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King County Washington home

Stormwater: Advancing Fee Structure, Oversight, and Spending Strategy Could Improve Results

September 28, 2026

King County’s surface water management (SWM) fee and discount structure is dated and does not consistently align a parcel owner’s fees with the parcel’s contribution to King County’s stormwater burden. In addition, some mining parcels receive significant discounts but do not demonstrate compliance with discount requirements for stormwater mitigation. The Water and Land Resources Division (WLRD) uses SWM fees to fund efforts that mitigate the impacts of stormwater runoff and reduce pollution of local waterways and Puget Sound. However, the division has not implemented essential governance elements for the Surface Water Management Program, limiting the division’s ability to direct SWM funds to achieve the surface and stormwater mitigation objectives set in King County Code. Finally, data gaps and planning deficiencies in the Stormwater Services Section hinder division-level decision-making, which is important in the context of potentially high costs to maintain the County’s aging stormwater infrastructure.

Audit Highlights

King County’s surface water management (SWM) fee and discount structure, which is set in King County Code, does not consistently meet the policy intent of basing charges on a parcel’s contribution to King County’s stormwater burden to the degree now feasible and widely practiced across jurisdictions. Additionally, some discounts may exceed the value of the benefits they provide. The Water and Land Resources Division (WLRD) does not ensure mining parcels meet discount requirements, increasing risk of environmental damage in an industry with documented ecological permit violations.

WLRD has not yet developed essential governance elements of the Surface Water Management Program, such as a strategy for allocating SWM fee revenues to the most essential efforts for reducing stormwater impacts. Relatedly, the Stormwater Services Section (SWSS) has not identified section-level goals or funding needs, hindering effective resource decisions at the section and division levels. Both WLRD and SWSS have taken steps to prioritize the needs of the program but have not yet completed their efforts. This work is especially important now because estimates for repairing King County’s aging stormwater infrastructure show that costs are likely to be significant.

We recommend WLRD establish governance structures for the Surface Water Management Program, to include strategies to guide and monitor its use of SWM fees and implement a capital project prioritization approach to help ensure the division funds the most essential work for managing stormwater impacts. We recommend WLRD conduct a comprehensive rate study to assess SWM rates, service charges, and the discount structure, and propose legislation to update charges and discounts and bring them in line with industry standards and county goals. We also recommend WLRD ensure sufficient oversight of mining operations.

Annually, about 118 billion gallons of untreated stormwater carry toxins and pollutants into local waterways and Puget Sound, threatening the survival of native salmon, orca, and other wildlife. Stormwater can also contaminate drinking water and cause flooding, erosion, and sedimentation that can endanger human safety and property.

Accordingly, the federal Clean Water Act and the Washington State Department of Ecology require King County to manage untreated stormwater, and multiple county initiatives aim to reduce the impacts of runoff, including the King County Clean Water Health Habitat program and the King County Comprehensive Plan. Without governance structures to guide WLRD’s varied efforts, King County risks ineffective and inefficient use of SWM fees to mitigate the effects of runoff.