Stormwater F.A.Q.

The Stormwater system is made up of an interconnected system of catch basins/stormdrains, underground piping, and storm water facilities (like ponds, underground vaults, swale/ditches, and more). This system receives rainwater called “stormwater or surface water” as it runs off of impervious services like parking lots, roadways, sidewalks, driveways, pavement, roofing, and more. The job of this system is to transport clean rainwater through our city and back into local water bodies to keep the water cycle going and maintain local environmental health. 

Stormwater and Surface Water are 2 terms for the same thing. Both are names for rainwater that runs off of impervious surfaces like parking lots, roadways, sidewalks, driveways, pavement, roofing, and more. 

Pet Waste contains harmful bacteria and/or pathogens that can contaminate stormwater. These harmful bacteria and/or pathogens can be conveyed through the stormwater system into local water bodies that could be harmful to local residents interacting with the water body or aquatic life living in the water body. So remember, always scoop, bag, and properly dispose of pet waste. Visit Mill Creek City Hall to receive 1 free pet waste bag dispenser you can attach to your pets leash to ensure you always have bags to clean up after them! 

Look out for any spills into the stormwater system and report them to the spill hotline at 425-582-6000

Maintain any stormwater facilities or infrastructure that are on your property. For more information on this visit our stormwater facilities page here.

Join in on city offered stewardship opportunities. You can find these on our education and outreach page here. These are great if you are looking for volunteer hours!

Contact the City via email to see about other non-city local organizations, programs, or events to participate in by emailing SWM@millcreekwa.gov 

An easy way to remember is “Only Rain Down the Drain”. The City only wants clean rain water entering the local stormwater system. Things that shouldn’t go down the drain are called “illicit discharges or prohibited discharges”. The list below lists some common items that shouldn’t go down that drain. This isn’t the full list, for the full list review Mill Creek Municipal Code Section 15.14.230 by clicking here.

• Automotive fluids and oil
• Pet Waste
• Soaps and detergents
• Paints
• Yard Waste or Debris
• Trash
• Pressure washing water
• Cooking Grease
• Construction Waste
• Chemicals 

Call the Spill Hotline 425-582-6000 right away and be prepared to tell the operate where the spill occurred, how much was spilled, what was spilled, if it has entered water ways or stormwater system features like catch basins or ponds, and who the responsible party is if known. 

To do construction in Mill Creek first contact the permit counter to see any required permits applicable to your project by calling 425-551-7254.

When planning your construction project, determine possible impacts to local stormwater. Your project may require you to submit a Temporary Sediment and Erosion Control (TESC) Plan to ensure you have the correct supplies and Best Management Practices (BMPs) to ensure you project doesn’t contaminate local stormwater. These plans should outline what materials and BMPs will be used to stop contamination of stormwater. Common BMPs are catch basin inserts to catch sediment, waddle to slow flow and sediment, spill supplies like absorbent pads or granular absorbent, and more.

Depending on the size of your project you may be required to complete a Stormwater Pollution Prevention Plan (SWPPP). These are more in-depth than regular TESC plans and are typical for large construction projects.

For more information on if you project requires a TESC Plan or SWPPP please call 425-921-5752. 

Washing your car in your driveway or the street may lead to soaps or detergents as well as heavy metals and automotive fluids spilling into the local stormwater system. This is prohibited by Mill Creek Municipal Code Section 15.14.230. There are some solutions that can avoid this:

Wash your car on top of a permeable surface like grass, dirt, or gravel. A permeable surface allows wash water to be absorbed into the ground and no convey into the local stormwater system. Using biodegradable soap will allow the soap to break down in the soils to not contaminate soil.

Take your car to a commercial car wash! Commercial car washes collect wash water and discharge it into the sanitary sewer system which is then treated to remove any contamination.

Create or purchase a containment bay to collect the wash water. Then using a sump pump or similar device, pump the dirty water via hose into a permeable area like a garden, lawn, or backyard.

If you are looking to do a local charity car wash, please call 425-921-5752 or email SWM@millcreekwa.gov to get information on the requirements to conduct your carwash. Charity car washes are subject to closer and code enforcement action if wash water is discharged into the local stormwater system. 

If you, or a contractor, are pressure washing the exterior of your building, home or property, driveway, or pavement you could be contaminating local stormwater. Pressure washing can create sediment when cleaning that getting into the wash water from the pressure washer. This sediment filled wash water then conveys into a catch basin which collects the sediment and can stop proper function of the catch basin. This is prohibited by Mill Creek Municipal Code Section 15.14.230. There are solutions to this problem!

Placing a catch basin sediment into the nearest basin that collects the wash water. These inserts catch sediment and allow clean wash water to flow through. After completion of the cleaning project, simply remove the insert and clean it out over a permeable area like a garden, lawn, or backyard or into sanitary sewer like a sink, shower, or toilet.

Use a waddle or absorbent sock to create a berm in the area before the receiving catch basin by placing them in a U shape towards the flowing water. Then make sure it stays in place by placing a reasonably weighted object on either end of the waddle or sock. This will allow water to pass through but collect sediment in the U-shaped area which can be swept up after completing your project.

Remember, if a discharge of prohibited material, like sediment, comes from your property. The property owner is responsible for managing it. So, when hiring contractors for this kind of work, make sure they know how to manage their wash water. You are responsible to ensure that contractors you hire do not pollute the storm drain system.