The storm drain system and sanitary sewer system are both large conveyance systems of underground pipes. This leads to the misconception that the systems are one and the same. They are in fact separate and serve different purposes.
The sanitary sewer system transports domestic sewage to a treatment plant. Domestic sewage includes wastewater from household and commercial plumbing, such as toilets, showers, and sinks. In Lomita, sewage travels from private plumbing pipes into the City’s sanitary sewer system, which eventually carries it to the Joint Water Pollution Control Plant in the City of Carson. There, contaminants are removed from the sewage through a multi-stage process, which includes settling, filtering, and biological and chemical treatment. The treated water is then discharged into local waterways or used as reclaimed water.
The storm drain system, on the other hand, was designed to prevent cities from flooding. Its purpose is to quickly transport rain runoff (stormwater) away from the city and into the nearest waterway, without treatment. And so, any pollution carried by stormwater also enters our waterways untreated.