Urban Runoff

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.

Storm Water Is Not Treated

Unlike the wastewater that flows through the sanitary sewer system to the City's 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, in turn, feeds the Sacramento River.

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. Trash, yard clipping debris, and other solid waste materials left in streets and gutters are also carried into the storm drain system.

Pollutant Examples

Examples of pollutants commonly found in storm drain systems include:

  • Construction waste and residues (concrete, mortar, sawdust)
  • Fertilizers
  • Motor oil and other automobile fluids
  • Paint
  • Pesticides
  • Pet waste
  • Soil and gravel
  • Trash
  • Varnishes and solvents
  • Yard waste (leaves, grass, sticks, branches, mulch)

Major Problem

Because of these factors, urban storm water runoff remains the nation's largest source of water quality problems, according to the U.S. Environmental Protection Agency.