Illicit Discharges

Did you know that only rain should enter the storm system? Learn more about what illegal discharges are, why only rain and snow melt should enter the storm sewer system, and what to do if you see a weird color in a stream.
Page updated on April 17, 2025 at 12:58 PM
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What is That Stuff in the Stream?

Illegal discharge in stream
Brown stream water
Orange Water in Stream photo
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Illegal discharge in stream
Cloudy/Milky: If the water in the stream is a cloudy or milky color it is likely that something has been dumped either in the stream or in a storm drain.
Brown stream water
Brown: If the water in the stream is brown and hard to see through, there is too much sediment in the water. This could be caused by a large amount of water entering the stream, like during a water main break, or it could be because a construction site is not controlling sediment leaving the site.
Orange Water in Stream photo
Orange Slime: There are some streams in the City that have orange slime along the bottom. While this orange slime can look out of place it is actually completely natural and is caused by iron bacteria that are naturally occurring in the groundwater in the City. The most common place to see this orange slime is in Hooff’s Run, but any stream in the City that is fed by groundwater can have it.

What is an Illicit Discharge?

An illicit discharge is what happens when pollutants are poured directly into a storm drain, stream, or waterbody, as well as when pollutants are left out on the ground and can be carried by rain to a storm drain, stream, or waterbody. Because the storm drain system (also called a storm sewer) is not treated, everything that enters the system goes directly to local streams. These illegal discharges are enforced through City code.

Virginia DEQ's website for guidelines on the release of swimming pool water. 

illicit discharges

Is That Rainbow Sheen Natural or Oil?

Did you know that sometimes rainbow sheen on water can naturally occur? Natural sheen is caused by the same iron bacteria that cause the orange slime above. This bacteria is naturally occurring in groundwater. 

So how do you tell the difference between a natural or oil rainbow sheen? The easiest way is to use a stick to poke into the sheen to try and break it apart. If the rainbow sheen stays broken up in pieces, it is most likely natural sheen. If the rainbow sheen swirls back together, it may be caused by oil or petroleum. An oil or petroleum sheen will also usually smell like oil or gas. If you believe there is an oil/petroleum spill, call the Alexandria Fire Department at 911. For other illicit discharge concerns, use Alex311.