Storm Water & Dry-Weather Runoff

The Importance of Storm Water & Urban Runoff

Storm water is the water that flows through gutters and into storm drains when it rains. During dry weather, water also flows into gutters and storm drains as a result of pavement washing, runoff from excess lawn irrigation, residential car washing, and other activities.  Unlike the wastewater that flows through the sanitary sewer system to the Water Pollution Control Facility, water that flows through the storm drain system is not treated. It is released directly to local waterways. In Woodland, storm water is conveyed from west to east, by gravity, through canals and pipes to a pump station, where it is pumped into a canal that flows from the Yolo Bypass to the Tule Canal, which feeds the Sacramento River.  Click here to view the storm water flow diagram for Woodland.

Rain water and dry-weather runoff pick up many kinds of pollutants as the water flows across pavement and landscaped areas and carries them into the storm water system and then to waterways. Trash, yard clipping debris, and other solid waste materials left in streets and gutters are also carried into the storm drain system.  Because of these factors, urban runoff (also called nonpoint source pollution) remains the nation's largest source of water quality problems, according to the U.S. Environmental Protection Agency.

Clean Water Act Compliance

The City's storm water system discharges must comply with requirements of the federal Clean Water Act.  The state of California administers these requirements through the National Pollutant Discharge Elimination System (NPDES) permit process.  The City's blueprint for permit compliance is its state-approved Storm Water Management Plan, which includes 46 measures to help reduce the potential for pollutants to enter the storm drain system.  Each year, the City must report its progress in implementing these measures to the state.  Click on the links below for the report from the most recent reporting year:

Storm Water Management Program 2012/2013 Annual Report
Appendix A
Appendices B & C

Examples of pollutants:

  • Yard waste (leaves, grass, sticks, branches, mulch)
  • Soil and gravel
  • Construction waste and residues (concrete, mortar, sawdust)
  • Pet waste
  • Paint, varnishes, and solvents 
  • Motor oil and other automotive fluids
  • Pesticides and Fertilizers
  • Litter 
  • Solvent/degreaser

Guidelines for Preventing Storm Water Pollution

  • Report any observations of pollutant discharges or dumping into gutters, storm drains or canals in the City's system to us at 661-5962.
  • Drain your swimming pool into your sewer cleanout or onto landscaping. Only drain to the gutter if you can verify that the water has been dechlorinated and is free of algae.
  • Place yard waste piles in the street only if your green waste cart is full and only in accordance with the green waste program schedule.  Place piles away from the curb and drain inlets to allow for free movement of storm water in the gutter.
  • Use pesticides and fertilizers sparingly and do not over-water the lawn.
  • Dispose of pet waste in the trash, never in yard debris piles.
  • Sweep up and properly dispose of household construction debris like concrete and mortar.
  • Wash brooms and tools used for concrete work in a wheelbarrow or tub of water. Let that water evaporate and throw away the concrete waste, or pour the water out on a contained, paved surface where it can dry and be swept up.
  • Repair auto leaks.
  • Recycle used motor oil (contact Waste Management at 530-662-8748 for container).
  • Dispose of household hazardous waste, used auto fluids, paint and batteries at designated hazardous waste collection or recycling locations. Free household hazardous waste drop-off days are held at the Yolo County Central Landfill.


Frequently Asked Questions

What is storm water pollution?

Storm water pollution occurs when pollutants such as automobile fluids, sediment, chlorinated water, pesticides and plant material are poured or washed down storm drains. Rain water picks up pollutants as it flows across paved surfaces and carries them into the storm water conveyance system and out to local waterways.

Are sewers and storm drains the same thing?

Sewers and storm drains are not the same thing. Sewers collect wastewater from indoor plumbing such as toilets, sinks, washing machines and floor drains. Sewer water is treated at the Water Pollution Control Facility before it is discharged to local waterways. Storm drains transport rainwater and dry-weather urban runoff; these flows are not treated before being discharged to local waterways.

If yard clippings and leaves are natural, why are they considered pollutants?

As yard clippings and leaves decompose, they deplete water of dissolved oxygen that aquatic species, including fish and turtles, need to survive. Excessive plant material also encourages algae growth.  In addition, many yard clippings contain small amounts of pesticides that are used in lawns and gardens and around structures to control insect pests.  These pesticides from urban runoff have been found to be having detrimental effects on aquatic life forms in the state's waterways. 

What is an illegal discharge?

An illegal discharge is any non-permitted or non-exempt discharge of pollutants to the storm water conveyance system. Examples of exempt discharges are dechlorinated swimming pool water, air conditioning condensate, potable water, and water line flushing. Pouring or washing carpet cleaning water, motor oil, pesticides, chlorinated swimming pool water, or any other materials that are potentially harmful to the environment, into gutters and drain inlets is considered an illegal discharge.

What is an illicit connection?

An illicit connection means any physical connection to the storm drain system that is not expressly authorized by the City.

What do I do if I see someone dumping oil, trash or other pollutants into drain inlets?

If you see someone dumping oil, trash or other pollutants into storm drains, please report the incident to us at 661-5962.  Note the address where pollutants were dumped, what pollutant(s) were dumped, and, if possible, approximately how much pollutant was dumped and the responsible party if known.  The incident will be handled by the City and/or County.

Where can I take hazardous materials, including paint and automotive fluids, that I need to dispose of?

Hazardous materials can be taken to the Yolo County Central Landfill on Household Hazardous Waste Drop-off days. Visit the Landfill website and click on Household Hazardous Waste Events for more information on dates, times and materials accepted.