Storm Water System

The storm water system refers to important infrastructure that prevents flooding when it rains. The system, also known as a Municipal Separate Storm Sewer System or MS4, works to move water away from an area to a local water body, such as a creek or river. The storm drain system includes street gutters, inlets, pipes, outfalls, and our local creeks. Because the MS4 flows directly into water bodies without any treatment it is critical to keep it pollutant free.

The City's storm drain system includes over 75 miles of open channels/ditches, over 320 miles of public underground pipes, and over 18,000 structures representing over $200 million in storm drain infrastructure investment.

To protect residents and our local creeks the Storm Water Team monitors water quality to assess local creeks and focus on local pollutants of concern including elevated temperatures, sediment, and bacteria. Monitoring includes chemical and biological sampling during storm events and the low flow season. Chemical monitoring provides concentrations of constituents while biological tests show the response of actual living organisms to creek samples or conditions.

Permits & Regulations

The work the City of Santa Rosa does to prevent storm water pollution is regulated under the jurisdiction of the North Coast Regional Water Quality Control Board (Regional Board), the enforcement arm of the State Water Resources Control Board (Water Board).

The Regional Board has been issuing a National Pollutant Discharge Elimination (NPDES) Storm 
Water Permit (PDF) jointly to the City of Santa Rosa, County of Sonoma and the Sonoma County 
Water Agency. The permit governs a variety of activities in the City of Santa Rosa such as 
industrial and commercial businesses, new and redevelopment projects, construction sites, storm 
drain operation and maintenance, creek monitoring, pesticide applications, and illegal dumping 
of water and other pollution in the City's storm drain (for more information visit our pollution 
prevention page). In early 2013, jurisdictions that had been designated as Phase II 
municipalities within the Russian River Watershed were provided an option to align with the 
Phase I program in an effort for watershed-wide consistency and collaboration. The City of 
Cloverdale, the City of Cotati, the City of Rohnert Park, the City of Healdsburg, the City of 
Sebastopol, the City of Ukiah, the Town of Windsor, and the Phase II designated portions of the 
County of Sonoma elected to participate in the Phase I program as Co-Permittees.

The City enacted a stormwater ordinance (Ordinance No. 3272) on July 30, 1996 to obtain legal authority needed to implement the provisions contained in the NPDES permit for storm water discharges.

Storm Water Assessment

The City of Santa Rosa Storm Water Assessment (Assessment) was approved for parcels within the City of Santa Rosa in 1996 and is intended to offset storm water runoff impacts.  The Assessment is based on the County of Sonoma’s records of the parcel’s land use, lot size, the amount of impervious surface and value, and is adjusted each year by the Consumer Price Index (CPI).  The amount will only increase by the CPI unless you make a significant change to your property, such as re-zoning or major improvements. Each parcel is assessed separately (there is no stipulation for senior citizen waivers/reductions).  For 2017-18, the average single family dwelling parcel will be assessed $32.56/year.   The County of Sonoma collects the Assessment on behalf of the City of Santa Rosa on annual property tax bills. Visit to the Storm Water Assessment web page for more information on how funding is used.