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For questions on discounts, call Stormwater customer service at 206-477-4811

Stormwater facility discount

Residential and non-residential property owners may be eligible for SWM fee discounts for managing runoff using King County-approved flow control facilities, water quality facilities, features and/or best management practices (BMPs).

Qualifying residential parcels may receive a discount equal to 50 percent of the current residential fee. Call Stormwater Services Section customer service to arrange a site visit with an engineer and find out if your parcel qualifies for the discount.
Qualifying facilities and practices can be found in the King County Surface Water Design Manual.

The non-residential discount program offers percentage discounts up to a maximum 90 percent discount for these stormwater controls:

  1. A maximum 20 percent discount for flow control facilities that meet any current or previous King County standard of design.
  2. A maximum 20 percent discount for flow control facilities that meet modern design standards adopted in the 1990 or later versions of the King County Surface Water Design Manual.
  3.  A maximum 20 percent discount for flow control best management practices or infiltration facilities meeting King County standards that infiltrate or disperse runoff into pervious areas on the parcel to minimize the impact to the surface water system.
  4.  A maximum 20 percent discount for King County standard water quality treatment facilities that meet King County design standards that remove pollutants from runoff before it flows to the surface water system or to groundwater.
  5. A 10 percent discount for parcels where stormwater discharges from at least 50 percent of the parcel are regulated under a National Pollutant Discharge Elimination System (NPDES) stormwater permit. Call Stormwater Services Section customer service at 206-477-4811 to find out whether you qualify for this discount.

Discount for forested or native conditions

Residential and non-residential property owners may qualify for a 65-10 discount if the parcel:

  • is at least 65 percent forested or native condition; and
  • has no more than 20 percent effective impervious area; and
  • has no more than 10 percent effective impervious area (areas that flow directly to drainage systems without using flow control best managements practices to disperse or infiltrate runoff); and
  • any impervious area over 10 percent uses flow control best management practices for dispersing or infiltrating runoff.

A residential parcel may qualify to receive a discount equal to half the residential fee. Non-residential parcels may qualify to receive a discount of 80 percent of the SWM fee. King County will verify your parcel conditions. Other conditions may apply and at least one site visit by SWM engineers will be required for approval. This discount may not be combined with other runoff mitigation discounts.

Cost share and credit program

Non-residential properties trying to reduce impervious areas may be eligible for 50 percent of costs up to $20,000 by converting those areas to:

  • native-vegetated landscape or
  • compost-amended lawn or 
  • grassed, modular-grid pavement

King County engineers can answer your questions about what is needed to submit a proposal and the responsibilities of the property owner in fulfilling the cost-share project. Cost-sharing is available on a first come, first served basis until the annual funds are spent; the cost share is payable once the project has been completed and inspected.

Open space discount

Non-residential properties that are classified as open space per King County Code 9.08.010, may be eligible for an Public Benefit Rating System (also known as Open Space) discount.

Visit the Surface Water Management Fee questions for answers to other surface water management-related questions. For technical information refer to SWM Fee Protocols.

Surface water management fee