Listed in Stormwater Management
Stormwater systems are designed to carry rainwater; not wastewater, chemicals, or other pollutants. When something other than rain or snowmelt ends up in the storm drains, it's called an illicit discharge, and it can cause serious harm to local waterways, ecosystems, and even public health.
For highway departments, especially those operating under MS4 (Municipal Separate Storm Sewer System) requirements, being able to identify signs of illicit discharge is essential. Here’s what to look for during your inspections or routine maintenance rounds:
Common Indicators of Illicit Discharge
1. Flow During Dry Weather
Stormwater pipes shouldn’t have significant flow during periods without rain. If you see water running out of a pipe on a dry day, especially with no recent precipitation, that’s a red flag. This could be caused by:
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Illegal connections from sinks, toilets, or washing machines
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Groundwater infiltration
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Industrial or commercial dumping
2. Unusual Odors
A telltale sign of contamination is smell. Foul, chemical, or sewage-like odors near stormwater outfalls or catch basins can point to wastewater or chemical discharges. Always approach with caution - some fumes may be hazardous.
3. Discoloration or Cloudy Water
Stormwater should typically be clear or lightly tinted with sediment after a storm. Water that appears milky, soapy, oily, or brightly colored may indicate the presence of:
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Paints
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Solvents
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Detergents
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Food grease
4. Stains or Residue
Check for:
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White, gray, or yellowish stains on outfall pipes or the ground below
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Oily sheens on standing water
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Foam or suds accumulating in ditches or drains
These residues are often left behind by cleaning agents, petroleum products, or industrial runoff.
5. Unusual Vegetation Growth or Death
Localized areas with bright green vegetation, or, conversely, dead patches, may signal chemical or nutrient-rich discharges. Fertilizers and certain waste products can alter plant growth dramatically near stormwater outlets.
6. Trash or Floating Debris
Consistent accumulation of plastic wrappers, grease balls, or hygiene products at outfalls may indicate illegal dumping or a sanitary sewer cross-connection.
What to Do if You Suspect an Illicit Discharge
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Document the location, time, and visual details (photos help).
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Avoid direct contact with suspicious water or residue.
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Report the issue internally and, if required, notify your state environmental agency or MS4 program coordinator.
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Immediately contact your local Soil and Water Conservation District office. They will offer the necessary guidance on how to resolve the issue.
Why It Matters
Illicit discharges can:
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Pollute drinking water sources
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Harm fish and wildlife
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Create public health hazards
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Put municipalities out of compliance with environmental regulations
By staying vigilant and training your team to recognize these warning signs, highway departments can play a critical role in protecting watershed health and staying in environmental compliance.
If your town participates in an MS4 program, regular inspections and proper documentation aren’t just good practice - they’re often required. Roadwurx helps streamline that process, so nothing slips through the cracks, except clean stormwater.