University of Missouri Extension

WM6011, New June 1994

Storm Drains and Water Quality

Marie Steinwachs
Office of Waste Management

Improving water quality: The responsibility rests on all our shoulders

Government regulation of business and industry has improved Missouri's water quality. However, not all pollution comes from these sources. Improper disposal of motor oil, pet wastes, yard debris, litter, and misuse of pesticides and fertilizers also threaten our water resources.

This guide describes how storm drains are linked to water quality and what you can do to prevent water pollution.

The U.S. Environmental Protection Agency has determined that nonpoint source pollution is a major cause of our nation's water quality problems.

Household wastes are a significant source of nonpoint source pollution. Household wastes often enter our waterways via storm drains, negatively impacting water quality by depleting oxygen reserves and contaminating the water.

Aquatic plants and animals need sufficient oxygen and clean water to survive. Storm drains should never be used to dispose of household wastes.

Storm drains

Storm drains or catch basins are the square metal grates at the sides or curbs of streets. They are designed to collect stormwater to prevent streets and property from flooding. When it begins to rain, the first raindrops soak into the ground.

But once the soil is saturated, or if the soil has been replaced by cement or another impervious barrier, the rain runs along the surface and is caught in storm drains.

Any debris or garbage from driveways, backyards or streets, including products and wastes applied to the ground, can be washed into the storm sewer system.

For many communities, the storm sewer system carries runoff water through pipes to larger pipes or trunk lines buried underground. These pipes then take the water and empty it untreated into the nearest waterway, such as a stream, river or lake. In parts of Missouri, the storm sewer trunk line empties into a sinkhole, which is a direct conduit to groundwater.

In some communities, the storm sewer system (stormwater) is combined with the municipal sewer system (wastewater). This is called a combined sewer system. Both water streams are carried through pipes to the wastewater treatment plant.

The water is treated at the plant according to the level of available treatment. However, when there is a large flow of water from a storm, the water at the wastewater treatment plant may be released with minimal treatment. As a result, raw sewage and stormwater enter the waterway.

What you can do

Following is information on specific types of wastes that enter our waterways through storm drains and how you can prevent this pollution.


Antifreeze is primarily composed of ethylene glycol, a sweet and poisonous compound which can kill or injure pets, birds, fish, and other wildlife when carelessly disposed into the environment.

It can also contain heavy metal contaminants picked up from vehicle engines during use.



Fertilizers contain large amounts of phosphorus and nitrogen which can cause algal blooms in aquatic areas. These blooms deplete the oxygen in water, resulting in fish kills.


Motor oil

Motor oil can damage or kill underwater vegetation and aquatic life.

Each year in the United States, do-it-yourself motor oil changers improperly dispose of 192 million gallons of used motor oil into our environment.

This is more than 17 times the oil spilled by the Exxon Valdez. One gallon of used motor oil can contaminate 1 million gallons of water. When used motor oil is applied to roads, more than 90 percent of it leaves the road surface on dust particles or in surface runoff.

The use of motor oil as a dust suppressant on a road, a parking lot, a driveway or other similar surface is prohibited in Missouri.

Since Jan. 1, 1991 Missouri solid waste disposal areas cannot accept used motor oil for disposal.



Paint, even latex paint, can contain a variety of hazardous ingredients including lead, mercury, and organic solvents, all of which can impact the environment when disposed of improperly.

Paint rinse water can also contain sufficient hazardous materials to harm the environment.



Pesticides contain toxic materials that are harmful to humans, animals, aquatic organisms, and plants.

When it rains these toxic materials can run into storm drains and waterways.


Other household hazardous wastes

Many other household products such as paint thinners, automotive waxes, cleaners, and swimming pool chemicals, contain hazardous ingredients that can be a threat to human health and the environment when improperly disposed.


Pet wastes

Pet waste is raw sewage. Allowing it to enter our waterways releases both potentially harmful bacteria and oxygen-consuming materials.


Street litter and plastics

Street litter, such as plastic bags, cups, candy wrappers and cigarette butts, are washed from the street by stormwater and end up floating in area streams and lakes.

Many animals mistake plastic for food and, as a result, become ill. Plastic can take hundreds of years to degrade and so will continue to contaminate our waterways and threaten their inhabitants.


Yard wastes and erosion

Leaves and grass clippings allow bacteria, oxygen-consuming materials, phosphorus, and nitrogen to be released into our waterways. Yard wastes can also clog storm drains, making them ineffective and causing local flooding. Soil that erodes from your yard increases the sediment load in waterways, blocking sunlight essential for aquatic plants and suffocating animals.


Other water protecting activities

Current legislation

In November 1990, the U.S. Environmental Protection Agency (EPA) issued a final rule to implement Section 402(p) of the Clean Water Act, federal legislation aimed at preserving the quality of America's waters.

This final rule requires cities with populations greater than 100,000 that have separate storm sewer systems to obtain a National Pollutant Discharge Elimination System (NPDES) permit.

Cities must apply for this permit to ensure the EPA that their storm sewer systems are operating as efficiently and cleanly as possible.

Some privately owned businesses are also required to file for a permit if they discharge anything into the storm sewer system. Cities filing for an NPDES permit must, among other requirements, identify ways to improve the system and educate the public about nonpoint source pollution.

Although this permit application is only required for cities larger than 100,000 and for specified counties, all other cities, towns, and counties should be aware of the problems caused by nonpoint source pollution.

Local rivers and streams often receive pollutants that can damage the water quality of any town, regardless of size. The government is trying to improve water quality, but it is largely the responsibility of the citizens of Missouri to tackle nonpoint source pollution and stormwater runoff.

Missouri Storm Drain Stenciling Project

One way you can become involved in water protection is to participate in the Missouri Storm Drain Stenciling Project. Stencils bear the message "Dump No Waste, Drains To Stream," which serves as a reminder that storm drains should never be used to dispose of household wastes. Kits contain stencils and everything else needed to start a community education program.

The Missouri Storm Drain Stenciling Project was developed by the Household Hazardous Waste Project with assistance from the Missouri 4-H Youth Programs. Funding was provided by the Missouri Department of Natural Resources, and the Missouri Stream Team.

Contact the Household Hazardous Waste Project for information on how to obtain a free kit, or for information on storm drain stenciling in your area.

The Household Hazardous Waste Project is a program of the MU Extension System in cooperation with the Environmental Improvement and Energy Resources Authority.
Copyright 1994 by the Environmental Improvement and Energy Resources Authority. Published by the MU Extension Household Hazardous Waste Project in cooperation with EIERA.
WM6011 Storm Drains and Water Quality | University of Missouri Extension

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