Non-point source pollution occurs as a result of uninformed people dumping toxic waste into a waterway or an oil spill from an unknown source. People performing daily tasks can also contribute to non-point source pollution. For example, individuals pouring motor oil and dumping yard waste down the sewer system and throwing trash onto the street. Sewer Drain Stenciling is one way to constantly remind the public that sewers are for water and not trash. The Metropolitan St. Louis Sewer District s Sewer Drain Stencil Project provides guidelines for stenciling both storm drains and combined sewers.
Storm drains collect stormwater and helps to prevent streets and properties from flooding.
Any debris or waste in the flow s path is washed into the storm drains. The runoff flows through pipes underground and is released untreated into a local waterway, like a nearby creek. The water is carried through a system of pipes to a wastewater treatment plant. At the wastewater treatment plant, the water is treated and approximately 90 to 95 percent of the pollutants in the wastewater are removed. However, during a heavy rainfall, the water may by-pass the treatment plant and is released untreated into the river.