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Annual surface water management fee rates
Annual surface water management (SWM) fee rates for 2023 and 2024
| Rate class | Description | % Impervious Surface | Fee |
|---|---|---|---|
| 1 | Residential | N/A | $323.00 per parcel |
| 2 | Very light | ≤ 10% | $323.00 per parcel |
| 3 | Light | > 10.1 ≤ 20% | $898.04 per acre |
| 4 | Moderate | > 20.1 ≤ 45% | $1,680.99 per acre |
| 5 | Moderately heavy | > 45.1 ≤ 65% | $2,868.55 per acre |
| 6 | Heavy | > 65.1 ≤ 85% | $3,996.00 per acre |
| 7 | Very heavy | > 85.1 ≤ 100% | $4,916.64 per acre |
Fee appeals
For questions on your surface water management (SWM) 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 SWM 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 that reduce flooding, improve water quality, and recharge groundwater. Discounts also encourage landowners to preserve natural areas.
Cost-sharing program
We have some limited funding available for stormwater retrofit grants. Stormwater retrofits are improvements made to existing developed parcels to reduce the impacts of stormwater runoff. These retrofits may also qualify a parcel for SWM fee discounts.
Projects are chosen based on the total cost of the project and how much stormwater the project is expected to treat. Stormwater retrofits meeting the goals of this program often include those qualify for our RainScapes program.
See Section 4 of the SWM Fee Protocols (217 KB) for more information on this grant funding and how to apply for it.
Visit the Surface Water Management fee webpage for other surface water management questions.