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Guide to Storm Water BMPs (Best Management Practices)

What is a BMP?

A storm water BMP reduces water pollution and can reduce flood risks. It can be:

  • something we do, such as cleaning up spills of oil or paint on our driveways. 
  • specially-designed structures created by people, such as rain gardens, that keep excessive pollution from entering our creeks and streams
  • efforts to preserve natural structures that reduce pollution such as wetlands

Storm water runoff is rain that is not absorbed into the earth.  Instead, it runs off streets, rooftops, parking lots, even lawns.  As it flows, storm water picks up pollutants such as pesticides, fertilizers, bacteria, oil and sediment. 

In Charlotte-Mecklenburg, storm water is piped directly to creeks.  It does not go to a wastewater treatment plant.  70% of the pollution in our streams, rivers and lakes is carried there by storm water.

How can BMPs help?
BMPs are designed to improve water quality by reducing pollution in our streams, rivers and lakes.

Nonstructural BMPs are good housekeeping practices such as not using too much fertilizer or pesticide, cleaning up pet waste regularly, properly disposing of used oil and cleaning up spills, doing preventive maintenance on vehicles, and decreasing impervious surfaces to allow storm water to soak into the soil.

Structural BMPs are nature's water treatment facilities. They treat storm water runoff by retaining it until harmful chemicals are allowed to settle, be absorbed by plants, or be filtered through the soil.

Putting oil down a storm drain is not a best management practice
Putting oil down a storm drain is not a
best management practice

Edwards Branch Wetland
Edwards Branch Wetland

In addition to removing or treating pollutants, many BMPs detain storm water and release it at a slower rate into storm drains, streams, rivers and lakes.  This reduces erosion and the danger of flooding.

Some examples of Structural BMPs include wetlands and rain gardens.  Wetlands usually occur naturally but can also be created by people.  Wetlands store floodwater, maintain surface water flow during dry periods, and the plants and soil filter many of the pollutants out of storm water.  

Rain gardens are bowl-shaped gardens near homes or businesses designed to absorb storm water runoff from impervious surfaces such as roofs and parking lots.  The plants in rain gardens remove many of the common pollutants in storm water. 

Other structural BMPs include:
    sediment retention ponds
    vegetation strips
    grassy swales

These BMPs collect storm water runoff, reduce soil erosion and remove many pollutants.

Mint Hill Rain Garden
Mint Hill Rain Garden