Illicit Discharge Detection and Elimination Program

In an effort to proactively keep illicit discharges from happening, the City implements a program of inspections, dry weather field screening, and monitoring to detect any potential illicit discharges to the Stormwater System.

Our goal is to get spills contained and cleaned up as quickly as possible. Spills of hazardous materials can be reported to City staff day or night through our 911 system at (503) 635-0238. Dumping of anything other than rainwater to storm drain inlets and streams can also be reported to our Watershed Hotline: (503) 675-3982. The Watershed Hotline is staffed during business hours (M-F 8am-5pm); after-hours calls will be returned the next business day.


We have received reports of a number of illicit or improper discharges recently, including:

  • Untreated sewage (typically resulting from floor drains connected to storm sewer lines or improper cross-connections between sanitary sewer and storm sewer lines, but also possible from RV waste dumping);
  • Hazardous waste such as paints, pesticides, and used automotive fluids;
  • Excess sediment;
  • Muriatic acid;
  • Concrete saw cut slurry and waste concrete;
  • Drainage from pools and spas; and
  • Runoff from power-washing.


City residents and businesses have a role to play in preventing illicit discharges as well.  Here are five things you can do:

  1. Correct any improper cross-connections you discover.
  2. Contain car-wash water by using a commercial car wash or washing your car on the lawn. The City maintains car wash kits that can be used for charity fund raisers.  Information on reserving the kits is available.
  3. Use pesticides and fertilizers sparingly and dispose of excess safely.  Review usage and disposal suggestions.
  4. Protect adjacent storm drain inlets by using filter inserts if removing lawns or doing other landscaping in areas that drain to them.  Inserts can be found at home improvement stores or by searching under “erosion and sediment control” retailers. Larger scale landscaping, or landscaping mixed with exterior hardscaping, may require an erosion control permit.  Read information on the City’s erosion control permit.
  5. Don’t dump or wash anything down storm drain inlets that you don’t want in your drinking water.  We ask that courtesy of people who live upstream of our water intake – so let’s do that for those who might have water intakes downstream of us. That means no paint, leftover automotive fluids, pressure-washing runoff, concrete wash out water (which is as alkaline as drain cleaner), cleanout from RV waste systems, used cooking grease, water from hot tubs, or trash like leftover medications, cigarette butts and coffee cups.

Links for these and other water-wise resources can be found at the "Water...Do Your Part" website. Lake Oswego is one of KOIN's Clean Water Partners.