In 2006, a bioswale was constructed alongside Newport Boulevard in Newport Beach, California to treat an estimated 30,000 gallons per day (gpd) of urban runoff (400 acre watershed) before entering Newport Bay.
The bioswale proved effective in removing dissolved pollutants and bacteria. However, trash such as cigarette butts, food packaging, cans and bottles, and plastic waste was collecting in the bioswale; some of which was making its way into Newport Harbor. This trash not only detracted from the aesthetics of the bioswale and the harbor, it also posed a threat to marine life and the public health.
In 2012, the City of Newport Beach applied for a Measure M Grant to address this issue. The Measure M Grant Program is administered by the Orange County California Transportation Authority and is designed to mitigate the more visible forms of pollutants, such as litter and debris, that collect in storm drains prior to being deposited in waterways and the ocean.
The grant application was approved, and in December, 2013 a CDS hydrodynamic separator and a diversion structure were installed upstream of the bioswale. The CDS system screens, separates and traps debris, sediment, and oil and grease from stormwater runoff prior to entering the bioswale. The indirect screening capability of the system allows for 100% removal of floatables and neutrally buoyant material, without clogging. It is also easy to clean and maintain.
This application represents a growing use of the CDS system to pretreat land-based BMPs.