Storm water discharges in California are regulated through National Pollutant Discharge Elimination System (NPDES) permits. The Federal Clean Water Act (Clean Water Act) prohibits certain discharges of storm water containing pollutants except in compliance with a National Pollutant Discharge Elimination System (NPDES) permit. The NPDES storm water program regulates some stormwater discharges from three potential sources: municipal separate storm sewer systems (MS4s), construction activities, and industrial activities.

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.  With the focus on storm water as a resource for local landscape and agricultural irrigation, and groundwater recharge. To protect these resources, municipalities, communities, construction companies, industries, and others, use stormwater controls, known as best management practices (BMPs). These BMPs filter out pollutants and/or prevent pollution by controlling it at its source.

• Low Impact Development (LID) refers to systems and practices that use or mimic natural processes that result in the infiltration, evapotranspiration or use of stormwater in order to protect water quality and associated aquatic habitat. Unlike traditional storm water management that collects and conveys storm water runoff through storm drains, pipes, or other conveyances to a centralized storm water facility, LID takes a different approach by using site design and storm water management to maintain the site’s pre-development runoff rates and volumes.
• Green Infrastructure (GI) refers to the management of wet weather flows using these processes, and to refer to the patchwork of natural areas that provide habitat, flood protection, cleaner air, and cleaner water. This expands the low impact development approach to a larger community scale and presents similar sustainable opportunities to local governments and regional projects.

Monitoring and tracking storm water quality helps us understand how well these programs, activities by permittees, and/or best management practices are working.

RESOURCES

National Pollutant Discharge Elimination System (NPDES) Stormwater Program

Storm Water Management in California

Strategy to Optimize Resource Management of Stormwater (STORMS)

California Stormwater Quality Association (CASQA)

VIDEOS

After the Storm - A Citizen's Guide to Understanding Stormwater

What is Stormwater?

Central Coast Stormwater, California 

The Napa Countywide Stormwater Pollution Prevention Program (NCSPPP) is a joint effort of the County of Napa, cities of American Canyon, Napa, St. Helena and Calistoga, and the Town of Yountville to: 

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

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

For Eco-Friendly pest management practices, a website called, Our Water Our World has been developed to assist consumers in managing home and garden pests in a way that helps protect our water. Among other things, this website offers:

• Assorted fact sheets/forma informativas on specific pests and methods to manage them without using hazardous materials.
• Pocket guide to less toxic products for managing common pests.
• Information on where to buy less toxic pesticides, including fungicides and herbicides.
• A list of products by brand name that are considered less toxic alternatives to more conventional pesticides.
• A list of products by the pest they target.
• An Ask the Expert feature that allows you to ask a specific question and receive a personal reply.

Napa County is committed to being an environmental steward of its land and water resources. The Napa River flows 55 miles from Mount St. Helena to the San Pablo Bay with a total watershed area of approximately 245,724 acres. To ensure the sustainability of the Napa River Watershed and its water quality, the County, in collaboration with the Napa County town and cities, has embarked on an effort to identify opportunities to improve stormwater capture and retention through groundwater recharge and green infrastructure projects. Green infrastructure represents control measures that mimic natural systems to absorb and filter stormwater, which removes pollutants and slows or reduces runoff into storm sewers and surface waters. In addition to the benefits of removing pollution and reducing runoff, green infrastructure can reduce erosion and flood risk, protect water quality for humans and aquatic organisms, and impound (or retain) water to allow it to recharge groundwater critical for human and environmental uses within the Napa River Watershed.

For more information on water resources in Napa County, please visit napawatersheds.org.

Water Quality Concerns

Stormwater is runoff from rain or snowmelt that travels over impervious surfaces, such as paved streets, parking lots, and building rooftops, and does not soak into the ground. As urban development has expanded, impervious surfaces have increased throughout the watershed. When stormwater is absorbed into soil, it is filtered and ultimately replenishes aquifers or flows as groundwater into streams and rivers. When stormwater is not absorbed, it is often considered a nuisance because it mobilizes pollutants like trash, chemicals, oils, dirt, and sediment. In most cases, stormwater flows untreated directly to water bodies through sewer systems, carrying pollutants with it that can harm streams, rivers, lakes, and coastal waters. By reducing stormwater runoff from impervious surfaces across the Napa River Watershed, we can reduce numerous negative environmental impacts.

What's in the Stormwater Resource Plan?

The Napa River Watershed Stormwater Resources Plan (SWRP) was created to facilitate the identification of opportunities and the future development and implementation of stormwater management projects and programs that provide multiple benefits including water quality, reduced localized flooding, increased water supplies, and community enhancement. A SWRP is required by the State Water Resources Control Board to be eligible for grant funding of projects by the State, and therefore is a necessary first step to identifying future project opportunities. The SWRP utilized Geographic Information System (GIS) data to identify publicly owned land with the highest suitability for multiple benefits using a metrics-based evaluation. The SWRP methodology includes identifying parcels suitable for projects, scoring each parcel using an automated metric-based evaluation, and ranking scored projects based on their weighted benefits. Suitable parcels were scored across six benefit categories:

• General Suitability
• Water Quality
• Water Supply
• Flood Control
• Environmental
• Community

Each benefit category was equally considered. Finally, all parcel scores were weighted to prioritize projects and parcels with the greatest number of benefits. A full methodology can be found within the SWRP. Napa County is interested in hearing from stakeholders and community members. The County is accepting public comments on the Draft SWRP until March 2, 2023. Please download the draft and submit your comments on the plan to info@napawatersheds.org.