Berm’s opening marks big step of San Dieguito Lagoon restoration

New wetlands ready for tidal flushing, as years-long environmental project nears end

DEL MAR — An $87 million restoration of the San Dieguito Lagoon reached another milestone last week with the opening of a berm to let ocean tides flow into 64 acres of newly created salt marsh wetlands east of Interstate 5.

Bulldozers and earth-movers have been working for more than two years in the low-lying areas along the San Dieguito River, near the Del Mar Fairgrounds. Planning began in 2012, said Kim Smith, senior regional planner for the San Diego Association of Governments.

“This is what ties it all together,” Smith said Thursday, standing at the end of a dirt road overlooking the marsh inlet. “The majority of this project is creating new tidal wetlands. This area used to be old tomato fields.”

More than 1 million cubic yards of silty earth were removed from the lowest areas and placed on higher ground within the project area. The upland disposal site will be covered with fresh soil planted with native sage scrub.

Together, the wetlands and upland areas in the project total 160 acres at the intersection of three cities: Del Mar, Solana Beach and San Diego.

SANDAG, as San Diego County’s regional planning agency, designed and obtained funding for the project. Most of the money is from TransNet, the half-cent sales tax approved by county voters. Caltrans oversees construction and the various contracts involved.

The restoration is one of the environmental mitigation projects included in the 40-year, $6 billion North Coast Corridor Program, most of which focuses on transportation improvements to Interstate 5 and the coastal rail corridor.

A similar project in the massive transportation program was the $120 million restoration of the San Elijo Lagoon completed in 2022. That effort produced nearly 440,000 cubic yards of clean sand that was piped onto the beaches at Cardiff in southern Encinitas and at Fletcher Cove in Solana Beach.

The current San Dieguito site is adjacent to a separate wetlands restoration finished in 2010 by Southern California Edison Co. and San Diego Gas & Electric Co. as one of several mitigation projects required for the San Onofre Nuclear Generating Station. The Edison-led project cost $93 million and restored about 150 acres along the San Dieguito River.

“The continued restoration of the San Dieguito Lagoon is and has been an important project for the city of Del Mar,” Mayor Dave Druker said Thursday. “These restoration projects have allowed the mouth of the lagoon to remain open since 2008.”

Keeping the lagoon open to the ocean prevents stagnation and flooding, which can occur when a sand berm builds up at the beach. The project also helps the neighboring cities meet state goals for environmental sustainability, Druker said.

The lagoon’s natural habitat has been degraded by more than a century of human activities.

In addition to its past agricultural uses, the land for years was home to the San Dieguito Air Field, built in the 1920s by the Navy and used by the military through World War II.

Later renamed the Del Mar Municipal Airport, the airfield was used mostly for recreational flights in the 1950s and occasionally by the wealthy to visit the Del Mar Fairgrounds, according to old newspaper stories. Most of the aviation facilities were demolished to make way for Interstate 5 in the 1960s. Some of the last traces were eliminated by the Edison wetlands restoration.

The restoration recreates a type of rare habitat that has largely disappeared, taking its unique creatures with it. More than 90 percent of California’s coastal wetlands have been lost to development.

The California Coastal Commission and other government agencies require new development to mitigate additional habitat losses by restoring or creating wetlands. At San Dieguito, that builds space for wildlife such as the light-footed Ridgway’s rail and least Bell’s vireo, two native California birds listed by the federal government as in danger of extinction.

“We have a pair of Ridgway’s rails that have already moved in,” Smith said. The bird, also called a clapper rail, is noted for its distinctive clacking or grunting-like call.

Other desirable bird species that could inhabit the lagoon are Belding’s savannah sparrow, which nests in dense stands of pickleweed, the California least tern, which prefers protected sandbars, and the coastal California gnatcatcher, an inhabitant of the coastal sage scrub.

Native plants such as sage, buckwheat and lemonade berry used in the restoration are propagated locally at places such as the Nature Conservancy in Encinitas.

A small portion of the current project serves as environmental mitigation for a new, wider bridge to be built across the San Dieguito River at El Camino Real in the next few years by the city of San Diego.

Also part of the project was the relocation of several SDG&E utility poles away from the wettest areas of the lagoon. That job was one of the largest single expenses, costing about $7 million, Smith said.

The San Dieguito project includes a new pedestrian trail, which is expected to open to the public in the fall along El Camino Real at the eastern end of the lagoon.

The trail will connect to the existing Dust Devil Nature Trail and the San Dieguito River Park’s partially completed 71-mile Coast to Crest Trail that eventually will go from Del Mar to Volcan Mountain, near Julian. About 50 miles of the Coast to Crest Trail have been finished so far.

Remaining work on the lagoon restoration, primarily planting more native vegetation and cleaning up trails and access roads, is expected to continue through the summer.

Once it’s completed, SANDAG is required to monitor the wetlands areas for 10 years and the upland habitat for five years, or until it meets criteria for success such as water quality and vegetation growth.