San Joaquin Marsh Wildlife Sanctuary in Irvine, California, is a 300-acre constructed wetland on the floodplain of San Diego Creek above Upper Newport Bay. Owned by the Irvine Ranch Water District, it was restored between 1988 and 2000 from land previously used for farming and duck hunting. The sanctuary combines habitat restoration with water treatment through ponds built in 1997 that help remove nitrates while supporting native vegetation and birdlife. More than 120 bird species have been recorded there, and former Duck Club buildings preserve traces of the site’s earlier use while serving community and conservation groups.