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• San Joaquin Marsh
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Treating Urban Runoff. The Process.

IRWD began treating urban runoff in 1997 by reconstructing wetlands at the San Joaquin Marsh and Wildlife Sanctuary in Irvine. A large portion of the urban runoff in San Diego Creek is diverted into the system of manmade ponds where it flows for seven to 10 days. This gives plants and soils in the ponds time to naturally remove nitrates and other pollutants. The cleaner water is delivered back into the creek to continue its journey through Upper Newport Bay to the ocean. 

Bacterial Removal

Sunlight provides ultra-violet radiation that reduces harmful bacteria before the water reaches the bay.

Nitrogen Removal

Up to 70 percent of the nitrogen in urban runoff is removed simply by giving the water time to interact with plants and soils in the ponds of the San Joaquin Wildlife Sanctuary. The end product is harmless nitrogen gas, which makes up 79 percent of the air we breathe. Less nitrogen in San Diego Creek means fewer algae blooms and a healthier Upper Newport Bay.

Phosphorus Removal

Phosphorus is removed from runoff when it precipitates and binds to the clay soils in the ponds. Phosphorus is further reduced in sediment removal basins within San Diego Creek adjacent to the San Joaquin Marsh and Wildlife Sanctuary. Limiting phosphorus discourages the growth of unwanted algae and other nuisance plant forms.