Stormwater Quality

Stormwater Program

The City of Napa’s General Plan, Envision Napa 2020, establishes a goal of a restored, healthy, living Napa River, which is the vibrant central defining feature of the Downtown and the City of Napa. View the City of Napa's General Plan page for details.

The City of Napa is required by the Federal Clean Water Act to obtain a permit to discharge stormwater, view the Federal Clean Water Act page for details. This General Permit (Order No. 2013-001 DWQ effective July 1, 2013) requires the City of Napa to:

  • Develop and implement a Storm Water Management Plan (SWMP) that describes Best Management Practices (BMPs), measurable goals, timetables for implementation, and to implement the current Phase II Municipal Separate Storm Sewer System (MS4) permit requirements.

Reducing Pollution

To more effectively reduce stormwater pollution in the Napa River watershed the City of Napa joined with the City of American Canyon, Town of Yountville, City of St Helena, Town of Calistoga and County of Napa to establish a county-wide stormwater pollution prevention program.

The Napa Countywide Stormwater Pollution Prevention Program (NCSPPP) is a joint effort of Napa’s cities, towns and unincorporated areas to:

  • Comply with State and Federal regulations
  • Preserve beneficial uses of local waterways
  • Prevent stormwater pollution
  • Protect and enhance water quality in creeks and wetlands

Though the County and each of the five cities and towns carry out their own individual stormwater pollution prevention programs, NCSPPP provides for the coordination and consistency of approaches between the individual participants and documents their efforts in annual reports.

NCSPPP is funded by the member agencies and is administered by the Napa County Flood Control and Water Conservation District.

Reporting Illicit Discharges

Illicit discharges are any discharges into a storm drain system that are not composed entirely of stormwater, prohibited by local ordinances, state or federal laws. Illicit discharges may range from excess irrigation runoff to major spills of hazardous materials. Suspected illicit discharges may be reported to the City by the public, other agencies, or the City’s own staff by calling the Stormwater Hotline at 707-257-9600. Discharges may also be reported using the City’s online Service Request Center. In the event a suspected illicit discharge is not known or suspected to be hazardous, please call 911.

Ducks floating on River


All individuals undertaking public or private construction or ground disturbing activities must take steps to prevent discharge of pollutants resulting from these activities. To find out what level of Best Management Practice (BMP) implementation is required for a project, applicants may refer to the Stormwater Quality Submittal Requirements Checklist for applicability. Projects that disturb less than one acre (less than 1 acre) of soil may refer to the Erosion and Sediment Plan Guidance document adopted January 1, 2015. Projects that disturb more than one acre (more than 1 acre) of soil are subject to the State's Construction General Permit (CGP). These projects must apply for and comply will all requirements of the CGP.

Post Construction

Developers shall incorporate post development measures (BMPs) into the projects design to mitigate impacts to water quality. The Post Construction Water Quality Management Manual had been updated!, “BASMAA Post-Construction Manual” dated July 14, 2014, was prepared by the Bay Area Stormwater Management Agencies Associated (BASMAA) Phase II committee. This manual is designed to ensure compliance with the requirements, facilitate review of applications, and promote integrated Low Impact Development (LID) design. The BASMAA Post-Construction Manual has been updated! The latest version dated January 2019 is now available. This update includes very minor edits with the intention of providing clarity to some of the design aspects in the manual.