San Francisco Bay lost more than 80 percent of its tidal wetlands. The Hamilton Wetland Restoration Project represents a significant step in reversing historic habitat loss and recovering imperiled wildlife.

Project History

Hamilton Airfield Restoration Timeline

Following closure of the Hamilton Army Airfield under the Base Realignment and Closure (BRAC) process in 1994 and development of a Reuse Plan by the City of Novato for much of the former military base, the State Coastal Conservancy assumed the lead in developing a wetland restoration plan for the former airfield and adjacent properties. In 1996, staff of the Conservancy and the San Francisco Bay Conservation and Development Commission (BCDC) collaborated in restoration planning and facilitating BCDC’s efforts to restore wetland habitat using dredged sediment. In April 1999, the Conservancy adopted the Hamilton Wetlands Restoration plan and certified the Environmental Impact Report (EIR) and Environmental Impact Statement (EIS) for the project. During 1998 to 1999, the Conservancy entered into agreements with the U.S. Army Corps of Engineers to study the feasibility and design of the project. In the Water Resources Development Act (WRDA) of 1999, the U.S. Congress authorized the Hamilton Wetland Restoration Project (HWRP) under the ecosystem restoration authority of the Civil Works program. Subsequently, the project received federal funding to carry out project design, development and construction.

In 1999, the Conservancy also signed an agreement with the Army for the transfer of the Airfield parcel as a no-cost, public benefit transfer for wildlife conservation. The Conservancy acquired the Army Airfield parcel in 2003. A remnant 18-acre portion of the Airfield, owned by the Navy, was later transferred in 2006, under a similar BRAC conveyance. The Army and Navy BRAC programs undertook extensive contaminant investigation and remediation prior to transfer. Contaminant investigations were reviewed and approved by the state Department of Toxic Substances Control, Regional Water Quality Control Board and other state and federal regulatory and resource agencies. The adjacent North Antenna Field property, which contained communications equipment, small-arms and skeet ranges, and several disposal areas, was cleaned up by the Army Corps of Engineers under its Formerly Used Defense Sites (FUDS) program.

In 2002, the Conservancy entered into a Project Cooperation Agreement (PCA) with the Army Corps of Engineers to construct the project. Under the PCA, the Army constructed the project using suitable dredge material pursuant to federal law and practice, and the Conservancy, as the non-federal sponsor, paid 25% of project costs.

In 2014, the Hamilton Bayfront levee was breached to allow bay water to move in and out of the site through daily tidal action. The site currently provides habitat for thousands of migratory waterbirds, fish, and other organisms. Over time, it is expected that the site will become thickly vegetated in most areas with a complex network of tidal channels, providing critical tidal wetland habitat for several threatened and endangered species.

In 2001, the Conservancy purchased the 1600-acre Bel Marin Keys Unit V (BMK) property for wetland restoration purposes, with the intent of adding it to the existing Hamilton project. The Supplemental EIR/Supplemental EIS and General Re-evaluation Report (2003) were used as the basis for an amendment to WRDA to allow for the expansion of the project to include BMK. In 2007, a WRDA bill was adopted by Congress, allowing for BMK to be added to the federally-authorized Hamilton Wetland Restoration Project (“Bel Marin Keys Unit V Expansion of the Hamilton Wetland Restoration Project”).

Bel Marin Keys (BMK) Portion – Project Planning

Bel Marin Keys

Bel Marin Keys

Restoration of tidal wetlands on the BMK property requires constructing similar features as constructed for the Hamilton Airfield. To create tidal marsh, site elevations will be brought back up to mean-higher-high water, a point at which marsh vegetation normally thrives. Raising the site elevation involves the placement of clean fill, natural sedimentation provided by tidal action, or a combination of both. Therefore the focus of the expanded Hamilton project is on the design and construction of earthen structures, flood control levees, dikes and berms and the placement of large volumes of imported fill, mainly sediment that will be pumped ashore from an offloader. The SEIR assessed and disclosed the impacts of constructing the site features, and the changes to the landscape after construction is complete and tidal action is restored to the land.

Public Access

A 2.7-mile segment of the San Francisco Bay Trail, which will one day encircle the Bay, was constructed along the southern and western perimeter of the Hamilton wetlands. Visit Hamilton Wetland for more details.

Minimization of Greenhouse Gas Emissions

Filling of the Hamilton Airfield was accomplished using an electrically-driven offloading system, which minimized localized diesel emissions. Much of the offloaded sediment came from dredging projects that otherwise would have disposed to the Deep Ocean Disposal Site (DODS). The ocean disposal site is located approximately fifty miles off shore of the Golden Gate. Because the Hamilton site is located so much closer to point of origin, the air impacts are lessened significantly when material is brought to the restoration. Furthermore, disposal at the ocean site requires ocean-going barge tugs and scows which generate more diesel emissions than bay-running equipment. The Army Corps has specified in recent contract solicitations that onsite construction equipment comply with the latest emissions standards for diesel trucks (e.g. particulate filters). Lastly, in 2007, the project opted to grind its own road base by recycling onsite concrete from the former Airfield runway and taxiways rather than import rock from a Marin county quarry. This reduced heavy truck traffic transiting to the site by 80-85%.