More than a square mile of former salt ponds north of Mountain View is headed for transformation back into wetland habitat as work begins to return that portion of the bayshore to its natural state after more than a century of industrial salt production.
Construction crews will truck in enormous amounts of dirt to the North Bayshore area of Mountain View – hundreds of thousands of cubic yards of the stuff – to shore up old levees, protect landfills and create new habitats for marsh creatures to thrive in. All of this is in preparation for breaching a man-made barrier to bring tidal flows back to an area parched and cut off from the Bay.
The effort is part of a multi-agency strategy, launched in the early 2000s, to acquire 15,000 acres of privatized Bay Area shoreline used for salt production and restore most of it to its natural state – or at least as close to it as possible. Negotiations headed by Sen. Dianne Feinstein led to acquisition of the land from the global conglomerate Cargill, which had signaled it planned to cease 61 percent of its South Bay operations.
The latest chapter of the regional effort, known as "Phase 2" of the South Bay Salt Pond Restoration Project, includes reversion of salt ponds back to tidal marsh habitat across 710 acres north of Mountain View and 300 acres bordering Menlo Park. Work on the latter is already underway along the edges of Bedwell Bayfront Park.
The future of the entire stretch of the baylands can be previewed at the northeast corner of Bedwell. To the north lies Greco Island, a verdant expanse of tidal marshes home to several protected species, including the endangered California Ridgway’s Rail and salt marsh harvest mouse. To the east lie hundreds of acres of former salt ponds abutting Facebook's original campus, with a grayish-white cracked crust resembling the surface of the moon. Other salt ponds throughout the Bay Area take on a pink, green, yellow or rust color depending on the algae, minerals or tiny organisms present.
In a multi-step process, these salt ponds are designed to take in limited water from the Bay and circulate it through a system of "evaporator" ponds aimed at gradually increasing salinity. Water fully saturated with salt is then pumped into crystallizer beds, where salt is harvested and sent to a processing plant in Newark. This process has been ongoing in the baylands since the mid-1850s, hitting its peak by 1959, when companies were producing roughly a million tons of salt annually.
Environmental protections were hardly a consideration at the time of rapid development prior to the turn of the last century, said David Lewis, executive director of Save the Bay. About 90 percent of the Bay's wetlands have been lost due to human activity, and it took a concerted effort starting in the 1960s to raise awareness that these public assets needed protection, he said.
"It's not that those original salt-making companies that destroyed the Bay habitat did anything illegal; there were just no environmental laws," he explained.
Some of that Bay habitat is long gone – diked off and paved over – but Lewis said he and other advocates at Save the Bay began pressuring public officials 15 years ago to restore marshes that remain salt ponds along the shoreline. With more than 15,000 acres now in the hands of public ownership and a new funding source in the Measure AA parcel tax, Lewis said, the region is poised to reverse the damage.
Shoring up levees
Step one in the restoration process is to shore up levees and fill pits dredged for industrial uses, and that means hundreds of truckloads of dirt coming in daily, said Jared Underwood, a refuge manager with the U.S. Fish and Wildlife Service. About half a million cubic yards of dirt is needed, he said, and a fortunate side effect of the booming local economy is that there's plenty of it to go around. Private development, including Apple's new "spaceship" campus, left construction companies with huge piles of dirt, and project managers have developed a mutually beneficial relationship with companies willing to have it dropped off by the Bay instead of the dump.
"As they dig out dirt, they're working with us to test it and ensure it's clean," Underwood said, adding that it has to be free of pesticides, hydrocarbons and heavy metals. "It's a very strict standard, and instead of putting it in the landfill they can bring it to the ponds."
While the old channel networks that used to move water around the marshes still remain mostly intact, restoration isn't as simple as breaching the levee and stepping back as plants regrow and birds return. Allowing the free flow of water back into salt ponds amounts to bringing the Bay – and anticipated sea level rise in the coming decades – right to the doorstep of buried landfills, parks and some of Silicon Valley's most prominent tech campuses.
Flood risk to public infrastructure is one of the biggest concerns of project managers, according to Dave Halsing, a consultant working on the restoration project. The existing levees were never engineered to protect the low-lying nearby developments, and efforts need to be made to shore up their limited protection against the wind and waves of a storm surge.
"All of the salt pond berms were not made as levees; nonetheless, they do provide some protection, and we want to make sure if we open up the ponds that we don't get rid of that protection," Halsing said.
Central to that goal is creating so-called upland transition zones, a gradual slope to act as a buffer between the sloshing Bay waters and shoreline development. Much of the second phase's southern border has an abrupt and vertical edge shaped like a bathtub, which is not only vulnerable to sea level rise but also makes it tough for marsh creatures to survive. During king tides or a big storm, animals like harvest mice, rails and voles find themselves stuck between flooded marshes and developed areas, and they've got virtually nowhere to hide, Underwood said.
"There's a little tiny bit of habitat – we're talking 6 feet from the top of the levee down to the marsh, and it's very steep. And what happens now is predators can pick them off a lot easier," he said. "During high tide you can see the hawks kind of lined up along the edges to eat what they can."
This kind of transition zone would typically be adjacent to the salt ponds rather than in it, but most of the nearby land has been developed into housing and businesses or – even worse – former landfills that have been capped and pose a serious risk if they were to erode. The 30-to-1 gradual slope should steel the region for the inevitable sea level rise.
"This is something that we're doing for the survival of the species in the marsh for the next 100 years," Underwood said.
Ambitious plans to restore the Ravenswood pond cluster north of Menlo Park and the ponds north of Mountain View were scaled back during the complex planning process for Phase 2 that started more than a decade ago, due to competing environmental interests. For example, the Charleston Slough to the northwest of Shoreline Park was originally included in the restoration efforts, but was ultimately dropped due to environmental concerns.
At the Ravenswood ponds, the cracked and barren 270-acre pond abutting Facebook's campus was axed from the tidal marsh restoration plans in order to protect wildlife. Birds like the threatened Western snowy plover have come to rely on the large expanses of shallow and dry salt ponds, and restoring the wetland marshes would effectively amount to habitat destruction for them.
"They used to nest on beaches," Underwood said. "Lots of species have come to rely on the ponds."
Despite the narrowed scope of both projects, Lewis said he and his organization were not disappointed, and that it was clear from the start that the huge scope of salt pond restoration had to be "adaptive" based on monitoring data and sensitivity to protected species. Leaving out Charleston Slough and one of the Ravenswood ponds is a sign that project managers aren't rushing headlong into what should be a deliberative, decadeslong process.
"It's not a setback; in fact, I think it's proof that the effort (can) be modified to adapt to what the species and what the Bay need," he said.
As with any project involving baylands, more than a dozen public agencies, companies and organizations are playing a part in the restoration efforts. Several agencies, including the California State Coastal Conservancy, the California Department of Fish and Wildlife, the U.S. Department of Fish and Wildlife, and the Santa Clara Valley Water District, have a hand in managing the project.
Despite planning for Phase 2 beginning so many years ago, Lewis said things are going to move much faster now that more money is on the table. Up until recently, he said there wasn't much pressure or a need to speed up the planning and permitting process because it wasn't clear how any of the salt pond restoration projects would be financed. But that changed when voters passed the Measure AA parcel tax in 2016, which he said is going to kickstart restoration projects like the ones north of Menlo Park and Mountain View.
"There wasn't much public funding available for implementation," Lewis said. "The passage of Measure AA really changed that, and now suddenly there's a half a billion dollars over 20 years that's going to be generated. Things are moving faster now."
Kevin Forestieri is a staff reporter for the Mountain View Voice, The Almanac's sister publication.