Stormwater Quality Program

General Questions

What is stormwater pollution?  

Runoff from rainstorms is called stormwater. Stormwater becomes polluted by flowing over dirty surfaces, such as parking lots. Stormwater pollution also takes place when someone dumps materials, like oil or paint, directly into the storm drain. Polluted stormwater flows without treatment directly to creeks and rivers, where it can be harmful to aquatic life. 

What are catch basins or storm drain inlets?  

Catch basins and storm drain inlets are curbside receptacles that catch surface water runoff from rainfall and deliver it to the storm drain system, where it's eventually delivered to local creeks and rivers. 

Are sewers and storm drains the same thing?  

No. Storm drains and sanitary sewers have two distinct functions. Storm drains are intended to collect and transport runoff from rainfall. Storm drain systems do not remove pollutants from water before it is discharged into streams and rivers. These are typically the drains found in streets and in parking lots. Sanitary sewers collect wastewater from indoor plumbing such as toilets, sinks, washing machines and floor drains and take it to a sewage treatment plant. The treatment plant removes many pollutants from wastewater before it is discharged to the river. 

Do drain inlets get cleaned out?  

Yes. County crews maintain approximately 61,000 drain inlets, 33,000 manholes and thousands of miles of storm drain pipelines countywide. 

Why doesn't the County clean out all of the storm drain inlets right before a storm?  

Seeing as Sacramento County maintains more than 61,000 drain inlets, there are too many to clean in a short period of time. Storm drain inlets are maintained on a year-round schedule. 

Why doesn't the County install filters or screens in front of drain inlets?  

It sounds like a good idea, but during a rainstorm, trash is quickly swept into drain inlets. Any screen or filtration device placed in front of the drain inlet would cause trash to accumulate and clog the grate, preventing proper drainage and potentially creating a flood hazard. With approximately 61,000 drain inlets in Sacramento County maintenance crews would be unable to keep up with cleaning these devices potentially creating flooding hazardous. However there new technologies being developed in the form of filtration or screening devices to be installed and inserted inside drain inlets. The Stormwater Program Engineering groups are always evaluating these new technologies for possible future use.

What types of pollutants are found in the storm drain system?  

Heavy metals paint thinner and paint products, motor oil, pesticides, fertilizers, human and animal feces, antifreeze, and dead animals - are all but a few examples of the pollutants typically found in the storm drain system. 

How much water passes through the system?  

On a typical dry summer day, an average of one million gallons of water flow through the system. This flow comes from over landscape irrigation runoff (primarily lawns) fire hydrant pressure releases, and car washes throughout the region, just to name a few.

In a heavy rainstorm, this flow can increase to billions and billions of gallons a day. 

Is it necessary to line channels with concrete? Can't they be natural waterways?  Go back to top

No. Many channels in Sacramento County were concrete lined to accommodate runoff from large storm events while using the least amount of land. The County is now realizing that naturally vegetated channels provide many benefits that concrete channels do not. These benefits include improved water quality, animal habitat and recreational value. The County's current policy calls for design of natural channels rather then concrete lined channels. ​