National Pollutant Discharge Elimination System (NPDES) Information
The National Pollutant Discharge Elimination System (NPDES) was originally created as an amendment to the Clean Water Act (CWA) in 1972 and established a permit program to control water pollution by regulating the discharge of pollutants into waters of the United States. Initially, NPDES permits focused on regulating point source pollution which originates from a definite source, such as industrial facilities, and discharges at a specific point. In the early 1970s, only one-third of the nation’s waters were considered safe for fishing and swimming. Through the advancement of CWA and NPDES, two-thirds of the nation’s waters were considered safe by the mid 1990s.
In 1987, an amendment to the CWA directed the NPDES program to address non-point source (NPS) pollution through a phased approach. NPS pollution does not have a specific origin or discharge location but is considered to be general surface runoff containing pollutants from streets, parking lots, construction sites, homes, businesses and many other sources.
- Phase I of the NPDES permit program began in 1990 and applied to construction sites disturbing 5 or more acres of soil and municipalities with populations equal to 100,000 or more.
- Phase II of the NPDES permit program became effective on March 10, 2003 and applied to construction sites disturbing between 1 and 5 acres of soil and municipalities with populations between 10,000 and 100,000.
NPDES is a federally mandated program that is implemented and enforced locally. Currently, all construction sites disturbing 1 or more acres of soil must obtain an NPDES General Permit from the State Water Resources Control Board (SWRCB). The County of Sonoma has obtained Municipal Separate Storm Sewer System (MS4) permits from the North Coast Regional Water Quality Control Board (NC RWQCB) and the San Francisco Bay Regional Water Quality Control Board (SFB RWQCB).
Municipal Separate Storm Sewer Systems Permits (MS4 Permits)
Phase II – San Francisco Bay Region (PDF: 1.22 MB)
Municipalities are required to obtain Municipal Separate Storm Sewer Systems (MS4s) Permits which regulate storm water discharges. MS4 permits are issued by Regional Water Quality Control Boards (RWQCB) and are usually issued to a group of co-permittees encompassing an entire metropolitan area. Since Sonoma County has two major watersheds regulated by two RWQCBs, we have two MS4 permits.
One municipal permit is a Phase I MS4 Permit for municipalities serving more than 100,000 people and is administered by the North Coast RWQCB. The County of Sonoma is a co-permittee with the City of Santa Rosa and the Sonoma County Water Agency for the Phase I boundary which includes the City of Santa Rosa and unincorporated areas near the cities of Healdsburg, Windsor, Santa Rosa, Rohnert Park, Cotati, and Sebastopol.
The other municipal permit is a Phase II General MS4 Permit for municipalities serving between 10,000 and 100,000 people and is administered by the San Francisco Bay RWQCB. The County of Sonoma is a co-permittee with the Sonoma County Water Agency for the Phase II boundary which includes the unincorporated areas near the cities of Petaluma and Sonoma.
View Larger Map in PDF Format(PDF: 7.8 MB)
Map of MS4 Permit Boundaries
The MS4 permits require the discharger to develop and implement a Storm Water Management Program with the goal of reducing the discharge of pollutants to the maximum extent practicable. The County has developed a Storm Water Management Plan for each of the two MS4 Permits which specifies what BMPs will be used to address certain program areas. The program areas include public education and outreach, illicit discharge detection and elimination, construction activities, post-construction storm water management, and good housekeeping for municipal operations.
Visit the SWRCB website for more information regarding MS4 Permits and associated requirements.
The Industrial Storm Water General Permit Order No. 97–03–DWQ is an NPDES permit that regulates discharges associated with 10 broad categories of industrial activities. The General Industrial Permit requires the implementation of management measures that will achieve the performance standard of best available technology economically achievable and best conventional pollutant control technology. The General Industrial Permit also requires the development of a Storm Water Pollution Prevention Plan (SWPPP) and a monitoring plan. Through the SWPPP, sources of pollutants are identified and the means to manage the sources to reduce storm water pollution are described. The General Industrial Permit requires that an annual report be submitted each July 1.
The ten categories covered under the Industrial Storm Water General Permit include:
- Facilities subject to storm water effluent limitations guidelines, new source performance standards or toxic pollutant effluent standards.
- Manufacturing facilities.
- Oil and gas/mining facilities.
- Hazardous waste treatment, storage or disposal facilities.
- Landfills, land application sites and open dumps.
- Recycling facilities.
- Steam electric power generating facilities.
- Transportation facilities.
- Sewage or wastewater treatment works.
- Manufacturing facilities where industrial materials, equipment or activities are exposed to storm water.
The SWRCB website has more information regarding Industrial Permits and associated requirements.
Applicants of construction projects disturbing 1 or more acres of soil are required to file for coverage under the State Water Resources Control Board (SWRCB), Order No. 99–08–DWQ, National Pollutant Discharge Elimination System (NPDES) General Permit No. CAS000002 for Discharges of Storm Water Runoff Associated with Construction Activity (General Permit). Construction activities include clearing, grading, excavation, stockpiling, and reconstruction of existing facilities involving removal and replacement.
Project owners are required to submit a complete Notice of Intent (NOI) package to the SWRCB. A complete NOI package consists of an NOI form, site map and fee. The General Permit also requires the development and implementation of a Storm Water Pollution Prevention Plan (SWPPP). The SWPPP should contain a site map which shows the construction site perimeter, existing and proposed buildings, lots, roadways, storm water collection and discharge points, general topography both before and after construction, and drainage patterns across the project. The SWPPP must list Best Management Practices (BMPs) the discharger will use to protect storm water runoff and the placement of those BMPs.
Agricultural construction related to reservoirs, access avenues and structures are still subject to the General Permit requirement.
The SWRCB website has more information regarding the General Permit and associated requirements.
Even if a construction project is exempt from the General Permit, it is not exempt from discharging polluted runoff under Sonoma County Code Chapter 11.