State of Washington Department of Commerce Proportional Residential Development Impact Fees and System Development Charges Guidebook

Housing affordability is a growing challenge across the U.S., and the State of Washington is no exception. Communities need new housing at all affordability levels, but additional housing often results in the need for additional capital facilities ranging from expanded water and sewer systems to new roads, parks, schools, and fire stations. The construction of the necessary capital facility expansion often requires significant funding. While property taxes and utility rates cover ongoing operations, development impact fees and system development charges (SDCs) help fund the infrastructure needed to support growth. Setting these fees fairly, especially across different housing types and sizes, can be a challenge for local governments.

To address this, Washington State’s Legislature has passed new laws aimed at making fees more proportional. Recent bills require that impact fees and SDCs be calculated based on the type and size of the housing unit, supporting smaller, infill, and multi-unit developments. This ensures that fees better reflect each project’s actual impact on public infrastructure.

Harris & Associates was selected to develop Washington State’s first-ever Guidebook on Residential Proportional Impact Fees and System Development Charges, a significant milestone for our team and our first statewide guidebook. This Guidebook walks jurisdictions through legislative changes, explains the legal context (including “rough proportionality” and “rational nexus” requirements), and offers practical tools for implementing fair, proportional fees relative to unit size. Delivered on an accelerated schedule, the project demanded close collaboration, creative problem-solving, and a deep commitment to quality. The final product is a comprehensive, user-friendly resource designed to support jurisdictions across Washington in implementing consistent, equitable impact fee and SDC practices. Our selection for this work underscores the strength of our team, the quality of our work, and the trusted relationships we’ve built through decades of leadership in impact fee policy and infrastructure funding. By aligning costs with real impacts, jurisdictions within the State of Washington can support housing affordability while providing the infrastructure communities need to thrive.

Key contributions of Harris & Associates in developing Washington State’s first Guidebook on Residential Proportional Impact Fees and SDCs included:

• Interpreted new state legislation and translated requirements into practical guidance, ensuring local jurisdictions can implement proportional fee structures that align with Washington’s housing goals.
• Developed and updated methodologies for calculating impact fees and SDCs by housing type and size, incorporating a regression analysis and innovative approaches to ensure proportionality and support smaller, infill, and multi-unit development.
• Managed stakeholder engagement, facilitating complex discussions and integrating feedback from diverse perspectives to create a practical, user-focused resource.
• Delivered quality assurance and technical reviews, maintaining consistency, clarity, and accuracy throughout the document while meeting a highly accelerated schedule.
• Enhanced readability and accessibility, with professional editing, plain language compliance, and the creation of user-friendly layouts.
• Created user-friendly resources, including high-quality graphics, visuals, examples, and step-by-step instructions, that simplified complex concepts, ensured consistency, and aligned with state branding guidelines.
• Coordinated all phases of the project from initiation to final delivery, ensuring deadlines were met while balancing quality and timeliness through close collaboration, rigorous reviews, and efficient processes.
• Strengthened statewide understanding and access, providing jurisdictions with a consistent, equitable framework for impact fee and SDC practices that support housing affordability and infrastructure investment.