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Otay River Estuary Restoration Project in South San Diego Bay

Historically, greater than 90% of California’s wetlands were lost following European settlement. Along the coast, these wetlands have been filled, diked, paved over and built upon. Further, in many locations, the links between watershed sources of sediment supply and coastal habitats have been severed, reducing their ability to adapt to climate change through sediment accretion. Therefore, creation or restoration of coastal wetlands is an urgent priority for the state as a key adaptation strategy to combat sea level rise. Such projects also direct scarce conservation dollars to the habitats and associated species that are most vulnerable. Earlier this year, CMSF joined one such effort to address the loss of coastal wetlands, the Otay River Estuary Restoration Project, (ORERP).

ORERP is a 125 acre tidal wetland restoration project now underway in South San Diego Bay. Once completed, this project will serve as compensatory mitigation for the loss of marine life associated with a Carlsbad desalination facility in San Diego’s north county. The project is proceeding under the requirements of a development permit issued by the California Coastal Commission to Poseidon Resources, which owns and operates the desalination facility.Desalination plants are known to sometimes kill fish and other marine larvae through the intake of ocean water and subsequent processing for salt removal. CMSF’s role in this project is to monitor both physical and biological aspects of the restoration to ensure that associated marsh lands, tidal mudflat and subtidal habitat function at a level equivalent to natural coastal wetlands in southern California. CMSF staff member, Dr. Laurie Koteen, is the primary staff member designing and overseeing the monitoring program under the advisement of a scientific panel composed of Dr. Richard Ambrose of UCLA, Dr. Peter Raimondi of UC Santa Cruz and Dr. Brett Sanders of UC Irvine.

The shore of South San Diego Bay with a flock of Elegant Terns in flight
Elegant terns in South San Diego Bay. Photo courtesy of Ian Shive

Currently, ORERP is in the early stages of construction, having completed a substantial environmental review process and a restoration design plan that anticipates habitat migration in step with sea level rise. The wetland construction design process is unique in that it relies on the excavation of one location along the floodplain of the Otay River where it empties into San Diego Bay, and the fill of a second location with material excavated from the 35-acre floodplain site. This second location, an area of 90 acres, is a former salt pond that was until recently part of a large salt works operation, dating back to 1872.

Construction of the wetlands should be completed by early 2025. The final elevations of both sites will be suitable for supporting coastal habitats, which in turn will support a wide array of marine plant, fish, bird and invertebrate species. In addition to monitoring of the restored sites, CMSF will simultaneously monitor the habitats and species of up to four additional southern California wetlands, which will serve as reference sites for ORERP. By monitoring these additional wetlands, CMSF will ensure that project goals are achieved. Once the ORERP sites are found to have met all performance goals for a period of 30 years, the restored wetlands will be incorporated into the San Diego Bay National Wildlife Refuge, with management transferring to the US Fish and Wildlife Service.


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