Power Generation - Marine Mitigation

San Dieguito Lagoon Restoration

The San Dieguito Lagoon Restoration project is restoring 116 acres of coastal tidal wetland to mitigate the estimated impact on marine fish populations of the cooling water systems for San Onofre Nuclear Generating Station (SONGS) Units 2&3. The California Coastal Commission’s (CCC) 1997 revised coastal development permit for SONGS Units 2&3 includes the wetlands restoration requirement. The San Dieguito Lagoon is located at Del Mar, just north of San Diego, California. Del Mar became the proposed project site after years of deliberation between other cities, resource agencies, and stakeholders because it presented the best opportunity to meet the objectives required by the CCC’s permits. Del Mar is also a location that is in proximity to the impacted site at SONGS.

Planning History

Southern California Edison (SCE), representing SONGS’ owners, continues to work in partnership with the San Dieguito River Park Authority (JPA) and has just completed the lagoon and inlet dredging of the restoration project (September 2011). The San Dieguito Wetland Restoration Project has been very carefully designed so that the rejuvenated lagoon will serve as a thriving fish hatchery, a refuge for migratory waterfowl and as an open space for recreational opportunities for local and regional communities alike.

Five criteria have been met during the design and construction stages of the lagoon, according to the California Coastal Commission’s specifications:

The project would not cause flood water to reach any higher than ‘existing conditions,’ including the so-called 100-year flood event
The project must maintain an open ocean inlet to the lagoon
The project must not increase river scour (erosion caused by water flow)
The project would not cause sand loss along the Del Mar beach
And the project must result in at least 116 acres of restored tidal wetlands.

Scope of Project – History of the design and permitting phase, 1997-2005

Design Phase:

A public working group consisting of agency representatives, non-governmental organizations, and interested members of the public, worked towards developing a range of practical means of restoring the San Dieguito Lagoon. As required by the Permit, SCE submitted a Preliminary Restoration Plan in September 1997 which was later approved by the CCC in November 1997. Following the approval process, the wetland restoration project entered the environmental review process, pursuant to the California Environmental Quality Act (CEQA) and the National Environmental Policy Act (NEPA). This entailed a submittal of an Environmental Impact Report (EIR), completed by local, state and federal agencies including the US Fish & Wildlife Service, the San Dieguito River Park (JPA) and US Army Corps of Engineers. The JPA certified the Final Environmental Impact Report (EIR) for the project in September 2000, after considering extensive public comments, including recommendations of many technical experts. The adopted EIR selected and modified a Mixed Habitat Plan from five optional plans that were submitted.

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A lawsuit claiming that the project would impact the Del Mar beach delayed progress on the project for three years (2000-2003). During this time, SCE had to research in depth project design elements which were later presented in court. The arguments in court only confirmed the legitimacy of the project’s design.

Engineering Phase

The detailed design and engineering phase of the project took place between 2003 and 2005; a Final Restoration Plan (FRP)(PDF) concluded this process in November 2005, as the document fulfilled the specified Permit conditions and bestowed details of the project’s components. This Final Restoration Plan (PDF) is consistent with the JPA’s Park Master Plan (PDF) and the CCC’s permit requirements.

Permitting Phase

On October 12, 2005, CCC provided SCE with a Notice of Intent to issue the Coastal Development Permit (CDP), stating that 27 special conditions were to be fulfilled prior to the beginning of construction. These conditions took one year to satisfy (2005-2006) and involved the following Permitting Agencies:

California Coastal Commission
California Department of Fish & Game
California State Lands Commission
Caltrans
City of Del Mar
City of San Diego
Regional Water Quality Control Board
United States Army Corps of Engineers
United States Coast Guard
United States Fish and Wildlife Service
22nd District Agricultural Association

Scope of Project – Construction Phase, 2006-2011

The initial construction of the San Dieguito Lagoon finally began in August 2006.

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Construction of the lagoons and inlet continued through 2011, by which time approximately 2 million cubic yards of earth were excavated, creating a net of 116 acres of tidal wetlands, on both sides of Interstate 5. This excavation included the site of a former World War II US Navy blimp landing field, to the west of Interstate 5.

TIn the six-year construction period, one mile of berms was built. These berms direct the river-system sediment transport to the ocean and protect the newly created wetland lagoon areas from flood-borne sediments. Additionally, four nesting sites (two east and two west of Interstate 5), have been created within the constructed sub-tidal basins using sand as topping for the nesting habitats. This sand was obtained from part of the initial channel dredging. These nesting sites provide a safe habitat for birds, such as the endangered California Least Tern, the Belding’s Savannah Sparrow, the Snowy Plover and the Light Footed Clapper Rail.

TThe remaining excavated materials, not utilized for river berms or nesting sites, have been placed at the six upland disposal sites and, if found to be beach-grade sand, along Del Mar beach as sand nourishment. All of the excavated material has remained on-site and biologists and archaeologists monitored the various construction activities at the site full-time.

TA cornerstone of the project was to remove the sand that had periodically plugged the river channel over the years. Approximately 125,000 cubic yards of sand, total, was removed from the channel in March-April 2011 and from the inlet of the San Dieguito River in September 2011. SCE has agreed to keep the inlet open to the ocean in perpetuity as part of this wetland restoration project.

Even with the construction still finishing up in 2011, the CCC biologists have completed over a year of ecological performance monitoring and found that the wetland supports a promising population of snails, crabs, amphibians, small mammals, birds and provides fish a place to spawn and grow. Terrestrial animals have also become visible, such as the burrowing owl, cottontail rabbit and various reptiles.

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Future wetland plans

Two years following the 2011 completion of the wetland’s construction, the wetland will be fully vegetated. The clay soils will be interspersed with native salt marsh plants and a productive wetland complex will be thriving. The river park’s multi-purpose network of public trails will follow the marsh shoreline, punctuated by interpretive wildlife viewing platforms.

SCE is responsible to maintain the functioning wetland for a period equal to the operating duration of SONGS (presently expected to be 40 years.)

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