On the evening of January 7, 2025, Gate 6 1/2 homeowners Felicity Gordon and Blaise Simpson attended the third and final community meeting to discuss the Marin City Stormwater Plan. The meeting was held at the Senior Center in Marin City.
The plan was initiated in 2023 to reduce flood risk in Marin City. The goal of the plan is to understand existing flooding conditions and identify potential solutions that will enhance flood resilience in Marin City while accounting for community priorities. The Plan pinpoints areas for flood risk reduction, drainage improvement and preservation for public access. It will provide detailed recommendations for potential projects that local, regional, state or federal agencies may implement in the future. In addition, the plan will support grant funding applications necessary for project implementation. Previous meetings were held in June 2023 and March 2024 with members of the public from Marin City and Mill Valley. Members of the Floating Homes community also attended the meetings.
The plan, which will be finalized this April, intends to decrease flooding in Marin City by enhancing the size of the Drake Culvert that flows under Highway 101 from the Marin City Stormwater Pond into Richardson Bay at the entrance to Gate 6 1/2 dock. In addition, a new Drake Pump Station on the Marin City Pond will be constructed in order to push more flood water from outside of the pond through the culvert.
Already now, before these changes take place, the Drake Culvert outflow causes a fast-moving river of water to flow under and around houseboats at Gate 6 1/2. Because of it, large mud banks have built up, destabilizing the way the floating homes rest at low tide, leaving them to teeter on the edge of the banks. During winter storms when this action is amplified by weather and high tides, this river of water is likely to weaken the structural strength of floating home hulls as well as auxiliary structures, such as the main dock, gangways and floats.
Gordon, whose floating home is moored directly in front of the Drake Culvert outflow, previously expressed her concerns by email to Judd Goodman, the Senior Civil Engineer working on the plan. His reply was as follows: “this will not increase the maximum outflow rate from the culvert, which remains controlled by the culvert’s existing outlet capacity of 250 cubic feet per second.” However, it stands to reason that having more water flowing into the culvert from the new pumping station in addition to the already strong flow from the existing Marin City retaining pond will undoubtedly increase the amount of water that will flow through the Drake Culvert and into the community of floating homes located directly across the highway at the culvert’s terminus.
At the January 7 meeting, Goodman, who presented the nearly finished plan, did not address how having more water flowing through the existing culvert will affect Gate 6 1/2 homeowners. He did note that Caltrans will need to rebuild the culvert, which is cracked, and may make it larger. If that happens, the maximum outlet capacity would also increase, adding additional force and velocity to the stormwater stream.
To partially mitigate this issue, Goodman has proposed that another culvert be created north of Gate 6 1/2. Called the Phillips Drive Outfall in the plan, it would also flow under Highway 101 into Richardson Bay just off the floating homes on the north side of Gate 6 1/2. Goodman estimates that the new culvert would remove approximately half of the water that would otherwise flow through the existing Drake Culvert. However, depending on where the culvert is placed, it could compromise the floating homes on the north side of Gate 6 1/2, similar to what has already happened due to the Drake Culvert outflow.
The Marin County Flood Control & Water Conservation Board of Supervisors has reviewed 65% of the design package. Permit applications were submitted in Fall 2024. The remaining work under the current $883,636 grant scope (approved by the board in 2023) is the completion of studies required for CEQA, the California Environmental Quality Act, a state law that requires state and local governments to review the environmental impact of proposed projects, and then public outreach and finalizing of CEQA.
The formal public review process for CEQA is anticipated to begin in early spring 2025, even though the immediate goal is to get the pump station up and running during this winter — before the CEQA study is completed.
The grant pool that funded the preliminary design and CEQA work has since run out of money to fund phase two. The District is exploring additional grants for construction. The Army Corps of Engineers has approximately $14 million earmarked for flood abatement and Caltrans has $20 million, part of which could be used to construct the Phillips Culvert.
During the public question period, Simpson asked whether Caltrans might consider moving the existing Drake culvert to a location that wasn’t directed right at Gate 6 1/2. Goodman replied that it has not been suggested to Caltrans, as far as he knows.
Others in the audience were concerned about the quality of the water that flows off Caltrans property into the Marin City pond and wondered if it had been tested for motor oil, gasoline, rubber and other pollutants and whether Caltrans had any plans to try to clean it before releasing it into the Bay.
Since the public review period is coming up fast, it is imperative that floating homeowners review the Marin City Stormwater Plan, and particularly the Project Documents link which houses the updated plan that Goodman presented at the January 7 meeting. It is titled “Flood Zone Advisory Board meeting update on Marin City Stormwater Plan”. You may request a PDF copy from the editor, if you wish.
Renderings on the final pages show where the two culverts are proposed to flow into Richardson Bay at Gate 6 1/2. At this time, it is unclear whether their locations have been finalized and that is why our participation in the discussions of the plan with Marin County, Caltrans, Marin City, the Army Corps of Engineers and other parties will be very important.
If you are concerned about the potential harm to our floating home community, make your opinions known to Supervisor Stephanie Moulton-Peters, Assemblymember Damon Connolly or any other political contacts you have at the state or local level.