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Stormwater is an important natural resource that sustains our agricultural, economic, and recreational interests. Since all aspects of life depend on water, the County of Sonoma is committed to protecting and enhancing the quality of our waterways.

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

Stormwater runoff carries debris, chemicals, dirt, and other pollutants into our storm drain system. Anything that enters our storm drain system is discharged untreated into the waterbodies 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, concrete by-products from construction projects, and litter.

Through a joint endeavor with the City of Santa Rosa and the Sonoma County Water Agency, the County of Sonoma has established a Storm Water Management Program to protect our waterways and enhance our quality of life. Some of the program goals include raising awareness of stormwater quality issues through public education and outreach, providing information and resources to the construction and development industries to promote better stormwater management, and reducing polluted runoff to our receiving waters.

Municipal Storm Water (MS4)

Unincorporated Sonoma County falls into two (2) different Regional Water Quality Control Board regions depending on the ultimate drainage of the watershed. These different regulator boards have slightly different requirements including different development standards. Additionally, the development standards are different depending on if the property falls within Sonoma County’s MS4 boundary surrounding or draining into the more dense areas of development and Sonoma County’s stormwater drainage network.

Quality of water directly affects quality of life!

water flowing over rocks