To the cheers of distant onlookers, a yellow excavator sliced through a dirt levee to open a long-captive 19th century industrial salt pond to the wild San Francisco Bay on Wednesday morning, allowing tidal waters to gush in to a 300-acre future marsh in Menlo Park.
The project – part of the largest wetlands restoration ever conducted on the West Coast – is the latest addition to a growing mosaic of restored habitats for endangered wildlife, while providing flood protection and places to play for local residents.
Flanking the north side of the Dumbarton Bridge, the now-barren pond will gain a more natural and lovely palette. Once filled with water and fresh sediments, it will support seeds that float in from adjacent marshes, then plants will germinate. This will welcome the arrival of little crustaceans, like crabs, as well as invertebrates, birds and fish.
“This day feels incredible to me. It’s the culmination of years of work to restore the tidal marsh and open ponds for the first time in over 100 years,” said Dave Halsing, manager of the South Bay Salt Pond Restoration Project, at Bedwell Bayfront Park, a former landfill site overlooking the former Pond R4.
Wednesday’s event marked the 20th anniversary of the restoration project, a landmark deal brokered by the late Sen. Dianne Feinstein that paid Minneapolis-based Cargill Salt $100 million for 15,100 acres of its salt ponds, which stretch from Hayward to San Jose to Redwood City, to state and federal agencies.
Celebrants included key partners on the restoration project, including the U.S. Fish and Wildlife Service, State Coastal Conservancy, San Francisco Bay Restoration Authority, San Mateo County, the city of Menlo Park and the nonprofit Save The Bay.
In this unusual back-to-nature experiment, it will take more than $1 billion and an additional 30 years of close supervision to roll back the clock to the Bay’s pre-industrial conditions.
The project is rivaled in size only by efforts to restore the Florida Everglades and Mississippi River Delta in Louisiana.
Since the 1850s, the Bay has endured dredging, draining, diking and pollution by mercury and other toxics. San Francisco International Airport, Foster City, Redwood Shores and other major commercial and residential development projects gobbled up wetlands.
An estimated 85% of the Bay’s rich marshes have been lost, with water quality, fisheries, and wildlife all suffering dire declines.
According to Cargill, the South Bay is particularly suited for salt making, with clay soils and a Mediterranean climate – just enough rain in fall, winter and spring, followed by warm dry summers with steady breezes and summer sunshine. The company’s thousands of acres of salt evaporation ponds crystallize up to 500,000 tons of sea salt each year.
From an airplane, travelers flying into the South Bay have long marveled at the pond’s bright colors. Against a backdrop of white salt and black iron sulfide soil, they support a mosaic of brine shrimp and colorful microbial communities of diatoms, dinoflagellates, protozoa, fungi and bacteria.
The brightest hues are created by an orange microalgea called Dunaliella salina, which can survive in salinity levels as high as 40%.
Many of the ponds remain active, especially along the Bay’s eastern edge of Fremont and Newark.
The restoration and upkeep of the new marshes are costing much more than the $100 million purchase price, because of the aquatic complexity of the Bay and the extensive work necessary to undo the effects left by a century of industrial salt-making.
There were regulatory and logistical challenges, said Halsing. “Everything is a little harder than an idealist might think it should be.”
Several other major ponds have already been opened and restored. Initial efforts focused on the region around Alviso, Sunnyvale, Mountain View and Milpitas, and restoration is also happening at the “Baumberg Ponds,” south of the San Mateo Bridge in Hayward and Union City.
The project is also managing about 700 acres of unopened ponds, where tide gates regulate the flow and depth of water. Some are brackish, while others will slowly turn fresh.
A few ponds, such as one in Eden Landing, will stay very saline, because salt-loving creatures such as brine shrimp now depend on them. And federally protected snowy plovers which have adapted to nesting on the ponds’ crusty bottoms.
The restoration must be slow, cautious and data-driven, as experts seek the best balance between artificial and wild environments for the creatures that depend on the Bay, according to experts. New islands will be built, and predators will be controlled.
The challenge is that several types of birds, such as migratory shorebirds, have become reliant on the salt ponds over the past century. And many of these birds’ original habitats have disappeared in the meantime.
Already, the Bay’s fortunes are rebounding. Two endangered species — the salt marsh harvest mouse and a handsome bird called the Ridgway’s rail — are returning to early restoration sites to live and reproduce, proof that the ambitious project is helping nature heal. Both species arrived only nine years after excavators breached the walls of ponds, allowing natural tidal flows to resume.
As tidal marshes expand their hold, biologists hope to see healthier runs of fish and other species. Areas that were once barren are benefiting from twice daily tidal flows. As the sites revegetate, the ponds will become green and full of life.
In addition, the restoration project has built nearly seven miles of recreational trails, a kayak launch, and several viewing and interpretive areas that open up the shore to public access. Next year, a new public trail will open at this spot in Menlo Park.
Several major projects had to be completed before the Menlo Park pond could be safely opened.
Project managers first had to create several interior berms and levees so the pond wouldn’t increase the flood risk to nearby neighbhorhoods. That meant finding several hundred thousand yards of clean and uncontaminated dirt.
They also built “habitat transition zones,” a sloping gradient of soil, around the edge of the pond, and planted native vegetation..
Gazing through binoculars, Wednesday’s crowd thrilled to the sight of the water’s slow flow.
“It’s just an amazing joy to take a moment out of our busy lives to appreciate this accomplishment,” said Lewis. “We are reassembling so many pieces of the puzzle to make the Bay stronger and protect the communities next to it.”