; and,
  4. Moderate implementation risks and moderate cost-effectiveness.

The SCWD relies on imported water for 90% of the drinking water supply. What is the projected contribution of different water supply sources ten years from now?

Our project water supply portfolio in the year 2035 includes:

32% - Doheny ocean desalination

26% - Metropolitan Water District imported

17% - Recycled

15% - Indirect/direct potable reuse

10% - Local groundwater

Having a reliable diverse water supply portfolio will provide SCWD and its customers with water security in the face of numerous future water uncertainties. Additionally, as a coastal agency, we have the option to evaluate ocean water desalination as a potential water supply, something many other agencies do not have the opportunity to do.

How has public awareness of water scarcity and acceptance of unconventional water sources such as desalination evolved in recent years?

The persistent drought conditions plaguing Southern California, and much of the west, have increased the urgency and acceptance of water districts to seek local and sustainable water supplies, even at a higher unit cost. Both the regulatory and public focus in the past leaned heavily towards conservation and we’re now at a place where both sides are understanding that we cannot conserve our way out of moderate to extreme drought conditions and that it is prudent to seek drought-proof sources.  

Could you share the SCWD’s initiatives to increase water efficiency and conservation, and to what extent they have been successful?

Although our initiatives were prompted by legislation and regulations, our staff response and community receptivity have been excellent. We’ve implemented a Drought Response Task Force to regularly discuss drought response; water-use efficiency; progress on minimizing water loss through monitoring top users, leak monitoring and repairs, and strategies the District will take to meet necessary conservation goals.

A reliable diverse water supply portfolio will provide SCWD and its customers with water security in the face of future uncertainties

SCWD has a robust potable water irrigation run-off surveillance programme. Staff are patrolling the District’s service area on an ongoing basis to identify and cite any violations of SCWD’s Water Conservation Ordinance. We work very closely with MWDOC and MWD (i.e., our imported water wholesalers) to provide numerous indoor and outdoor rebates for customers to implement water conservation devices and technologies, at their homes or place of business. In addition to the rebates, we offer free assessments and inspections to help our customers ascertain which efficiency and conservation devices would be most useful to them. Since our District contains a high number of resorts and golf courses, our Water Conservation team works directly with them to assess and convert, where feasible, their irrigation systems to recycled water.

Lastly, we have a robust marketing and communications programme that keeps our community aware and informed of all the water efficiency and conservation efforts the District has in place. The overall success cannot be attributed to any one programme; more so, it is attributed to the overarching effort and diligence with which our staff works with the community to implement these initiatives.