NPDES Stormwater

Storm water is defined by US EPA as the runoff generated when precipitation from rain and snowmelt events flows over land or impervious surfaces without percolating into the ground. Storm water discharges in California are regulated through federal National Pollutant Discharge Elimination System (NPDES) permits. Storm water is often considered a nuisance because it mobilizes pollutants such as motor oil and trash and is often directed into storm drains which then discharge to nearby creeks and rivers. However, storm water may also act as a resource and recharge to groundwater when properly managed. The Water Boards are actively involved in initiatives to improve the management of storm water as a resource. The goals of the Storm Water Program are to:

  • Prevent or minimize the discharge of pollutants contained in storm water runoff to waters of the state.
  • Promote low impact development (LID) techniques and green infrastructure planning to maintain pre-development runoff rates and volumes, and lead California towards more water-friendly landscapes.  

Studies have shown that storm water runoff is a significant source of water pollution, causing declines in fisheries, restrictions on swimming, and limiting our ability to enjoy many of the other benefits that water provides. Common pollutants contained in storm water runoff include:

  • Sediment – Disturbed soils are a significant concern and priority for the North Coast Region. Excessive sediment in water can adversely affect the respiration, growth, and reproduction of salmonids and cause aesthetic impacts to receiving streams.
  • Nutrients - Sources include fertilizer, lawn clippings, and car exhaust, which contain nutrients like phosphorous and nitrogen. An overabundance of nutrients can accelerate the growth of algae, which is a key factor in the decline of water quality.
  • Bacteria- Sources include failing septic tanks, sewer overflows, decaying organic material, and the improper disposal of household pet fecal material. Some bacteria found in storm water runoff can result in disease. High levels of bacteria can lead to a variety of human health issues and can make streams and beaches unsuitable for swimming.
  • Heavy metals and toxic chemicals - Sources include vehicles (brake pads, grease, oils, fuels, etc.), pesticides, and herbicides. Maintaining and cleaning vehicles can release solvents, paint, rust, and lead. These chemicals can adversely affect aquatic organisms as well as drinking water supplies.
There are three types of permits required under the federal program: Construction, Industrial, and Municipal permits.

    Construction Program

    Construction activities that disturb one (1) or more acres of soil or whose projects disturb less than one acre but are part of a larger common plan of development that in total disturbs one or more acres, are required to obtain coverage under the General Permit for Discharges of Storm Water Associated with Construction Activity Construction General Permit Order 2009-0009-DWQ. Construction activity subject to this permit includes clearing, grading and disturbances to the ground such as stockpiling, or excavation, but does not include regular maintenance activities performed to restore the original line, grade, or capacity of the facility. The State's general permit for discharges of storm water from construction activities requires the site owner to apply with the State, to prepare and implement a Storm Water Pollution Prevention Plan (SWPPP), and to monitor the effectiveness of the plan.

    The Construction General Permit requires the development of a SWPPP by a certified Qualified SWPPP Developer (QSD). Many California Board of Professional Engineers, Land Surveyors and Geologists (CBPELSG) have self-certified. In addition, the California Stormwater Quality Association (CASQA) has a lookup tool to find licensed QSDs: CASQA QSP/QSD Lookup Tool.

    To obtain coverage for construction or linear project see the State Water Board’s Construction Storm Water Program Page

    Industrial Program

    Storm water discharges to surface waters from companies involved in manufacturing operations, transportation facilities where vehicles are maintained (maintenance includes fueling and washing), landfills, hazardous waste sites, and other similar operations must be covered by a storm water discharge permit. See Attachment A of the permit for a complete list of facilities covered by the Industrial General Permit. For coverage under the State's Industrial Storm Water General Permit (Order 2014-0057-DWQ), each facility must submit an application to the State, prepare and implement a Storm Water Pollution Prevention Plan, and monitor the flow of pollutants leaving the site. Although the plan does not have to be submitted to the Regional Board, the permittee must keep the plan available to onsite inspectors and submit an annual report to the Board. With State approval, the general permit allows group monitoring, where only selected facilities within a group are monitored to characterize the whole group. Also, a company may be exempt from all or part of the general permit if industrial materials (including wastes, products, machinery, roof exhausts, etc.) are not exposed to rain.

    In the adoption of the IGP in 2014, the State Water Board recognized the need for a comprehensive training program to provide a statewide training specifically for individuals assisting Dischargers with compliance of this permit, standardized knowledge of implementing the Industrial General Permit through training, and required quality assurance, sampling methods, and protocols for storm water discharge sampling. Obtaining storm water discharge data that is higher in quality is crucial for future regulations in the permit.

    To obtain coverage under the Industrial General Permit see the State Water Board’s Industrial Storm Water Program Page

    Municipal Program

    The Municipal Storm Water Permitting Program regulates storm water discharges from municipal separate storm sewer systems (MS4s). Storm water is runoff from rain or snow melt that runs off impervious surfaces such as rooftops, paved streets, highways or parking lots and can carry with it pollutants such as: oil, pesticides, herbicides, sediment, trash, nutrients, bacteria and metals. The runoff can then drain directly into a local stream, lake or bay. Urban areas commonly include large impervious cover which contributes to an increase in runoff flow, velocity and volume. As a result, streams are hydrologically impacted through streambed and channel scouring, instream sedimentation and loss of aquatic and riparian habitat. In addition to hydrological impacts, large impervious cover contributes to greater pollutant loading, resulting in turbid water, nutrient enrichment, bacterial contamination, and increased temperature and trash.

    Pursuant to the Federal Water Pollution Control Act (Clean Water Act) section 402(p), storm water permits are required for discharges from an MS4 serving a population of 100,000 or more. The Municipal Storm Water Program manages the Phase I Permit Program (serving municipalities over 100,000 people), the Phase II Permit Program (for municipalities less than 100,000), and the Statewide Storm Water Permit for the State of California Department of Transportation. The State Water Resources Control Board (State Water Board) and Regional Water Quality Control Boards (collectively, the Water Boards) implement and enforce the Municipal Storm Water Program.

    Phase I Program
    There is one Phase I MS4 permit in the North Coast Region, Order No. R1-2015-0030. This permit regulates the discharge of pollutants from the City of Santa Rosa, portions of unincorporated County of Sonoma, Sonoma County Water Agency, the City of Cotati, the City of Cloverdale, the City of Healdsburg, the City of Rohnert Park, the City of Sebastopol, the City of Ukiah, and the Town of Windsor.

    Monitoring and Reporting Program (Revised August 11, 2021)
    Sonoma County Phase I MS4 Boundary Map

    Non-Storm Water Best Management Practices (BMP) Plans
    Each Co-Permittee (except Cloverdale) has developed a draft Non-Storm Water BMP Plan (BMP Plan) to eliminate or minimize the discharge of pollutants to the MS4 related to select types of discharges. The discharges are allowable non-storm water discharges provided they meet all required conditions in the MS4 Order, are not a significant source of pollutants, and are conducted as specified in the Co-Permittee's approved BMP Plan.

    Phase II Program
    There is one state wide general permit which regulates the discharge of pollutants from small MS4s, State Water Board Order No. 2013-0001 DWQ. In the North Coast Region, the following municipalities have been designated as small MS4 and are currently responsible for implementing the requirements of Order No. 2013-0001.

    Mendocino County
    City of Fort Bragg
    Portions of Unincorporated Mendocino County

    Humboldt County
    City of Eureka
    City of Arcata
    City of Trinidad
    City of Fortuna
    Portions of Unincorporated Humboldt County
    Humboldt State University

    Siskiyou County
    City of Yreka

    Sonoma County
    Sonoma State University
    Petaluma Coast Guard Training Center
    State of California Department of Parks and Recreation

    Caltrans Program
    Storm water and non-storm water discharges associated with operations and maintenance activities by the California Department of Transportation (Caltrans) highway system, properties, facilities and activities are regulated under Order No. 2012-0011-DWQ.  Caltrans properties include all Right-of-Way (ROW) including, but are not limited to, maintenance stations/yards, equipment storage areas, storage facilities, fleet vehicle parking, maintenance areas, and warehouses with material storage areas.

    For additional information see the State Water Board’s Caltrans MS4 Program Page.  

    Trash Provisions
    On April 7, 2015, the State Water Board adopted an Amendment to the Water Quality Control Plan for Ocean Waters of California (Ocean Plan) to Control Trash and Part 1 Trash Provisions of the Water Quality Control Plan for Inland Surface Waters, Enclosed Bays, and Estuaries of California (collectively referred to as "the Trash Amendments"). The Trash Amendments  (1) establish a trash narrative water quality objective, (2) prohibit the discharge of trash, (3) provide implementation requirements for permitted storm water and other discharges, (4) set a time schedule for compliance, and (5) provide a framework for monitoring and reporting requirements. Following adoption, the Trash Amendments were submitted to both the California Office of Administrative Law (OAL) and the U.S. Environmental Protection Agency (U.S. EPA) for review and approval. The OAL approved the Trash Amendments on December 2, 2015. The U.S. EPA approved the Trash Amendments on January 12, 2016.

    For more information, please visit the State Water Board Storm Water Trash Implementation Page.

  (Page last updated 8/29/23)