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Stormwater Quality

Keep it clean from drain to stream!

The stormwater system is completely separate from the sanitary sewer system, and stormwater is not process or treated before it is discharged to our waterways. The City and County of Denver maintains different types of stormwater management facilities such as retention ponds, grassy swales and other kinds of buffers that help naturally filter out pollutants before they hit the waterways, and works with residents to reduce pollutants before they reach the stormwater system. 


Stormwater runoff is generated when water from rain and snowmelt flows over land or impervious surfaces (like paved streets, parking lots, and building rooftops) and is not absorbed into the ground. As the runoff flows over the land or impervious surfaces, it accumulates debris, chemicals, sediment or other pollutants. If those pollutants get into our waterways, they can cause problems for wildlife, algae blooms and flooding during storms.

Pollutants in waterways can cause problems for public health, spreading through flooding during storms. Denver will implement new treatment methods to preserve the health of neighborhoods and larger waterways.

To mitigate the impacts caused by impervious surfaces, Denver is prioritizing new green infrastructure projects, using parks, open space areas, and urban design to create networks that filter water for natural treatment before it discharges to waterways.


Be a Water Watch Dog!

Help safeguard our lakes and streams. 

Contact the Division of Environmental Quality at 720-865-5452 if you notice any of the following unusual conditions in our lakes and streams:

  • A change in color of the water 
  • An unusual or foul odor 
  • Suds when there is no precipitation occurring 
  • Any unusual-looking substance discharging from a storm outlet 
  • Illegal dumping activity 
  • Unusual discharges from construction sites or industrial sites 
  • Large number of dead or dying fish or crayfish

Preventing pollution

  • Wash your car at a car wash or on your lawn, not in the street or on your driveway. Soap residue can lead to algae blooms in waterways.
  • Keep your car tuned to prevent gas and oil from ending up on our streets.
  • Try to collect any litter you see in streets or parking lots, and pick up after your pet to keep bacteria and nutrients from the waterways.
  • Use fertilizer sparingly and appropriately, and never fertilize before a rainstorm.
  • Cover any loose dirt when doing home improvements and try to berm construction areas to keep sediment from washing into the storm drain system (which can cause flooding and endanger aquatic wildlife).

Clear Choices brochure covers: Caring for your Lawn and Garden, Managing your Household Wastes, Managing your Construction Site

"Clear Choices" tips (PDF)

silver sedan on the streetThe problem: 
Gas, oil and other fluids from cars end up on streets and get washed into the stormwater system during storms or snow melts.

What you can do:
Keeping your car tuned can not only help keep pollutants out of the waterways, but can also save you money and prolong the life of your car. 


Here are 5 small things anyone can do to keep your car running smoothly:

  1. Check tire pressure — If your tires are under-inflated, you're losing miles per gallon off your fuel efficiency, which increases the amount of pollution your car creates. 
  2. Change the spark plugs — This will help your car burn gas more efficiently, so you use less fuel and less fuel ends up in the street unburned.
  3. Check your air filter — If your car can't breathe, it can't burn fuel. Replacing a dirty air filter is cheap and easy and will improve gas mileage, increase horsepower and reduce the amount of pollution your car creates.
  4. Watch for oil leaks — An oil leak isn't just bad for our waterways, it can be really bad for your car. If ignored, it could be disastrous. If your car is leaking oil (if you see oil spots in your parking space), you should have a mechanic look at it. 
  5. Check other fluids — If you're losing anti-freeze, brake fluid or any other fluid in your car, it ends up in the waterways. It's also a sign of a problem with your car, and often the small problems can turn into big problems if not addressed.

The problem:
Sediment gets into the stormwater runoff, clogging the storm drain system. If it reaches waterways, it can muddy the waters, reducing oxygen levels and raising the temperature of the water, harming aquatic wildlife.

What you can do:

  • Don't sweep dirt from driveways or other impervious areas into the street. 
  • Cover any loose dirt or mulch piles with a tarp before rainstorms.
  • Berm any home construction projects to keep dirt from washing into the stormdrains.

Erosion Control Criteria

Denver's Erosion Control Guide for formatting and minimum plan design criteria, standards and requirements used to regulate stormwater plan preparation, permitting, field implementation, and enforcement of the City and County of Denver (Denver or City) Stormwater Criteria for Construction Activities.

NOTE: Formally titled  Erosion Control Permits

green grass growingProblem: 
Excess fertilizer washes off lawns and ends up in waterways where it can cause algae blooms and harm aquatic wildlife. 

Be sure you're applying fertilizer properly.

Here are 5 tips on how to keep your lawn looking good while helping keep Denver's waters clean.

  1. Get Tested
    Have your soil tested for pH levels and the need for additional nutrients. This will help determine which fertilizers and supplements are needed.
  2. Slow It Down
    Select lawn-grade fertilizers that include Slow Release Nitrogen to prevent lawn burn, reduce runoff and leaching of nutrients into groundwater.
  3. Be Well Read
    Read and follow all label directions when applying fertilizer. Incorrect application such as spilling onto paved surfaces can result in fertilizer being washed down storm sewers and ending up in our waterways.
  4. Chill Out
    Grass will not use fertilizer when it is not actively growing. To prevent runoff pollution of lakes and streams, never apply fertilizers to frozen ground or pavement.
  5. Spread It Out
    Be sure your spreader is working and adjusted properly. Read and follow the spreader setting instructions on the fertilizer label so that your spreader applies the correct amount of fertilizer.

pet puppyThe problem:

Pet waste can be a major source of bacteria and excess nutrients in local waters. When it rains, any pet waste on lawns, parks or streets washes into the storm drain system and ends up in local waterways, resulting in high e coli bacteria levels and making waterways unusable for swimming, boating or other activities.


What you can do:

  • Please pick up after your dog when out for a walk. You can request free pet waste bags with our online form.
  • Do you have extra shopping bags that you want to get rid of? If they're free of holes, you can put them in a Do-It-Yourself bag holder (made from a milk jug) and hang it on a signpost near popular dog walking areas.

lawn mower on green grassThe problem:
Yard waste (such as grass clippings, leaves and dirt) get into the storm drain system. This can clog the system and cause floods, and harm aquatic wildlife.

What you can do: 
Leave the height of your grass long when mowing and leave clippings on your lawn to decompose. "Grass-cycling" is a great source of nitrogen and saves water and fertilizer (which also saves you money).

Look into composting. You can compost leaves, yard debris, and non-meat food scraps. They make great soil for the garden.