Desalination:  Solution to Cambria's Long-Term Water Supply

CCSD’s long-term water supply planning calls for continued aggressive water conservation, recycled water for non-potable uses, and seawater desalination to augment its existing potable water supply. Potable water from a future desalination project would protect residents, businesses, and visitors to Cambria from droughts and other emergencies, while also helping to preserve the area’s sensitive coastal stream habitats.  The desalination recommendation is the result of many years of study, which included incorporating much public review and comment. 

 

This review and study process culminated in a Water Master Plan that was adopted by the CCSD Board on September 25, 2008. 

Cambria relies solely upon two narrow and thin groundwater aquifers for its potable water supply.  The CCSD's main supply aquifer is drawn down during the summer dry season and peak tourist period before being recharged during the winter rainy season.   Due to drought periods or the late arrival of seasonal rainfall during average years, the CCSD's aquifers can become perilously low during late summer and early fall.  If uncharged during the subsequent late fall or winter rainy season, low aquifer levels can lead to saltwater intrusion of the main supply aquifer and a host of other operational problems.  Depending upon well levels and other factors, the CCSD has invoked drought surcharges and other measures to curb demands.  The chronic pattern of dry season shortages also resulted in the CCSD declaring a Water Code 350 emergency in November 2001, which is still in effect.  

 

The CCSD's service area is isolated from inland areas by the Santa Lucia mountain range to the east and the Pacific Ocean to the west.   There are no nearby aqueducts from which to import freshwater into the area, which was one of the factors resulting in the CCSD's decision to pursue seawater desalination.   Further discussion on various long-term supply alternatives can be found in the CCSD’s June 2004 Water Master Plan entitled Final Report: Assessment of Long-Term Water Supply Alternatives.

Seawater desalination will further diversify the CCSD’s water supplies, which will greatly improve overall water supply reliability.   Besides addressing droughts and seasonal dry periods, such an additional water source will allow the CCSD to maintain operations during major fire emergencies, or should both of its existing well fields ever be incapacitated at the same time due to a chemical spill, earthquake, wild land fire, or other disaster.   The additional supply also allows CCSD staff greater flexibility in taking critical system facilities (e.g., well pumps, electrical panels, generators, treatment processes) out of service for maintenance and repairs. 

Key environmental concerns associated with seawater desalination include potential impacts to marine life at the intake due to impingement and entrainment, returning seawater at salinity concentrations greater than naturally occurring background levels, greenhouse gas emissions from the power used to operate the facility, and secondary impacts caused by growth within the community. 

 

These concerns and others will need to be further analyzed to determine ways to avoid or otherwise mitigate their potential impacts within a project-level Environmental Impact Report/Environmental Impact Statement (EIR/EIS).  To avoid potential impingement and entrainment of marine organisms at the seawater intake, the CCSD is in the process of studying ways to applying a subterranean intake well and concentrate return well system.  Examples of subterranean seawater well intakes can be found in Spain for fish farms and desalination facilities, and also at San Francisco’s Ocean Beach for the Steinhart Aquarium. 

 

Seawater concentrate concerns are normally addressed through careful design of diffusers to ensure rapid mixing and dilution of the return stream; or, through blending the return stream with another water source such as treated wastewater or brackish groundwater underflow within a naturally occurring seawater-freshwater interface.   To address greenhouse gas emission concerns, the CCSD is planning to use renewable power as well as including the most energy-efficient treatment technology available within the future facility.  To address growth concerns, the CCSD developed a Buildout Reduction Program (BRP), which was adopted as a mitigation measure within its Water Master Plan’s Program- level EIR.   Following the collection and analysis of additional geotechnical data, the CCSD will further develop and define desalination project alternatives that will be made available for public review within a project-level EIR/EIS. 

 

Desalination costs have been estimated in terms of 2008 dollars at $14 million without including the cost of a renewable power system (solar/photovoltaic), and at $17.2 million when including the cost of a renewable power system.  These costs are for a system sized to produce 602 acre-feet of potable water over a typical dry season in Cambria, or an average span of 184 days per year.   As with any supply project, costs will increase over time due to inflation.  When assuming a four-percent per year inflation rate and a mid-point of construction during June of 2012, the project costs inflate to $16.4 million without renewable power, and approximately $20.1 million including renewable power. 
 

Cambria was fortunate to have received a $10.3 million Federal Water Resources Development Act (WRDA) authorization for its desalination project.  The WRDA program is administered by the Army Corps, and relies upon subsequent fiscal year appropriations for actual funding.  Typical WRDA project funding is based on a 75% Federal and 25% local cost sharing formula.   However, because the CCSD spent a considerable effort on an earlier desalination project during the 1990s, a local credit of up to $3 million was authorized in the 2007 WRDA bill for Cambria.  This credit is currently under review by the Army Corps. 

In April 2009, the Army Corps also received $2.5 million in funding through the American Recovery and Reinvestment Act (ARRA) to develop Cambria’s desalination project. This funding is part of President Barack Obama's "stimulus package" program passed in February 2009. 

Besides outside funding, construction of the CCSD’s desalination facility construction will rely on future connection fees from its existing water wait list customers.  In addition, existing CCSD wait list customers have also proposed a Mello-Roos tax assessment on their properties to help cover the initial project costs. 

The Army Corps of Engineers is currently managing a geotechnical investigation proposed at the Santa Rosa Creek beach area.  This study will be a detailed follow-up analysis to an earlier 2008 geophysical investigation commissioned by the CCSD.   The earlier 2008 work found a main paleochannel with an estimated depth to bedrock of 140 feet, as well as two secondary paleochannel areas.   The more detailed study to follow will focus on sampling and characterizing the nature of the deposits within the paleochannel areas to confirm whether subterranean intake and substerranean concentrate return systems could be developed for this area.   If confirmed, a project alternative for this area will be developed along with the CCSD’s earlier San Simeon Creek area alternative.   The alternatives will then be analyzed and reviewed as part of a project-level EIR/EIS.    The start of the Army Corps field investigation at the Santa Rosa Creek beach area is subject to their completion of environmental and permitting clearances that are anticipated by the fall of 2009. 

Key Links
International Desalination Association