In an effort to restore habitat and address future sea-level rise in the Bolinas Lagoon, the county is looking for input on options for the future of the lagoon’s north end and surrounding infrastructure. Three draft alternatives, drawn up by the county contractor AECOM, address problems of roadway flooding, projected sea-level rise and habitat degradation.
The release of the alternatives in October was the most recent step in the North End Wetland Enhancement and Sea Level Rise Adaptation Project, which the county kicked off in 2015 and for which it has so far spent hundreds of thousands of dollars on a site report and developing conceptual options.
The alternatives, each emphasizing different priorities and taking place in phases, will be refined and presented at the State of the Lagoon Conference early next year, said county planner Veronica Pearson. The final project, she added, could include elements from different alternatives. The official deadline for comments is Nov. 14, but she said comments are welcome after the deadline.
“To have a project like this, which is pretty substantial, is exciting,” said Kiren Niederberger, a member on the Bolinas Lagoon Advisory Council.
The first alternative focuses on ecosystem restoration. Two creeks leading into the lagoon, Wilkins and Lewis Gulch Creeks, would have their floodplains restored by plugging their primary channels, a technique known as “plug and pool.”
“The idea is to put [the creeks] back where they used to be,” Ms. Pearson said. New primary channels could be recreated in an effort to help spawning coho salmon and steelhead trout. There are no current fish surveys for the two creeks, so the county plans to fund studies on fish populations.
The first alternative attempts to deal with sea-level rise by excising the short connector road in the wye—a move common to all alternatives—as well as raising Highway 1 onto a series of three short causeways after it splits with the Olema-Bolinas Road. The beginning of Fairfax-Bolinas Road could be raised or relocated further south.
The second alternative offers a smaller-scale approach to restoration and sea-level rise, at a lesser cost. It would restore just Wilkins Gulch Creek and raise Highway 1 on two small causeways; a small section of Olema-Bolinas Road near the wye would also be lifted onto the causeway. A few culverts would be built under that road to mitigate flooding.
“This alternative is more economical,” Ms. Pearson said. “It’s doing something to help sea-level rise and habitat improvement, but not the full shebang.”
The third alternative focuses largely on shrinking the road footprints in the floodplain and restoring water connectivity in the area. “This alternative is really looking at sea-level rise in the long term,” Ms. Pearson said.
A span of Highway 1, from near the Olema-Bolinas Road split to where Salt Creek meets the lagoon, would be elevated onto a single causeway to make room for rising waters. In perhaps the most dramatic change, Olema-Bolinas Road would be decommissioned entirely and Horseshoe Hill Road would become the primary route to Bolinas. The beginning of Fairfax-Bolinas Road would be decommissioned and rerouted further south, Wilkins Gulch Creek would be restored and Lewis Gulch Creek would be left in its current channel.
For Ms. Niederberger, the third alternative doesn’t seem realistic. “But in putting the option out there, it’s the county’s way to tell the public that they looked at everything,” she said.
There are no cost estimates available for the three alternatives yet, but Ms. Pearson expects them to follow geotechnical investigations for which the county is now seeking permits. “This is a really complex geologic area,” she said. “There are three faults converging right at this location. There are unknowns about what the substrate looks like.”
Information about the alternatives can be found at marincountyparks.org/depts/pk/our-work/os-main-projects/north-end-project.