Drainage Rate Schedule

Small Residential Annual rate per parcel (1)

Under 2000 sq. ft. (2) $183.47
2000-2999 sq. ft. (2) $298.75
3000-4999 sq. ft. $414.26
5000-6999 sq. ft. $558.27
7000-9999 sq. ft. $705.09

All Other Properties Annual rate per 1,000 square feet

Undeveloped (0-15% Impervious)
Regular $46.05
Low Impact (3) $27.40
Light (16-35% Impervious)
Regular $68.75
Low Impact (3) $53.85
Medium (36-65% Impervious)
Regular $97.86
Low Impact (3) $79.21
Heavy (66-85% Impervious) $129.50
Very Heavy (86-100% Impervious)(4) $154.60

(1) Single Family Residential & Duplex parcels less than 10,000 square feet which are charged a flat rate per parcel rather than a fee based on the percent impervious. Rates for other properties are per 1,000 square feet based on the percent of impervious surface.

(2) Beginning in 2016, the under 3,000 sq. ft. tier was split into two tiers to minimize the variance between properties in each group in terms of lot size and percent impervious.

(3) A customer in the Undeveloped, Light or Medium rate category with a significant amount of highly pervious (absorbent) surface may qualify for the Low Impact rate.

(4) "Very heavy" does not necessarily mean heavily developed. A parking lot would be classified as "very heavy" since it is 100% impervious.

Drainage fees do not appear on your utility bill but are collected with your King County property taxes. The fee is shown on your tax bill as SWM (Surface Water Management) or Drainage. You can view your drainage fee by entering your property tax ID in the King County Property Tax Information System.

Eligible low income customers can receive a credit. Learn more about the Payment Assistance Program.

Related links

Understanding Your Drainage Bill FAQ
King County Property Tax Information System