Storm Water

Storm water runoff occurs when rainfall flows over the ground. Impervious surfaces like parking lots, rooftops and streets prevent storm water from naturally soaking into the ground. More impervious surfaces means more storm water runoff entering the County’s storm drain system which includes curb inlets, underground pipes, road side ditches, creeks, streams, and rivers.

Non-point source pollution is caused from pollutants of varying origins and occurs when storm water runoff picks up and carries debris, chemicals, dirt and other pollutants into our storm drain system. Anything that enters our storm drain system is discharged untreated into the water bodies we use for swimming, fishing, recreation and drinking water.

Some common pollutants found in storm drains and creeks include: motor oil, yard clippings, fertilizers, pesticides, milky water from paint, soapy water from car washing, eroded sediment and concrete by-products from construction projects and litter. Because all runoff cannot be captured and treated like sewage, the best prospect for cleaner water is to prevent runoff from becoming polluted in the first place.

Clean Streams in Southern Sonoma County

Permit Sonoma is part of a public/private partnerships to reduce pollution in the Sonoma Creek and Petaluma River watersheds.

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Storm Drain Systems vs. Sanitary Sewer Systems

A storm drain system is designed to prevent flooding by collecting surface runoff through various inlets (like curb openings and parking lot grates) and conveyance systems (like ditches, swales and pipes) then discharging to a natural waterway (like a creek or river). Storm drains are also known as storm sewers. The water in the storm drain system does not receive any treatment. Anything located outside that can be washed away by water has the potential to enter a storm drain system and our waterways. This includes motor oils in driveways, pet waste on lawns and soapy water from car washing.

A sanitary sewer system collects and transports waste from indoor plumbing fixtures to treatment plants. Private septic systems also collect waste from indoor plumbing fixtures but the contents are contained within the owner’s property. Septic systems should be maintained on a regular basis and should not be discharged over land or into a storm drain system.