Skip sidebar navigation

Environmental Services

Private Water Quality Facilities

Stormwater facility maintenance handbook

Private water quality facilities detain and treat stormwater runoff to remove pollutants and alleviate flooding.

These facilities:

  • Are required for new and redevelopment to treat stormwater runoff
  • May be above ground (ponds, swales or rain gardens) or below ground (vaults, drywells or detention pipes)
  • May be publicly or privately owned:
    • City staff inspect privately owned facilities to ensure they're working properly.
    • Privately owned storm drains and underground vaults should be cleaned annually to ensure they function properly.
    • Other systems may require less frequent maintenance, but inlets and outlets should be inspected and cleared often during the rainy season.
  • Maintenance Guidelines
  • New Facilities
  • Additional Resources
Maintenance Guidelines

Stormwater facility maintenance handbook

General guidelines:

  • Inspect the facility several times a year to look for obstructions to inlets or outlets, as well as litter and invasive weeds.
  • Check for excess sediment, which indicates the facility needs to be more thoroughly cleaned.
  • Establish a no-spray buffer zone of 20 feet to prevent pesticides from reaching streams and always follow pesticide instructions.
  • If herbicides are needed to control invasive plants, use aquatic-approved formulas within the 20-foot buffer zone.
  • Prevent soil erosion by planting native plants and adding rock to dissipate energy.
  • Establish lower-maintenance, no-mow areas to provide meadow habitat for wildlife.
  • Do not pile grass clippings in the stormwater management area. As the clippings break down, they rob the water of oxygen, which is harmful to wildlife and contributes to algal blooms.
New Facilities

Stormwater management facilities are required for new construction or redevelopment. Facilities designed to be privately owned and maintained must file a maintenance agreement when the deed is filed with Multnomah County.

Additional Resources

Contact us

To find out if a facility is privately owned or to request free technical assistance, contact us at 503-618-2525 or Karen.Bromley@GreshamOregon.gov.