The $118 million park project, opening in late Spring of 2020, is part of a wetlands restoration movement across the Bay Area that will benefit all species - including us - facing the uncertain future of climate change.
Lew Stringer, Associate Director of Natural Resources of the Presidio Trust, is a scientist by training. But when he envisions the ancient El Polin Spring above us in the forested Presidio hills reconnected to Crissy Field Marsh, he waxes poetic.
"The spring is like a pearl necklace," Stringer says. "These pearls have been unearthed and strung together in these multiple projects that are 3-5 acres in size all along the watershed."
Stringer is leading a tour of the massive renovation of the entire watershed on the Presidio's waterfront. The next string of pearls to be unearthed is Quartermaster Reach, a 7-acre salt marsh on the south side of Mason Street. Quartermaster Reach will be restored by an 850-foot stream buried inside a pipe. Two thirty-six foot wide culverts will be placed under Mason Street to connect the new marsh to Crissy Field Marsh, closing a section of Mason Street for six months beginning December 2.
The real treasure for Stringer is the alchemy of the freshwater from the spring being reunited with the saltwater from the Bay, creating a rare, brackish environment. While crossing a pedestrian bridge, he points out part of the unearthed pipe, sticking out of the bottom of a creek.
"That whole pipe was underground here in 2012. We dug out the earth and about twenty Eucalyptus trees here." Saltwater is pushed up by the pipe during high tide to create the brackish environment, a rare and biologically rich habitat that has already lured in gobies, sticklebacks, and other fish.
Some funding for the massive project comes from the Wetland Mitigation Fund from the San Francisco Airport. According to EPA rules, when the airport fills in runways and loses wetlands, they have to mitigate these losses elsewhere.
The mention of the EPA on the tour brings up recent charges from the Trump administration about water quality in the Bay being trashed by needles and feces from homeless people. Stringer shares the view of local authorities that extensive screening and monitoring of what goes into the Bay has not turned up piles of needles or feces. But he does advocate for more wetlands in urban areas for those truly worried about water quality.
"A healthy wetlands have microbes that live in the sediment that can deal with many pollutants." Wetlands are renowned for being able to treat heavy metals, such as lead. Some of the Presidio work is performed on old army fills where contaminants are trapped in the sediment.
Restored wetlands also help harden cityscapes by directing water into the ground instead of pipes, so the combined water and sewage system will not be overwhelmed during the rainy season.
"It helps with the overall infrastructure," Stringer says. "There's less freshwater within the sewage system that occupies space in the pipes. The water is spread across the landscape."
As far as climate change, sea-level rise has the potential to put marshes underwater before the sediment is built up. "If we get on it now, salt marshes then have the capacity to actually grow with sea-level rise. But we need to do this now for the marshes to evolve with sea-level rise."
That's why many environmentalists and residents opposed the recent EPA decision to allow Cargill Salt Ponds to develop land right on the Bay.
"New housing on the Redwood City salt ponds would put people at risk from rising seas, destroy habitat for fish and wildlife, lack an adequate water supply, and worsen traffic," a group of nearly 60 federal, state, county, and city officials, and environmental groups said in a prepared statement in August. "To combat climate change and create more resilient and equitable communities, the Bay Area needs more affordable housing near transit hubs and city centers, not on Bay wetlands."
John Krause, Environmental Scientist with the California Dept. of Fish & Wildlife, manages the Eden Landing Ecological Reserve in Hayward, part of the South Bay Salt Pond Restoration Project. The South Bay Salt Pond Restoration Project is similar to the work at Crissy Field but on a massive scale.
"When you have 15,000 acres of wetlands being restored near 6 million people, the benefits are tremendous," Krause said by phone before the tour. "We already see the impacts to the region during bigger storms when coupled with annual King Tides."
Back on the tour, Stringer agreed with the benefits of the South Bay Salt Pond Restoration project for the overall health of the Bay.
"Salt marshes break the energy of these waves that claw at the land. If you were to put condos in, they would be on the front line of that battle. Salt marshes are also some of the best places to sequester carbon - even better than forests."
The tour pauses on a rise right before Doyle Drive, and Stringer highlights the two key features of the project: the 14-acre park, Tunnel Tops, running over the two tunnels to the east of us, and the beginning of Quartermaster Reach Marsh, already filling up from groundwater, under Doyle Drive below us.
On Tunnel Tops, over 200,000 plants, including scrub, marsh, and dune grasses, will be added to 90,000 cubic yards of soil, inviting birds, insects, and a whole new ecosystem within a bustling metropolis. 6,500 square feet of new construction will also be added, including the dynamic Crissy Field Center Youth Campus.
Once completely filled for the Panama-Pacific International Exposition in 1915, the restored Quartermaster Reach Marsh will become a habitat for frogs, fish, salamanders, and the native Olympic oyster.
"We're just in the beginning of the process of massive ecological restoration all over San Francisco Bay," Stringer says.
Our presence startles a great blue heron into awkward flight about a dozen feet away. There's just enough new marsh for a runway for the heron to clear Doyle Drive and land in one of the shimmering pearls of Crissy Field. A connection that once was, restored.