SWM Service Charge 

The City Council determines the revenue needs of the surface water management (SWM) program, also referred to as the SWM utility, and imposes an annual service charge on all developed property in the City, pursuant to City Council resolution. The City Council reviews service charge rates approximately every 5-6 years to ensure adequate funding is provided to the surface water management program, which includes operating costs, capital costs, and debt service. 

All developed parcels in the city are subject to the SWM service charge.  The SWM service charge is determined by applying a rate to seven classifications of property throughout the city, which include single-family residential and six other classifications.  Properties that are not single-family residential are classified into a range of six categories based on the percentage of impervious surface area on the parcel (calculated as acres of impervious area divided by total parcel acreage).  Single-family residential properties and properties with less than 10% impervious area are charged a flat rate, and the remaining properties are charged their corresponding classification rate multiplied by the acreage of the property. 

King County, through an interlocal agreement with the City, collects the City’s surface water management service charge annually on each property’s annual tax statements and provides those payments to the City. 

Utility Tax 

SWM service charge rates are subject to a utility tax as authorized by Chapters 35.21 and 35A.82 RCW.  City Ordinance 22-0563 established a 6% utility tax on SWM service charges beginning January 1, 2023.  This tax is applied to the base rates set by resolution by City Council.  

SWM Service Charge Exemption 

Residential property owners may qualify for an exemption from the SWM service charge if they meet King County’s thresholds for household income, age, and disability status.  Please refer to King County’s tax relief website for more information (click here) or contact the King County Assessor’s office directly by emailing Exemptions.Assessments@kingcounty.gov or calling (206) 296-3920.  This exemption is administered by King County. 

 2024 SWM Service Charge Update  

On November 22, 2023 City Council adopted Resolution 23-406. The adopted rates for residential developments as part of the Rapid Progress + plan are as follows: 

Additional information including City Council Agenda packet can be found below in "Helpful Documents and Links"