Madrona Marsh: Phosphate Removal in Stormwater Runoff

Innovative engineered wetland technology reduces orthophosphate levels to protect one of the last remaning vernal marshes in southern California.


Surrounded by a densely-built urban setting, lies an amazing anomaly. Madrona Marsh Preserve, located in the City of Torrance, is the last vernal marsh remaining in the South Bay area of Los Angeles and one of a very few remaining urban wetlands anywhere. The land is covered with native plant species. Kestrels and Red-Tailed Hawks roost in the trees. Egrets and Herons take refuge in the marshland. On a small island in the middle of the marsh, surrounded by willows, one can nearly forget the city that surrounds.

Saving the Land

Once, like much of the region, it was owned and used for oil production, which in the end, helped save the land from development.   Spearheaded by Friends of Madrona Marsh (FOMM), the community sought to acquire the land and prevent it from being developed. The idea was for the city to purchase the land, but the price was out of reach. The land owner, which also owned Del Amo Mall, directly adjacent the marsh, formed an investment group to focus on building condominiums in a 164 acre area which included the marsh. In the end, the city formed an agreement with the developer, allowing higher density in a portion of the project in exchange for 54 acres surrounding the marsh.

Restoration and Education

After acquiring the land, the city hired a naturalist to design and implement a plan for restoring the Preserve. Using county park bond funding, the City built the Madrona Marsh Nature Center adjacent the Preserve. The Metropolitan Water District of Southern California provided funding to establish a native plant garden at the center, as a resource to educate the community on how to create a beautiful landscape that does not require heavy irrigation, thus saving water. The Preserve also received assistance from the Santa Monica Bay Restoration Project, formed as a collaboration between the U.S. EPA and the State of California.