By Ariel Rubissow Okamoto
Breaching the outboard levee near Marin County’s Hamilton community this May is cause for both a whoop of celebration and a sigh of relief. Celebration because it was an ambitious wetland restoration project with a complicated design and multiple partners that wasn’t easy to pull off, yet in just a few months it’s become a beautiful landscape filled with blue water, green shoots, yellow flowers, quacking ducks, and happy neighbors. Relief because at times the costs and challenges of moving so much mud to the site, in order to the raise the elevation of subsided wetlands, seemed overwhelming to those in charge. But they did it. And now they need to do it again; only this time they hope it won’t be such a bear.
“If we don’t get creative about how to import sediment more efficiently and finish the expansion into Bel Marin and the antenna field, we could lose the opportunity forever,” says State Coastal Conservancy project manager Tom Gandesbery.
Importing mud from an Army Corps deepening project in the Port of Oakland to the Hamilton site cost a pretty penny – about $95 million all told. A recent federal-state review suggests using the same approach to raise the land level for planned restoration of314 acres remaining on Hamilton’s air and antenna fields, and an additional1,600 acres of adjacent Bel Marin Keys hay fields, would cost $340 million.
For Hamilton, project partners built a five-mile-long pipeline from out in the middle of San Pablo Bay — where the water was deep enough for barges to offload — across vast mudflats to the onshore restoration site. Next, they stationed an “off loader” at the end of the pipeline. The offloader sucked the dredged material out of the barges, mixed it with water to make a slurry, and pumped the resulting soupy mix on shore.
“With the off loader, you have a crew and large, expensive equipment just sitting and waiting for material to come, and you can only serve one barge at a time, all of which can drive up the cost,” says Gandesbery.
For the Bel Marin expansion, project partners are now thinking about a simpler approach, both in the design of the restoration site and the method of mud delivery. The new plan is to just raise apart of the Bel Marin site and leave the rest in farmland or managed wetlands. And on the sediment side, planners are exploring everything from stationing a smaller off loader at the mouth of the Petaluma River — that could work more continuously at more reasonable cost — to creating an ATF.
While the acronym may call to mind drug busts and gun running, it actually stands for “aquatic transfer facility.” An ATF is a depression dug in the bottom of the Bay, where dredgers can dump, and the sediment stays put, until it can be retrieved later for restoration work. As proposed in a 2008 EIR, this ATF would have a footprint of 58acres in San Pablo Bay, where the water is 27 feet deep (MLW) and the lack of currents make conditions depositional– in other words, things settle to the bottom and stay there. Once dug, the ATF would be about 18-33 feet deeper than the current bottom.
“The idea is to strategically locate the basin in a hydraulically appropriate area and create a basin deep enough to keep the sediment all together until it can be economically dredged in large volumes all at once,” explains the SF Bay Conservation and Development Commission’s sediment program manager Brenda Goeden.
“The ATF lets us decouple the restoration projects from the dredging projects. They don’t have to work out logistics and contractual issues and navigation issues. It’s basically a sediment recycling center,” says Gandesbery.
The proposed location is next to the existing approved dredged material disposal site in San Pablo Bay. So dredgers can take material to the new ATF instead of one of the four in-Bay disposal sites, or the far off ocean site. This has the added benefit of reducing net emissions from ocean-going tugs; replacing the big off loader with an ATF cuts C02 emissions 33 percent for the proposed project.
Penciling out the dollar costs for the Bel Marin and remaining Hamilton restorations, the ATF approach costs 50percent less than the off loader – about $164 million. But it’s the environmental costs that are holding up approval. While the magnitude of the impacts is difficult to determine, no one has the money to do pilot experimentation and monitoring. “The biggest worry is entrainment of endangered fish by the hydraulic dredge at the ATF,” says Goeden.
Like all in-bay disposal of dredged material, moving mud from one place to another in the Bay can smother or bury bottom-dwelling animals, while hydraulic dredges can suck up longfinsmelt, salmon or sturgeon, not to mention other native fish. Such concerns were detailed in a 2008 EIR, and also explored in technical workshops hosted by the Army Corps in 2012.
Mitigation measures could work, like screening suction heads or requiring dredgers not to switch on the pumps till the head is in the mud, not the water. Or they might not. “No one really knows if fish like green surgeon get sucked in, or if they get curious about the muddy water or potential prey, so are more at risk,” says Gandesbery. In the meantime, where fish are concerned, the off loader approach is still preferred because it doesn’t create local turbidity or disturb the bottom.
Of course, environmental impact reports tend to look only at the site and project in question, not at the regional benefits of a diminishing sediment supply put to work to save marshes –and the cities behind them – from the accelerating creep of sea level rise.
And there are other regulatory and policy hurdles. “We can easily permit off loading activities, but an ATF might require a San Francisco Bay Plan amendment, ”says Goeden.
For the moment there seems to be a stalemate among the various responsible agencies due to the loss of funding to move forward and unresolved environmental concerns. “There’s no current ongoing coordination at this point,” says Goeden.
Gandesbery sees no other path but to try to get the Bel Marin project shovel ready and to keep actively exploring each and every mud-moving option. “The amount of sediment we need to do these large scale restorations around the Bay is staggering,” he says, noting it would take 8-10 years of maintenance dredging to dump enough material in any ATF to restore Bel Marin and the antenna field alone. Meanwhile, Skagg’s Island and Sears Point wait in the wings for their share of the mud lift that might save them and their respective endangered species — salt marsh harvest mice and California clapper rails — from climate change impacts in future. “We need new, less costly ways, to move sediment. The alternative is for the seareas to go underwater forever,” says Gandesbery. ARO