Chelsea Wetlands is a riparian marsh on lower Pinole Creek and a tidal wetland at its mouth on San Pablo Bay, in Contra Costa County, northern California. It is located within the city of Hercules, in the East Bay region of the San Francisco Bay Area. 
Originally part of a much larger tidal marsh complex that fringed San Pablo Bay, including along the shoreline of West Contra Costa County. The Chelsea wetlands are the remaining 12 acres (4.9 ha) of undeveloped coastal marsh within Hercules. The seasonal marsh was diked off and a large portion of it filled sometime in the late 19th/early 20th century during the development of the Pinole/Hercules area. It has been further degraded by the dumping of soil from more recent surrounding construction projects.
Hercules was seeking to restore funds for habitat restoration of lower Pinole Creek in 2012, to protect against flooding into the adjacent city neighborhood, and to restore tidal marsh, floodplain storage, and floodplain habitat functions — to support the flora and fauna native to the Chelsea Wetlands in the riparian zone and the bottom land tidal flood plain.  
- Chelsea Wetlands Restoration Archived 2011-06-08 at the Wayback Machine, City of Hercules website, 23-06-2008, access date 30 March 2016.
- Bay Area IRWMP.org: Chelsea Wetlands Restoration Project Archived 2017-01-10 at the Wayback Machine, with detailed project description and benefits; accessed 30 March 2016.
- Forcechange.com: Restore Chelsea Wetlands In Hercules, California"
- "Bay Area IRWMP.org: Friends of Pinole Creek Watershed". Archived from the original on 2017-01-10. Retrieved 2016-03-30.
- City of Hercules: Chelsea Wetlands Restoration project — with links to the "Final Conceptual Chelsea Wetlands Restoration Plan" + "Biological Evaluation Report ."
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