Kennewick, WA Accessory Structures: ADU Impact Fees (2026)

Washington's impact-fee framework is at RCW 82.02.050 through 82.02.110 (GMA Impact Fees). Counties, cities, and towns planning under the GMA may impose impact fees for system-improvement components of (1) public streets and roads, (2) publicly owned parks, open space, and recreation facilities, (3) school facilities, and (4) fire protection facilities — but not for libraries, water/sewer (handled through connection fees), or other categories. Fees must be reasonably related to the new development's impact, not exceed a proportionate share, and the funds must be spent within 10 years (RCW 82.02.070(3)). HB 1337 in 2023 added RCW 36.70A.696, which provides that 'the impact fees for an accessory dwelling unit may not be greater than 50 percent of the impact fees that would be imposed on the principal unit' for the categories where a fee is charged. School impact fees collected by Kennewick on behalf of Kennewick School District are passed through under interlocal agreement and the District's capital facilities plan. Water and sewer connection fees, called system development charges or general facility charges in Washington practice, are imposed under RCW 35.92.025 and similar statutes; they are not 'impact fees' subject to the 50 percent ADU cap, but Kennewick may waive or reduce them for ADUs by ordinance. Permit fees themselves (building permit, electrical, plumbing, mechanical) are set under RCW 19.27.085 and KMC and are based on cost-of-service rather than capped by the ADU rule.