Countywide Stormwater Pollution Prevention Program

Foam Pollution (Stormwater)


Q: Are sewers and storm drains the same thing?
No.  They are two separate drainage systems.  Wastewater from homes, industry, etc., travels through the sewer system where it is treated at sewage treatment plants before reuse or discharge into the Napa River.  Runoff from streets, parking lots, yards., etc., enters the storm drain system, receives no treatment, and flow directly to creeks and other waterways.

Q: What kind of pollutants are found in the storm drain system?
A: Sediment, yardwaste, paint products, motor oil, fertilizers, pesticides, styrofoam cups, paper, pet waste, and antifreeze are but a few of the pollutants routinely found in the storm drain system.

Q: What is an illicit discharge?
A: An illicit discharge is any discharge to a stormwater conveyance system (e.g., street, storm drain, ditch, etc.) that is not free of pollutants to the maximum extent practicable.  Maximum extent practicable is a standard that relies upon source control as the primary defense to prevent pollution.  Additional treatment control measures may be required to prevent illicit discharges.  Please refer to your local stormwater ordinance for more information on the legal requirements concerning stormwater.

Q: What are source control and treatment control measures?
Source control measures prevent stormwater from becoming contaminated with pollutants whereas treatment control measures attempt to remove pollutants from contaminated stormwater.  Source control measures are always the most effective means to protect water quality.  Examples of source control measures include pre-sweeping paved surfaces before powerwashing, avoiding the use of copper in pools and fountains, and using straw mulch to prevent erosion. Treatment control measures include wastewater filtration systems and silt fences.

Q: What are the cities, town, and Napa County doing about illegal dumping and illicit discharges into storm drains?
Each entity has passed ordinances that makes it illegal to dump or discharge trash, debris, chemicals, contaminated water, or any other liquid or solid material into the storm drain system.  Violators are now subject to stiff fines and criminal prosecution.  Illegal dumping and illicit discharges may be reported to the local  Stormwater Hotline  for investigation and enforcement.

Q: Is it illegal to wash my car in my driveway?
No.  Each of the municipalities in Napa County have exempted non-commercial carwashing from their discharge prohibitions.

Q: Yard clippings and leaves are natural, so they don't cause problems if swept into storm drains, right?
Grass, leaves, and yard clippings that are repeatedly swept into catch basins can clog the drain, causing flooding and the potential for becoming a breeding ground for rodents and insects.  Additionally, grass and leaves will decompose in a creek or wetland and deprives fish of their oxygen.  In many cases, the fish and other aquatic organisms may die from a lack of oxygen.