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Annual SWM rates for 2019 and 2020
Rate class Description % Imperv. surface Fee
1 Residential NA $289.00 per parcel
2 Very light ≤ 10% $289.00 per parcel
3 Light > 10.1 ≤ 20% $803.51 per acre
4 Moderate > 20.1 ≤ 45% $1,504.04 per acre
5 Moderately heavy > 45.1 ≤ 65% $2,566.60 per acre
6 Heavy > 65.1 ≤ 85% $3,575.37 per acre
7 Very heavy > 85.1 ≤ 100% $4,399.10 per acre

Fee Appeals

For questions on your fee or discounts, call Water and Land Resources customer service at 206-477-4800. We can check that:

  • the impervious surface calculation on your property is correct, or if it needs to be re-measured
  • the calculation of your SWM fee is correct
  • a discount has been properly applied to your SWM fee.  

We will review your parcel’s SWM fee and inform you of any options available to reduce the fee.

Low-income senior exemption

If you are a low-income senior as determined by the King County Assessor and you own your personal residence, you may be exempt from the surface water management fee. Only residential properties are eligible. Call the King County Assessor’s Office at 206-296-3920 to verify your eligibility.

Fee discounts

SWM fee discounts help support eligible property owners in addressing stormwater issues. These may include features such as a flow control facility, water quality facility, and flow control best management practices to more efficiently reduce flooding, improve water quality, and recharge groundwater. Discounts also encourage landowners to preserve natural areas. Find discounts at SWM fee discounts.

Cost-sharing program

King County may share the costs of converting impervious area on a non-residential parcel to native-vegetated landscape, compost-amended lawn, or grassed modular grid pavement. Reducing impervious surface on your parcel may place you into a lower rate category and reduce your fee.  Find out more at SWM fee cost-sharing program.

Visit the Surface Water Management Fee Questions for other surface water management questions. For more details and technical information go to SWM Fee Protocols and Public Rule.

Surface water management fee