IRWD has created a network of wilderness habitats. They naturally clean runoff, protecting Upper Newport Bay and the ocean.
Visit a Natural Treatment System site and you’ll discover a wilderness oasis. IRWD owns and protects almost 50 such sites, scattered throughout our urban environment. Each is a welcoming wetland refuge for wildlife — particularly birds such as wrens, bluebirds, swallows, roadrunners, and hawks. But this land has another important job: naturally treating dry-weather runoff that flows from our yards into storm drains.
Irvine Ranch Water District began treating urban runoff in 1998 by diverting it into a series of constructed ponds at San Joaquin Marsh, a 300-acre wildlife sanctuary in Irvine.
95% of the dry-weather runoff in San Diego Creek is diverted into the Marsh. It flows through ponds for two to four weeks as plants and microorganisms remove nitrogen, phosphorus, and many other pollutants.
Healthier water is returned to the creek, where it continues its journey to environmentally sensitive Upper Newport Bay and on to the Pacific Ocean.
In 2006, we began expanding this concept to a network of smaller wetlands, which we call our Natural Treatment System.
The smaller wetlands, built throughout the 76,000-acre San Diego Creek watershed in central Orange County, begin removing pollutants from urban runoff before it reaches San Diego Creek and the San Joaquin Marsh for final treatment.
In Irvine Ranch Water District, storm drains and sewers are separate networks. Storm drains capture runoff. Sewers carry away water that goes down drains and toilets inside your home, delivering it to treatment plants for recycling.
For runoff, natural treatment is more cost-effective than combining storm drains and sewers, which would require water agencies to build bigger sewers to accommodate the increased demand.
Combined systems can also overwhelm treatment plants during heavy rain, resulting in sewage spills.
It’s one of our core responsibilities. Stewardship is one of our values.
Section 35539.12 authorizes us to build, maintain and operate urban runoff treatment facilities.
The Marsh cleans 1.7 billion gallons of dry-weather runoff annually.
46 sites clean a total of 241.5 million gallons annually.
