Salt Ponds Restoration, Hamilton, Eelgrass, Living Shorelines Few restoration efforts anywhere rival the South Bay Salt Pond Project in scope, expense, or complexity. “We’re celebrating the tenth anniversary this year,” said Project Manager John Bourgeois, who heads the multi-agency collaboration. Bourgeois is responsible for transforming a Manhattan-sized expanse of former salt production ponds and other wetlands, much of it acquired from the Cargill Salt Company in 2003. Restoration here isn’t just a matter of breaching the dikes and letting the Bay in. “There are tradeoffs,” Bourgeois explained. “The salt ponds have been here for 150 years, and a suite of species has utilized them. In restoration, we’re taking away habitat for certain species and giving it to others. On a landscape scale, we need to ensure we’re not doing more harm than good.” One example is the endangered snowy plover (Charadrius nivosus), which prefers to nest in the moonscapes of the salt pannes. Project scientists have also detected increased mercury concentrations in the eggs of fish-eating birds.
Adaptive management will be necessary as the process advances. “At minimum, the goal is to get to 50 percent tidal marsh,” Bourgeois added, although the ultimate proportion could be as high as 90 percent. “In Phase 1 we picked the low-hanging fruit and got some of the easy projects done: taking down levees, letting natural processes back in. We’ve been pretty successful so far; the sedimentation rate is exceeding expectations, and the revegetation rate has been rapid.” Eight of nine Phase 1 projects have been completed. “We’re doing certain things that don’t look like natural ecosystems, building in a robust capacity to manage water, and experimentally constructing nesting islands for birds.” By next year, Bourgeois said, 3,750 acres will have been restored: “We’re trying to move rapidly in the face of sea level rise and get as much tidal marsh restored as we can.” To date, the project has cost $190 million, mostly allocated for land acquisition. “Funding will be a challenge moving forward,” he acknowledged. “To get from here to 50 percent tidal marsh, we need money. To get to 90 percent, we need money and science. We need to understand more about sediment dynamics and how wildlife uses the restored areas. With state bond money and federal appropriations drying up, we need new sources, especially to fund the science program.”
In the North Bay, meanwhile, the Department of Fish and Wildlife, Ducks Unlimited (DU), and other government, nonprofit, and private-sector partners have been engaged in another ambitious project. “It’s been called a national model for restoration,” said DU’s Renee Spenst. Restoration efforts began when the state acquired nearly 10,000 acres of former Cargill salt production ponds in Napa and Sonoma counties in the early 1990s. To date, 5,000 acres have been restored, another 2,000 enhanced. Challenges included handling the concentrated brine at the 1,360-acre Napa Plant Site, the thick salt crust on crystallizer beds, land subsidence, and the need to work around existing infrastructure such as Highway 37, railroad and power lines. Work on the Napa Plant Site culminated in 2010 with the South Unit breach. Spenst reported gratifying responses from wildlife. “The Plant Site is now excellent habitat for ducks,” she said. Shorebirds flocked to the restored ponds, and the endangered California least tern (Sterna antillarium browni) began nesting in 2009. Chinook salmon (Oncorhynchus tshawytscha), steelhead (O. mykiss), and Sacramento splittail (Pogonichthys macrolepidotus) are also using the new habitat: “It’s surprising how quickly fish are coming into the site.” Uncertainties remain, notably funding. “Monitoring is a continued challenge—how to monitor meaningfully, feeding back into the project as we move forward,” Spenst noted. She also stressed the need to connect areas of good wetland habitat, provide upland space that will enhance resilience to sea level rise, and develop better incentives for reusing sediment.
While engineers contended with toxic brine in Napa, those working on Hamilton Field wrestled with tarmac. “We left the runway in place and put mud on top of it,” said Tom Gandesbery of the California Coastal Conservancy, the sponsoring agency. “It would have been too expensive to remove.” As it was, converting the former military air base into a wetland took “money, time, and a lot of hard work.” After being diked, drained, farmed, and used as an airfield, the site had subsided six feet below sea level. Fixing that provided a showcase for the beneficial reuse of dredged material under the Long Term Management Strategy. The US Army Corps of Engineers provided 5.6 million cubic yards of clean sediment from the deepening of Oakland Harbor, pumped to the site through a pipeline under San Pablo Bay from an electric powered offloader 5.5 miles offshore. “It was powered by the world’s longest extension cord,” Gandesbery joked. When completed next year with the breach of a bayside levee, Hamilton will feature tidal and seasonal wetlands, an upland transition zone, and wildlife migration corridors. The Coastal Conservancy is also building 2.7 miles of public trail at Hamilton, a future segment of the Bay Trail system. An on-site nursery grows native plants destined for the seasonal wetlands and transition zone. Some have been put into the ground already by volunteers: “It’s a great way to get the local community to take ownership of the project,” Gandesbery said. Next, the Conservancy will take on Bel Marin Keys north of Hamilton, which will require a different approach. “There are many more restoration sites than we have mud for,” Gandesbery explained. “With 2 million cubic yards per year dredged in the whole bay, there’s not enough to go around. The Oakland deepening project is done and there are no other big projects on the horizon.” One long-term solution may be stockpiling dredged material at an underwater drop-off spot, which would decouple offloading and pumping from the dredging process.
Scaling down from those three megaprojects, Katharyn Boyer of San Francisco State University’s Romberg Tiburon Center described the work of the San Francisco Bay Living Shorelines Project at two smaller test sites. Her group is using two native species, Olympia oyster (Ostrea lurida) and eelgrass (Zostera marina), in experiments that may help restore lost ecological functions and build a more resilient Estuary. The Living Shorelines concept, which was pioneered on the East and Gulf Coasts, involves providing living spaces for organisms that will protect the shoreline from increased storm surge and other consequences of climate change. “Oysters create a heterogeneous reef space that allows other organisms to come. Eelgrass traps sediment, reduces erosion, sequesters carbon builds habitat and provides foraging areas for other organisms,” Boyer said. Off San Rafael, Boyer installed a mix of oyster-only, eelgrass-only, combination, and control plots. Structures made out of “baycrete”—Portland cement mixed with oyster shell and sand—and shaped into reef balls, blocks that interlock “like Legos,” provide settlement sites for planktonic oyster larvae, as do shell-bag mounds. At Eden Landing near Hayward, eelgrass collected at nearby sites has been planted and shell mounds created for the oysters. After a year, over 2 million oysters have settled on the San Rafael mounds alone: “It’s wall-to-wall oysters out there,” Boyer said. Shellfish weren’t the only species drawn to the settling surfaces; crabs, sea slugs, anadromous fish, and birds, including the locally uncommon black oystercatcher (Haematopus bachmani) showed up, too. “There’s so much life on these reefs,” Boyer said. Her team is also tracking changes in wave energy and sedimentation. At Eden Landing, oyster recruitment has been low, possibly impacted by the predatory Atlantic oyster drill snail (Urosalpinx cinerea), but eelgrass has established well. Both sites will be monitored through 2017.