The restoration of tidal and seasonal wetlands on the former Hamilton Army Airfield and the adjacent North Antenna Field (NAF) and Bel Marin Keys Unit V (BMK) properties is a joint project between the US Army Corps of Engineers, San Francisco District, and the California State Coastal Conservancy. The Conservancy is the non-federal sponsor and landowner (with the exception of the NAF which is owned by the State Lands Commission). The U.S. Congress authorized the Hamilton Wetland Restoration Project (including the NAF) in 1999 and the addition of the BMK property to the project in 2007. The combined project site comprises approximately 2,600 acres, located 25 miles north of San Francisco, along San Pablo Bay, in and adjacent to the City of Novato, Marin County, California.
Around the turn on the 19th century, marshes at the site were diked, dried out, and farmed. The rich organic soils oxidized, causing the land to subside. Decades of farming left the land at an elevation below the lowest tides – too low for wetland plants to become established. Between 2008 and 2013, approximately 6 million cubic yards of dredged sediment, primarily from the Port of Oakland’s Harbor Deepening Project, was placed on the airfield to raise the land surface to elevations suitable for creating tidal marsh. This entailed the largest beneficial reuse of dredged sediment, which would have otherwise been disposed of in the bay or ocean, that had ever occurred previously at a wetland restoration site. In April 2014, the bayfront levee was breached, connecting the former airfield property to the bay for the first time in more than 100 years and enabling the process of ecological succession to tidal marsh. The next major phase of the project is to restore tidal and seasonal wetlands at the NAF and BMK properties, an area three times larger than the restored airfield.