Stormwater Management

The City of Saint Charles’ stormwater system includes over 200 miles of stormwater pipes with over 12,000 inlets, manholes and other structures, and more than 70 roadway crossing culverts and bridges. This system is maintained by the Public Works Department and designed to help control urban flooding events by directing stormwater runoff into detention basins, creeks, and streams. The storm sewer system is separate from the sanitary sewer/wastewater system - stormwater discharges directly to local waterbodies without any treatment. 

Stormwater Quality

The City of St. Charles has responsibilities under the Federal Water Pollution Control Act and Missouri Clean Water Law to implement programs and practices to protect water quality. St. Charles became a regulated small Municipal Separate Storm Sewer System (MS4) under Phase II of the National Pollutant Discharge Elimination System (NPDES) in 2003. As required by law, the City has developed codes and standards intended for preventing stormwater pollution. 

Stormwater runoff is water from rain or melting snow that flows across the land and does not soak into the ground. The amount of runoff increases in developed areas where there are more impervious surfaces like building rooftops, parking lots, driveways, and streets. Runoff can pick up and deposit harmful pollutants such as trash, dirt, lawn chemicals, and pet waste into streams, lakes and other waterbodies. 

Get Involved! 

Here are just a few ways you can help improve water quality:

Only Rain in the Storm Drain

One of the ways the City is promoting stormwater pollution prevention is by marking storm drains with messaging such as “No Dumping – Drains to Stream.” Storm drains are often misused by the public and businesses. They’ve been used for dumping paint, motor oil, pet waste, construction debris, and grass clippings among other things. These pollutants end up in our local creeks and pollute recreational and drinking water resources. Storm drains are not trash cans!

You may be contributing to stormwater pollution without even realizing it. Here are some common residential pollutants:

  • Grass Clippings & Leaf Litter

The problem: Yard waste placed or dumped in a storm drain or along a creek bank will lead to flooding problems, contribute to creek bank erosion, and harm aquatic life. These materials can accumulate in storm sewers and clog them leading to drainage problems. When placed on a creek bank yard waste covers the ground and hinders growth of natural vegetation that holds the bank in place. Decomposing yard waste decreases the dissolved oxygen levels in water, suffocating aquatic organisms. 


The solution: Bag up grass clippings and leaves and have them picked up by a curbside yard waste collection service. Sweep or blow grass clippings on driveways and sidewalks bank into the lawn. You can also consider composting yard waste for use as a natural fertilizer: 


  • Fertilizer & Pesticides

The problem: Lawn chemicals can be transported by stormwater runoff into waterways. The nutrients in fertilizers that promote lawn growth also promote excessive algae growth in waterbodies which degrades water quality.   


The solution: More is not better when it comes to lawn chemicals. Use them as directed on the packaging and sweep any excess chemicals from pavement back into the lawn. Consider natural alternatives to chemicals such as compost to fertilize. Don’t apply lawn chemicals before a heavy rain as they will not have had time to absorb into the soil before being washed away. Use native plants in landscaping.


  • Pet Waste

The problem: In addition to being unsightly and unpleasant to step in, pet waste contains harmful bacteria and parasites that will wash into our waterways when it rains. 


The solution: Pick up pet waste and dispose of it the trash. 


  • Cigarette Butts

The problem: We’ve all seen cigarette butts discarded from car windows or onto sidewalks or parking lots. They are then swept into storm sewers with rainfall and end up in waterways. Cigarette filters are made of plastic fibers that take a decade or more to degrade.


The solution: In public places dispose of butts in designated receptacles. At home, use an ashtray and empty unlit ends into the trash. 

Stormwater Management Plan

The City of St. Charles has developed a stormwater management plan for MS4 permit compliance. This plan can be viewed here: 



Creek Maintenance

Creek channel and bank maintenance is the responsibility of the property owner. Most of the creeks in St. Charles are on private property and not maintained by the City. However, in certain cases where an obstruction in a waterway impedes the free movement of water, City crews may intervene to clear the blockage. 

St. Charles County, the City of Wentzville, and St. Charles County Soil & Water Conservation District collaborated to publish the Stream Care Guide, which provides tips on protecting water quality, preventing and minimizing erosion, and avoiding flooding impacts for property owners.

Residents with property located along creeks suffering from erosion may apply for the Rock and Soil Program, which provides rock and/or soil to be used towards controlling the erosion. Visit the Residential Programs page for more information. 

Useful Links

St. Charles County Recycle Works: 

University of Missouri Extension Soil Testing: 

St. Charles County Stream Care Guide: 


Drain Markers