The newest levee in the Palo Alto Baylands will look nothing like the others.
Once completed, it will stand between Harbor Marsh and the Regional Water Quality Control Plant, gradually rising from the tidal marshes of the bay and toward the grassier landscapes around Byxbee Park and the wastewater plant. Unlike the existing levees, which tend to be more steep, hulky and rocky, the new one will function as an ecotone — a transitional zone between the two habitats and a new refuge for endangered Baylands species such as the Ridgway's rail and the salt marsh harvest mouse.
At its highest point, the horizontal levee will terminate in an impermeable berm. A vegetated slope will connect the marsh and the berm. Irrigating the new vegetation: an underground pipe from the wastewater plant delivering treated water.
Most crucially for Palo Alto and nearby cities, the vegetated slope would serve as a shield and a prototype. It will help to protect crucial public infrastructure from the threat of sea-level rise and, if plans proceed, could spawn imitators both within the Baylands and throughout the region.
Samantha Engelage, senior engineer in the city's Department of Public Works, noted at a recent public hearing that the "horizontal levee" has taken on regional importance, with strong support from the San Francisco Estuary Partnership and California Coastal Conservancy. Thanks in large part to assistance from these groups, the project has already secured $4.4 million in grants. Cost estimates are about $1.3 million to design and $3.8 million to construct, Engelage told the Parks and Recreation Commission at the March 28 hearing.
"A lot of people are looking at this and really hoping it gets built soon so that they can then feed it into the sea-level rise planning that they're trying to do," Engelage said. "Especially wastewater treatment plants that are along the bayside throughout the San Francisco Bay."
The horizontal levee represents a rare point of consensus in Palo Alto's heated debate over what types of projects are appropriate for the Baylands. The gently sloping structure would stand next to the 10-acre site that the city has eyed as a possible location for a new waste-to-energy plant. The idea gained momentum in 2011 with the passage of Measure E, which removed the "parkland" designation from the site to accommodate the new technology. The idea gradually fizzled in the ensuing years as the city determined that shipping out organic waste would be more economically feasible.
The City Council on Monday debated whether to restore the site's "parkland" designation (the preferred option of local conservationists and groups like the Sierra Club) or to continue to explore clean-energy technologies (the option favored by climate-change advocates and the local group Carbon Free Palo Alto). It ultimately sided with the latter and refrained from rededicating the Measure E site, instead directing city staff to evaluate other waste-management technologies.
The levee, on the other hand, is proceeding with little debate or dissent. The Parks and Recreation Commission unanimously backed the project on March 28, with a recommendation to approve a park improvement ordinance that would enable construction. Engelage said the work is expected to take place in 2024 over about 100 working days.
She described the horizontal levee as a "permanent pilot program": permanent in the sense that it is here to stay and pilot in the sense that it will serve as an example for future improvements, including a larger levee that could be built closer to the water treatment plant.
It will also be the first levee of its kind that uses treated wastewater for irrigation before it is discharged and seeps into the bay. The city's plan calls for stretching a 1,650-foot underground pipeline from the wastewater treatment plant to the levee site. The pipe will run along Embarcadero Road and Harbor Road before it reaches the horizontal levee.
What the public can expect
The city is now finalizing the design plans, which are expected to be completed by the middle of this year. The project will still require permits from various environmental agencies, including the San Francisco Bay Conservation and Development Commission (BCDC), the San Francisco Bay Regional Water Quality Control Board and the U.S. Army Corps of Engineers. Construction would begin in mid-2024, according to a report from the Public Works Department.
To accommodate the levee, the city plans to relocate a portion of the Marsh Front Trail, bringing it closer to Embarcadero Road and farther from the salt marsh. While staff believe that the trail will continue providing similar public access as it does today, the BCDC had suggested that the new location would "degrade the overall public experience of using the Trail," which is part of the regional Bay Trail network and which would be shortened by about 80 feet to accommodate the new alignment.
The city also hopes to enhance educational opportunities around the new levee by installing signage with information about both the wastewater project and the history of the land, including its traditional use within the Native American territory. The new report notes that the project team plans to contract with the Association of Ramaytush Ohlone to conduct site stewardship and support the outreach plan. It also plans to engage environmentalist organizations such as Save the Bay, Environmental Volunteers and Nuestra Casa to coordinate community science programs, support adaptive management of the site and assist with data collection, according to the report.
The Parks and Recreation Commission, which had split over the prospect of building a waste-to-energy facility at the Measure E site, strongly endorsed the levee project at its March 28 meeting. Commissioner Amanda Brown spoke for the majority when she called the horizontal levee "a good example of a lot of the ingredients we look for in the project."
"I think this does a good job of balancing human use with the need to protect the natural environment and the habitat and species," Brown said during the hearing.
Commission Chair Jeff Greenfield and Commissioner Shani Kleinhaus similarly praised the city's approach in planning for the levee. Kleinhaus said it’s the kind of project that the city wants to see "more and more of." Greenfield said there's a lot to love about the project, including the funding, the outreach and the overall care that staff has taken with the design process.
"I'm particularly excited about the overall project and the value of creating an experiment that's worthwhile and that will be creating valuable data for us on a regional basis," Greenfield said.