Doheny Ocean Desalination Project

The South Coast Water District proposed the Doheny Ocean Desalination Project to produce approximately 5 to 15 million gallons per day (mgd) of potable drinking water. The project would consist of a subsurface slant well intake system, raw (sea) water conveyance to the desalination facility site, a seawater desalination plant, brine disposal through an existing wastewater ocean outfall, solids handling facilities, and potable water delivery to adjacent distribution infrastructure. The project location included the lower San Juan Creek lagoon and onshore and nearshore habitats near the mouth of San Juan Creek at Doheny State Beach and Capistrano Beach Park near Dana Point, California.

MBC assisted GHD, Inc. regarding biological and water quality resources of the lower San Juan Creek and nearshore marine environment. MBC provided a Technical Memo which summarized existing conditions throughout the project area, including: aquatic and riparian resources in the lower San Juan Creek; community resources at Doheny and Capistrano beaches; marine water quality, oceanography and sediment quality in the nearshore environment; biological communities and resources of the nearshore marine environment, including Essential Fish Habitat; and reviews of sensitive species and habitats in the project area. MBC produced separate technical letters to propose guidance to the assessment of potential impacts to southern steelhead in the lower San Juan Creek and offshore impacts in the vicinity of the discharge. MBC utilized the results of modeling to assess potential impacts to benthic and water-column communities under a variety of mixing and discharge scenarios. MBC’s Technical Memo provided an analysis of potential impacts and regulatory and permitting concerns and made recommendations for mitigation measures to reduce the potential for impacts from the project. Information from the Technical Memo was incorporated into the project EIR, and MBC assisted GHD respond to technical comments from regulatory agencies and stakeholders for the preparation of the Final EIR.

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