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Topanga Lagoon Restoration Project Overview
Background
Topanga Lagoon, located within Topanga State Park, is a special place – it is one of the last remnants of a coastal wetland in California. Its unique mix of salt and freshwater habitats acts as a natural filtration system to protect water quality. Topanga Lagoon and Creek also host some of the rarest fish and wildlife species in the area. Its beach is not only a popular place to sunbathe and pursue outdoor recreation activities, but also buffers local facilities from storm damage.
Once containing 30 acres of pristine wetlands, Topanga Lagoon has been whittled down to less than 1 acre due to long-term development patterns. By restoring Topanga Lagoon in a coordinated and proactive way, we can preserve this haven of unique biological, cultural and recreational resources, while improving existing public infrastructure. The Topanga Lagoon Restoration project provides an opportunity to enhance coastal access, expand recreation opportunities, and develop buffers for projected sea level rise.
Key Restoration Goals
The overarching goals of the restoration of Topanga Lagoon are to expand and restore the lagoon ecosystem; integrate public access, recreation, and visitor serving needs; and proactively address sea level rise, all the while protecting existing biological, cultural and recreational resources. Specific project objectives include:
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Expand and restore the lagoon ecosystem to improve estuarine hydrologic functions, water quality, species and habitat diversity and protections for sensitive species.
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Replace the aging Pacific Coast Highway (PCH) bridge to support lagoon restoration and recovery of endangered steelhead trout and tidewater goby.
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Improve resilience of important structures and habitats to sea level rise and storm surge.
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Enhance local beaches by nearshore placement of native soils, while maintaining the integrity of the surf break.
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Establish a “Gateway Corner” at the NW corner of the intersection of PCH and Topanga Canyon Boulevard to provide coastal access and visitor services for the entire project area.
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Integrate and improve recreational facilities, emergency services, and coastal access for the entire project area, including improvements for pedestrians, cyclists, and visitors with disabilities.
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Minimize harm during construction: protect existing sensitive species, surf break and beach recreation.
Schedule
We have completed the planning phase. The Draft Environmental Impact Report for the project was released in February of 2024 for a 60-day public review period. The Proposed Final Environmental Impact Report (FEIR) was released on July 15, 2024 and was available for public review until August 13, 2024. The FEIR was certified and Preferred Hybrid Alternative 3A was approved on September 4, 2024.
The Topanga Lagoon Restoration Project has moved into the design and permitting phase. Design for the project is anticipated in Fall of 2024-2026, with project permits being sought towards the end of that time frame. Construction is anticipated in 2027+ with the ultimate schedule based on the availability of funds and construction resources.
Project Alternatives
Topanga Lagoon connected to ocean during 2023 storm.
The Draft Environmental Impact Report (DEIR) considered one “no project” alternative, and three “build” alternatives that seek to address the challenges and threats to onsite biological and cultural resources and find ways to expand and enhance them. The “build alternatives” also sought to expand and improve coastal access, recreation, and visitor amenities, while proactively addressing sea level rise (SLR) and the related threats to coastal infrastructure and ecosystems.
As noted in the DEIR, State Parks committed to identifying a Preferred Alternative after receiving input from the public and regulatory agencies and prior to certifying the Final EIR. The chosen preferred alternative is a hybrid of three of the build alternatives and is described in the FEIR.
State Parks and project landowners reviewed comments received on the DEIR during the 60-day public review period from February to April 2024. Based on that feedback, Preferred Hybrid Alternative 3A was selected.
What the Alternatives Have in Common
All project alternatives would replace the 79’ long Caltrans Pacific Coast Highway (PCH) bridge with one that is 460’ long, thereby allowing the expansion of the lagoon/creek habitat to increase to 7-10 acres, providing more refugia for endangered tidewater goby and steelhead trout. All alternatives provide ~1 acre of additional beach habitat and will identify the fate of the degrading Topanga Ranch Motel to determine if it will be removed or restored. Unified trail, parking, and emergency response systems would be developed for the entire project area. State Parks would create a new visitor hub at the Gateway Corner (NW corner of the intersection of PCH/Topanga Canyon Blvd.) where visitor services such as an interpretive pavilion, parking, restrooms, bus stop, picnic area, employee house and maintenance facility would be developed. Wastewater management options on State Park property would be improved and would include either a 1-mile sewer line connection along PCH to Los Angeles County Sanitation District facilities or would install advanced wastewater treatment options onsite. Los Angeles County would relocate the lifeguard/restroom building and parking facilities further inland and at a higher elevation to protect them from SLR. A new helipad would be developed adjacent to the lifeguard building.
During restoration, earthwork will occur largely outside the edge of the riparian woodland to avoid impacts to wetted habitats. In-water work within Topanga Creek is anticipated to be limited to an ~0.33-acre area associated with removal of the existing PCH bridge.
166,000-256,000 cubic yards of native fill would be removed during restoration activities and is proposed to be placed off Topanga Beach between 15-25 feet depth for nearshore nourishment. Based on the chosen alternative and wastewater option, construction will take about 5-6 years to complete.
How the Alternatives Are Different
Alternative 1, No Project: No project occurs resulting in no restoration of the lagoon and adjacent open space areas. Species such as the endangered steelhead trout and tidewater goby would face potential local extirpation due to greater environmental stressors associated with SLR, a shrinking lagoon, and extreme weather events. The Topanga Ranch Motel would continue to degrade, and County beach facilities and associated natural resources would continue to be threatened by SLR.
Current aerial lagoon overlay.
Alternative 2, Maximize Lagoon: Would maximize lagoon/creek restoration by fully removing the Topanga Ranch Motel resulting in ~9.5 wetted acres, ~23 riparian/transitional upland acres restored and beach expansion to ~4.39 acres. No change to the PCH alignment would occur. Would result in significant and unavoidable impacts to historic cultural resources.
Alternative 3, Maximize Historic: Would retain and restore most of the Ranch Motel (20 of 25 structures) for State Parks usage as either low cost overnight accommodation or a mix of park interpretive, office, employee housing, and maintenance uses. This would result in ~7.7 wetted acres, with ~23.7 riparian/transitional/upland acres restored and beach expansion to 4.42 acres. No change to the PCH alignment occurs. All impacts would be less than significant with mitigation.
Alternative 4, Maximize SLR Resiliency: Would retain and restore a smaller portion of the Ranch Motel (15 of 25 structures) for State Parks usage as either low cost overnight accommodation or a mix of park interpretive, office, employee housing, and maintenance uses. This would result in ~7.6 wetted acres, with ~23.7 riparian/transitional upland acres restored and beach expansion to ~4.56 acres. The PCH would shift north to maximize beach and associated facility retreat. Would result in significant and unavoidable impacts to tribal resources.
An overview of the DEIR Build Alternatives 2-4.
Preferred Hybrid Alternative 3A, Balanced Resource Protection: Combines elements from Alternatives 2 – 4 and meets all Project Objectives. Alternative 3A incorporates all components of Alternative 2 south of and including the PCH and the new bridge. This includes all areas of Caltrans PCH ROW and Topanga Beach.
Preferred Hybrid Alternative 3A-Balanced Resource Protection was selected based on public, regulatory and landowner feedback. This alternative both protects endangered species and ecosystems through lagoon restoration and protects and restores important cultural resources for the public benefit. Sea Level Rise resilience and improved coastal access are also incorporated.
For areas north of PCH within State Parks property, the new Alternative 3A would incorporate the footprint for the parking area and single concession identified in Alternative 3 and would retain and restore the smaller Topanga Ranch Motel footprint (up to 15 structures) consistent with Alternative 4. The resulting lagoon footprint would therefore be aligned with what was presented in Alternative 4 with a similar level of material available for the nearshore. Preferred Hybrid Alternative 3A would avoid significant and unavoidable historic and cultural impacts, similar to Alternative 3. The Gateway Corner will be consistent with the elements described in Alternative 3. Alternative 3A would incorporate Wastewater Management Option 2, Seepage Pits.
Graphics of Preferred Hybrid Alternative 3A - Balanced Resource Protection. Click each image for a detailed description of what is being shown.
Vision for the Future
Imagine what a restored Topanga Lagoon and new and integrated development of visitor services could look like! Below are some visualizations of how the extent of lagoon and facilities would change from existing conditions (Alternative 1) to those under the Preferred Hybrid Alternative 3A.
Visualizations of the lagoon today (Alternative 1) and post-restoration (Alternative 3A). Credit: RCDSMM, 2024.
Project Partners & Stakeholders
The Topanga Lagoon Restoration Project area is managed on behalf of the public by the California Department of Parks and Recreation (State Parks), California Department of Transportation (CalTrans), and County of Los Angeles Department of Beaches and Harbors (Beaches and Harbors). The Resource Conservation District of the Santa Monica Mountains (RCDSMM) is the grant and project manager for the project in coordination with the public landowners. Funding for the project has been provided by the Wildlife Conservation Board, State Coastal Conservancy, California Department of Fish and Wildlife, California State Parks and through the efforts of former Assemblymember Richard Bloom. Additional in-kind support has been provided by California State Parks, County of Los Angeles Department of Beaches and Harbors and CalTrans. Additional project stakeholders include a lengthy list of regulatory agencies, area universities and research institutions, environmental organizations, local stakeholders and the public.
