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San Diego Creek Watershed Natural Treatment System
Location:
Orange County, CA
Area of Focus:
Clean Water, Smart Growth
Local Contact
John Hills, Director of Water Quality
Irvine Ranch Water District, (949)453-5850
hills@irwd.com
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The Irvine Ranch Water District (IRWD) was established in 1961 to provide potable water, sewage collection and treatment, and water reclamation for a 133 square mile area in Orange County, California. The IRWD's boundaries coincide with the San Diego Creek Watershed. The San Diego Creek, located in an urbanized watershed and the primary tributary to Newport Bay, is listed as an impaired waterbody due to excess nutrients, sediments, pathogens, and toxics. As a result of this listing, the IRWD made a commitment to improve the water quality of the San Diego Creek.
The most significant sources of contaminants in the San Diego Creek are stormwater and urban runoff. In order to deal with these sources, IRWD developed a unique program to reconstruct the San Joaquin Marsh, an historic wetland on IRWD property. Since 1997, the IRWD has successfully treated San Diego Creek water runoff through a system of ponds. These ponds naturally remove sediment, phosphorus, and nitrates from the water. The stormwater spends seven to ten days moving through the pond system before reentering San Diego Creek and ultimately Newport Bay and the Pacific Ocean.
Based on this success, the IRWD plans to implement a project entitled the Natural Treatment System (NTS) within the San Diego Creek Watershed. The NTS is a water quality improvement system that is both cost effective and environmentally sound. This system will involve the creation of small, man-made wetlands placed in strategic locations throughout the watershed. Extensive scientific review and environmental assessment of the watershed will determine the most environmentally suitable locations for these smaller wetlands and the number of sites needed to achieve maximum cleanup potential. Planners initially studied 68 possible locations throughout the San Diego Creek Watershed and have now reduced that list to the 31 best sites in terms of treatment effectiveness, availability, cost, and constructability. Many of these sites include public facilities such as county retention basins where water quality wetlands can be constructed without interfering with their primary purpose as flood control mechanisms.
Real Results
Modeling has shown the potential to improve water quality in San Diego Creek and Newport Bay. In fact, the Natural Treatment System is expected to remove 126,000 pounds of nitrogen annually, 21,000 pounds of phosphorus annually, and reduce fecal coliform levels by 26 percent. The NTS also serves multiple functions as a natural resource, riparian habitat, and open space. Moreover, the NTS is expected to cost significantly less than what would otherwise be required to build new or upgrade existing wastewater and stormwater infrastructure systems. Perhaps most importantly, the NTS will provide a regional, watershed-wide approach to solving a water quality problem.
Updated Date: 08/03/2010
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