Ocean Plan Amendment Compliance Carlsbad Desalination Plant Catches the First Wave

The Claude “Bud” Lewis Carlsbad Desalination Plant (CDP), pictured in Figure 1, has been operating for nearly 3 years, producing approximately 50 million gallons per day (MGD) to meet 10 percent of the City of San Diego’s daily potable water demands. The plant has been operating under a temporary State Water Quality Control Board (Water Board) permit that will expire following decommissioning of the cohabitated Encina power plant, which operates a shared ocean water intake structure. A new permit will be required to comply with the Water Boards’ Ocean Plan Amendment (OPA), which were adopted by the Water Board in May 2015. A concept to meet the OPA was tentatively approved when the temporary permit was issued with plant construction in 2013. However, OPA requirement interpretation by the Water Board has changed since that time, requiring Poseidon to consider alternative concepts to comply with updated interpretations. Over the last three years, Poseidon has been identifying and evaluating alternatives to both satisfy the OPA and stakeholder’s primary goal to supply drinking water in a safe and cost effective manner. Over 25 alternatives were considered, culminating in a two-phase construction project to comply with all permitting requirements, including those within the OPA. The Water Board has accepted the two-phased approach and adopted the first OPA permit to be issued on May 8, 2019. The following sections describe the OPA requirements and the steps taken to address those requirements.

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