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Nudging Natural Magic– Oro Loma Horizontal Levee Sea Level Rise Adaptation Pilot

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  • Preliminary results of the Oro Loma horizontal levee experiment on the San Lorenzo shore (SF Bay) include off the charts levels of removal of nitrogen and pharmaceuticals from wastewater passed through the system and growth of willows, cattails, and wet meadows.
  • Modernizing the planning and regulatory context for resilience projects is an emerging regional priority.
By Ariel Rubissow Okamoto December 2017 SF Estuary Partnership   read full Estuary article here

“Miraculous” isn’t a term that comes easily to the lips of scientists and engineers. But the word, along with a quickly quelled gulp of incredulity, cropped up more than once in interviews concerning the preliminary results of the horizontal levee experiment on the San Lorenzo shore – including off the charts levels of removal of nitrogen and pharmaceuticals from wastewater passed through the system and growth of willows, cattails, and wet meadows

This pilot sea level rise adaptation project, led by the Oro Loma Sanitary District, combines precision engineering, native plants, irrigation via treated household wastewater, and a hump of bay mud, sand, and gravel. The idea is to test which ingredients –liquid, solid, vegetable –in what doses and combinations make the levee bulk up and leaf out fastest, and best “polish” (clean) the wastewater….

…But perhaps the most extraordinary early result is coming from an examination of the quality of the treated wastewater that passes through the levee and all its elaborate hardware, soil zones, and root systems. Researcher Angela Perantoni is one of a team intensely monitoring exactly what gets put into pipes at the top of the experimental levee and what comes out at the bottom, or what engineers call the “toe” of the slope. “A lot of constructed wetlands designed to polish wastewater are monocultures made up of pea-sized gravel and common reeds,” says Perantoni. “This project took the time to create a more diverse, native situation.”…


Participants in the Resilient by Design challenge visit the horizontal levee in fall 2017, with the jungle of plant growth behind them and a wet-weather basin to be tested this winter out front. Photo Ariel Rubissow Okamoto

….Though these preliminary results are just beginning to be tested under colder, wetter, more wintry conditions, planners and engineers are already thinking about bigger, longer versions of the horizontal levee in Palo Alto, Richmond, Novato, and Hayward. Each of these new levees might, however, have a different emphasis than the one at Oro Loma in terms of habitat or flood control or water quality.

….“Based on the current regulations, they can’t treat us any differently than a developer who wants to construct a Walmart at the edge of the Bay,” says Warner.  The district had to spend a million before it even knew it could get a permit, he says, as well as construct new wetlands to replace old degraded ones and build an expensive berm around the entire project to preclude any leaks.

Modernizing the planning and regulatory context for resilience projects is an emerging regional priority. Indeed creating new pathways for building multi-benefit natural infrastructure projects is an action item regional partners have already agreed was needed in the 2016 Estuary Blueprint.  Progress in this endeavor includes regulatory analysis and guidance under the Flood 2.0 project, and continued public-private collaboration around projects like Oro Loma….

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